Category Venture for Affordable Housing

An important means of achieving affordable housing is by running an efficient business. Good business planning, organization, and control are essential to keeping costs as low as possible.

Because affordable housing construc­tion may require regulatory changes and relief from the community, it becomes very important that resultant
cost reductions are not offset by business and job site inefficiencies.

Production planning and control combine, in the best possible way, the resources available. This will assure that management, money, manpower, machines, materials, and marketing are integrated in the best way possible to produce affordable housing when the market wants it.

Hitting the right market at the right time, with the right product, can save thousands of dollars in carrying costs on land, infrastructure, sales centers, model homes, advertising, office overhead, etc. So careful market research is important.

All JVAH builders realized that the primary reason for building affordable homes was that they were priced for the largest unserved market segment in their respective communities. Some found they grossly underestimated the demand. Their buyers included those who could afford more expensive homes but preferred the JVAH units.

But, even if market potential for affordable housing may appear to be obvious, there are still many decisions that must be made and, when possible, contingencies planned for. Therefore, long – and short-range goals should be developed. Questions that may be

helpful in formulating company goals include:

• What markets are not being served today?

• What can be done if inflation increases building costs?

• What features will produce significant market advantage?

• What expensive features are unnecessary for the target market?

• What if interest rates increase? ..decrease?

• What related business could be entered successfully?

• If the firm were to redesign its construction methods from scratch, what techniques would be adopted?

In an affordable housing market, faster turnover will reduce land and infrastructure finance carrying costs. Land should be zoned for higher densities than in upper-end housing. Designs will be smaller, simpler, and more production-oriented with fewer options. High-speed production equipment and techniques are appro­priate. Less skilled, less knowl­edgeable employees of all types can perform high-quality work on the simpler tasks required in lower-cost houses. Mass media advertising, open houses, and sales centers may be appropriate to this market.

Substantial savings can be gained by organization and control of direct costs – material, land, labor – and indirect costs – marketing and sales, finance, equipment depreciation and maintenance, and management.

Labor costs can be controlled by preplanning and scheduling of work,

using properly-sized crews, good supervision, and instilling high-quality standards in workers. See the "Production Planning and Control" and "Labor Cost Control and Reduction" sections in Construction Cost Control, available from NAHB, 15th and M Streets, NW, Washington, DC 20005.

Methodical preplanning of work reduces lost time. For example, a carpentry crew can frame a wall faster if the crew leader has detailed pull lists, cutting lists, component lists, and wall layout drawings, than if the leader has to do all the thinking on the site while his crew awaits orders.

Efficient scheduling saves time, and "time is money." The longer it takes to build a house, the greater the time-related costs which are incurred – construction loan interest, insur­ance, security, overhead per unit, maintenance and rate of capital utilization.

The optimum schedule is one that is reasonably attainable with some effort. The complexity of the scheduling sys­tem should not exceed that required for adequate control.

The most efficient construction crews usually have three members, although larger crews can be efficient if they form smaller work groups to do the majority of their tasks. One skilled worker on each small crew is usually enough. Having too many skilled people usually means the crew is being overpaid. Specialization improves productivity; workers who are assigned a specific task to do over and over become much more efficient at that task than a general "all-around" worker who might do the task only once every few weeks.

This is why in many cases a sub­contractor, although he adds overhead and profit to his labor cost, still costs the builder less for a particular task than the builder’s own crew; the subcontractor is faster because he specializes in one task.

Good supervision saves money. A crew leader must be able to provide clear directions and keep his men working when he himself is planning, thinking, or doing his own task.

Higher level supervisors should make scheduled inspections from inspection checklists.

At each level, a supervisor should be knowledgeable enough to instruct his workers on how to accomplish any of his assigned tasks. He should consistently demand the highest quality work so that workers learn to "do it right the first time" in order to reduce expensive callbacks and rework, and to enhance the company’s reputation. He should praise good work and effort, but make the employees redo all substandard work.

Material costs can be controlled by accurate estimating, source selection, ordering, expediting, receiving, handling, and inventory control.

Careful estimating reduces waste and delays due to material shortages. Effective source selection techniques are important, such as requests for bids which evaluate payment terms, lead times, and delivery service, as well as price.

Maintaining histories of supplier performance – price, quality, service, willingness to expedite late shipments, and response to claims for shortages and damages — is useful.

Purchase orders should be used to ensure that the price, terms, and conditions are explicit so that suppliers can be held to every condition later. Invoices received from suppliers and subs should be checked against purchase orders.

To evaluate suppliers for future purchases, records should be kept of all past purchases, including quantities, prices, delivery time, quality, and any problems encountered. Suppliers should load material in such a way that when unloaded, that which is to be used first is on top. They should place it on the construction site where it will minimize handling labor. They should deliver the right amount of material to the right place at the right time. They should protect the material from weather, and, at the builder’s request, band it together for security.

On stocked items, economic order quantities and reorder points based on past usage and predicted future demand, should be calculated to minimize inventory carrying cost.

Estimated quantities and prices should be compared with actual quantities used and prices charged with variances calculated for quantities, prices, and total material costs. Positive quantity variances may mean too much material is being sent to the site which fre­quently results in extra waste, pil­ferage, and handling costs. Negative quantity variances mean there have been shortages which may have de­layed production and required expen­sive emergency orders.

Land costs should be controlled as carefully as those of labor and material. A "quantity discount" — low price per lot – often can be gained by purchasing a large tract of land, and if not used immediately, the land may increase in value. On the other hand, it may depreciate if adjacent land is used for an industrial or commercial purpose. In addition, the longer the land is held, the greater the interest carrying cost, especially if some investment has been made in roads and utilities, etc.

Similarly, if a developer installs the infrastructure for an entire develop­ment at one time, he may receive lower prices from his subcontractors. However, he will also have to carry the interest on a large investment during the entire construction period. For this reason, and to reduce the investment required, many developers phase infrastructure installation. Also, if conditions stall sales, the developer is more likely to survive until sales pickup. Because of this risk, many builders stay out of land development entirely and buy developed lots as they need them.

Control of indirect expenses can reduce the overhead allocation applied to each housing unit.

Marketing and sales expenses must be carefully budgeted and controlled. Advertising must be aimed at the particular market segment that fits the product, and the proper advertising channels used to reach potential buyers. In some developments, a sales center which later becomes a community building is an effective marketing tool. In other develop­ments, low unit prices are most impor­tant, and amenities such as pools, community buildings, parks, etc., raise costs beyond the reach of the target market. Often there are too few units in the development over which to spread the cost.

For some developments, demand is strong enough to justify large newspaper display ads, open houses, and full-time sales personnel. In others, classified ads and the sub­contracting of sales to realtors makes sense.

Computers are making an increasing impact on the efficient flow of information used to control sales and production. For more information on computer systems, see Data Processing for Builders. National Association of Home Builders, 15th and M Streets, NW, Washington, DC 20005.

As much integration as feasible should be achieved. It should be possible to use quantities developed in the estimating procedure to automatically print requests for bids and purchase orders when accepted prices and terms are entered. Labor, material, and subcontract estimates should feed into the standard job cost system as budgeted costs against which actual costs are compared in variance reports.

For greatest timeliness, posting to the job cost system should be done when purchase orders are placed; any changes can be recorded later with change orders.

When payroll, subcontractor and material invoices are paid, the system should automatically post the general ledger and update other accounting reports.

Although no systematic effort was made to determine or document cost savings due to business and market efficiency, some examples came to light

John Crosland Company sought land zoned for low-density development which they thought they could get zoned for higher-density development. They were successful in this strategy at Lynton Place and were able to increase density and reduce their land cost per unit.

Crosland did extensive market research which indicated that a mixed develop­ment with condos and medium-priced single-family homes would be success­ful. They generated early traffic by putting a sales trailer on the site. TV and newspaper display advertising invited people to put on their "muddy boots" and come see the plans and site.

Later, they built a sales center -­future community building with two swimming pools — and seven model homes. Company personnel performed the sales duties at both the trailer and sales center. Crosland subcon­tracted all construction and bought wall panels for the condominium portion of the construction; the remainder was "stick-built."

In contrast, "Pup" Robertson of Robertson-Tomberlin Homes used a low-budget strategy to market his low-cost high-value brick ramblers.

His only advertising was one-column one-inch newspaper classified ads. He built two homes "on spec" and sold them. Thereafter, he and a realtor sold the remaining homes from plans.

Robertson bought all material himself, since in his area, subcontractors were small, and his buying power exceeded theirs. In his rural locale where subs were few and not as highly specialized as in urban areas, he found it cheaper to hire employees by the hour than to pay subcontractor markup and profit.

Santa Fe, Mike Chapman used the exterior shell New Mexico of the first home built as an on-site shop, which was used for fabricating balcony and stair railings, cutting and finishing trim, and general storage of high-value materials. When the project neared completion, he closed down the shop, installed partitions and fixtures, and sold the home.

Because HVAC system design is complex, judgement on system type, size, and location of ducts is often left to the expert – the HVAC subcontractor. But the builder should understand some basic facts to insure that the most efficient, cost-effective system available is being installed.

Select the most appropriate economical system according to home design, local climate, fuel availability, and market ^reference. If a ducted system is to be used, a concise guide is available тот the National Association of Home : Builders, 15th & M Streets, NW, Washington, DC 20005. Titled Residential Duct Systems, this guide describes the most efficient duct methods according to fuel, type of equipment, operating efficiencies, and relative cost.

Design starts with accurate heat loss calculations (and heat gain for cooling). This is the only real basis for selecting equipment and designing the system. Too often equipment is selected based on past experience and judgement.

But, since each home design is unique, the HVAC system should be tailor made for that home. Guidelines on how calculations are made are presented in the Residential Duct Systems manual mentioned above as well as in the Insulation Manual for Homes and Apartments, also available from NAHB.

The standard calculation procedure used in the HVAC trade is in Manual J. Load Calculation for Residential Winter and Summer Air Conditioning available from Air Conditioning Contractors of America, 1228 – 17th Street, NW, Washington, DC 20036.

Avoid the tendency to oversize HVAC equipment. Some believe that if a certain size equipment is adequate based on proper calculations, a size larger will be even more desirable. Since the incremental cost of upsizing appears not too excessive, it is tempt­ing to oversize. However, equipment based on sound heat loss-gain calcula­tions is almost always more efficient and uniform in heating and cooling than oversized units. Also, be aware of unit efficiency.

For each 1 /2-ton heatpump or air conditioning reduction, equipment and duct costs can be reduced by about $275. Wiring costs may also be reduced since a lighter circuit may be possible.

Downsized or redesigned duct systems will be possible in energy-efficient homes where HVAC equipment is smaller. In addition, the system will perform better since proper velocity and air flow will be maintained. Another standard guide for residential duct design is Manual D – Duct Design for Residential Winter and Summer Air Conditioning, from the Air Conditioning Contractors of America, 1228 17th Street, NW, Washington, DC 20036.

In small, single-story homes with a central hall that abuts all living areas, consider using a dropped-hall ceiling plenum system. In this system, the hall ceiling and walls are drywalled as usual. Then another ceiling, dropped 6 inches to 8 inches below the con­ventional ceiling, is framed and drywalled, thus providing a plenum for air distribution.

High inside wall registers to each adjoining room are connected to the plenum by a short sheet metal boot through the wall. Although the system described has worked well in many installations, some local inspec­tors insist on sheet metal ducts within the ceiling cavity. If so, the system is still more cost effective than most.

The CABO One and Two Family Dwelling Code permits such "gypsum ducts" up to 125 degrees F., which would accommodate low output temperature equipment such as most heat pumps or electric furnaces. Fossil fueled equipment generally exceed this temperature limit.

Radial duct systems are often the simplest duct systems to install.

Branch ducts connect directly to the equipment plenum without trunks. Radial systems are typically installed where it is not necessary to conceal the duct work and where the equip­ment is centrally located. The basic simplicity of the system provides cost savings through reduced materials and less labor.

In smaller, well-insulated homes where central air conditioning is not re­quired, electric baseboard heat with individual room thermostats offers significant construction cost savings, and depending on comparative fuel costs and availability, may offer operating cost savings because of the ability to "zone" heat the house.

One very innovative heating/cooling system that has enjoyed some regional success is the underfloor heating/cool­ing plenum, being marketed by the wood industry under the name "Plenwood." Instead of using heating and cooling ducts, the entire under­floor space is used as a sealed – plenum chamber to distribute warm or cool air to floor registers in the rooms above.

Several of the JVAH builders used innovative HVAC systems to reduce costs. In Santa Fe and Phoenix, bathroom ventilation fans were eliminated, saving about $150 per unit in ventilation ana electrical wiring.

In Crittenden County, Arkansas, the builder used the ductless dropped ceiling approach to air distribution in homes with central air conditioning.

In Christian County, Kentucky, a radial duct system was used instead of one large trunk line throughout the center of the crawl space with lateral ducts. This system saved an average of $125 per house.

The most innovative HVAC system built in the JVAH program was in Tulsa, Oklahoma, where the Plenwood system described earlier was installed. Wayne Hood used the underfloor area as a ductless return air plenum (See Footings and Foundation Section) with a pressure treated wood foundation. Hood estimated that foundation, floor and heating/cooling costs were reduced by a total of $1,470 per unit.

Electrical codes and their implemen­tation are normally not very flexible. But costs can still be reduced by several methods within the codes.

Floor plans can often be adjusted to reduce electrical costs by reducing length of wiring or eliminating outlets while staying within the code. For example, since one outlet is needed for each 12 feet of wall, shortening or eliminating walls or moving door locations can reduce wiring, recep­tacles, switches, etc.

If all points requiring heavier appli­ance circuits are clustered and located close to the distribution panel, expen­sive heavy cable can be minimized.

Check the house during construction to make sure extra outlets are not arbitrarily installed. Relocate closet doors or other openings to avoid short walls over 24 inches wide which will require an outlet. Remember outlets are not required in hallways.

In some locations, entire homes are traditionally wired with #12 wire and 20-amp devices for general wiring. However, most codes allow the bulk of a house to be wired with #14 wire and 15-amp devices.

Each required lighting point can be switched by a single switch. Also, bath fans can be switched with the bathroom light. Light fixtures that are not required by code can be pull – chain operated and need not be separately switched.

Smaller homes do not need heavy service load centers. Many can be served by a 100-amp load center. A switched receptacle may be substituted for overhead lights in habitable areas. Only one light fixture is required in a basement. Attic storage or equip­ment service areas require light fixtures. Otherwise, attic lighting is not required.

Extra branch circuits are often routinely installed by electricians to simplify the arrangement of breakers in the panel. Maximize the number of devices on a circuit, and normally one or two circuits per home can be eliminated.

Separate circuits are not required for the refrigerator or garbage disposal. Extra circuits cost about $25 each for additional home run wiring and breakers.

Heavy 240-volt circuits are required for the range, clothes dryer, water heater, electric furnace, and heat pump or air conditioning unit. If house design permits, locating as many of these heavy circuit appliances near the load center will reduce costs.

The large feeder cable required for an electric furnace is very expensive. In addition, if the furnace is located near the breaker panel, a separate discon­nect is not required at the unit, saving between $75 and $100.

Plastic utility boxes reduce costs by about $1 per wiring point and are allowed by most codes.

The Portland demonstration subdivision was arranged in clusters of four detached units. The city allowed one 1 1/2-inch PVC water line to run from the main to each cluster and 3/4-inch PVC from there to each unit. This was instead of one 1-inch line from the main to each unit. Cost savings amounted to $32 per unit.

Rough plumbing was installed in a trough above the slab so the plumber would make only one site visit. All plumbing was clustered to reduce DWV and supply pipe lengths. A standard­ized DWV plumbing "tree" was used; therefore, much of the DWV system could be prefabricated. The plumbing wall was prefabricated with supply pipe and DWV installed. Polybutylene plastic pipe was used instead of copper. Total plumbing cost savings averaged $182 per unit.

Polybutylene supply pipe, fiberglass bathtubs, and cultured marble lavatory/vanity tops were used instead of copper pipe, cast iron bathtubs with ceramic tile surrounds, hardboard vanity tops, and ceramic lavatories. Total cost savings amounted to $367 per unit.

Many of the demonstration projects used trusses and several used the simplified trim details described above. However, several projects also used vaulted ceiling rafter framing to provide more open space in relatively small homes. In some houses the vaulted ceilings provided lofts and expandable space.

An excellent opportunity exists to reduce construction costs through innovative plumbing. But plumbing is also one of the more difficult areas to get innovations adopted. In spite of the fact that present model plumbing codes are updated periodi­cally, the process is lengthy and uncertain, so none of the model codes reflect current state-of-the-art.

In addition, comprehensive model plumbing codes cover all types of buildings and are overly complex for dealing with relatively simple re­quirements of single family dwellings.

The four major model plumbing codes are the BOCA Basic Plumbing Code. the SBCC Standard Plumbing Code, the NAPHCC National Standard Plumbing Code, and the ІАМРО/ ICBO Uniform Plumbing Code.

Many local jurisdictions use one of the model codes with their own modi­fications. In almost all cases, local modifications are more restrictive in material and design than the parent model code.

Confronted with these facts, the NAHB National Research Center has compiled a state-of-the-art manual for residen­tial plumbing. This effort, sponsored by NAHB and HUD, resulted in Residential Plumbing Guidelines which contains all requirements to assure a safe, functional, durable, and cost – effective residential plumbing system. NAHB submitted proposed code changes to the Council of American Building Officials (CABO) in 1984, and the proposed changes were adopted in January, 1986.

Substantial changes were made in some areas of the code. Following is a synopsis of the more relevant changes that affect the installed cost of plumbing.

The load on the drain, waste, and venting (DWV) system is determined by drainage fixture unit (d. f.u.) values.

This is a measure of the probable discharge into the drainage system by various types of plumbing fixtures and is used to size DWV piping systems.

The newly adopted d. f.u. values are, in every case, less than those in the old CABO code. The old values are basically the same as those used in the other major model codes.

The new CABO code includes d. f.u. values for plumbing fixture groupings. These values are less than the sum of individual fixture units, which recognizes the fact that d. f.u. values are not additive when the probability of simultaneous use is very, very low.

The new CABO code allows 75 foot spacing of cleanouts versus 50 foot spacing in the old code. This is consistent with standard available snake lengths.

The new CABO code allows smaller size traps and trap arms for some fixtures. Below-grade drain pipe mini mums were reduced from 2 to 11/2 inches in diameter because of power driven cleanout equipment capabilties.

In practice, large diameter drain pipe is often perceived to be desirable. However, with the lower discharge rates of modern residential fixtures manufactured to water conserving standards, large diameter drains have very low flow rates which promote deposition of solids.

Smaller diameter pipe with higher flow rates actually provides improved transport characteristics. This is a classical case where bigger is not necessarily better and where tradi­tional thought is outdated.

The new CABO code allows an increase in maximum trap arm lengths. This provides a degree of architectural flexibility such as the location of kitchen sinks under windows.

The purpose of the venting system is to maintain atmospheric pressure within the DWV system and to provide venting of gasses by circulating air throughout the system. At low flow rates, characteristic of residential construction, vent pipes need only be of small diameter. In addition, vents need not penetrate the roof. Rather, vents can extend through an exterior wall or roof overhang and terminate downward.

According to the new CABO code, "A common vent may be used for two waste fixtures connecting at different levels in the stack but within the same branch interval, provided the vertical drain is one pipe diameter larger than the upper fixture drain, but in no case smaller than the lower fixture drain. The vertical piping between fixture connections serves as a wet vent for the lower fixture." (Section P-2207.7.1, One and Two Family Dwelling Code).

The CABO code also states, "Stack venting, with certain preconditions relating to drainage loads and vent­ings, fitting types and sizes, and placement of connections, shall be permitted as a system that allows fixtures and fixture group to be independently connected to a soil or waste stack without individual fixture venting." (Section P-2207.8, One and Two Family Dwelling Code).

The significance of these paragraphs cannot be overlooked inasmuch as the total cost of plumbing DWV in an average home can be reduced substan­tially. When combined with other DWV innovative practices, total costs have been reduced by as much as $400, depending on which code was used as the comparison.

Because of this (and the fact that the techniques have been proven for many years to be safe and reliable), it will be well worth while for builders to push for adoption of the plumbing section of the CABO code.

Water Service As with DWV piping, water service
and Distribution requirements in the CABO code have

been changed significantly toward cost reduction and efficiency. Health standards have been maintained in all cases.

In all major model codes acceptable water service pipe materials include copper, galvanized steel, PVC or CPVC plastic, polyethylene plastic, and polybutylene plastic. Some local codes are more restrictive, especially in use of plastic pipe.

The lack of competition in materials often tends to keep the cost of the only acceptable materials high. If for no other reason, a variety of acceptable materials is desirable.

Section P-2405.3 in the new CABO code, individual fixture stops are considered optional for single-family housing. Experience has shown that individual fixture stops often deterio­rate between time of installation and time of their eventual use to the degree that they may require service or replacement. They also create potential sources of leaks. This is a case where possible convenience is offset by more probable inconvenience. ‘ In any case, convenience items should not be codified.

Water supply fixture unit (w. s.f. u.) values have been changed in the new CABO code and are consistent with established values in fitting standards. The new w. s.f. u. values for both hot and cold water provides for selection of pipe sizes based on reasonable estimates of peak demands. Measure­ments made m numerous field and laboratory tests have confirmed these values.

Minimum size offixture water supply pipes for all fixtures, except dish­washers and lavatories, is 3/8 inch in the new CABO code. For dishwashers and lavatories, minimum size is 1/4 inch. Fixture group main minimum sizes are either 3/8 inch or 1/2 inch, depending on number and size of fixture branch pipes connected.

The CABO code also recognizes the different flow rates of different pipe materials and the w. s.f. u. values vary accordingly. Therefore, supply pipe often can be reduced in size depending on the number and type of fixtures.

The significance of the new CABO One and Two Family Dwelling Code cannot be overemphasized. Studies have shown a total cost reduction in supply piping of as much as 24 percent even when the same piping material is used.

For more information on the innova­tions discussed herein, write the Council of American Building Officials, 5203 Leesburg Pike, Suite 708, Falls Church, VA 22041.

There are methods to reduce plumbing costs regardless of code restrictions. Some may require negotiating with the plumbing subcontractor to get full benefit, others may require market evaluation to determine consumer acceptability.

Cluster the plumbing. This cost-saving design principle is to arrange plumbing groupings back-to-back in a common wall and to shorten distances of other plumbing runs as much as possible. In multiple-story buildings, fixtures should be located over each other to minimize DWV and supply piping. Savings can amount to as much as 10 percent. Plumbing subcontractors often bid on a "per fixture" basis so the value of clustered plumbing may not be passed on without negotiation.

White plumbing fixtures are less expensive than colored fixtures. A savings of $40 to $75 per bath can be realized. From a consumer standpoint, any accent or decorating color can be used with white fixtures.

Consider fiberglass bathing modules. They often are less expensive than other bathtub/shower materials.

Wall hung lavatories can reduce costs although vanities have become standard. Wall hung units may be a marketing problem, but they should be considered, especially in powder rooms and/or second bathrooms.

Size water heaters according to intended use. Smaller homes intended for small families do not need large water heaters. Thirty-gallon gas or 30- to 40-gallon electric water heaters are generally adequate. Also, water heaters with a five-year warranty cost about $20 less than units with a ten – year warranty. This reflects an lV additional five-year insurance policy, not the basic construction of the water heater.

Consider polybutylene supply piping. This material is flexible and, there­fore, requires only about 1/3 the number of fittings as rigid pipe materials. It normally costs much less to install and has some ad­vantages in flow characteristics.

Field studies have shown cost savings of between 30 and 50 percent.

Growing pressures on land availability and housing affordability are resulting in an increase in demand for attached homes. Zero-lot-line configurations are becoming more popular for detached homes because of more innovative use of small lots. The principal added code consideration for attached and zero-lot-line homes is the requirement for fire barriers.

Requirements of the major model codes are not always clear and are often subject to local interpretation and/or amendment. It is important to under­stand that all major model codes have an "Alternate Materials and Systems" section and that local code officials have the discretion to approve alternate construction. Appropriate documentation is, of course, usually necessary.

To be acceptable, firewall construc­tions must be rated by a recognized testing laboratory in accordance with ASTM El 19, Standard Methods of Fire Tests of Building Constructions and Materials. Many different one – and two-hour wall constructions have been approved and are listed in literature available from the Gypsum Association, 1603 Orrington Avenue, Evanston, IL 60201; the National Concrete Masonry Association, P. O. Box 781, Herndon, VA 22070; and other industry associations and product manufacturers.

For zero-lot-line homes, each unit must have an independent one-hour fire-resistive rating. The Standard Code (Southern) Uniform Building Code (ICBO), and the One and Two Family Dwelling Code (CABO), all require one-hour ratings for homes built less than 3 feet from the property line. The Basic/National Code (BOCA) requires a one-hour rating on exterior walls less than 6 feet from the property line. None of the codes permit unprotected openings through a firewall. Normal electrical, plumbing, and ductwork are generally allowed.

The most common one-hour firewall is of wood frame construction with 5/8- inch type X gypsum wallboard or gypsum sheathing attached to each side with 6d coated drywall nails 7 inches on center. Joists are required to be staggered at least 24 inches on center on each side.

For attached homes, a two-hour firewall is required, either as two separate one-hour walls or as a common two-hour wall at the property line. Check your local Code. The two-hour common wall typically built is a single wood frame wall with two layers of 5/8-inch type X gypsum wallboard on each side or concrete block. Two-hour walls typically have restrictions on electrical wiring, plumbing, and ductwork within the wall.

In addition to the firewall, some provision is required to block the spread of fire to the roof of an adjoining unit. For zero-lot-line detached homes, codes are somewhat vague because there is no adjoining roof.

In addition to confusing major model code firewall and roof treatments, some local codes require that firewalls be built of masonry construction.

This requirement is prohibitive for factory-built construction.

As mentioned, three of the four model codes require a firewall if within 3 feet of the property line. The other code, BOCA, requires a firewall if within 6 feet of the line. If a home is built 37 inches from the property line (73 inches under BOCA), no firewall is needed.

If an easement for use of that narrow strip of land is assigned permanently to the house next door, a zero-lot – line effect is obtained without cost of a firewall or roof parapet. It will be worthwhile to check local interpreta­tion of firewall/roof treatment requirements prior to construction.

Since the major model codes are difficult to interpret and have not seriously addressed detached zero-lot – line homes in many cases, a complete review and rewrite of all codes should be undertaken.

Three JVAH sites, (Lacey, WA; Everett, WA; and Santa Fe, NM), all built under UBC, ran into the problem of firewall and roof treatment requirements.

In Santa Fe, the normal city require­ment is a masonry firewall between attached garages, including a parapet above the wall. The builder obtained the Fire Resistance Design Manual from the Gypsum Association which shows wood frame firewalls.

In addition, he pointed to the 1,000 square foot per floor exception for roof fire treatment in UBC. These convinced the city that a common two-hour wood-framed firewall with no parapet or roof treatment was adequate.

In Lacey, the city required either a parapet extending 30 inches above the roof or that all framing elements (trusses, wall plates, studs, etc.) within 5 feet of the two-hour separation wall be of one-hour fire resistance construction.

The builder, John Phillips, pointed out that none of the other major model codes had this requirement and that fire-resistive sheathing, installed at least 4 feet from the wall, provides adequate fire safety according to building code experts. The city accepted his documentation which resulted in substantial cost savings.

In Everett, zero-lot-line homes were built with one-hour fire walls. The city accepted the builder’s documenta­tion that type X fire-rated gypsum board under roof sheathing, within 4 feet of firewall was adequate to comply with the intent of the code.

The standard roof truss has become the most common and most cost – effective method of roof framing. Light-weight trusses are the most highly engineered component in new home construction and form the basis of a very efficient roof system. They are easy to install and adapt to many basic designs. Therefore, if cost is the primary consideration, standard roof trusses are recommended.

The "in-line" framing concept dis­cussed in the House and Lot Design section of this manual works very well with roof trusses. That is, the 24- inch on-center roof trusses align with the 24-inch on-center wall studs which in turn align with the 24-inch on- center floor joists. The key to this consistent alignment is to start all layout from the same corner.

Simplification of roof overhang and trim details, consistent with design and function, provides opportumties for cost reduction. For example, the ■ rake overhang is essentially nonfunc­tional on a gable end roof. A simple fascia board at the siding/roof junction serves to cover the rough edge of the siding and conceal inaccuracies of fit. Several of the nation’s largest builders use this detail on all their production homes.

Roof overhangs are desirable for most designs and provide rain protection for the front and rear of the house. They also can provide summer shading for some windows. When an overhang is used, an inexpensive "open" soffit will eliminate much of the cost of the traditional cornice. All trim details on the underside of the overhang may be
eliminated, leaving the truss or rafter tails exposed. Blocking between trusses or rafters and a 1×6 fascia board are the only finish items needed. If soffit venting is needed, screening between trusses or rafters can be used instead of blocking.

Three-eights-inchplywood roof sheathing with metal plyclips is an acceptable alternative to 1/2-inch plywood.

EXAMPLES FROM THE DEMONSTRATION PROJECTS Posted by admin on 16/ 11/ 15 Most JVAH sites used some aspects of Optimum Value Engineered wall systems to minimize costs. The most commonly used techniques were in-line framing with 24-inch stud spacing, single top-plates, 1×4 bottom plates, two-stud outside corners, metal drywall clips instead of wall and ceiling nailers, and elimination of headers and jack studs in nonbearing walls. Besides using OVE techniques which saved $448 per unit, Pup Robertson saved 3,000 bricks per house by starting the brick at the bottom of the wood floor instead of below grade, eliminating gable brick and reducing the wall height to 7’6"; moreover, since each house required less brick than normal, he was often able to buy odd-lot quantities at substantial savings. These techniques saved $1,685 per unit on brick veneer. Tom Webb used 2×6 exterior walls and 2×4 interior partitions on 24-inch centers. Costs were reduced by over $1,200 per unit. Ryland Homes has been using efficient construction techniques for years. For the JVAH demonstration, modular housing units were used with 24-inch on-center wall framing, two-stud corners, and no headers in nonbearing walls. Costs were reduced by $850 when compared with more typically used 16-inch on-center framing. John Crosland had already adopted most of the OVE techniques. In addition to 24-inch on-center wall framing, he also used sections of plywood truss floor joists for window and door headers. This not only was less expensive than typical built-up wood headers, but also provided space for insulation. John Phillips used almost all of the OVE framing techniques in the demon­stration homes. He also had a very innovative floor system (see floor framing section) and used single-layer plywood siding without a separate sheathing. He saved almost $1,200 per unit. Phil Hamby reduced costs by $425 by using OVE framing techniques and single-layer plywood siding in his JVAH demonstration.   Knox County, Tennessee   Knoell Homes built exterior walls on 16-inch instead of 24-inch centers because the single-layer hardboard siding used required 16-inch stud spacing. However, most other OVE techniques (two-stud corners, elimi­nation of partition posts, no headers over openings in nonbearing walls, elimination of soffits over kitchen cabinets, etc.) were used.   Phoenix, Arizona   Chapman homes built exterior walls with 2×6 studs, 24 inches on center. He also used most other OVE tech­niques, including single-layer plywood siding. Exterior wall framing costs   Santa Fe, New Mexico   were about the same as conventional 2×4,16-inch on-center costs. But in order to get the same insulation R­value (R-19) with a 2×4 wall, costs would have been $460 per unit higher. Interior partition costs were reduced by over $200 per unit by use of OVE techniques. 235 * aAfjhadt akingdea З/a’c-D |?Sy. Aheath. i.n< Ґ* or jjOJcia 3/e“C-D pfiq. 4 і"х4’Чл. ілп totuAH. Ill рйц. aiding By using OVE techniques, Rex Rogers saved $495 per unit even though he used 2×6 exterior wall construction instead of the more typical 2×4,16- inch on-center construction. He had been using OVE for years and has one of the most efficient framing layouts observed in the JVAH program. 2”x6“- 24“ o. c. Й-І9 loadt inanfiation 273" imtham   nominad З’ьіаЬ on. compactid лапd –   concAetfL ЬлісЬл.- f, inuK укаАя.-^   ‘”4miS. paiij’.” m iit une. bantiA 4" лід id po£g – лідЛйуіс bfioed   Valdosta, Georgia Gary Minchew has long been a propo­nent of the OVE framing system. His detailed cost recording system pro­vided a unique breakdown of where costs were saved with OVE. Total reduction amounted to over $1,200 per unit when compared with conventional construction in the area. Tulsa, Oklahoma Wayne Hood used 24-inch on-center framing with two-stud corners on all nonbearing walls and partitions, saving $250 per unit. Burlington, Vermont Bill Hauke had been using OVE techniques in Vermont for years. He estimated that these methods saved him over $450 per unit in the JVAH In-fill Demonstration Project. Mesa County, Colorado Roger Ladd used two-stud corners and single-layer plywood siding on 16- inches on-center exterior walls. Partitions and common walls were framed 24 inches on center. WALLS AND PARTITIONS Posted by admin on 14/ 11/ 15 The key to economical wall and parti­tion construction is preplanning to eliminate unnecessary materials and labor. Carpenters usually find extra material is needed here and there to accommodate doors and windows. They may also follow traditional training by adding studs where partitions intersect exterior walls, blocking at mid-height of walls, double studs and headers at openings in nonbearing walls, and similar practices. Each of these excessive material uses is avoidable through proper attention in the planning stage. They add significantly’to cost without benefit to the home buyer. Cost savings will be greatest when the overall out-to-out dimensions of the house and the location of wall openings coincide with a module of 2 feet. This provides maximum use of materials that are available in 2-foot increments and reduces scrap and waste. An important side benefit to preplan­ning will be education of the car­pentry crew. When the crew has built a number of units in accordance with cost saving techniques presented in this section, less detailed instructions and fewer on-site modifications will be required. Tilt-up wall construction continues to be the preferred method for reducing labor and material costs. Assembling wall sections to the greatest extent possible prior to erection is beneficial since materials do not have to be held up while they are being fastened. This includes framing and sheathing (if used), as well as siding, windows and exterior trim. Fabrication can be done on a shop table or right on the floor deck. Use end nailing, not toe- nailing, to fasten plates to studs. Engineering analysis and testing have resulted in widespread acceptance of many changes in traditional wall framing techniques. Many of these OVE (Optimum Value Engineered) techniques were developed and tested by NAHB National Research Center. Building 7’6"high walls instead of 8’0" saves approximately one course of siding or two courses of brick, 6 percent of wall insulation, 3 percent of painting labor and material, one tread and riser on a flight of stairs, and 9 to 12 inches of stair landing space. A lower ceiling height also increases the structural capacity of studs acting as a column. The savings in material and labor more than offset the extra labor to cut 6 inches from the top of the gypsum wallboard panels. Placing studs 24 inches on center, instead of 16 inches, reduces framing labor and material. The 24-inch on – center spacing is permitted in most areas of the country for one story and the second story of two story construction. Use of 24 inch spacing saves nearly a third of the regular studding. Single top plates can be used when studs and trusses are in line on 24- inch centers so that the weight of the truss bears directly on the stud. Special connectors to splice joints in the top plate or to tie corners are not required because the floor or roof system attached to the top plate serves this function. This technique eliminates one-third of the plate material. When studs sit directly over floor joists, the bottom plate is used only to facilitate alignment of the studs, and to provide a nailing base for wallboard, sheathing and baseboard, and not to carry weight from the stud to the joist. Since the bottom plate doesn’t have to be as strong, a 1×4 is sufficient. Because the maximum load on the corner studs in an exterior wall is one-half or less than the load on a regular stud, two-stud comers are more than adequate structurally. The third stud in the normal three-stud corner post serves only to back up the interior finish, and can be eliminated. Metal drywall clips or wood blocks can be used to backup the wallboard. Similarly, partition posts built into the exterior wall for attachment of. interior partitions can be eliminated. The partition can be nailed to a mid­height wall block, and wood blocks or drywall clips can be used to backup the wallboard. Ceiling nailers can be replaced with drywall clips. Since they secure the ceiling gypsum board to the walls, the clips offer the additional advan­tage of keeping the ceiling and wall gypsum board from separating. Mid­height "firestop" wall blocking can be eliminated. Wall plates, floor sheath­ing, and insulation provide sufficient constriction of air flow within the wall to minimize fire spread, and the blocking is not required for structural bracing. Headers or lintels, and jack (jamb) studs which support them are required only where loads must be carried to the sides of window and door open­ings. If the loads don’t exist, or if other members, such as roof trusses, joists, joist bands, large areas of structural sheathing, or second story headers carry all or part of the loads across the openings, headers can be eliminated or downsized. Openings in nonbearing walls can have single 2×4’s on each side to which windows and doors are fastened. Headers and jack studs can also be eliminated in load-bearing walls when windows 22 1/2 inches or less in width are used and placed between the studs. Other types of headers may be more economical than the single or double 2×8 header. Glue-nailed plywood box headers normally cost less and also provide extra space for insulation. These headers are formed by glue- nailing a plywood skin to one or both sides of framing members above openings in a load-bearing wall. Water resistant structural adhesives of the casein, urea formaldehyde, urethane or phenolresorcinol type should be used to glue the plywood, and nails spaced 6 inches or less along all frame members. . The face grain of the plywood must be oriented horizontally over the opening, and the top plate must be continuous across the opening. Jack studs are not necessary on openings 4-feet wide or less. Use American Plywood Association exterior grade AC plywood. If used on the inside surface, butt gypsum board to the plywood, tape and spackle the joint, and apply a thin coat of spackling compound to any plywood rough spots or patches. When* painted, there is no apparent dif­ference between the plywood and gypsum board surfaces. Manufactured plywood joists and trussed joists can also make cost- effective headers while providing room for extra insulation. Check with the manufacturer for engineered sizes and prices. Brick veneer costs can be reduced by: starting the brick at floor joist level on 8-inch blocks resting on 16-inch footings, instead of below grade on 12-inch blocks resting on 20-inch footings; using other materials above and below windows and in areas less subject to deterioration, e. g., the gables and the top half of a wall; building the walls 7’6" high instead of 8 feet. Single-layer panel sidings (plywood and hardboard) are available for application directly to studs, eliminating the need for a separate sheathing. Returning gypsum wallboard to the windows and using drywall corners instead of using wood stool and casings saves money. Similarly, using drywall returns on bi-fold or bypass closet doors eliminates wood jambs and casings. Providing a full width opening at the front, dimensioned to receive a standard width bi-fold or sliding door, eliminates jacks and studs beside the opening, and floor-to-ceiling doors eliminate framing and drywall over the opening. Drywall contractors often charge for a full wall even if only partially covered. Interior nonbearing partitions can be built from 2×3 studs. Also, if floor sheathing is 5/8 inch or thicker, no blocks or joists need to be framed below nonbearing partitions. Where partitions are parallel with ceiling joists or roof framing overhead, use precut 2×4 blocks spaced 24 inches on center to secure the top of the parti­tion and to provide drywall backup. Cabinet bulkheads can be eliminated. Install ceiling high cabinets, or let the top of standard height cabinets be an extra "shelf. Light gage steel studs have been available for a number of years and are used extensively in commercial and high-rise apartment construction. They are usually installed by the drywall contractor. Steel studs are often cost effective, especially when lumber prices are high, but have not been widely used in single-family or low-rise multi-family construction. WOOD FRAME FLOORS Posted by admin on 14/ 11/ 15 Most wood frame floors utilize nominal 2-inch thick joists placed on a center­bearing beam and covered with sheath­ing. Floor trusses have recently become more popular and post-and – beam crawl space floors have been in use in some areas for years. Floor design is based on a number of factors, such as: • Design load • Lumber species, size, and grade • Clear span between supports • Floor sheathing materials and thickness • Fastening techniques Utilization of full span capacity of lumber joists can often save between 6 and 8 percent of joist framing costs. If allowable spans for joists presently used exceed the spans shown on the floor plan by 1 foot or more, impor­tant savings may be realized by changing either the joist grade, spacing, or size. Built-up wood girders are usually more cost effective and easier to work with than steel girders. Floor sheathing adds stiffness to the floor and, depending on thickness and fastening methods, can result in reducing the size and/or increasing the spacing of framing members. When a plywood subfloor is properly glued and nailed to the joists, the subfloor and joist act together as a composite T-beam and as such will span a greater distance than if the subfloor is fastened with nails only. Glue-nailing is also effective in reducing floor squeaks and stiffens the floor. A single layer tongue-and- groove system is usually less costly than a separate subfloor and under- layment system. Bridging or blocking between floor joists at mid-span has been proven ineffectual in almost all cases. An extensive series of tests conducted by the NAHB National Research Center in the early 1960’s proved that mid-span bridging adds nothing but cost to most floor systems. Major model codes require bridging only in floors with joists exceeding a depth-to-thickness ratio of 6 to 1 based on nominal dimensions. In other words, joists up to and including 2x12s do not require mid-span bridging. Another common but unnecessary practice is to double floor joists under nonbearing interior partitions. In fact, it is not necessary to locate nonbearing partitions over any joist when 5/8-inch or 3/4-inch plywood subfloor is used. The weight of the partition does not warrant extra support. Load-bearing interior walls usually run perpendicular to joists and do not require added support. If load­bearing walls run parallel to floor joists, a supporting girder sj’stem is required. Wood frame floors must be anchored to the foundation to resist wind forces acting on the structure. In conven­tional construction practice, 2×6 sill plates are attached to the foundation with anchor bolts, and floor joists are toe-nailed to the sill plate. Metal anchor straps are available for embedding in the foundation concrete or mortar that do not require holes in the sill plate. Such straps are less exacting and do not interfere with joist or band joist framing as anchor bolts often do. Sill plates can be eliminated altogether if the top of the foundation is suffi­ciently level and accurate. Joists, however, must rest on a solid surface and not over the cores of concrete block. Anchorage can be provided by anchor straps attached to the joists and firmly set in foundation concrete or mortar. Floors built on pressure treated wood foundations do not require separate sill plates or anchoring devices. Joists are toe-nailed directly into the foundation wall top plate. Stairwell framing costs can be reduced in the design stage by positioning stairwell openings parallel to floor joists. Double joists (trimmers) on each side of the opening are not necessary where the header which they support is located within 4 feet of the end of the joist spans. A single header is generally adequate for openings up to and including 4 feet in width. The band joist (sometimes called the rim or header joist) typically is the same size as floor joists. The major function of the band joist is to keep the floor joists vertical. Therefore, if wall studs and floor joists are aligned, a nominal 1-inch thick board or plywood band is adequate. In certain cases, the band may be eliminated altogether. When a structural exterior wall sheathing is used, it can extend over the ends of the floor joists where the band would normally be. Joists must be temporar­ily braced until the wall sheathing is applied. The typical wood frame floor has two joists lapping over the center girder, each joist acting independently from the other. This system creates pro­blems with plywood sheathing layout, one side of the floor being 11/2 inches out-of-kilter with the other. The allowable span of floor joists may be increased by maintaining continuity over the center bearing – that is, if the joist is continuous rather than lapped over the girder. If two joists of unequal length are spliced together so that the splice occurs at a point off center, an increase in stiffness of up to 40 percent is possible. This off-center- spliced-joist technique can result in reduced lumber size, increased spacing, or both. In addition, subfloor layout is greatly simplified. EXAMPLES FROM THE DEMONSTRATION PROJECTS However, the added cost of end trimming and splicing the joists must be considered. A Research report titled Off-Center-Spliced Floor Joists (143-51 is available from NAHB. 15th & M Streets NW, Washington, DC 20005. Floor trusses are becoming more popular as alternatives to conventional wood frame floors. They are usually more costly but have the advantage of greater spans between supports, thereby creating greater floor plan flexibility. There are several different floor truss designs, some with open webs and some with a continuous plywood web. Open web trusses have the added feature of providing plumb­ing, wiring, and sometimes HVAC chases without drilling or cutting. The major disadvantage of single-span floor trusses is the height of the trusses. In order to span greater distances, the truss must be much deeper than conventional 2x framing. This adds extra costs to sheathing, siding, stairs, etc. These, plus the extra cost of the floor itself, should be analyzed versus the value of the clear span. JVAH Floors Innovative floor framing methods were used on several JVAH sites. Some were unique while others were known methods not normally used in the local area. Tulsa, Oklahoma As discussed in the Foundation section, Wayne Hood built the Plenwood system in his demonstration homes. The wood frame floor portion of the system consisted of 2×8 floor joists spaced 24 inches on center with glue-nailed 3/4-inch plywood. John Phillips constructed one of the most innovative wood frame floors in the demonstration. Typically, in the Lacey area, the foundation/ floor system consists of a conventional spread footing, a cast-in-place concrete foundation wall, a post-and – beam center bearing girder, 2×10 joists spaced 16 inches on center, and a two layer sheathing/underlayment system. Phillips designed and built a system that used 2x6s, spaced 24 inches on center, spanning about 8 feet between post-and-beam supports. Band joists were eliminated. Floor framing did not come into contact with the perimeter foundation at all. The first interior support girder was placed about 4 feet from the foundation wall and the joists cantilevered about 2 feet toward the foundation. The 2-foot gaps at the ends of the floor joists and the 2-foot spacing where the joists are parallel to the foundation were easily spanned with 3/4-inch tongue-and-groove glue-nailed waferboard. Floor construction costs were reduced by an average of $852 when compared to the conventional floor. Christian County, Pup Robertson also built an innovative Kentucky floor system that saved $295 per house. Instead of the conventional 2×8,16-inch on-center joists over a single center girder, he used two box girders spaced about 8 feet on center and 2×6 joists at 24 inches on center. He used 3/4-inch glue-nailed T&G plywood instead of the more conven­tional 1/2-inch underlayment. Tom Webb designed and built a cantilevered front porch deck by continuing the interior stair landing joists through the front door opening. This eliminated deep porch footings and foundations which are very susceptible to frost heave in Fairbanks. EXAMPLES FROM THE DEMONSTRATION PROJECTS Posted by admin on 13/ 11/ 15 Several JVAH sites used innovative approaches to foundation construction that reduced costs while maintaining structural integrity. In some cases it was necessary to provide results of soil bearing tests and engineering data to the city building department. In every case, less costly foundations resulted. Crawl space foundations in Christian County typically are built of one course of 12x8x16 block and two courses of 8x8x16 block. The 12-inch block serves as a brick ledger. The builder, Norris "Pup" Robertson, used three courses of 8x8x16 block stacked without mortar and bound together with glass fiber reinforced surface bonding cement. This reduced the concrete footing from 20 to 16 inches wide and eliminated 16 inches of brick veneer. Cost savings amounted to $203 per unit for the footing and foundation, and $410 per unit in brick for a total savings of $613 per unit. The typical Santa Fe single family home foundation consists of an 8×16 concrete spread footing and an 8-inch thick, 22-inch high cast-in-place foundation wall. Mike Chapman, builder, decided to build a thickened-edge, monolithic slab which is common in some areas but not in Santa Fe. This allowed a one-step operation instead of three steps and saved two days of construc­tion time. Cost savings amounted to $106 per unit. Typically, Tulsa single family homes are built with concrete slab-on-grade foundation/floors. Crawl space homes with wood floors are rare and usually more expensive. Wayne Hood, builder, decided to build a system unique to Tulsa – the underfloor plenum system on a pressure treated wood foundation. Instead of using heating and cooling ducts, the entire underfloor space is used as a sealed plenum chamber. Basically, it consists of wood floor construction with sealed and insulated foundation walls. In the Tulsa JVAH homes, the underfloor area was used as a return air plenum with a conven­tional up-flow furnace. In most cases, the underfloor area is used as a supply plenum without duct work. Information on the system can be obtained from the American Plywood Association, the National Forest Products Association, the Southern Forest Products Association, and the Western Wood Products Association. It is being marketed under the name Plenwood. According to Hood, cost savings amounted to $ 1,470 per unit versus conventional slab-on-grade foundations with overhead heating/cooling ducts. Knoell Homes conducted soil bearing tests on the site and found the soil had a bearing capacity of over 3,000 psi. Because of this and because of minimal disturbance to the soil, Knoell received a waiver to reduce slab thickness from 3 1/2 to 2 1/2 inches and to eliminate fill under exterior concrete. Savings amounted to $195 per unit. Gary Minchew eliminated reinforcing rods from footings and welded wire mesh from the slab. In addition, he eliminated a metal "key – way" control joint down the center of each slab, saving $132 per unit in labor and materials. Rex Rogers reduced concrete slab – on-grade thicknesses from a nominal 4 inches to a nominal 3 inches, and reduced concrete strength from 2,500 psi to 2,000 psi, saving $160 per unit. Pressure treated wood basement foundations were used in all Fairbanks JVAH homes. Tom Webb had been building wood foundations for several years and found no sales resistance. Because of the high concrete costs in Fairbanks, the wood foundation was especially attractive. It also allowed Webb to extend the building season which was very important in Fairbanks. Cost savings amounted to $1,035 per unit. Karl Witt used pressure treated wood foundations in two units but was reluctant to build more because he anticipated negative market reaction. None occurred. 1 2 Next » Tweet Copyright © 2025 Library builder - Articles about the repair, construction, interior design and landscaping, plumbing, electrical, waterproof wire, wire gas, building materials, construction machinery and equipment ...