Interaction Between Percolating Water and the Pavement

In the road environment, contaminants are almost entirely moved by water-based or air-based processes. Air-based processes are, principally, by dust and spray, but these are not discussed further, being beyond the scope of this book. In water – based processes, contaminants are carried in and/or by the water through soil or aggregate pores, over the top of the pavement and through drainage systems. As water moves through the sub-surface, water that is fairly pure will have the abil­ity to pick-up chemicals from the soil through which is flowing and to carry these elsewhere while runoff water that arrives from the pavement surface may percolate into the construction carrying impurities with it which are then “dropped” by one mechanism or another into the layer. The interaction between water and contami­nants is the subject of Chapter 6 with methods of measurement being described in Chapter 7.

Подпись: Fig. 1.7 “Source - Pathway Receptor” framework Подпись: Source Interaction Between Percolating Water and the Pavement

Movement of contaminants is often considered using a “Source – Pathway – Receptor” framework (Fig. 1.7). In the context of the highway, the “source” would probably be the surface runoff water (although its antecedents of vehicle cargoes, atmospheric pollution, etc. could also be considered as the source) or the pavement

construction. The contaminated water then moves through the pavement and the drainage system which provides the “pathway” for the contaminant to move. Even­tually it arrives at a place where it has a potentially deleterious impact – the “re­ceptor”. In an ideal understanding the receptor is a human, animal or plant that is affected by the contaminant. In practice, policing of impacts on humans would be almost impossible to monitor and, anyway, too late to change an undesirable response. So, instead, it is normal, in most practical circumstances, to treat either the surface water body (river, lake, etc.) or the ultimate groundwater body (e. g. drinking water aquifer) as the receptor. Monitoring their quality is the subject of Chapter 7.

Chapter 12 gives information that, with the help of Chapter 13, can be used to mitigate problems due to contaminant movement in and with the water percolating in the near-pavement environment. Usually, these involve either interruption of the pathway or removal of the source or target.

HOUSE AND LOT DESIGN

Factors which distinguish good design from poor design are somewhat subjective and vary from buyer to buyer, from builder to builder, and from architect to architect. There are certain qualities of good design that most can agree upon. These include a sense of comfort and good taste in the combination of materials, spaces, and equipment so that a feeling of inner satisfaction comes to the occupants of the home.

Good design and affordability are not incompatible. In fact, poor design at any price is difficult to market. The JVAH program proved that well-
designed small "affordable" homes actually enhance the neighborhood and add to property values.

Smaller lots present more of a challenge for placement of homes than do larger, more forgiving lots. Space for parking, utility locations, drainage, and driveway lengths are more critical. Privacy, topography, view, and natural growth are important factors in house placement. If natural features are absent, manmade features such as stormwater retention ponds, parks, and landscaping offer opportunities for interesting placement of homes to provide visual variety.

HOUSE AND LOT DESIGN

HOUSE AND LOT DESIGN

For smaller homes, it becomes more important to orient central living areas to outdoor spaces or views. Single-story homes preserve privacy because they do not look out over fences and more rooms can be placed around patio space.

Second story windows should be oriented away from neighbor’s yards and toward natural views whenever possible. By promoting outdoor living with decks, patios, porches, and garden seats, small homes become much more attractive and lose the small feeling.

Подпись: Dwelling Plan Analysis

A well-designed floor plan will consider the functions of different areas of the house; i. e., sleeping, living, working, dining and circulation spaces and their relationships to each other.

By orienting major living areas to the south, you can take advantage of the winter sun and provide a measure of passive solar heating. Likewise, by placing storage space and seldom used windowless rooms on the north elevation, heat loss to the sunless side of the house will be minimized. These techniques will, of course, be more important in certain climates than others.

Where heating is of little consequence, orientation is not as important.

Where heating and cooling are both

important, shading of south facing windows in the summer becomes very important.

HOUSE AND LOT DESIGNMinimize the distance between parking and the kitchen. This not only provides relief from carrying heavy shopping bags, but also reduces tracking in dirt across carpeted areas. An entrance from parking through a work zone such as a laundry room provides an area for muddy shoes and heavy outer garments.

Circulation area is, in effect, wasted for most other uses. The exception might be a pass-through work area. Otherwise, small homes cannot afford the luxury of space that is intended solely to travel from one area to another. Good design will hold such space to the absolute minimum without undue traffic through living areas. Placement of entry doors and closets will dictate traffic patterns.

Small homes often seem more spacious by careful use of sight distances.

That is, when in a closed-in room, it does not matter whether the house contains 1,000 or 2,000 square feet. Perception of size ends at the walls. Therefore, eliminate interior walls and provide angles where the occupant can look through other spaces, preferably to the outdoors through a large window or sliding glass door.

However, looking through a work space is not normally considered desirable.

з

 

HOUSE AND LOT DESIGNHOUSE AND LOT DESIGNSeveral of the small JVAH homes used vaulted ceilings and clerestory windows to provide a feeling of open space. Loft space with a balcony not only provides real space but also the illusion of much more space in small homes. Lofts are also perceived as luxury features even though they are no more costly to build than closed-in space. Open riser stairs to lofts reduce visual blockage and create an "open" feeling.

There are some basic architectural rules that have been proven successful and marketable for small homes. One major rule is do not simply take a large house plan and scale it down. This does nothing but accentuate the smallness.

The number of small families, singles, and empty-nesters is growing rapidly. Most of these are not interested in unusable space. They are more interested in good design and ■ amenities.

HOUSE AND LOT DESIGNHOUSE AND LOT DESIGN
Good plans are made up through room – by-room analyses. How can you tell a good room from a bad one? Before a room can qualify as being well planned, it must pass two tests:

1. Does circulation work inside the room?

2. Is there a place to put furniture and arrange it properly after circulation and stairs are taken care of?

Possibly the most important room is the living area, but it is not neces­sarily the most difficult room to plan. Kitchens, laundries, bedrooms, bathrooms, family rooms, and storage areas all present planning problems.

The good living room is free from through traffic and designed for best furniture arrangement. It will be designed for both interior views (T. V., fireplace, feature areas) and exterior views. In a good layout, furniture doesn’t have to be moved every time

you wish to look at your favorite T. V. program, watch the fire, or look out the window.

A good kitchen is not necessarily "glamorous" or "gadgety," although some glamour or gadgets may be marketable. Primarily, a good design is one that works. Is it laid out efficiently? Does it have the right kind of storage in the right places and in the right amounts? Does it make the user feel like a prisoner or does it make the time spent relatively pleasant? Is it located properly in
relation to the rest of the plan?

Above all, is the kitchen the control area for the rest of the house?

Modern laundries are designed to save precious small home space. But this does not mean laundries should be crammed into a left-over corner. The laundry-utility core should be located near the kitchen or a bathroom. Garages or basements are alternative locations although they have draw­backs. Arrahge laundry appliances logically with good outside light if possible.

HOUSE AND LOT DESIGN

Bedroom space in small homes is often too small. Don’t throw away space in excessive hallways. Large windows make the bedroom look bigger and provide plenty of light and ventilation. Master bedrooms should contain adequate space for at least queen-size or twin beds.

attic storage with pull-down stairs may be feasible. The most important things to remember about storage are:

1. There is never enough of it.

2. It should be located according to. frequency of use.

HOUSE AND LOT DESIGN

The argument for small windows because of privacy considerations is not valid since curtains or drapes are pulled over even the smallest windows. A good bedroom will have unob­structed closet space. Other live storage, where circulation is likely to occur throughout the day, should be placed elsewhere in the house.

Bathrooms, especially in small one-bath and bath-and-a-half homes, should be able to accommodate more than one person at a time with privacy provided for the toilet. They should provide plenty of storage for all the items that functionally belong there. Generous mirror surfaces make the bathroom seem larger. If space is available, a master bath/dressing area off the master bedroom is a desirable feature.

Storage areas often are overlooked in small homes. These areas are even more critical in smaller homes than large ones, where a spare bedroom can double as storage. Small homes on small lots have almost the same storage requirements as large homes. Depending on roof structural design,

It should be designed, dimen­sioned, and subdivided accurately for articles to be stored, not just vaguely tossed into a plan as a "closet" or "shelf.

Подпись: Exterior Appearance Design does not end with a good floor plan. The exterior style and combina­tions of shape and mass are equally important. Pleasing visual proportions and textures are not limited to larger, luxury homes. Uncluttered, simple appearances can be pleasing in small, less expensive homes too.

HOUSE AND LOT DESIGN
In fact, simplicity and restraint in exterior appearance tends to be acceptable to more buyers than expensive scrollwork, bric-a-brac, and gingerbread which often leads to architectural chaos. This is especially true in small homes where one can be deluged with too much "style" in a short visual scan. In other words, it is often better to simplify and spend less on exterior appearance for better design.

Horizontal and vertical elements of the entry facade need to be balanced and well-proportioned for visual continuity. Selection of exterior surface materials should be made with the market in mind.

Do not ignore what has been success­ful in the community, but also do not arbitrarily assume that certain sidings and styles will not work. Builders are traditionally much more conservative than the home buying public. This is understandable when one considers the risk involved in doing something different. An award winning design is useless if it does not sell. But pent-up demand for different styles of homes often goes untapped because of too much conservatism.

In the JVAH, Santa Fe builder Mike Chapman risked putting a contem­porary, plywood-sided, sloped-roof house on the market in an adobe/stucco, flat-roofed, Spanish architecture community. He was of the opinion that the only reason this style home was not "marketable" was that it had not been built. He conducted a marketing survey that indicated there was, indeed, a pent-up market. The 47-unit first phase sold out in two weeks. The entire 154-unit subdivision sold out one year ahead of schedule. Chapman paid a lot of attention to both interior and exterior design.

Good design rules are not carved in stone for all houses and communities. A California contemporary design might not sell on Cape Cod. A Cape Cod cottage might be out of place m Arizona. But an astute builder will take advantage of a market that all others ignore because of "tradition."

Basically, however, there are some rules that transcend local preferences.

HOUSE AND LOT DESIGNFor the roof, provide a strong fascia on overhangs. Depth and style of overhangs should complement the overall appearance. A cascade of roofs at the same slope can be visually pleasing if not overdone.

Normal transitions, say from the house to the garage, are the best places to change roof lines. Roof overhang changes for a porch or sun shading of windows also create a visual break. Remember, however, each change in roof lines adds to costs.

The home entry should be clearly recognizable at first glance. Full – height windows and sliding glass doors on the front of the house need to be easily distinguished from the primary entry. This can be done by creating a transition space to the front entry by using paths, steps, or landscaping.

Once inside, there should be an entrance "space" that clearly defines the area. A separate vestibule or entrance room is not necessary, but the area needs to be defined by a change in floor surface, railings, closets, etc. Ideally, entrance "control" should be maintained from the kitchen. That is, the primary entry should be visible from the primary work area – the kitchen.

HOUSE AND LOT DESIGNHOUSE AND LOT DESIGNSince the garage is often the main entrance for much of the family, it can be designed as a positive entry rather than just a passage door to the garage.

Keep window and door heads in line. Wall thickenings add interest (but also add cost), as do front entry setbacks. Carefully select windows to fit overall design and locate them for best natural ventilation and for architec­tural balance,

The rear elevation is often the "forgotten" elevation. Because much time is often spent in the back yard and because the rear elevation is often viewed by the neighbors or from another street, care should be taken to make it attractive also.

For small homes, it is difficult to maintain good width/height balance.

If the house sits on a high foundation, proportions often are not the best and the house looks "boxy" and even smaller. A lower profile elevation tends to make the house appear larger. The building to ground connection can be softened by landscaping, steps, terracing, etc. This tends to reduce the high boxy look.

f’

 

HOUSE AND LOT DESIGN

Подпись: Designing for EconomyWithin the framework of good marketable design, there are methods to ensure that costs are lowered without sacrificing marketability.

First, use modular dimensioning. Most building materials are produced in increments of 2 feet, including trim, lumber, sheathing, and some sidings. The most efficient use of these materials will be obtained if overall house dimensions are laid out on a 2-foot grid. The, most efficient plan is a basic rectangle which allows simple floor and roof structures on the 2-foot grid.

For design variation, two offset rectangles provide a break in roof lines as well as an elevation change. An offset garage also can be used to break up the flat front look. Keep in mind, however, that each variation from the basic rectangle adds cost. Depth of the most cost effective rectangle is limited by the allowable span of roof and/or floor framing members.

House shape and configuration effect total cost for the same amount of floor space. For example, an "H" shaped plan has 46 more linear feet of wall, 8 more corners, 4 more roofing areas, 2 more gable ends, and 4 more valleys than a rectangular plan.

The most cost-effective plan is one that encloses the desired floor area

Unit Plan Shape (1,200 $q. ft. average area)

Exterior Walls

Roof System

Lin.

Comers

Roofing

Gable

Hip

Ft.

Out

In

Areas

Ends

Valleys

Hips

Valleys

I I Square Plan

140

4

2

2

4

I I Rectanaular Plan

142

4

2

2

4

* I ‘ I Offset Rectanaular Plan

156

6

2

4

3-4

NA

NA

Q=3 “L" Plan

152

5

1m

4

3

2

5

1

Ш "U” Plan

172

6

2

6

4

4

6

2

И "H" Plan

188

8

4

6

4

4

8

4

with the least amount of exterior wall. The, ratio of floor to wall should be as high as possible within design parameters. For example, a 28×40 plan has 1,120 square feet of floor area and 136 linear feet of wall for a floor/wall ratio of 8.24. A 24×46 has 1,104 square feet of floor area and 140 linear feet of wall, a ratio of 7.89. The 28×40 plan is more efficient.

The high floor-to-exterior-wall ratio approach can also apply to the interior partitions. That is, the "open planning" concept of space limits the total length of interior partitions. As mentioned earlier, this is also a technique to make a small house seem bigger inside.

Defining areas by floor textures, railings, ceiling height changes, etc., eliminates the need for some interior partitions. It also results in lower costs for framing, drywall, painting, and, very importantly, for electrical wiring.

Plans that provide for future expan­sion may be desirable in some markets. If done, give special attention to problems of access, circulation, and plumbing and heating extensions. It can be a useful marketing tool, especially to first time home buyers with small families.

Future usable space within the exterior shell was provided in the Santa Fe, Lincoln, Tulsa, and Baltimore County JVAH demonstrations.

HOUSE AND LOT DESIGN

Slab-on-grade designs minimize cost and foundation problems in many areas of the country. If basements are perceived necessary because of marketing or site considerations, use multi-level designs which increase habitable space at minimal cost.

Подпись: Use cantilevered floors over basements, crawl spaces, or first floors on two-story homes to provide design variations or to increase floor area at minimal extra cost. Cantilevers of up to 2 feet are generally permissible and help reduce out-of-square foundation problems. Cantilevered floors must be well insulated to prevent heat loss and frozen pipes. When laying out interior partitions, locate them to intersect with an If the foundation type is optional, remember that it is almost always less expensive and more desirable to add habitable space above ground than below ground.

HOUSE AND LOT DESIGN

HOUSE AND LOT DESIGN

UPPER FLOOR PLAN

 

HOUSE AND LOT DESIGNHOUSE AND LOT DESIGNHOUSE AND LOT DESIGN

exterior wall stud (on the 2-foot grid). This provides a tie-in without extra framing or blocking and provides one side of drywall backup.

At least one side of window or door framing can coincide with normal modular framing in almost every case. It may be necessary to move the rough opening a few inches in one direction or the other to save a stud or two and, in most cases, the architectural balance will not be affected enough for anyone to notice.

If trusses are used, gable end walls are essentially nonbearing. Because of this, structural headers over openings are not necessary. Therefore, locate large openings in the gable ends if consistent with exterior design and floor plan.

Likewise, interior partitions are usually nonbearing. Openings do not require structural headers. If a load-bearing interior wall is necessary, limit the number of openings in that wall.

Most major model codes allow a 7’6" ceiling height. For small homes, this height may provide a better exterior scale. It also reduces siding and may eliminate one step from stairs in a two-story home. However, extra costs can be expected on drywall applica­tion. Studs must be trimmed unless they can be purchased precut for 7’6" ceiling heights.

When possible, plan for straight-run stairs, parallel to floor framing members, and coordinate the stairs with normal joist positions on one side to reduce floor joist disruptions.

As shown in the framing section, stair trimmers and headers can be reduced if properly laid out.

Attic/crawl space access doors should be located between framing members to eliminate structural headers. If framing members are spaced 24 inches on center, ample access space is provided.

Consider centralized ‘back-to-back" plumbing around a common stack to minimize piping requirements. In two-story homes, arrange upper level over lower level plumbing connected to the same stack. It will be necessary, no doubt, to point out these features to the plumbing contractor in order to get a reduced bid from him. Also lay out plumbing to minimize disrup­tions to structural members. Con­centrate as much plumbing as possible in the same wall.

Plan chases for ducts and flues to allow ample clearances and to avoid disruption or displacement of struc­tural members. Too often, duct placement is an afterthought which requires expensive solutions.

When practical, locate heating/cooling equipment in a central location to reduce duct runs and sizes and to provide good distribution. For small houses, a centralized system often means duct runs of less than 10 feet if high inside wall or ceiling registers are used. However, be sure to follow manufacturers’ recommendations concerning placement because some equipment is designed specifically for outside wall locations.

Develop complete working drawings and specifications covering all important details for the construction process. Where possible, concentrate details for specific trades on a single drawing. Avoid tight or highly critical dimensions where possible (such as cabinets between walls). If such

HOUSE AND LOT DESIGN

critical dimensions are necessary, show in bold lettering, by underlining, or by some other method that leaves no doubt that these dimensions must be accurate.

All design recommendations apply equally to site-built, factory-built (modular and HUD code), and com – ponentized housing. Most JVAH demonstration sites consisted of site – built homes, but modular units were used in Springfield, MA; Orange, NJ;

and Elkhart, IN. HUD code-manufac­tured units were used in Oklahoma City, Stevenville, TX, and Elkhart. Panelized units were erected in Sioux Falls, SD, and White Marsh, MD.

The first step toward cost-effective construction is efficient design. Many costly details can be corrected in the design process. Therefore, the importance of merging good design for marketability and efficient design for construction cannot be overemphasized.

Builders in the affordable housing demonstration were not given specific designs to build. Rather, they were asked to design homes they thought would be marketable in their areas, and to submit these designs to HUD and NAHB/NRC for evaluation and suggested cost-saving revisions.

Подпись: EXAMPLES FROM THE DEMONSTRATION PROJECTSSince the builders were not subsidized, they could accept or reject sugges­tions. Most were very successful in offering high-quality, well-designed homes at affordable prices.

Подпись: >'ЩПодпись: Santa Fe, New MexicoHOUSE AND LOT DESIGN

Mike and Walton Chapman were exceptionally daring, building homes that, for Santa Fe, were unconven­tional for the market. Floor plans were simple and uncluttered. Vaulted ceilings with lofts gave a feeling of spaciousness.

They also offered expandable, do-it- yourself space, but most buyers opted for the builder to finish the space. Living rooms and dining areas were contiguous, which allowed 24-foot unobstructed front-to-rear visual continuity. Sliding glass doors were located to further increase the line-of-sight. Houses were located on the lot in a "pinwheel" configuration. Garages were attached at the lot-line. Solar greenhouses were offered as options.

Подпись: Lacey, WashingtonThe JVAH site was a mixture of townhouses, quadplex, zero-lot-line, and pinwheel cluster cottages. Density was eight units per acre.

The cottages contained two bedrooms and one bath in 880 square feet.

John Phillips, the builder/developer, had previously built another sub­division of these small, inexpensive homes and received national attention in Professional Builder magazine as an award-winning project.

Sixty-four of the 176 units were these cottages. They were basically square in design, giving the best floor area to exterior wall ratio. A small 4-foot offset provided a break in the front elevation and also allowed a break in the roof lines.

The floor plan was very functional with minimal circulation area. The living/dining areas were combined into
a "great room" of approximately 360 square feet. A vaulted ceiling over the 14×18 living room area added to the feeling of spaciousness.

A sliding glass door off the living area leading to a small fenced-in yard also helped in making a small home seem very large. A window off the kitchen area facing the front door provided entrance control.

Although it contained only one bath, Phillips provided a second lavatory in a dressing room off the large master bedroom walk-in closet. The bathroom featured a skylight, cultured marble shower surround, and a "step-up" bathtub which added a sense of luxury at minimal extra cost.

HOUSE AND LOT DESIGN

The one-bedroom "loft" home quadplex units were designed for singles, newlyweds, and others who needed minimal space. They were arranged in a back-to-back configuration, each with its own private entrance and small yard.

The zero-lot-line homes contained two bedrooms and one bath with a small loft overlooking the living area.

Each featured a two-car garage.

Floor plans were more traditional than other styles within the project, but the loft added interest and the vaulted ceilings created space.

HOUSE AND LOT DESIGN
HOUSE AND LOT DESIGN

HOUSE AND LOT DESIGNThe smallest loft home contained 648 square feet and the largest, 674 square feet. The main level consisted of a living room with a vaulted ceiling, a dining area with vaulted-open beam ceiling and a kitchen. The upper loft area contained one bedroom and a bath.

The bedroom was open to the living area below, separated by a 4-foot high wall. This provided, in effect, one large open area for all rooms in the unit. The only full height interior partitions were for the bathroom and closets.

The living room/dining room/ kitchen combination created a large front-to – rear "great room." Interior partitions were minimized by this open approach.

HOUSE AND LOT DESIGNПодпись: Phoenix, Arizona

HOUSE AND LOT DESIGN

The townhouses were also designed with openness in mind. Living rooms leading into dining areas and vaulted ceilings with lofts made the small two-bedroom units seem much larger.

Knoell Homes designed the house plans with the goal of making the small units attractive and saleable while paying attention to production efficiencies.

Innovative use of interior space, such as vaulted ceilings and living areas opening onto outdoor patios, created a sense of openness.

Three models of townhouses and three basic models of zero-lot-line detached homes ranged in size from 770 to 1,295 square feet. The largest detached home had alternative floor – darts providing either two or three

HOUSE AND LOT DESIGN

HOUSE AND LOT DESIGNПодпись: Mesa County, ColoradoThe builder did an outstanding job of combining design with production efficiencies by designing major outside dimensions in multiples of 4 feet and minor dimensions in multiples of 2 feet. Since most construction materials come in increments of 2 feet, there was very little scrap and labor time for cutting, and fitting was reduced.

The JVAH project consisted of 50 townhouse units on 2.87 acres, or 17.4 units per acre. Two models, a one bedroom and a two master-bedroom, were built.

The market was determined to be first time buyers, including singles and newly marrieds. The one-bedroom unit contained 896 square feet. The lower level consisted of a large living/ dining great room and the kitchen.

The upper level contained one large bedroom and a large bathroom/laundry.

The two-bedroom unit contained 1,088 square feet. The lower level con­tained a 15 1/2×18 great room, kitchen, and powder room. The upper level contained two bedrooms, a single bathroom and separate vanities for each bedroom.

HOUSE AND LOT DESIGN

The Coventry

 

HOUSE AND LOT DESIGN

Подпись: Everett, WashingtonПодпись: шлмшшHOUSE AND LOT DESIGNПодпись: Crittenden County, ArkansasThe Everett JVAH site, Sunridge, consisted of 81 units on 12.2 buildable acres. Three basic zero-lot-line detached models were built, ranging in size from 1,076 to 1,624 square feet. Sunridge homes were designed to make the units energy efficient, attractive, marketable, and affordable.

The builder, Rich Boyden, was especially attentive to details that appealed to his target market, including interesting angles, privacy, and an abundance of light.

All units were designed with the bulk of the glazing facing south for maximum passive solar gain. Clere­story windows and other large areas of glass made the homes very energy efficient. In addition, Boyden installed small wood burning stoves in all units which proved to be a very desirable feature. Interviews with occupants indicated that, during the winter of 1985-86, total heating costs were between $15 and $50 per month, depending on the use of the wood burning stove. The south-facing windows are shaded in the summer.

Rex Rogers determined that there was a market for very small (504 square feet to 960 square feet) homes on small lots. Rogers believed basic, no-frills housing would sell in his area.

HOUSE AND LOT DESIGNHOUSE AND LOT DESIGNFour models were offered: a 504- square-foot efficiency unit, a 638- square-foot two-bedroom unit, a 782- square-foot three-bedroom unit, and a 960-square-foot three-bedroom unit. The efficiency unit, which was nothing more than one large room with an accordion wall separating the bedroom area did not sell. However, the other units sold well.

A popular option was a loft which added from 384 to 528 square feet. The homes sold from about $27,000 to about $35,000 without the loft or garages.

Although the units were small and basic in design, they were built with quality materials and workmanship. Exterior walls were built with 2×6 framing, 24 inches on-center, and contained R-19 insulation.

The floor plans have proven to be marketable in other areas of Arkansas. Through the efforts of HUD Area Office Manager, John Suskie, the JVAH program has become extremely successful in the region.

LEAD-BASED PAINT REMOVAL

A significant number of state-maintained steel bridges are coated with lead-based paint. Steel bridges were coated with lead-based paint for more than 40 years. The coating sys­tems have an expected effective life of 15 to 25 years, and those on many bridges are now deteriorating. Life extension and overall protection of the bridges from corrosion are dependent on refurbishing deteriorating coatings.

The public has become increasingly aware that lead can represent a significant human health and environmental threat. When intact and in good condition, the paint does not pose a significant health risk. It is when paint is removed to prepare the surface for coating replacement, or as the paint deteriorates, that the risk of significant health risks escalates.

Many highway structures are located in urban areas where lead-based paint removal has the potential to affect adjacent properties and to expose the public to hazardous concentra­tions of lead. Bridges are often constructed over water bodies where lead-containing dust from removal operations can affect water quality and the aquatic environment.

Mastic

Mastic is the second largest component of stone matrix asphalt (SMA); it is approxi­mately 20-25% by weight of the mixture and 30-35% by volume. About 35-40% (v/v) of the compacted coarse aggregates is made up of voids, and after filling the aggregate with mastic, 3% to 5% (v/v) of empty space will be left.

Mastic[9] consists of the following:

• Fine aggregate

• Filler

• Stabilizer (drainage inhibitor) in the form of fibers or other additives

• Bituminous binder

Filler and binder make up mortar. Blends of the fine fraction of the filler with binder act like binders and can be tested as a binder, but blends of the total filler and binder act more like a mixture and can be tested in that manner (e. g., BBR1- stiffness, resil­ient modulus, and tensile strength) (Brown and Cooley, 1999).

In the preceding chapter we discussed how coarse aggregate particles make up a skeleton. The task of the coarse aggregate skeleton is different from that of the mas­tic. The functions of mastic are as follows:

• Binding (sticking together) the coarse aggregate skeleton

• Lubricating the coarse grains during compaction and enabling a proper aggregate structure in a compacted surface course

• Sealing the layer, or filling the voids in the compacted aggregate structure to provide it with high durability and resistance to other external factors such as water or deicers

• Withstanding stresses caused by load and temperature

Figure 3.1 shows the close packing of fine (passive) aggregate among coarse (active) grains.

Now let us deal with the mastic components.

INTERMEDIATE TO DIFFICULT

Framing and sheathing. These tasks are enjoy­able if you can swing a hammer accurately and work with someone more experienced to explain how to raise walls. If you use a power nailer to speed up the job, read the operation manual care­fully. Hard hats and eye protection are a must.

Hanging windows and doors. A well-framed rough opening (RO) makes the job a lot easier. You’ll need patience to plumb, level, and center the pre-cased unit in the RO, adjusting and readjusting shims till everything’s perfect.

Installing flooring. To get a good floor, make sure underlayment is level and solidly attached, measure and cut flooring carefully, and use appropriate fasteners or adhesives.

Plastering. This is difficult for the novice.

Plaster consistency and technique and the room’s temperature are all crucial. The skill of plastering takes time to master.

Refinishing floors. Take your time doing this, especially with power sanders. Be conscientious about vacuuming and sanding lightly between finish coats. Use a respirator mask with filters.

Installing pre-built cabinets. Like hanging doors, this job takes careful planning, accurate measurement, and lots of patience. Shimming the bottoms of base cabinets is the key to leveling cabinets and aligning them with one another.

Installing interior trim. This takes patience, careful measurements, and a quality miter saw.

Installing exterior trim and siding. You need patience and a good miter saw. Be sure to caulk and weatherize carefully.

Stripping a roof. This is miserable work and dangerous. Don’t do it. Instead, hire an insured tear-off crew.

Reroofing. Hire pros if the roof pitch is steep. Keys to a good job: correctly flashing and align­ing the shingle courses. This work is inherently unsafe, however, because you’re high up on a sloping surface without a net to catch you.

Running ductwork. Cutting and running ducts isn’t difficult, but balancing the heat output to all rooms takes skill. Consider hiring a pro.

Plumbing and electrical wiring. You could learn a lot by working with a licensed pro for a day or two, but local codes may prohibit you from doing your own work. The work is enjoy­able, steady, and logical—and requires close attention to detail. Don’t do it if you’re not fastidi­ous. Either trade requires specialized tools.

JUST PLAIN TOUGH

Framing stairs and complex roofs. Many angles need to be reckoned with to do these jobs.

Masonry. Each masonry unit—whether brick or block—must be placed exactly. This takes strength, dexterity, patience, and a sure eye.

Changing bearing walls. Be sure to obtain the guidance of a structural engineer or a seasoned contractor.

Adjusting the furnace. Other than basic main­tenance tasks, leave this to an HVAC pro.

Tiling in fresh mortar. It takes years to learn how to prep the surface correctly, mix the “mud” to the right consistency, trowel it on, and then screed it off until the plane is flat. Hire a pro to create the mud bed. Then you can concentrate on tiling.

COMMENTS ON THE PRESENTED METHODS

A downward trend that has been recently evident in Germany involves reducing the aggregate blend gradation discontinuity and establishing an upper limit on the coarse aggregate (bigger than 2 mm) content. These changes have been justified as ways to secure a more durable wearing course and to improve its compaction.

Although in some respects very appealing, another viewpoint on building a very strong SMA skeleton with coarse grains only is not without controversy. From a technological point of view and also from Dr. Zichner’s original principles, SMA is almost a gap-graded mixture. But are all gap-graded mixtures SMAs? Certainly not. If something is going to be called SMA, namely Splittmastixasphalt, its dis­tinctive feature should be a gradation with ratios at least similar to those listed in Table 2.1.

The evolution of requirements for SMA gradation is also apparent in the United States. Some U. S. guidelines require SMA mixtures marked by very distinct gap gradation while other guidelines do not differ much from the German regulations. This trend may be well illustrated by comparing the SMA 0/12.5 mm gradation curves according to the American Association of State Highway and Transportation Officials (AASHTO)[6] [7] M 325-08 standard with those from the National Asphalt Pavement Association Quality Improvement Series No. 122 (NAPA QIS-122) guide­lines, as shown in Figure 2.8. It may be easily noticed that SMA gradations based on NAPA QIS-122 may be marked by substantially more single-sized aggregate and a stronger skeleton of 9.5- to 12.5-mm grains (up to 73% of grains retained on a 9.5-mm sieve), while gradation curves according to AASHTO M 325-08 look more continuous.

a

Подпись:Подпись:Подпись:Подпись:Подпись:image20a

2.2 AMONG THE SKELETON GRAINS

Having formed an adequate skeleton of coarse grains, we have to remember to place mastic between the active grains. Achieving the proper volume of mastic is critical; there must be the right amount of mastic to coat the coarse grains but at the same time to leave some free, unoccupied space. Figure 2.9 illustrates one way to look at the packing of SMA by reflecting the volume contents of coarse aggregates, mas­tic, and voids.

It may be concluded from Figure 2.9 that the volume of voids among the coarse aggregates has to be properly determined at the aggregate skeleton design stage. The ideal laboratory design method is one that accurately defines the volume of the free space between the coarse aggregates as they would exist after field compaction.

The design method may not accurately reflect the mixture volumetrics after field compaction, especially if the field compaction is a more effective compaction than assumed at the SMA design stage. This would result in a mastic volume that is too big in relation to the free space among the coarse aggregates, and as a result, mastic may be squeezed up to the surface,[8] causing fat spots to appear. It is also interesting that in such circumstances an unexpected decrease of free space for the mastic may result. But that is the subject of the following chapters.

Thus we have reached the moment when we have to deal with the mastic.

Voids in stones

Подпись: StonesMastic

Voids in final SMA mixture

____________ Total volume of SMA mixture after compaction___________________

FIGURE 2.9 Volumes of SMA coarse aggregate skeleton and mastic. (Modified from Voskuilen, J. L.M., Ideas for a volumetric mix design method for Stone Mastic Asphalt. Proceedings of the 6th International Conference Durable and Safe Road Pavements, Kielce (Poland), 2000. With permission.)

2.3 SUMMARY

• SMA mixtures belong to a group of coarse aggregate-sand mixtures with a continuous coarse grain matrix—that is, their skeletons are formed by interlocked coarse aggregate particles that transmit loads.

• The term coarse aggregate skeleton is a conventional notion meaning a structure made up of grains with a specified lower limit of size. The most frequently accepted limit is the 2-mm (or 2.36-mm) sieve, though in many countries, such as the United States, it depends on maximum grain size.

• The SMA aggregate grains may be divided in two types: those forming a skeleton and carrying loads (so-called active grains) and those filling voids and carrying virtually no loads (so-called passive grains). The basis for developing an active grain skeleton in an SMA is to ensure contact exists among the active grains.

• A discontinuity in the SMA aggregate blend gradation (gap gradation) is produced by the lack of in-between fractions of aggregate bigger than 2 mm.

• A coarse aggregate skeleton as defined by the German method (the original method, after Dr. Zichner’s idea) consists of an adequate proportion of all aggregate fractions greater than 2 mm.

• A coarse aggregate skeleton defined by some other methods, such as the U. S. method, consists of an aggregate blend with a decisive predominance of coarse aggregate and a distinct gap gradation, which results in establish­ing stone-to-stone contact.

Protecting Lumber from Decay

Moisture and warmth will promote decay of most woods. To prevent decay, naturally durable woods or preservative-treated wood must be used when the wood is exposed to moisture.

Decay-resistant woods include redwood, cedar, black locust, and black walnut. Preservative-treated wood is treated according to certain industrial specifications. Preservative-treated wood is most commonly used because of its availability.

Preservative-treated or naturally durable woods should be used in the following locations:

1. On concrete foundation walls that are less than 8" from exposed earth.

2. On concrete or masonry slabs that are in direct contact with earth.

3. Where wood is attached directly to the interior of exterior masonry or concrete walls below grade.

4. For floor joists if they are closer than 18" to the exposed ground.

5. For floor girders if they are closer than 12" to the exposed ground.

Подпись: Ground Protecting Lumber from Decay
Protecting Lumber from Decay

Exterior wall

8" or less

When pressure treated lumber is cut on the job site, apply treatment to the end by soaking or brushing

Protecting Lumber from DecayProtecting Lumber from DecayProtecting Lumber from Decay (continued)

Framing on a concrete slab

Protecting Lumber from Decay Подпись: Bottom plate Подпись: Required unless slab is separated from ground by an impervious moisture barrier

Подпись: Ground level

Protecting Lumber from Decay Подпись: 12" or less Protecting Lumber from Decay Подпись: Ground
Подпись: Framing furring wall on a concrete foundation
Подпись: Stud
Подпись: Bottom plate
Подпись: Vapor retarder may be applied with non-protected wood.
Подпись: Bottom plate
Подпись: Framing crawl space from ground

Stud

Design for the future

Consider building a wheelchair ramp leading to an entry or at least providing гост fora ramp to be built in the future. An accessible ramp has a 1 – in-12 rise (1 ft. of rise for every 12 ft. of length). When designing a house, its smart it) look beyond what your needs are today. Try to think about and allow for expansion in the future. An addition to the family—whether a new child or an elderly parent—often requires adding a bedroom. If you plan ahead, you 11 have room to expand when vou need to. This can save a lot of work and monev down the line.

Small doesn’t mean boring

Whether we admit it or not, we all respond emotionally to our surroundings. Buildings create interior environments that can be drab, distinctive, inspiring, or discouraging. How a building looks, how its laid out, the materials used—all these influence how we feel. Ive vis­ited huge, expensive homes that were not very inviting. Just because a house is big does not mean that it is warm and attractive.

Подпись: DETAILS MAKE A DIFFERENCE. Built-in drawers, painted wood paneling, and a well-crafted valance above the window make this small space extra Special. [Photo • Richard Stringer.] Подпись: Helping HandПодпись: Practice building with a scale model. By assembling a scale model of your house, you can troubleshoot the building process, solving problems before you begin full-scale construction. You can buy balsa wood in different dimensions and other model-making supplies from a well-stocked hobby shop or craft supply store.

Even a small, plain house can be made to feel inviting and uplifting, giving us pleasure, raising our spirits, and making us feel safe and secure (see the photo on the facing page). In the years that IVc been a Habitat volunteer,

Eve had the opportunity to give a few humble houses a bit more personality and life than they’d otherwise have had. In this book, J’ve

4

tried to include many of the lessons I’ve learned—things such as ensuring that there are two sources of light in every room. Simple things like this can help make rooms bright

and cheerv.

/

Ask the right questions

Getting the details right will make life more

convenient when vou move into vour house.

/ /

Details also present many opportunities to make spaces special by using color schemes, hardware, unique materials, and built-in features (see the photo at right). As you’re working out your house’s design, ask yourself these key questions: “Is there a place to set groceries when I enter? Where will we hang up our coats or take off our boots when we come inside in the winter? Is il easy to get food to the table and to clear the dishes?” More than anything else you do, thinking about how you will actually live in the house will help you refine its design and ensure that the experi­ence of living in it is a pleasant one.

Definition of an sma skeleton with other methods

In some countries (e. g., the United States and the Netherlands) a method of con­structing an SMA skeleton has been developed based on the control of stone-to-stone contact or a real gradation discontinuity. Based on these methods, the definition of SMA is expanded to mean an asphalt mixture containing mastic stabilizer (drainage inhibitor) with a gap-graded aggregate blend and a very high content of coarse aggre­gates in which smaller grains are seated among the bigger ones, filling voids among them but not shoving them aside. Based on this definition of SMA, it is necessary to determine the level of gradation discontinuity at which active grains are not shoved aside by passive ones.

Let us look at Figure 2.6a to d, which shows an idealized arrangement of grains (represented by smooth spheres) in an aggregate blend and illustrates the relation­ships between the radii of the active coarse grains (marked R) that form the skeleton and the radii of the passive fine grains (marked r). The proportions of the different grain sizes have been selected so that the smaller grains do not shove the bigger ones aside.

Thus we have two sets of spheres, here being examined two-dimensionally. Now we may theorize a bit on their significance for the sought-after discontinuity. [4]

image15,image16,image17
Подпись: = r + R 2 r = 0.41R

• Such an arrangement of grains as shown in Figure 2.6a and b is unnatural and unlikely. The one presented in Figure 2.6c and d is more likely. But it is easy to see that one consequence of a better (closer) distribution of coarse grains is the reduction of free space available for filling (passive) aggregate. Simple geometric analysis enables the calculation of the maximum dimen­sion of fine grains, equal to 0.16 R, to avoid shoving coarse grains aside in this scenario. If we look again at the example of the SMA 0/12 mm, apart from the active 8/12 mm fraction, the next material will be just the passive 0/2 mm (sand) fraction.* In the arrangement illustrated in Figure 2.6c and d, the necessary gradation discontinuity would consist of the absence of the 2/8 mm fraction.

These deliberations have been carried out on the assumption that the only active fraction is the 8/12 mm one, but this is by no means obvious. The SMA skeleton may also involve active grains smaller than the 8/12 mm fraction, such as grains bigger than 5 mm. Active grains of the 8/12 mm and 5/8 mm fractions would have a consid­erable influence on the formed skeleton owing to the following: [5]

• Better packing of coarse grains (here, larger than 5 mm)

• Reduction of the size of voids and therefore the size of the filling grains

If the 5/8 mm fraction is also active, the desired grain discontinuity may be secured by the absence of the 2/5 mm fraction. The Bailey method, described in detail in Chapter 7, is based on a similar geometric calculation; that approach assumes that each successive aggregate fraction should be equal to about 1/5 (0.22) of the larger fraction. This requirement is intended to prevent smaller particles from shoving the coarse aggregate skeleton aside. As we can see, the path from geometry to design method is not a long one.

These considerations are only theoretical because in a real mixture we do not deal with balls and the layout of grains is different. Yet those examples point out a signifi­cant issue; interfering with the gradation discontinuity (by adding aggregates of that size fraction) causes the loss of stone-to-stone contact of the coarse grains that form the SMA skeleton (Figure 2.7). This conclusion forms the basis of the U. S. method of SMA design and the so-called Bailey method (both presented in Chapter 7). The same conclusion has also been used in some Scandinavian solutions (e. g., in the real SMA concept).

image19

FIGURE 2.7 Interrupted discontinuity of gradation occurs when the presence of the in­between size grains disturb the action of the coarse aggregate skeleton.

A final remark—looking at Figure 2.4, we may be inclined to make a mixture of only one size fraction of coarse aggregate (8/12 mm) with mastic (0/2 mm). Obviously we would get a very strong aggregate skeleton, but we cannot forget the following technological consequences:

• Placement would be difficult; the coarse grains might be pulled by the screed plate.

• Compaction would be complicated; such a mixture is difficult to compact.

• We may have difficulty keeping the void content below 6% (v/v)* in the compacted surface course.

These reasons demonstrate the need for smaller, but still coarse, grains to participate in forming the skeleton. Further discussion on the features of such a mixture and anal­ysis of the influence of the coarse aggregate gradation will be found in Chapter 6.

Grading of Lumber: The Good, the Bad and the Ugly

Serious organic flaws such as large knots at the edge of a timber can greatly diminish both shear and bending strength. (I will explain the difference in Chapter 2, when the differentiation is more important.) Other defects are checks (shrinkage gaps), splits, and shake (separation of annual growth layers.) Shake weakens a timber considerably. This is where lumber grading becomes important. Trained lumber graders can certify a particular timber as being of a certain structural grade. However, the buyer must still be aware. At a meeting of sawyers I attended in December of 2002, an example was shown of a graded two-by-four stud purchased from a large building supplier. The grade stamp was clearly printed right on the stud. Because of poor quality, it took little effort to break the two-by-four in half by hand. The issue of using graded or non-graded lumber is a serious one and affects the owner-builder profoundly. Listen:

As I write, in early 2003, 48 of the 50 American states (including New York, where I live) have adopted the so-called International Building Code. (I say so- called because I cannot imagine that this 3-pound volume of codes would be of much use outside of North America.) One of the code requirements in this hefty volume is that all structural lumber be graded. Paragraph R502.1 says, “Load- bearing dimension lumber for joists, beams and girders shall be identified by a

grade mark of a lumber grading or inspection agency that has been approved by an accreditation body that complies with DOC PS 20. In lieu of a grade mark, a certificate of inspection issued by a lumber grading or inspection agency meeting the requirements of this section shall be accepted.” Paragraph R602.1 says the same thing with regard to “studs, plates and headers” and Paragraph R802.1 includes “rafters, trusses and ceiling joists.” In short, all structural wooden components in residential structures in 48 states must be graded.

On December 3, 2002, an emergency meeting of small sawmill owners came together near Lake Placid, New York, to discuss this provision, which was due to take effect on January 1, 2003. Most of the 200-odd attendees were rural sawyers, who, rightly, saw this new code as threatening their livelihood.

What happened next was a lesson of democracy in action. From all over the state, representatives of various sawmill and rural associations, supported by state senators and assemblymen, went to Albany to attend and speak at the December nth meeting of the New York State Code Council. The code council unanimously adopted a proposal by the Empire State Forest Products Association in concert with the Department of State and the New York State Department of Conservation to reinstate a “local option” regarding grade stamping for structural lumber.

Hundreds of letters and thousands of signatures on petitions helped turn the tide on this issue. According to a press release sent to me as a petitioner, the upshot is that now, as before, “Rough cut lumber can be used for structural purposes if the code enforcement officer allows it and the mill guarantees that the lumber meets minimum (grade 2 or better) standards. The mill will be required to sign a form that will be provided by the local code officer and this form will need to accompany the building permit application. These provisions apply to residential construction not exceeding three stories in height, and all other buildings not exceeding 10,000 square feet in area or 35 feet in height.”

Over the past several years, three or four of our students at Earthwood Building School have reported difficulty in using their own lumber or locally sawn lumber in the construction of their own homes, the local code enforcement officer insisting in each case that the lumber be professionally graded. The cases I have heard about have occurred in Michigan and Ontario, but it could happen almost anywhere in North America now, so the owner-builder needs to be aware. The sidebar on page 10 tells the story of Mark Powers’ battle for a permit in Michigan. His experience is by no means singular, and the wisdom he has garnered — and shares with us — may be valuable to the next owner-builder facing a similar hurdle.