SELECTING SMA GRADATION AND SIZE

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No matter the method applied when designing the SMA composition, the first step that must be taken is establishing the maximum particle size in the aggregate mix. The following factors should be taken into account when considering this issue: [23]

6.1.1 In Which Course?

Due to the outstanding performance of SMAs in surface courses, they have also been used in intermediate courses (e. g., in the United States, Australia, and recently Germany). Normally mixtures with larger maximum particle sizes (e. g., 0/19 or 0/22 mm) are selected for that purpose when they are permitted by local regulations. So far, aside from possible economic obstacles (high cost), it has not been stated that SMA is unfit to be used in intermediate courses. Consequently, if one can afford to and knows how to design and execute SMA intermediate courses, why not dare to?

When using SMA as a course on a bridge deck, the gradation should be selected rather conservatively (i. e., it should be finer). The composition of the asphalt mixture should also be designed with great care and mostly with the use of the type of poly­mer modified binders that increase the fatigue life of an asphalt mix. (See Chapter 13 for further discussion of SMA for bridge decks.)

Locate and drill bolt holes

Posted by on 13/ 11/ 15

Anchor bolts sometimes come out of the foundation at odd angles. You can straighten bent bolts with a length of pipe, as shown in the photo at left. Then set long, straight, pressure-treated sill boards in place for mark­ing and drilling. You can use a square and a tape measure to lay out the bolt hole locations

Подпись: A long pipe straightens a short bolt. A length of 1-in.-dia. pipe straightens any bolts that may have been bent during (or since) the foundation pour. [Photo © Roger Turk]ІІІІШІІІІШШШШШШШШШІІШІШШШМШІМШІІІШІІІІІІШІІІШШІІІШІІШШШШШШШШІІІІМШШШШШІІШШШШІІІШШШШШШІІІІІІІІШШШШІМШШІІІ

POSITIONING SILLS ON THE FOUNDATION

Подпись:Locate and drill bolt holesSiding without sheathing

Locate and drill bolt holes

Nut and washer

Sill

Locate and drill bolt holes

Anchor

bolt

Locate and drill bolt holes

Concrete

foundation

ABC

Sill plates can be set flush with the edge of the foundation (A) and the siding nailed directly to the walls. When sheathing the house frame with OSB or plywood, though, hold in the sill plates 1/2 in. (B). When using rigid foam to insulate a basement or a crawl space (C), position the plates so that the outside face of the sheathing is in plane with the outside face of the foam.

A bolt marker comes in handy. Use a bolt marker to transfer the bolt locations to the sills so you can drill the bolt holes accurately. [Photo by Don Charles Blom]

 

Locate and drill bolt holes

An electric drill is great for boring holes. Use a spade bit in an electric drill to bore bolt holes through a wood sill.

 

MAKING A BOLT-HOLE MARKER

 

Select an 18-in. by 11/2-in. by 1/8-in. metal plate strap. Cut a notch in one end of the strap so that it will fit around a 1/2-in. or 5/8-in. bolt. From the center of the notch, measure back 31/2 in. for a 2×4 plate and 51/2 in. for a 2×6 plate. Drill holes at those points and insert 3/16-in. by 3/4-in. stove bolts. Put a bend in the plate strap to make it easier to use.

 

A bolt-hole marker makes it easy to transfer the bolt location to the sill in preparation for drilling a hole.

 

Locate and drill bolt holesLocate and drill bolt holes

z/2-in. bolts. For 5/8-in. bolts, use a 3/4-in. bit.

Подпись: TERMITE CONTROL When I was studying at UCLA in the early 1950s, I lived in a small house that was held together by stucco on the outside and plaster on the inside.The wall framing had long been devoured by families of termites.Today, a number of defensive strategies are used to deter termites. Check with the building inspector and with builders in your area to find out which of the following strategies are used locally and how they work with different types of foundations. Termites like wood. Scrap wood buried at a job site can attract colonies of termites. And once they're finished with that lumber, they'll look for other wood sources, such as any wood siding that is in contact with the ground or even floor joists in the crawl space. Eliminate the supply of unprotected wood and you'll help eliminate any unforeseen termite troubles. ■ Pressure-treated wood.Today, most houses are required to have at least some wood that termites don't eat. Pressure-treated wood qualifies, but on most houses it's used only as the mudsill atop the foundation. A more extensive use of pressure-treated wood (in the joists over a crawl space, for example) provides good protection in termite-prone areas. ■ Pesticide treatment. A licensed pest-control contractor can apply termiticide (termite-targeting pesticide) around footings and foundations before backfilling to create a barrier that deters insects. ■ Termite shields.This metal flashing is installed between the top of the foundation and the mudsill.The shield makes it more difficult for termites to build their earth access tubes between the ground and the floor framing.The shield also makes the tubes easier to spot during an inspection. Remember that these shields are touching PT wood.They need to be galvanized to keep from corroding and deteriorating.

on the sills, but it’s a lot faster to mark the hole locations with a bolt marker. You can make a bolt marker or buy a ready-made ver­sion (see the illustration on p. 59 and Resources on p. 279). To use this layout tool, place each plate directly on the inside of the chalkline.

Once the bolt locations are marked, set the sill plates on blocks of wood or sawhorses and drill the holes. Use a 5/8-in. bit to make holes for

Install sill seal and termite shields

Sweep the foundation clean of debris, then put down a layer of sill seal insulation where the sills will be located (see the photo on the facing page). Sill seal does just what its name says. As an alter­native, you can run two heavy beads of silicone caulk between the sill plates and the foundation. This also prevents cold air leaks between the foundation and the sill. In areas where termite infestation is a possibility, you’ll also need to lay down a termite shield over the foundation bolts and under the sill. As shown in the illustrations on p. 50, the shield edges must extend beyond the foundation (including the foundation insulation) and the sill.

Place the sills over the bolts, put on the washers and nuts, and tighten the nuts with a crescent wrench, taking care to keep the inside edge of the sill on its layout. (Note: When work­ing on a slab, drill holes in the plates but leave them unbolted until after the wall is raised— see Chapter 4 for details.) Codes in earthquake and high-wind areas often require the use of larger washers (galvanized, /4 in. thick, and 2 in. square). These larger washers help secure the mudsill and keep it from splitting when under pressure from lateral forces.

If the measuring work you did at the begin­ning of this step told you that parts of the foun­dation were out of level, you can expect the sills to be that way, too. To correct slight discrepan­cies (up to /4 in. or so), you can insert pressure- treated shims underneath the sills. For larger errors, it’s best to call in a concrete contractor.

Techniques ENSURING PROPER DRAINAGE

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Techniques ENSURING PROPER DRAINAGE

WE NEED WATER. We just don’t need it in our base­ments or under our floors, causing dampness, mold, and rot. We may not be able to hold back the Mis­sissippi when it floods, but we can control most of the rainwater that falls around our homes. Follow the guidelines below and you’ll stand a good chance of keeping water on the outside of your foundation.

1. Don’t build on the lowest part of the lot.

2. Seal all holes around the pipes that go through the concrete.

3. Install perforated drainpipes at the bottom of the concrete footings around the outside of the founda­tion (see the photo at left).

4. Coat the foundation walls with a suitable damp-proofing or water­proofing treatment. Check with builders in your area or the local building department to find out which foundation coatings are rec­

ommended. Tar coatings are inexpensive but not as effective as more recently developed waterproofing treatments.

5. Compact loose fill as you backfill around the foundation, but be careful, because excessive com­paction can damage masonry walls. Make sure that the finished grade (ground level) slopes away from the foundation. But remember that loose fill can settle. A finished grade that slopes away from the house may later slope toward the house shojld set­tling occur.

6. Use gutters and downspouts to manage high roof water runoff. Make sure you keep gutters unclogged and install downspouts to direct water away from the house.

7. Get advice from your building department. The time to protect your house from water infiltration is while you are building. Fixing a leaky basement or a damp crawl space after the house has been built can be very expensive.

Water supply from Dur Untash, in the land of Elam

Posted by on 13/ 11/ 15

Elam, in the Susa region, is a very ancient civilization that developed expertise in hydraulic works starting in the IIIrd millennium BC. Three abundantly flowing rivers descend from the Zagros mountains and cross the region: the Kherka, the Ab-e Diz, and the Karan. Elam knew a brief period of glory when, between 1260 and 1160 BC, it took advantage of the weakness of the Babylonians to ravage lower Mesopotamia. Along with other spoils, the black stone on which is engraved the Code of Hammurabi passed through Susa at this time.

During this period Untash-Gal, sovereign of Elam between 1275 and 1240 BC, built a new city some forty kilometers to the southeast of Susa, next to the river Ab-e Diz; he gave the city his name in calling it Dur-Untash. But the course of the Ab-e Diz is below the elevation of the city, and the groundwater is brackish. So Untash-Gal dug a 100-km long canal to obtain water some twenty kilometers upstream of Susa from the Kherka, a river whose waters were known for their purity. The canal brings the water to a brick – lined reservoir just outside the wall of Dur-Untash. This reservoir, whose dimensions are 10.7 m long, 7.25 m wide, and 4.35 m deep, then feeds a basin just inside the city wall through nine openings. The city’s inhabitants could take water directly from this

basin.[74]

Efficient Houses Need Fresh Air

Posted by on 13/ 11/ 15

■ BY MAX H. SHERMAN

I

hear it all the time: "Houses are too tight." "Houses didn’t used to make people sick." These assertions seem well founded: The most serious chronic illness of American children is asthma, and the Environmental Protection Agency lists poor indoor-air quality among its top five environmental threats. Are tight houses poisoning us?

There’s no disputing the cause-and-effect relationship between tight houses and indoor-air pollution. In theory, the solu­tion is simple: If you build tight, you must ventilate right. In practice, though, ventilat­ing right is complicated and controversial.

In 2003, I chaired an American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) committee that passed the country’s first residential ventilation standard. It gives builders and designers guidelines for providing good indoor air while keeping utility costs low (see the sidebar on p. 37).

Houses Require Ventilation

Before I go farther, let me define ventilation. The word ventilate comes from the Latin ven – tuilare, and it means to expose to the wind. Although this might sound like some creep in a raincoat, the real story is more complex. Ventilation is used many ways when describ­ing how a house works: There’s crawlspace ventilation (often bad), ventilated siding assemblies (good), and roof ventilation (sometimes bad, sometimes good). We’re not talking about that stuff. Here, we’re talking about mechanical ventilation, using fans to blow out old air (exhaust), suck in new air (supply), or both (balanced ventilation).

Leaky Houses Are Not the Answer

On average, the air in older homes is re­placed once every hour (1 ACH, or air change per hour) because older homes have a built-in ventilating method that’s simple and reliable: leaks (or infiltration). The aver­age house in the United States has about 3 sq. ft. of holes in it, but infiltration is a pretty bad way to ventilate because it wastes

Подпись: Tight houses are energy efficient, but they X4 need to breathe ^D[ to be healthful — and comfortable Efficient Houses Need Fresh Aira tremendous amount of energy. You could plaster that 3 ft. of holes with $20 bills, and the work would pay for itself in less than a season.

Since the oil shock of the 1970s, houses are tighter and better insulated. Even conventionally framed new houses can be 5 times tighter than the general stock. Many builders and designers are tempted to take the Goldilocks approach and to look for a level of leakage that is just right, neither too little nor too much. Unfortunately, there is no hole for all seasons. The best a leaky house can do is waste energy much of the year and be underventilated the rest of the year.

Won’t open windows provide the ven­tilation we need? In principle, yes, but in practice, no. People are pretty bad at sensing exactly how much, how often, and for how long to open a window to provide optimal ventilation. Furthermore, noise, dirt, drafts, and creeps in raincoats dissuade people from opening windows.

AFFORDABLE HOUSING AND LOCAL GOVERNMENT

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The Affordable Housing Demonstrations show that active participation by local government is essential in encouraging the production of housing at prices opening the market to those needing housing. In establishing a climate supporting the production of affordable housing, local government must:

• Support the concept and specific activities at the highest levels, including elected officials and the principal executives of the participating agencies. Only their active advocacy of the program concepts and their direction to subordinate staff will assure that the message gets to the people who actually administer the various affected programs.

• Reach out to the local home building community, and respond to any overtures from these builders to develop the mutual trust and activities needed to identify old problems, and resolve them.

• Establish contacts with the opinion makers of the community to keep them informed of the goals of affordable housing and the steps being taken to encourage its development.

• Commit itself for the long haul, and assure that there is continuity of interest and action, even through administration changes. Affordable. housing must be a community effort, not just a current "buzz word" to be discarded when fashions change.

• Be willing to evaluate the results of housing projects using affordable housing principles, and to make changes in codes, regulations, and proce­dures which are suggested by successful projects.

This Chapter will focus on two areas of local government involvement – zoning and subdivision ordinance requirements, and administrative procedures. Details of local government participation in such areas as site planning, streets and rights-of-way, utilities, and stormwater systems are provided in ensuing sections.

Подпись: ZONING AND SUBDIVISION ORDINANCE HIGHLIGHTSLand use is regulated through zoning and subdivision ordinances. In general, zoning ordinances create the broad outlines of such regulation, while more detailed matters are dealt with through subdivision ordinances. Exceptions to zoning ordinances usually require substantial formal procedures, including a public hearing process. By contrast, variances in

subdivision ordinances are often granted by less formal administrative procedures. The actual coverage of the two types of regulation varies from community to community, so that a matter covered in one community by its zoning ordinance may be consigned in another community to subdivision regulation.

AFFORDABLE HOUSING AND LOCAL GOVERNMENTAFFORDABLE HOUSING AND LOCAL GOVERNMENTLand values are a central component of housing cost. The relationship of zoning to land value and to housing cost is direct. A recent Urban Land Institute study of the relationship between zoning restrictions and average lot prices showed that in the ten cities rated most restrictive by the Institute in their zoning require­ments, the average lot price in 1980 was $24,037. In the ten cities rated least restrictive, the average lot price in 1980 was $14,688.

The reason for this relationship is clear. Restrictive zoning and/or subdivision practices reduce the total supply of land available for housing. When buildable land becomes scarce, one must pay inflated prices for it. Increasingly, persons of moderate means can no longer afford to buy at all.

A key finding that emerged from virtually every project in the JVAH program is that improved zoning and subdivision procedures promote affordable housing. The projects demonstrated conclusively that review and revision of zoning and/or sub­division ordinance requirements to make more effective use of land can bring the cost of housing down. Local governments should:

• Consider the Planned Unit Development (PUD) approach to residential zoning and/ or sub­division regulation described below. Identify specific sites throughout the jurisdiction for this designa­tion.

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• Revise zoning codes and/or sub­

division regulations to reduce the land area requirements for Planned Unit Developments, thereby fostering their use. ,

• Conduct a broad general review of zoning and/or subdivision require­ments, particularly those that have been in effect for a substantial period of time. Consider revisions that will allow for moderate increases in residential density to accommodate contemporary market conditions. Such modifications can be directed toward the provision of as much land as possible in various density categories, to minimize the impact of land shortage on land prices.

• When and where possible, employ performance standards rather than uniform or arbitrary measurements, as the criteria for zoning and/or subdivision requirements. Perform­ance standards are directed toward matching zoning with the best possible use of the site and its particular features, and employ flexible criteria to achieve this goal.

“The use of performance zoning, or a negotiated approach to land development, allows the most effective balancing of environmental quality against affordable residential construction,” according to state and local planners surveyed by the National Institute of Building Sciences (NIBS).

• Adopt zoning-and/or subdivision regulations that provide an allowance for increased density in exchange for a developer’s commit­ment to provide open space, landscaping, and other amenities on the proposed development site.

• Increase zoning and/or subdivision flexibility for mixed use develop­ment, thereby allowing various _ types of housing, various densities, and in some instances a mixture of residential and light commercial use in areas now covered by less flexible criteria.

•

Подпись: Holland Development
Подпись:
Подпись: Oklahoma City demonstration project. Woodland Hills, part of mixed use development

Allow construction with little or no setback from property lines. Often called zero-lot-line zoning, this type of construction is described in an ensuing section on site planning. It allows the construction of houses on or very close to the property line on one or two sides of small lots, making the available land on such lots more attractive and usable.

• Give favorable consideration to density transfers, particularly on neighboring or contiguous parcels of land in which developers are allowed to exchange lower density rights on one tract for higher density rights on the other tract.

• Allow zoning and/or subdivision variances to build on lots that are currently below the specified minimum size for their locales, and to divide large lots that currently have excess space.

• Consider offering bonus points for affordability to builders who price quality homes below a specified cost that reflects median local prices of comparable housing. The bonus points could be applied to items such as higher density, elimination of sidewalks, reductions of setbacks, and other changes that will reduce the builders’ cost.

Подпись: Planned Unit DevelopmentIn the late 1950s and 1960s home builders and public officials began to use an approach to zoning and sub­division regulation called Planned Unit Development (PUD), also called Planned Residential Development (PRD), Comprehensive Residential Development (CRD), or Community Unit Plan (CUP). Projects developed under this concept usually incorporate a variety of housing types and land uses, higher density, and open space and common land managed by a community association.

PUD land use is characterized by flexibility, and encourages both public and private innovation to a greater extent than is true of more traditional zoning and subdivision controls. On one hand, this flexibility makes it possible for the developer to change long-term development plans to meet current market demands. On the other hand, it gives local authorities the latitude to negotiate with the developer, trading concessions on density, mixed use, and requirements for streets and utilities, for desired _ amenities, open space, and recreational facilities, for example.

Make Yourself At Home

Posted by on 13/ 11/ 15

A good dwelling offers more than shelter and security. A truly good house evokes a sense of home. Our sense of home comes from within us. It emer­ges when we enter an environment with which we can identify. This sense is not exclusive to one’s own house. It can surface whenever we feel safe enough to be completely ourselves — beyond all insecurity and pretension.

A house founded on pretension and insecurity will seldom, if ever, make us feel anything more than pretentious and insecure. For a place to feel safe, it must first earn our trust. It must be honest, and an extra couple of thousand square feet tacked on in a vain attempt to conceal our insecurity is not hon­est.

Home is our defense against what can sometimes seem like a chaotic and demanding world. It is a fortress built from the things and principles that we value most. The inclusion of anything else is like a crack in the fortress wall. Order and tranquility are compromised when things that are extraneous to our happiness surround us. Unnecessary elements in the home dilute the in­tensity of the life within. Only when everything in our immediate environment is essential to our contented survival will home and the life within take on a truly essential quality.

Too many of our houses are not a refuge from chaos but merely extensions of it. The sense that our lives may not be entirely whole results in a desire for something more to fill the perceived void. This can lead to the purchase of an oversized house in which substance is obscured by excess. The happiness we really seek cannot be found by purchasing more space or more stuff. Those who do not recognize what is enough will never have enough.

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Taos Pueblo 36

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A Sausalito houseboat

Preparing to Install a New Roof

Posted by on 13/ 11/ 15

Daily temperatures on a roof or in an unventilated attic can swing from 50°F to 150°F, thereby caus­ing tremendous expansion and contraction of roof materials. Improving ventilation under the roof, as shown in "Roof Venting,” on p. 76, can prolong shingle life somewhat, but the key to a long-lasting roof is the quality of the materials.

In the long haul, shingles with a 30-year war­ranty are a smarter buy than 20-year shingles because they last significantly longer, even though they cost only a little more. And most of a job’s cost is the labor.

WHEN IT’S TIME TO TEAR OFF

Short-term, you can save money by installing a new roof over an old one if local codes allow. However, new roofing applied over old (see p. 83) rarely lasts as long as roofing installed on a stripped and properly prepared substrate.

You must tear off existing roofing under the conditions at right:

Roof Longevity

MATERIAL

LONGEVITY (years)

Slate and tile*

80

Wood shingles or shakes

30-40

Metal

40-50

Asphalt shingles

20

Three-ply built-up roof

15-20

Four-ply built-up roof

20-25

*Underlayment quality also determines how many leak-free years you can expect. With 15-lb. building paper underneath, a tile roof might start leaking in 15 years; modified bitumin under tile could help create an 80-year roof.

image135

ISSUES

If you observe product defects such as pre­mature wear or curling, ask the company that installed the shingles to inspect them and advise you on warranty issues. (Always keep records of installations.) If the company is reputable, it probably has a longstanding rela­tionship with the manufacturer and can exert more pressure to settle disputes than you could. If you don’t know or can’t find the installation company, hire another licensed roofing contrac­tor to inspect the roof and, if possible, identify the shingle type and manufacturer. If that con­tractor concurs that the shingles are defective— rather than installed incorrectly—contact an attorney who specializes in building-related claims to explore your options.

The roof already has two roofing layers. Two

is the limit for most local codes, because it’s vir­tually impossible to install a third layer that will lie flat. Even if you could, three layers would be a nightmare to flash and nail correctly. Underlying shingle layers are a springy substrate to nail through, and old wood shingles often split and migrate. Besides, if the bottom layer is wood shingles over skip-sheathing (1-in. boards with spaces between), only half of the new roofing nails would be likely to hit sheathing. Conse­quently, additional layers would be poorly attached and therefore wouldn’t last.

Sheathing and rafters show extensive water damage. When you can’t determine exactly what’s been causing leaks, it’s time to strip. The previous roofers may have installed flashing incorrectly or not at all. Or reroofers may have left tired old flashing in place. Whatever the cause, if the remedy is stripping back extensive sections of roofing in order to replace faulty flash­ing, reroofing may be the most cost-effective cure.

Rafters and sheathing are undersize. If rafters are too skimpy, the roof will sag, especially along the ridge. If the sheathing is too thin, the roof will sag between rafters and look wavy. In either case, consult a structural engineer. The remedy may be stripping the roof and nailing h-in. ply­wood over old sheathing or bolstering undersize rafters with new lumber; but let a professional make the call.

Shingles are prematurely worn, curling, or missing. If a roof is relatively new and these symptoms are widespread, suspect product

Подпись: A stripping shovel is a flat-nose shovel whose blade is serrated to peel off shingles and grab nail shanks. The fulcrum on the back increases leverage as you pry up roofing. Подпись: TIPПодпись:Подпись: A hammer tacker allows you to staple building paper quickly, so it won't slide down the roof as you roll it out. Later, secure the paper with tabbed roofing nails. defects, inadequate ventilation, faulty installa­tion, or a combination of those factors. A layer of new shingles won’t lie flat over curling ones. So if shingles are curling—even if there is only a single layer of roofing—tear them off.

Adjacent roof sections must be replaced. This is a judgment call. When a house has additions that were roofed at different times, their need for replacement rarely coincides with that of the older roof—one section always has a few extra years left. Likewise, south-facing roof sections age 20 percent to 30 percent faster than north­facing ones. If you see signs of leaks, strip the whole roof, install flashing, and reroof.

Designing SMA Composition

Posted by on 13/ 11/ 15

Stone matrix asphalt (SMA) mixtures and courses made from them have many strengths. Naturally, these mixtures must be well-designed, but that attribute has various shades of meaning. A review of publications on this subject has not revealed a method that is clearly “the best.” There is as wide a variety of design methods as there are approaches to the roles of particular constituent materials.

Having decided to place such a mixture, a civil engineer faces a challenge. It is not an easy material to deal with, neither during design nor construction. The first essential task is to achieve the proper SMA composition. All the remaining aspects of SMA construction—namely, production, transportation, placement, and compac­tion—are affected by this first step. Most problems at subsequent stages of work with SMA can be avoided only by achieving a good mix design.

In the various sections of this chapter, the following issues will be presented and discussed:

• Selection criteria for an aggregate mix size (the maximum particle size) depending on the design thickness of the course

• Design method with gradation limits

• Designing the part of the aggregate mix greater than 2 mm

• Designing the part of the aggregate mix less than 2 mm

• Selection of the proper binder content

• Final assessment of the properties of the designed mixture

Chapter 7 presents an overview of selected SMA design methods developed in vari­ous countries.

Step 4-Nail Joists in Place

Posted by on 13/ 11/ 15

Three 8d common (2%" x.131) or three 3” x.131 nails, two on one side and one on the opposite side.

 

Three 16d common nails or four 3" x .131" nails into each joist.

 

Rim joist

 
Подпись: xw

Double plate

 

Stud

 

Turn joists crown up and nail into place.

 

Step 4-Nail Joists in PlaceStep 4-Nail Joists in Place