What type of

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construction system?

Roofs are constructed either with rafters (stick-framed roofs) or with trusses. Stick-framed roofs are usually made with dimension lumber but may also use com­posite materials such as I-joist rafters (see 151-154).

Stick framing originated before the development of balloon-frame construction in the 19th century. Antecedents of the modern stick-framed roof can be seen on ancient roofs around the world, and modern stick-frame roofing remains popular because it is the most flexible roof-framing system and the materials are least expensive.

Trusses are made of a number of small members (usually 2x4s) joined in a factory or shop to make one long structural assembly. Only in very simple buildings does the labor savings of a truss system compete with stick framing.

What type of

Wall Bracing

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Wall bracing is needed to keep buildings from falling. Sheathing the exterior walls is a typical way to provide bracing. The architect, engineer, or whoever creates the plans will specify when any special bracing is needed. Although you don’t need to know everything about wall bracing, it is good to have a basic understanding of it.

Two common exceptions to these methods are:

(1) the short wall often used for garages, and

(2) the 24" wide corner wall. Note that cripple walls have their own requirements.

The IBC states that braced wall panels must be clearly indicated on the plans. However, this is not always the case in the real world. Although shear walls are usually marked on the plans, braced wall panels often are not.

The IBC and IRC contain a table that shows braced wall panel limitations and requirements.

The limitations are related to the seismic design category, and to how many stories are built on top of the walls.

Where braced wall lines rest on concrete or masonry foundations, they must have anchor bolts that are not less than W in diameter or a code-approved anchor strap. The anchor bolts or straps should be spaced not more than 6 apart (or not more than 4 apart if the building is over two stories).

Each piece of wall plate must contain at least two bolts or straps. There must be one between 4" and 12" from each end of each piece. A nut and washer must be tightened on each bolt. In IBC seismic design categories D, E, and F, engineered shear walls

Anchor Bolts

require 0.229” x 3" x 3" plate washers. In IRC seismic design categories D0, D^ D2, and E, braced walls require 0.229" x 3" x 3" plate washers. (See “Anchor Bolts" illustration.) These requirements also apply to townhouses in seismic design category C.

The eleven basic construction methods for braced wall panels are as follows:

1. LIB—Let-in-bracing

2. DWB—Diagonal wood boards

3. WSP—Wood structural panel

4. SFB—Structural fiberboard sheathing

5. GB—Gypsum board

6. PBS—Particleboard sheathing

7. PCP—Portland cement plaster

8. HPS—Hardboard panel siding

9. ABW—Alternate braced wall

10. PFH—Intermittent portal frame

11. PFG—Intermittent portal frame at garage

Rafter Framing

Ridge boards must be at least 1" nominal in width and must be as deep as the cut end of the rafter.

Hip and valley rafters must be at least 2" nominal and must be as deep as the cut ends of the rafters connecting to the hip of the valley. Gusset plates as a tie between rafters may be used to replace a ridge board.

Rafters must have a bearing surface similar to that of joists at their end supports. Bearing needs to be Ш" on wood or metal and not less than 3" on masonry or concrete.

Drilling and notching have the same limitations for rafters as they do for floor joists. (See “Rafter Drilling & Notching" illustration.)

To prevent rotation of rafter framing members, lateral support or blocking must be provided for rafters and ceiling joists larger than 2 x 10s.

Bridging must be provided for roofs or ceilings larger than 2 x 12. The bridging may be solid blocking, diagonal bridging, or a continuous 1" x 3" wood strip nailed across the ceiling joists or rafters at intervals not greater than 8′. Bridging is not needed if the ceiling joists or rafters are held in line for the entire length with, for example, sheathing on one side and gypsum board on the other.

When rafters are used to frame the roof, the walls that the rafters bear on must be tied together by a connection to keep them from being pushed out.

If these walls are not tied together, then the ridge board must be supported by or framed as a beam in order to support the ridge. Ceiling joists are typically used to tie the walls together. The ceiling joists must be tied to the rafters, the walls, and any lapping ceiling joists. (See ceiling joists.)

Kitchens and Baths

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Подпись: Built in an Edwardian-Era spirit, this Piedmont, California, kitchen has 11-ft. ceilings; a massive marble and brass stove hood; a porcelain, steel, and cast-iron stove; and 2-ft.-sq. colored cast-concrete floor tiles you can clomp around on in big shoes.image621

No other rooms are renovated as often as kitchens and bathrooms, in part, because we’ve changed the way we live. In the old days, home­owners regarded kitchens and bathrooms as drab utility rooms, best situated at the back of the house, away from guests. Times change. These days, if you throw a party, everybody hangs out in the kitchen. Bathrooms aren’t exactly Spartan anymore, either. Today’s kitchens and baths contain so many cabinets, counters, fixtures, and appliances that it takes careful planning to make them all fit—and still have room for people to move around. This chapter will help with that.

Kitchen Planning

The best kitchens can accommodate your per­sonal tastes and lifestyles as well as your physical characteristics, such as your height.

WHAT GOES ON IN YOUR KITCHEN?

Start planning by imagining a day in the life of your kitchen, being as specific as possible about the activities—and the actors. Do you want a sunny spot to have coffee, read the paper, and wake up? Will the kitchen table double as a desk for homework? Or will the kitchen be a com­mand center in which you field calls and arrange after-school carpools while tossing the salad?

Keep a notebook in your present kitchen and jot down observations about what goes on—as well a wish list for what you’d like changed. Many entries will be cooking specific: Is there enough storage and enough counter space to prep several dishes? Does the cook like company? When you entertain, how large is the crowd? Is there a con­venient place for cookbooks? Such considerations will be useful in evaluating your kitchen and establishing priorities for the new one.

CABINET HEIGHTS AND CLEARANCES

Over the years, architects, appliance designers, and builders have adopted a set of physical dimensions that, in theory, make kitchens safer and easier to use. As shown in "Figuring Dimensions” below, these dimensions work for most people but, in the end, may not suit every­body. As a rule of thumb, a counter is the right height if you can place your palms flat on it, with

REFERENCE* SPACE

Water Influence on Mechanical Behaviour of Pavements: Experimental Investigation

Posted by on 21/ 11/ 15

Cane Cekerevac[24], Susanne Baltzer, Robert Charlier, Cyrille Chazallon, Sigur0ur Erlingsson, Beata Gajewska, Pierre Hornych, Cezary Kraszewski and Primoz Pavsic

Abstract This chapter presents laboratory and in-situ experimental techniques used to describe the mechanical behaviour of pavement material at different saturation stages. The use of repeated triaxial load testing to obtain stiffness characteristics as well as the ability of the material to withstand accumulation of permanent de­formation during cyclic loading is considered. For unsaturated soils, in addition to mechanical variables, it is shown that a moisture/suction control should be added. Several techniques are described to assist in this. A brief presentation of model pa­rameters and tests needed for model calibration are introduced. Evaluation of pave­ment structural capacity based on deflection measurements with non-destructive testing equipment are presented. Finally, some examples of laboratory and in-situ measurement are shown.

Keywords Laboratory testing ■ suction control ■ repeated triaxial test ■ CBR test ■ parameter calibration ■ field testing ■ laboratory and in-situ experimental results

10.1 Introduction

Besides proper construction design, the materials used in the construction of pave­ments should be such that the effects of excess moisture are minimized. To help achieve this purpose, several laboratory and in-situ methods can be used. For ag­gregates used within the unbound layer, performance, when subjected to traffic and moisture is mainly characterized by:

• the compaction properties;

• the amount of degradation;

• the composition (as determined by sieving analysis); and

• the evaluation of the quality of fines (in some cases).

All of these are index tests, which do not give us proper insight into the behaviour of the material under traffic loads and in different moisture conditions. A better under­standing of actual in-situ behaviour can be obtained with the cyclic load triaxial test and with the Falling Weight Deflectometer (FWD) and other in-situ tests. From June 2004 the manufacturers of aggregates in the EU are required to undertake the initial type test and Factory Production Control to ensure that their products conform with European Standard EN 13242 (CEN, 2002).

Water-purifying devices

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The modern equipment for water purification comprises very wide range of different devices – from enough small-sized home filters to the large-scale systems solving more difficult problems. Systems of the water-purifying equipment can differ from each other is dependent on functions carried out by them and criterion of operation. If you decided to Continue reading →

TRUSS ROOFS

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Truss roofs are engineered structures built in a factory. They combine the roof rafters (top chord) and ceiling joists (bot­tom chord) into one unit. Wooden braces, called web members, run between the chords, adding strength to the truss. Because of this, trusses can span long distances, bearing only on the outside walls. So rooms can be larger and door headers smaller than in a stick – built roof because they are not supporting ceiling joists or rafters.

Trusses can be built in many shapes and

Подпись: Conventional stick-built roofs can be framed as a simple gable or a complex roof with many different ridges, hips, and valleys. (Photo by Elmer Griggs.)

designs to fit most any house (see the drawing on p. 136). In general, they require less lumber and labor to build than conventional stick-built roofs and can be installed quickly on the job site. This is especially important in areas where you want to seal off a house quickly from rain or snow.

Trusses also work well on remodel jobs. With proper planning, I have torn off an old, sagging roof and replaced it with new trusses in one day. Besides impress­ing the homeowners, I didn’t have to worry about rain coming down and soaking their dining-room table.

Trusses are carefully engineered, so cutting them in any way may fatally weaken their structural integrity. With

the exception of gable-end trusses, which have gable studs and are nailed in place directly over an end wall, trusses should not be cut without consulting the manufacturer or an engineer. Because of the web bracing in trusses, attics in most truss-roofed houses have limited storage space. Maybe this is one of the reasons public storage places have sprouted like weeds across our country.

Ordering and storing trusses

Give yourself some lead time when ordering trusses. A busy company may not be able to get to your order for a week or so. I like to deliver (or fax) the truss plans directly to the company rather than order trusses over the phone. This helps avoid costly mistakes.

Подпись: COMMON GABLE^TRUSS DESIGNSTRUSS ROOFSTRUSS ROOFSTRUSS ROOFSTrusses usually arrive on the job site banded in bundles of a dozen or more (see the top photo on the facing page). These can often be unloaded and set right up on the wall plates with a small crane or forklift If the walls are not yet framed and braced, be sure to stack the bundles on level ground. Trusses can withstand heavy vertical loads, but they break easily when bent too far horizon­tally. I recall working on a tract of houses where one set of trusses was left lying

across a gully for a couple of weeks with the ridge section bending down. By the time they were ready to be installed, half of the gussets were pulled loose from the truss members. They were beyond repair and had to be reordered, holding up the framing on one house.

Installing trusses

Most trusses are installed 24 in. on center (o. c.), so you’ll need plenty of 22У2-ІП. spacer blocks to nail between the rafters at the plate line and ridge. No truss layout is required on top of the walls because frieze blocks keep the trusses properly spaced. If these blocks aren’t supplied by the truss company, they need to be cut about Vs in. shorter than the standard 221/нп. block to allow for the thickness of the metal gussets that join the wood members together. Have some long 1xs handy also, laid out 24 in. o. c. These nail near the ridge to hold the trusses steady and to keep them on layout. If the trusses are long, tall, or both, you will need some long 2xs to brace them as you pro­ceed. A strong gust of wind can topple unbraced trusses.

It is not easy to move a single truss from the ground up onto an 8-ft.-high wall, let alone a higher wall. To do so usually takes three people to keep the truss from bending and causing stress to the connectors, so it’s best to have the bun­dles set up on the walls when they are delivered. Lay the trusses flat on the walls with the ridge points sticking out over the end wall or stand them upright in the same location. Be careful when cutting the metal band that holds the bundles together. Under tension, a band can move quickly once it is cut and is sharp enough to slice a hand.

Individual trusses can now be laid flat across the walls in preparation for being nailed upright (see the bottom photo on the facing page). Experienced carpenters pull the first truss (a gable-end truss) off

TRUSS ROOFS

In most cases, roof trusses arrive in bundles of a dozen or more, which can often be unloaded and set right up on the wall plates with a small crane or forklift. However, if the trusses are stored, be sure to stack them on level ground. (Photo by Elmer Griggs.)

TRUSS ROOFS

In preparation for being nailed upright, individual trusses can be laid flat across the wall. The first truss has the ridge pointed outward, and subsequent trusses lay on top of the first about every 2 ft. like fallen dominoes. (Photo by Roe A. Osborn.)

STEP 1 SEAL PENETRATIONS IN THE WALLS, CEILINGS, AND FLOORS

Posted by on 21/ 11/ 15

When you think about sealing a house, remem­ber how much frigid air can go through a small opening in a sweater or a jacket. Even a tiny hole in a woolen mitten can make your finger numb with cold. The same thing can happen in a house. We had single-glazed, double-hung windows in that old prairie home where I grew up. In the spring, the windows were nice—we could open them wide to let in fresh breezes and the songs of meadowlarks announcing warmer weather. In the winter, though, that loose-fitting sash was a fright. My mother gave us thin strips of cloth to stuff between the window frame and

Multidirectional Slip Bases

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The multidirectional slip base design operates on the same principle as the inclined slip base design. The multidirectional design consists of a triangular slip base employing

FIGURE 7.19 Typical inclined, unidirectional slip base. Dimensions shown as mm: 100 mm = 4 in.

only three slotted bolt holes, as presented in Fig. 7.20. The bolts are positioned at the flattened corners of the triangular plate. An impact from any direction slides the bolts out of the slots and allows the signpost to separate from the anchor piece. The desired lifting action is obtained by a lift cone located on the bottom plate. The sign support is tubular and beveled at the top triangular slip plate to help the lift cone push the support off the anchor plate during impact. The anchor piece is encased in concrete to prevent

FIGURE 7.20 Details of multidirectional triangular slip base. Dimensions shown as mm: 100 mm = 4 in.

FIGURE 7.21 Frangible-coupling sign support.

movement. The pipe generally used for multidirectional slip bases ranges from 3 to 5 in (75 to 127 mm) in diameter. The design specification for each size must be checked, since the required bolt size, torque requirements, and lift cone design are dependent upon the size of the sign support.

Toddler Made Severely III by Carpet

Posted by on 21/ 11/ 15

B. J. is a two-year-old boy who was in excellent health until the age of 10 months, when he sud­denly developed seizures. These episodes of rigid­ity and tremors occurred up to 40 to 50 times a day. The baby was subjected to a series of invasive diagnostic evaluations by many different special­ists. The blood tests, brain scans, and electroen­cephalograms revealed no apparent cause of the seizures. The baby was placed on medication to suppress the central nervous system. The seizures persisted, although their intensity declined.

The baby’s grandfather, a building contractor, suggested that the culprit might be the expensive new carpet installed shortly before the onset of the seizures. The parents contacted a represen­tative from the carpet industry, who denied any similar complaints of neurological problems from customers. The parents suspected that this infor­mation was incorrect. They sent samples of the carpet to the independent Anderson Laborato­ries in Vermont for testing. Air was blown across the carpet samples into the cages of mice, whose symptoms were then observed and documented. After a short period of time elapsed, the mice de­veloped tremors, rigidity, and seizures. The parents were horrified by the report. It was clear that their beautiful new carpet had essentially poisoned their son. The carpet and pad were immediately removed from the home, the adhesive scraped off, and the house aired out. The seizures stopped. The child is now off all medication and doing much better, although blood testing shows immune system damage consistent with chemical injury.

Most standard adhesives for carpet instal­lation are solvent-based and contain harmful chemicals. Where a glue-down installation is required, avoid solvent-based adhesives. We have specified several healthier options be­low. In either installation procedure, seaming tapes will be needed to fasten sections of car­peting together. Safer seaming tapes are also specified below.

There are several untreated natural fibers available for wall-to-wall installations, includ­ing wool, coir, and sisal. When these are in­stalled with low-toxic or nontoxic backing and either tacked-down or using low-toxic glue, they will provide a safer solution than most standard installations. Warning: Wool carpets are often treated with highly toxic mothproof­ing pesticides. Therefore, an expensive 100 percent wool carpet is not necessarily a safer carpet.

Wall-to-wall carpeting, whether standard or natural, serves as a reservoir for dirt, dust, mold, bacterial growth, and toxins tracked in from outside, even when it is regularly vacu­umed and shampooed. It is also highly absor­bent and will readily acquire odors. Typical cleaning agents for wall-to-wall carpets con­tain harmful ingredients, including perfumes, chemical soil removers, brighteners, and anti­bacterial agents.

Although we strongly recommend the use of throw rugs of natural fibers, which can be removed and cleaned, instead of wall-to-wall carpeting, we offer the following guidelines for selecting the least-toxic carpeting for those who choose to use it:

Verify with the manufacturer that wool carpets have not been mothproofed.

Of the synthetic carpets, 100 percent nylon is considered one of the safest.

Choose carpeting that has little or no odor. Even the slightest odor on a small sample will be magnified many times in a fully car­peted room and can result in a very promi­nent, unpleasant, and unhealthy smell. Choose your carpeting as early as possi­ble so it will have the most time to air out prior to installation. Buy carpeting from a supplier who will agree to warehouse it for you. This means that the carpet will be un­rolled and aired out in the warehouse prior to shipping.

Avoid carpeting that contains antimicro­bial agents such as fungicides and mildew – cides.

Avoid carpeting containing permanent stain-resistance treatment.

Avoid carpeting or pads containing styrene-butadiene rubber.

Carpeting with woven backing is prefera­ble to rubberized backing.

Follow underpad and installation recom­mendations in these specifications.

Use nontoxic and odor-free shampoos, and maintain carpets regularly to pre­vent mold, bacteria, dust, and pesticide buildup.

To prevent moth infestations in untreated wool carpets, vacuum the carpets on a reg­ular basis, moving furniture if necessary to reach all areas where larvae may hide. A vacuum cleaner that is equipped with a true HEPA filter is a must if you have car­pet. It is the only type that collects very tiny particles such as dust mite feces and mold spores. Portable vacuums that are not

equipped with HEPA filtration will spew dust into circulation, often leaving a room with more ambient dust than was there prior to cleaning.

• Establish a no-shoes policy for your home.

• If the carpet or pad gets wet, dry it as quickly as possible to prevent microbial growth. Warning: Never use wall-to-wall carpet in bathrooms, kitchens, laundry rooms, or mechanical rooms. Carpeting in these areas inevitably becomes damp, in­viting mold and bacterial infestation.

In new construction, homeowners are typi­cally given an allowance and asked to choose the carpeting. This allowance can also be used toward the purchase of healthier floor cover­ings.

Sources for nontoxic underpadding in­clude:

• Endurance II: Synthetic jute pad in 20- or 32-ounce weights

• Enertia Padding: Wool-based carpet pad­ding without dyes, fire retardant, moth­proofing, or adhesives

• Hartex Carpet Cushion: Available in three weights

• Hendricksen Naturlich: Recycled felt un­derpadding, heat bonded with no chemi­cal additives

• Ultra Touch: 29-ounce carpet cushion of recycled fibers

Acceptable adhesives and seaming tapes for carpet installation include:

• AFM Safecoat 3 in 1 Adhesive

• Auro No. 382 Floor Covering Adhesive

• CHAPCO Safe-Set 3 Premium Fast Grab Carpet Adhesive

• Envirotec Health Guard Adhesives:

CASE STUDY 9.4

Replacing a Water Heater

Posted by on 21/ 11/ 15

Most municipalities require a permit to replace a water heater, primarily because they want to ensure that the heater’s TPR valve is correctly installed. Even though most local codes allow homeowners to replace water heaters, unless you have a lot of plumbing experience, hire a licensed plumber for this job. Plumbers know which brands and hookups require the fewest service calls and can assess the condition of vent pipes and replace them if needed. Besides, thanks to wholesale discounts, plumbers can probably install a new unit for only slightly more than it would cost you if you bought the heater and fit­tings at retail prices.

 

If the tub drain is not accessible, plumbing codes require that joints be glued together, to prevent leaks. To join the tub tailpiece to the trap assembly, use a Mission T-150 trap (1V2-in. tubular to 1V2-in. pipe).

 

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Подпись: Turn off the gas first—the stopcock will be perpendicular to the gas line—before removing an old gas-fired water heater. Use an adjustable wrench to disconnect the gas coupling. Подпись: PROnP Don't accept water heaters whose boxes are bashed or torn. Water-heater elements are sensitive. If the box has been handled roughly or dropped, anode rods, liners, or valves may have been damaged. llll

A plumber should also be willing to peer through the vent thimble with a flashlight and mirror to check the chimney’s interior. All man­ner of debris can accumulate in the bottom of a chimney—from soot to nests—and that debris can block a chimney, hamper flue draft, and pos­sibly force carbon monoxide into living areas. The National Fire Protection Association sug­gests annual chimney and flue inspections, and

image616

Once the gas line is disconnected, attach a hose to the drain at the bottom of the water heater and drain the tank.

whenever a new type of burning appliance is vented into the flue, but inspection is really not a plumber’s job. The Chimney Safety Institute of America offers a state-by-state listing of chimney services with certified staff (check out their Web site at www. csia. org).

Above all, installers should follow the water – heater manufacturer’s installation instructions closely to ensure a safe installation and to safe­guard the unit’s warranty should the water heater fail to function properly.

Draining the old water heater. The specifics of disconnecting power or fuel to the old unit will vary, depending on whether the water heater is gas fired, fuel-oil fired, or electric. Once the installer has disconnected the fuel or power source, the water should be shut off and the tank drained. Typically, a hose will be attached to the drain valve at the bottom of the tank. Using a pair of pipe wrenches, unions (if any) on the hot – and cold-water pipes will be taken apart; if there are no unions, pipes will be cut 6 in. to 12 in. above the top of the heater—or a couple inches above the cold-water shutoff valve—by means of hacksaw or a wheeled cutter. Caution: Recipro­cating saws aren’t used because the vibration may weaken nearby pipe joints and cause leaks.

Make way for the new. If the unit is gas or oil

fired, the installer will disconnect the draft hood and vent pipe and either wire them up out of the way or set them to one side. As noted earlier, the plumber should inspect the vent pipes. If the hood or pipes are rusty or corroded, they should be replaced. When the old tank is empty, it can be walked out of the way. Be mindful of sharp edges on the newly cut pipes and the area around the old tank. Note: If codes require strapping the unit, steel straps should be bolted to the wall behind before putting the new unit in place. Finally, if the pad beneath the old tank is in poor condition or badly tilted, consider installing a new prefab concrete pad. Then the new water heater can be walked into position.

Making connections. What the installer does next depends on the size and condition of the pipes, what fittings are present and, of course, what type of water heater it is. There’s no single right way to assemble pipes, but the photos at left show a typical installation in progress for a gas – fired unit. There are 14-in. brass nipples screwed in the tank inlet holes, flexible stainless-steel lines, sweat-to-threaded male adaptors, valves, and (at the top) 14-in. rigid-copper trunk lines exiting to the upper floors. Flexible stainless-steel or flexible copper supply lines are highly recom­mended for top-of-tank connections: Female nuts

Подпись: When replacing a water heater, put unions and lever- handle ball valves on both the hot- and the cold-water pipes. Code requires a shutoff valve only on the cold-water pipe, but having them on both can make periodic drainage and repairs easier.Подпись: llll

on both ends make them easy to disconnect for future repairs.

Installing a TPR valve. Many new water heaters have preinstalled TPR valves. If there is none, the plumber will install a TPR valve into the threaded outlet atop the unit or in a side outlet a few inches down from the top of the tank, lightly coat the TPR valves threads with pipe compound, and then use a pipe wrench to install the valve. Next, the plumber will install a discharge pipe into the TPR valve’s threaded outlet; the pipe may be gal­vanized or rigid copper—but not plastic!—and must slope downward. The discharge pipe should be terminated about 6 in. above the floor, at a safe location, where it won’t scald anyone if it discharges.

Note: Threaded pipe fittings should be coated with pipe compound or wrapped with Teflon™ tape to ensure a positive seal.

Final steps. The plumber will check the water heater for level, shim the base as needed, and tighten the earthquake straps, if any. When all fittings are connected, turn on the cold water to fill the tank. Open the hot-water faucets to expel air. When the tank is full, water will gush from the faucets. At that point, shut the faucets, and reconnect the fuel or power source as specified in the manufacturer’s instructions. Note: If the installer disconnected the bonding jumper wires from the hot – and cold-supply pipes, those wires should be reclamped now to ensure proper grounding for the house’s electrical system.

image617

A new gas-fired water heater, in mid-installation. The red lever-handled shutoff valve on the cold – water pipe is code required; the tempering valve on the hot-water pipe prevents scalding. After installing the TPR safety valve, plumbers will reattach the vent pipe.

 

Gas-Fired Water Heater

 

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