ROOM

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Basic Design for Porches, Decks, and Landings

The porches on Habitat houses are among their nicest features. All Habitat houses have a covered porch of some sort. On the Charlotte house, there’s a small porch tucked underneath the main roof, sheltering the main entry door. The side door has a landing that could grow into a larger deck sometime in the future (see the photo on the facing page). Most of the Habitat houses I’ve worked on out West have a porch as an attached structure. It has its own roof, which joins either the main roof or the gable end of the house (see the top photo on p. 178). In almost any form, a porch adds something special to a house. It’s a place to put some flowers, kick off your shoes when you get home from work, or just sit down and relax at any time of day.

I have built hundreds of decks and porches over the years, and I’ve no­ticed that people are more inclined to use them if they are 6 ft. wide or larger. Narrower than that and all you really have is a walkway or a landing. I’ve also noticed that a deck with a roof—a porch, in other words—seems to get more use than a deck that’s open to the elements. In northern regions, a porch can be enclosed and used as a mudroom in the winter. In southern states, porches are often screened to keep out insects.

Design Ideas for Decks and Porches

No matter what size deck or porch you decide to build, quite a few design considerations deserve attention (see Resources on p. 279). Take some time to evaluate the many decking materials that are available, including different types of solid wood and synthetic materials.

Подпись:Подпись: 6 Install the Railings p. 190ROOMOn a sloping site, it’s often better to build a multilevel deck that follows

Size a deck to minimize

Подпись:waste. Take advantage of standard lumber lengths when determining the size of a deck. For example, a deck that’s 5 ft. 11 in. wide can be framed with 12-ft.-long joists or beams. A deck that’s 61/2 ft. wide would waste В/г ft. of an 8-ft. beam or joist.

ROOM

Подпись:the natural contour of the land instead of a single-level deck that requires tall support posts. Houses built on a concrete slab can have a smaller slab poured to create a porch or patio area. Just make sure the slab is 1 in. or so below the floor slab to keep water from entering the house. To promote drainage, pour the slab with a slight slope, about ‘/4 in. per ft. Don’t forget to thicken the concrete and install a metal post base where the posts will be installed to hold the sup­porting roof beams.

Some Habitat houses are built with ramps to accommodate people in wheelchairs or those who have limited mobility. Ramps can take up quite a bit of room. They need to be built with a gradual slope and must be at least 36 in. wide. The slope rate is usually a 1 in. vertical rise for every 1 ft. traveled horizontally. So if the door entrance is 16 in. above ground level, the ramp will need to be 16 ft. long.

Before you begin to build, you should also know which railing design you plan to use. Drive around a few neighborhoods and you’ll

Подпись: Ill III III III III III III III III III III II III III III III III III III III III III III III III III II III III III III III III III III III III III III III II III III III III III III III III III III III III III III II III III III III III III III III III III III III III II III POST-AND-BEAM SUPPORT FOR A PORCH ROOF ROOMFraming con­nectors are worth checking out. If you haven’t discovered the vast variety of fram­ing connectors that are available, try to do so before building a porch or a deck. A well-stocked lumberyard or building supplier will sell connect­ing hardware designed to reinforce all kinds of joints among different framing members.

certainly come upon some interesting railing designs to inspire your own efforts. Finally, consider your electrical wiring needs. Overhead light is important for security reasons, but you may also want to install some low-voltage lights on or around the porch or in nearby walkway or garden areas.

SIGNING AND. ROADWAY LIGHTING

Posted by on 20/ 11/ 15

PART 1

SIGNING

Brian L. Bowman, Ph. D., PE.

Professor of Civil Engineering Auburn University Auburn, Alabama

Part 1 of this chapter presents a comprehensive review of the design, construction, and maintenance of highway signs. Both single – and multiple-mounted sign supports are addressed, with an emphasis on highway safety. Breakaway supports with various types of slip bases, frangible bases, and post hinging systems are explained and illustrated. Commercially available devices and alternatives are identified and discussed. Guidelines on use and construction are summarized. An extensive list of references, which are noted in the text, concludes the section. Much of this material was derived from studies made by the author under a Federal Highway Administration project, NHI 38034, “Design, Construction and Maintenance of Highway Safety Features and Appurtenances.”

71 TRAFFIC SIGNING NEEDS

The capability of roadways to safely and efficiently serve vehicular traffic is depen­dent to a large extent on the adequacy of traffic control devices. The majority of motorists drive in an orderly and safe manner, provided they are given reliable regula­tory, warning, and guide information. Motorists, through training and experience, develop expectations on when and in what manner they will be provided necessary information for safely controlling their vehicles. Motorists expect that similar traffic control devices will always have the same meaning and will require the same motorist action regardless of where they are encountered. This expectation has been enhanced by the use of uniform traffic control devices which enable motorists to consistently interpret the general intent of a device by its message, shape, and color.

The advantages of traffic control device uniformity were recognized long ago. The American Association of State Highway Officials published specifications of road markers and signs for rural roadways in 1925. A manual for urban roadways was pub­lished in 1929 by the National Conference on Street and Highway Safety. The unifica­tion of the standards applicable to the different classes of roadways was addressed by a joint committee of the American Association of State Highway Officials and the National Conference on Street and Highway Safety. The joint committee developed, and printed in 1935, the first Manual on Uniform Traffic Control Devices for Streets and Highways (MUTCD) [1]. That joint committee, although subsequently reorganized and named the National Committee on Uniform Traffic Control Devices (NCUTCD), has been in continuous existence and contributes to periodic revisions of MUTCD.

The benefits of traffic control device uniformity include increasing safety by providing the road user with required information for vehicle guidance or control at the right time and place and in the proper manner. Signs should be installed only where warranted. This can include locations where special regulations apply at specific places or specific times or where hazards are not self-evident. They also provide information of highway routes, directions, destinations, and points of interest. The general standards for signs provided in Chap. 2A of the MUTCD and those sections pertaining to the particular type of sign being installed should be followed to ensure proper placement and message uniformity [2].

Moving a wall in

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Moving a wall in

SHEATHING THE WALL

Anyone who has witnessed the damage caused by an earthquake or high wind knows the importance of properly in­stalled interior and exterior wall sheathing (shear walls). In the serious 1992 Northridge quake near Los Angeles, shear walls saved many buildings—and many lives.

Wall sheathing provides strong lateral (horizontal) and vertical strength. It helps hold buildings together. It also helps make a house windproof, which is espe­

cially important if you live where cold winds are a reality. The most common sheathing materials are exterior-grade plywood and OSB.

Most building codes allow wall sheath­ing to be installed vertically (see the photo on the facing page), with the long edges nailed to the wall studs. It’s okay to install panels horizontally, but be sure to nail in 2x blocking between the studs at the panel joints. The shear strength of a wall panel is weakened unless it is nailed to the wall on all four sides.

Подпись:Normally, shear panels aren’t the final, or finish, wall covering, so they don’t have to be installed perfectly. Once these rough panels are nailed in place and inspected by the building depart­ment, they’ll be covered with stucco, finish plywood panels, shingles, clap­boards, or even metal or vinyl siding. Before sheathing any wall, exterior or interior, check the plans to see what is required. Often, shear panels need to be longer than the standard 8 ft. so they can extend from the pressure-treated foundation sill, across the rim joist and wall studs, and nail into the plates at the top of the wall. This type of construction ties the entire frame together and gives the house added structural stability.

When sheathing the outside of a build­ing, begin at a corner. If the stud layout is correct, the edge of the first panel should fall on a stud 4 ft. from the cor­ner. Check to see that the corner is plumb. If the first panel is set straight and plumb, all those that follow will be easier to install.

Rough sheathing doesn’t have to be absolutely flush with the corner of the framing, and in fact may be set as much as 3/4 in. away from the corner, since it will be covered by housewrap, finish siding, and trim. But the sheathing does need to break on the center of a stud 4 ft. from the corner. If it doesn’t break on the center of a stud, you can rip the sheet to fit, move the wall stud, or put in an extra stud so there is proper back­ing for edge nailing the plywood.

Remember the formula 4-6-12 when fastening sheathing, which is the typical nailing schedule using 8d nails (see the drawing on p. 131). Around door and window openings, nail only into the king studs and leave the trimmers free until it’s time to set the frames. It’s always a
good idea to check with your local build­ing department if you have questions about the nailing schedule.

If you are using a pneumatic nailer, set the air pressure so that nails are driven flush with the surface of the panel.

Nails driven too deep break the skin of the sheathing and weaken the shear strength of the panel. Many codes also require that you use full-headed nails rather than the clipped heads that are driven by many pneumatic nailers.

In humid climates, leave a Vs-in. gap between panels to allow for expansion. When you come to windows and doors, you can sheathe right over them and cut

Finnish Example

Posted by on 20/ 11/ 15

Figure 8.10 and Table 8.1 show the weakening of a road structure after spring thaw. The stiffness modulus E2 of the whole pavement structure measured by the FWD is, on average, 13% lower in the spring time than it is before the next freezing period. According to the FWD indices, the reason is the weakening of the up­per structure. This is shown since the BCI-indices (which are a representation of deflection in the subsoil) remain about the same, but the upper structure is weak­ened: the SCI (which is a representation of near-surface deflections) rises by 22%. The reason for this is that there must be more moisture in the structure after the thawing than in late autumn. The temperature of the pavement has been taken into account in the calculation on the indices. The data is from a 5.5 km long old high­way section of highway #6 in Finland with an AADT of 6500, before rehabilitation measures.

Figure 8.11 shows an example of a poor quality aggregate base layer in the mid­dle of the above section. In the central length of the road the SCI is very high, indicating that there are a lot of fines in the base layer.

E2 (MN/m2),
SCI300, BCI (pm)

800

700 300

200

E2 (MN/m2),
SCI300, BCI (pm)

800

700

600

500

400

300

200

100

0

5000 5200 5400 5600 5800 6000 6200 6400 6600 6800 7000 7200

Distance (m)

Thawing, Field Study, Iceland

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Figure 8.9 shows the air temperature together with the volumetric water content at Dyrastadir in Nordurardalur in SW Iceland during spring thaw, monitored through an environmental program run by the Public Roads Administration in Iceland. One can clearly see that as the thawing period starts in early March the water content increases, initially close to the surface and later at greater depth, before it slowly reverts back to normal values. As the water content affects the stiffness of the struc­ture as well as the permanent deformation characteristics, increased deterioration or damage is expected at the high water content if no axle load limitations are applied.

Fig. 8.9 Volumetric water content (right scale) during a spring thaw period for a thin pavement structure with an granular base course. The air temperature is also shown, top, as well as a cross section through the low volume pavement structure

Poisson distribution

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The Poisson random variable is discrete, having a PMF fx(xi) = P (X = xi) given in Eq. (2.53). Dagpunar (1988) presented a simple algorithm and used the CDF-inverse method based on Eq. (6.7). When generating Poisson ran­dom variates, care should be taken so that e~v is not smaller than the ma­chine’s smallest positive real value. This could occur especially when the Poisson

parameter v is large. An algorithm for generating Poisson random variates is as follows:

1. Generate u ~ U(0,1) and initialize x = 0 and y = e~v

2. If y < u, go to step 3. Otherwise, x is the Poisson random variate sought.

3. Let u = u – y, x = x + 1, and update y = vy/x. Then go to step 2.

This algorithm is efficient when v < 20. For a large v, the Poisson distribution can be approximated by a normal distribution with a mean v — 0.5 and standard deviation of>. Then a Poisson random variate is set to the round-off normal random variate from N(v — 0.5^/v).

Other algorithms have been developed for generating Poisson random vari­ates. Rubinstein (1981) used the fact that the interarrival time between events for a Poisson process has an exponential distribution with parameter 1/v. Atkinson (1979) applied the AR method using a logistic distribution as the enveloping PDF.

PEX: The Rising Star of Supply Pipes

Posted by on 20/ 11/ 15

Подпись: In PEX water-supply installations, central manifolds distribute hot and cold water to individual fixtures or fixture groups. Flexible tubing requires far fewer fittings than do rigid materials.Подпись: PEX tubing does require specialized fittings, such as plastic support elbows at tight bends and proprietary clamps where tubing attaches to metal stubouts.

Cross-linked polyethylene (PEX) is a flexible tubing system that’s been used in Europe for radiant heating and household plumbing since the 1960s, but it wasn’t widely used in potable-water systems in North America till the late 1990s. Within 5 years, though, it had captured 7 percent of the mar­ket, even though it was unfamiliar to most plumbers and cost roughly the same as cop­per. Now approved by all major plumbing codes, PEX could overtake rigid copper pipe in popularity. And as PEX tubing, tools and tech­niques become more widespread, more and more weekend plumbers will be installing it. There’s a lot to like.

PEX Advantages

► It installs quickly. Because lengths of flexible tubing easily turn corners and snake through walls, PEX systems require far fewer connections and fittings than do other materi­als. PEX tubing runs to fixtures from hot – and cold-water manifolds with multiple takeoffs. Most of the fitting is simple, consisting of crimping steel or copper rings onto tubing ends. Fewer fittings also mean fewer leaks and quicker installations.

► It’s safe: No open flame, no flux, no sol­der, no pipe cements—in short, nothing toxic to leach into the water supplies. So there’s no funny taste. Because it’s chemically inert, PEX won’t corrode, as metal pipe will, when installed in "aggressive water conditions."

► It can take the heat. PEX can withstand water temperature up to 180°F at 100 psi, which is 40°F hotter than recommended water heater settings. And hot water will arrive faster at the tap because, unlike metal pipe, there’s minimal heat loss through conduction. Thus it’s also less likely to sweat during hot weather.

► It’s quiet. The tubing expands slightly, minimizing air hammer—the banging that takes place in rigid piping when taps are turned off suddenly and running water stops abruptly. That ability to expand also means less pronounced pressure drops (fewer scald­ing or freezing showers) and PEX tubing is less likely to rupture if water freezes in it.

► It’s easier to repair. Because tubing connects to an accessible manifold with a bank of lever valves, you can shut off water to one side of a fixture as simply as flipping an electrical breaker.

PEX Disadvantages

PEX is as costly as copper; you need propri­etary connectors and crimping tools for each brand of tubing; and it will break down when exposed to UV light (within 30 days to 90 days), so get it installed and covered quickly. Although PEX can withstand high water tem­peratures, it will melt when exposed to open flame. Thus it must not be directly connected to gas- or oil-fired water heaters and must be kept away from flue pipes, recessed lights, and other sources of excessive heat.

via no-hub couplings with inner neoprene sleeves, as shown in "Splicing a Branch Drain to a Stack,” on p. 285. The new pipe-fitting assembly should be 1 in. shorter than the cutout section.

Before cutting into cast iron, however, sup­port the pipe on both sides of the intended cut to prevent movement, which could weaken joints. Use stack clamps (riser clamps), if you’re cutting into a vertical section of pipe. Use strap hangers (see the top photo on p. 277) if cutting into a hor­izontal section. Mark cut-lines on the cast iron with a grease pencil. Then wrap the snap-cutter’s chain about the pipe, gradually tightening till the chain is snug and the tool’s cutting wheels align over the cut-lines. Crank the cutter’s handle to continue tightening the chain till the pipe snaps
cleanly. Make the second cut, and remove the old pipe section. Caution: Wear goggles during this operation.

Once the cuts are complete, slide the neo­prene sleeve of a no-hub coupling over each remaining pipe end. You may need to roll each sleeve back on itself, as you would roll up the cuffs of a long-sleeved shirt. Insert the transition fitting or replacement pipe section, unroll the neoprene sleeves onto the fitting or pipe, and then tighten the steel band clamps. You can also tie into a cast-iron drain without cutting into it, by building out from an existing cleanout, as shown in "Extending a Cast-Iron Main Drain,” on p. 286.

Working safely on a ladder

Posted by on 20/ 11/ 15

Over the years I’ve learned the hard way to be extremely wary of ladders. While they are often in­dispensable, they need to be treated with the same respect accorded a powersaw. A fall from a ladder can seriously injure or kill you, and every carpenter (and many homeowners) can tell of injuries related to a ladder mishap. Here are a few safety tips to make working on a ladder safer.

• Buy a quality ladder. Check the ladder’s label for a rating of 1 A, which means that the ladder is a heavy – duty one.

• If working near or with electrical wiring, it’s a good idea to own a nonconductive ladder. Fiber­glass is a good choice, although these are typically heavy and expensive. (Aluminum and wet wood ladders can conduct electricity.)

• Don’t stand on the uppermost steps of a ladder; get a longer ladder instead.

• Don’t reach too far to the side of a ladder. You can lose your balance.

• Don’t leave tools sitting on top of an unattended ladder.

• When using a stepladder, unfold it all the way, lock its braces, and set it on a solid surface.

• When using an extension ladder, make sure its feet are firmly and securely planted on a solid surface.

Working safely on a ladder

Drive a 16d toenail through the top plate into the double top plate to close any gap between plates. (Photo by Roe A. Osborn.)

 

Working safely on a ladder

Place the push stick under the top plate against a stud, parallel with the wall. Bend it down as shown, and then pull it up in the middle. As the board straightens, it will push the wall laterally. When the bubble is centered in the vial on the plumbstick, the wall is plumb. (Photo by Roe A. Osborn.)

 

important to do them correctly. This is one of those times when utmost accu­racy is important. Straight, plumb walls leave behind a lasting story of your skills. No professional carpenter wants to leave a job with crooked walls that lean to one side. If you make sure walls are plumb and lined, all the following work by every trade will go easier, and the finished house will look better.

Plumbing is done first. You’ll need a plumbstick with a level (see p. 35) and a push stick. If you don’t use a plumbstick,
make doubly sure you use an accurate level. A push stick is used to push walls end for end during plumbing. To make a push stick for an 8-ft. wall, cut a 1×4 or a 1×6 about 116 in. long. Try to use stock without a lot of knots; otherwise, it may break.

You’ll need a partner to plumb the walls. Start with the exterior walls. One person holds the plumbstick in a corner. Adjust this wall by pushing it in or out until the bubble is centered in the level’s vial. A short wall can often be moved by giving

Working safely on a ladder

it a shove with your body, but if you need more force, place the push stick under the top plate against a stud and running diagonally down to the floor (see the photo on the facing page). Keep the stick as close to parallel with the wall as possible. Bend the stick down, holding the bottom end against the floor with one foot. Now pull the middle of the stick up. As the board straightens, the wall will move. When the bubble in the level centers, the wall is plumb.

Once the wall is plumb, finish nailing in the metal framing braces. If you aren’t using metal wall braces, nail in tempo­rary 2x studs to hold the wall plumb (see the drawing above). Place one end of the stud about б ft. up in a corner and nail it with two 16d nails. Once the wall is plumb, have a partner nail the stud at the bottom with two more 16d nails.

After plumbing all the walls and nailing in all the braces, it’s time to line, or straighten, the walls. Lining a wall is pretty simple. The bottom plate is

Подпись: To line a wall, sight down the length of the walls and trust that your eyes can see when the top plate is straight. (Photo by Roe A. Osborn.)

straight because it has been nailed to a chalkline, and the top plates should be close to straight if you used straight stock when plating.

The easiest way to line a wall is to hop on a ladder in the corner and sight down the length of the walls (see the photo above). Trust your eye that you can see when the top plate is straight. Another method often used on long
walls is to check the walls with a dryline (see the drawing on the facing page). Nail a scrap piece of 2x to the top plates at each corner and drive an 8d nail part­way into the outer ends of each block. Hook a dryline to one of the nails, pull it taut, and tie it around the nail in the other corner. Then take another scrap piece of 2x and slide it along the wall, checking for a consistent 1 Умп. space between the line and the wall.

Working safely on a ladder

Any wall that isn’t straight needs to be moved in or out. For either job, you’ll need a partner. If a wall needs to be moved out, nail a 2x stud (with two 16d nails) flat against the edge of a wall stud about three-fourths of the way up on the wall (see the photo on the facing page). Hook the daws of your hammer under the stud and pry until your part­ner says the wall is straight. Then nail the bottom end of the stud to the floor with two 16d nails to brace the wall (see the drawing on p. 125).

If the wall needs to be moved in, nail a 2x stud on edge to the bottom of a wall stud. Let it extend to the outside, sitting on hard ground or on a short (1 – ft.) 2x block resting on the ground. Nail a 2x stud in place about three-fourths of the
way up on the wall with the bottom end positioned on the horizontal 2x (see the drawing on p. 128). Now you can move the wall in the same way that was used to move the other wall out.

Don’t hesitate to use plenty of tempo­rary braces as you plumb and straighten walls. Extra braces at this point will guar­antee that the building will be held plumb and straight until the rest of the framing is completed. I have worked on buildings where a temporary brace was knocked loose and the wall moved out of plumb because there were no other braces. This can cause a lot of anguish and extra work if it isn’t discovered right away. It’s not easy to straighten a wall once joists and rafters are nailed into it.

UPGRADED INSULATION

Posted by on 20/ 11/ 15

WALLS

UPGRADED INSULATION

Rigid insulation, with a potential R-value approxi­mately double that of batt insulation, is a very attractive alternative for upgrading the thermal performance of walls. The material is easy to install in large lightweight sheets, has sufficient strength to support most siding and interior finish materials, and can double as an air/ vapor barrier in some cases. Its disadvantages are high cost and potential for toxic offgassing in a fire.

Rigid insulation is most effective when used on the exterior of the building because it covers the entire skin of the building continuously without the interruption of floors or interior partitions. It can act as the backing for siding but does not provide the strength to act as structural sheathing. Alternative methods of bracing the building, such as structural sheathing (see 78A) or let-in bracing (see 77B & C), must therefore be used. Hybrid systems, in which structural sheathing is used only at necessary locations with rigid insulation elsewhere, can also provide cost effective insulation upgrades.

When applied to the exterior of buildings in cold cli­mates, the low permeability of rigid insulation can trap vapor in the stud cavities, causing structural damage. The reverse can be true in warm climates. It is there-

UPGRADED INSULATION

FURRING SAME THICKNESS AS RIGID INSULATION AT WINDOW & DOOR OPENINGS AND AS REQUIRED FOR NAILING OF Siding

UPGRADED INSULATION

vapor retarder

LOcATED AT INTERIOR

face of 2×6 stud wall

floor structure with insulation and continuous AIR/vAPOR BARRIER SEE 61-62

RIGID INSuLATION may Be

continuous over wall or foundation below

practicality of specific types of insulation with local professionals.

Used on the interior of a building in a cold cli­mate, rigid insulation can perform three functions at once: insulation, vapor retarder, and air barrier. To accomplish this, a foil-faced insulation board carefully taped at all seams and caulked and/or gasketed at top, bottom, and openings would be used.

fore advisable to carefully coordinate the use of rigid insulation with a high-permeability vapor retarder based on the specific climatic zone and to verify the

The use of interior rigid insulation requires deep electrical boxes and the need for extra-wide backing at corners and at the top plate.

@ RIGID INSULATION

roof or upper floor structure with insulation and continuous air/vapor barrier see 197 QR 63

Подпись:Подпись: VAPOR RETARDER HORIZONTAL 2X3 STRAPPING wITH HORIZONTAL INSULATION UPGRADED INSULATIONsingle 2X6 top plate

structural sheathing or other bracing batt insulation in 2X6 stud WALL

STRAPPING for NAILING around openings

horizontal 2X3 STRAPPING AT 24 IN. o. c. NAILED To studs horizontal batt insulation between

STRAPPING vapor retarder located at interior face of 2X6 stud WALL

WIRING AND PLuMBING

located within

STRAPPING LAYER

Подпись: @ STRAPPING

Strapping consists of horizontal nailing strips attached to the inside of a stud wall. The strapping touches the studs only at the intersection between the two, so thermal bridging is virtually eliminated. Strapping is used extensively in energy-efficient buildings. With 2×6 studs and 2×3 strapping, an R-25 value can be achieved.

The advantages of the system are that it is simple and straightforward and uses a minimal amount of extra framing materials. With two-thirds of the insula – tive value in the (2×6) stud cavities, an air/vapor barrier can be located at the inside face of the framed wall, thus eliminating the need to puncture it with services. In addition, the plumbing and electrical work itself is simplified by the creation of horizontal chases on the walls.

Strapping must be fastened securely to the studs to prevent rotation, but interior finish panels will ulti­mately tie the strapping together to keep it in place.

double strapping for

BASE TRIM NAILING floor structure WITH insulation and continuous air/vapor BARRIER SEE 61-62

Extra strapping is usually required for nailing at cor­ners, at window and door openings, and at the base of the wall (see drawing above). In addition, vertical blocks are required for the attachment of electrical boxes.

Strapping may also be applied to the exterior of a building. In this case, the strapping is more easily installed, but the advantage of a horizontal chase inte­rior of the vapor retarder is lost. Furthermore, the strapping insulation must be installed from the exterior, exposed to the weather.

UPGRADED INSULATION

SHEATHING

2X4 STUDS AT 24 IN. O. C. WITH BATT INSULATION AND ALIGNED WITH OUTER EDGE OF PLATE

2X4 studs AT 24 IN. o. c.

with batt insulation aligned with inner edge of plate & offset from outer studs

vapor retarder

2×8 or 2×10 PLATE

Staggered-stud framing is essentially a double stud wall framed on a single wide plate with the studs offset from one another so that there is negligible thermal bridging. The system is appreciated by builders for its minimal deviation from standard frame construction. Staggered-stud framing is substantially the same as platform framing, and subcontractors are sequenced in the same order as standard construction. With this technique, insulative values of R-.30 or more can be attained. A 2×8 or 2×10 plate with staggered 2×4 studs at 24 in. o. c. is most common.

Because there are effectively two separate walls, this system offers a special opportunity at windows and doors to splay the opening.

UPGRADED INSULATION

roof or upper floor structure with insulation and continuous air/vapor BARRIER see 197 QR 63

UPGRADED INSULATION

single top 2X top plate

plywood gusset ties stud walls at openings

UPGRADED INSULATION

STAGGERED 2X4 STuD WALLS FILLED WITH BATT

insulation

vapor RETARDER located at interior

FACE oF INNER FRAMED WALL

SINGLE 2X SoLE PLATE

floor structure with insulation and continuous air/vapor BARRIER SEE 61-62

By increasing the rough-opening size at the “inner wall,” the opening will be more generous from the inside and reflect light better into the room.

Подпись: @ STAGGERED STUD FRAMING

The disadvantages of the system also stem from its similarity to standard platform frame construction. Unlike strapping systems or double wall systems, stag – gered-stud systems have the air/vapor barrier located on the inside (warm) face of the wall, with the atten­dant problems of sealing perforations of the barrier from plumbing and electrical services.

Double wall framing is capable of achieving the highest insulation values of all the upgraded framing techniques. Values of R-40 are common. Slightly more framing materials and considerably more labor (than strapping or staggered stud) are required for the increased performance.

The outer framed wall is most commonly used as the bearing wall. This strategy has two advantages: The insulation and the inner wall can be installed under the roof out of the weather, and the shear walls are most easily installed and logically located at this (outer wall) location. However, finish detailing at the wall/ceiling joint is complicated if the inner wall is nonstructural, and the continuity of the air/vapor barrier is somewhat

Подпись: its continuity because plumbing and electrical servicesS3

difficult to achieve at the wall/floor intersection.

can be located within the inner wall without having to

Less common (and not illustrated) is the use of the
penetrate the barrier. To get the air/vapor barrier into

inner wall as the bearing wall. This system avoids the minor disadvantage of the outer bearing wall system, but has two major disadvantages: it requires support of the outer wall beyond the edge of the foundation and the outer wall and the extra insulation must be installed from the outside of the building, exposed to the weather.

The ability to locate an air/vapor barrier at the out-
side surface of the inner wall contributes significantly to

this position is simple with an interior bearing wall, but somewhat involved with an exterior bearing wall. It can be accomplished, however, by fastening the barrier to the (outer face of the) inner wall before it is tipped into place. The cavity can be filled with horizontal batts tied to the exterior wall before the inner wall is positioned or insulation can be blown in afterward through holes predrilled in the top plywood gusset.

@ DOUBLE WALL FRAMING

Thawing, Field Study, Canada

Posted by on 20/ 11/ 15

In cold climates, and with frost susceptible materials, freeze thaw phenomena play a major role in pavement deterioration. Figure 8.8 shows examples of measurements of deflection development, and of water content in the subgrade, performed in a full scale experiment, carried out in Quebec (Savard et al., 2005). The pavement structure consists of 18 cm of bituminous materials over a granular base (40 cm) and a 40 cm thick sand frost-protection layer. The pavement is subjected to frost indices exceeding 1000°C. days. The deep frost penetration (up to 1.5 m during severe win­ters) leads to large water content variations in the silty, frost susceptible subgrade,

which considerably affect the pavement deflections. The period of reduced bearing capacity lasts about 2 months (thaw period, followed by a recovery period, where the excess moisture dissipates).