INSTALLING FRIEZE BLOCKS BETWEEN. RAFTERS AND TRUSSES

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Подпись:Подпись:Подпись: RafterПодпись: When installed perpendicular to the rafters, blocking provides a stop for other types of siding.INSTALLING FRIEZE BLOCKS BETWEEN. RAFTERS AND TRUSSESINSTALLING FRIEZE BLOCKS BETWEEN. RAFTERS AND TRUSSESINSTALLING FRIEZE BLOCKS BETWEEN. RAFTERS AND TRUSSES

2x frieze block

Rafter

Double top plate

Stucco

When installed plumb, a frieze block provides backing for stucco.

2x frieze block

Siding

Trusses by themselves are rather fragile. They gain strength when they’re properly blocked and braced. I will now explain various blocking and bracing strategies, because this work needs to be done as the trusses are installed.

Hurricane clips and frieze blocks

A hurricane can tear a roof completely off a house. Hurricane clips, which are designed to prevent this, are required by code in some parts of the country. After the trusses are nailed in position, hurricane clips are easy to install from inside or outside the house. Drive nails into the trusses and the top plates of the wall (see the bottom left photo). Be sure to use the special short, strong “hanger” nails that are sold with the clips.

In many parts of the country, frieze blocks are required between trusses. I’m in favor of these blocks, which you can cut from the plentiful supply of 2x scrap that your crew has been collecting. Installed at the top of the wall, these 2x blocks connect the bottom chords or, depending on the truss design, the rafters of ad­jacent trusses. They provide extra rigidity near the truss ends (see the illustration at left).

I have seen firsthand how frieze blocks help hold truss systems together in high winds and earthquakes. They offer other benefits as well. The blocks can serve as exterior trim (with or without ventilation holes) if you plan to have an open soffit. If you are installing raised-heel trusses, as we did on this house, you’ll also need to install plywood or OSB baffles between the trusses to prevent attic insulation from spilling into the soffit area (see the top photo on p. 153).

Install a pair of frieze blocks after each truss is installed. Drive a pair of 16d nails

Hurricane clips tie trusses to walls. Required by code in many areas, these metal connectors are designed to fit around the bottom chord of a truss and against the top plate of a wall. Here, a volun­teer attaches a clip with an air hammer.

Подпись: Securing trusses. An air nailer (top) makes quick work of toenailing the truss's bottom chord to the wall plate. Drive two nails from one side and one nail from the other. To keep trusses parallel and spaced correctly, nail temporary 1x braces spaced at 24 in. o.c. across the top chords (bottom). INSTALLING FRIEZE BLOCKS BETWEEN. RAFTERS AND TRUSSES

through the truss and into the end of the frieze block, then nail the frieze block to the top plate. You can cut a supply of blocks quickly on a chopsaw. Make sure you cut them to the correct length. If they’re too long or too short, you may force the trusses off of their layout. The normal block length for trusses spaced 2 ft. o. c. is 22У2 in. However, if the blocks will butt against gusset plates, you’ll need to take the gusset thickness into account.

After you’ve nailed the first frieze blocks to the gable-end truss, swing the next truss upright. Shift it right or left, as necessary, to obtain the correct eave overhang, then toenail it to the top plate with two 16d nails through the joist chord on one side and one 16d nail on the other side (see the bottom photo at right). Install the next several trusses in this fashion. As you raise each truss, tack a series of 16-ft. 1x4s (laid out 24 in. o. c.) near the ridge of the rafter chord to keep the truss stable and properly spaced (see the top photo at right).

An efficient way to work when installing roof trusses is to have a worker at each eave toe – nailing the truss to the wall and installing frieze blocks while one or two crew members work on the ridge, moving trusses into position and nail­ing 1×4 braces to maintain proper spacing.

Dissolution/Precipitation

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Rainwater is able to dissolve gas present in the atmosphere (leading to acid rain, for example; see Section 6.2.6). Rainwater is also able to dissolve chemicals present at the road surface (e. g. metals, salts and some organics). Road materials are of course selected for not being soluble but trace elements present in natural and alternative materials can be released by dissolution when leached by seepage. The rise in a water table can also bring about dissolution. Dissolved elements can precipitate downstream where hydrous, pH and/or redox conditions differ from those upstream. Dissolution/precipitation sequences are also part of the circulation of chemicals. Dissolution of CO2, whether from the air or biological activity, is of great impor­tance to the pH of the soil solution, also in the road context.

Dissolution is the process by which a solution is formed when a soluble substance (a solute) is dissolved in a liquid (a solvent). A true solution is a uniform molecular or ionic mixture of one or more solutes in a solvent, as distinguished from a colloidal solution or dispersion in which the dispersed material is in the form of extremely small particles, 1 ^m or less. The solute can be a solid or a gas.

As a polar molecule, water can dissolve ionic substances such as salts but also substances consisting of polar molecules with which the water molecule forms hy­drogen bonds. The solubility (i. e. the maximal quantity of a chemical compound that can be dissolved per litre of solvent) is dependent on temperature, pH and activity coefficient.

Whether a substance is present in the dissolved or in the precipitated form is of crucial importance to its mobility and transport in the soil. This is especially true of heavy metals and other micro-pollutants (Ramade, 1998). Depending on variations in the chemical and physical properties of its environment, a given pollutant present in the soil can repeatedly change from being dissolved to being precipitated, and thus from being mobile to being less mobile. Some salts (ionic solids) are very soluble, for instance NaCl and CaCl2 which are used for de-icing and dust-binding, respectively.

The degree of solution of any salt MpXq is governed by the dissolution equilibrium:

MpXq(s) <-> pMq+ + qXP – (6.17)

where the solubility product Ks = (Mq+)p ■ (XP-)q. Thus, the greater the solubility product, the greater the solubility of the salt. This equilibrium can be coupled with other equilibria, e. g. acid-base, redox or complexation equilibria. The solubility of a salt is, e. g., dependent also on the pH and the redox status of the soil.

Carbonates are important to the mobility of heavy metals. Carbonates are dis­solved upon the interaction with water and with the carbon dioxide present in air, water and soil. Calcium carbonate (CaCO3) is a major constituent of calcareous rock. Where enough free carbonate ions (CO32-) are present, they will react with heavy metal ions to form immobile precipitates, e. g. lead carbonate. The mobility of many heavy metals is low in calcareous soils. On the contrary, heavy metals are often more mobile in acidic soils where carbonates are largely absent (Selim & Sparks, 2001).

Hydroxides of Fe and Mn also play a major role in natural waters and soils. The solubility of hydroxides depends on the acidity (pH) of the water or the soil solution. The solubility of hydroxides decreases when pH increases, passes through a minimum and then increases at higher pH.

Organic molecules that contain polar groups or create hydrogen bonds are to a great extent soluble in soil solution and water. This is the case for organic molecules with groups such as hydroxyl, amine, carboxylic acid, carbonyl, ester or ether.

In the road situation, adsorption and desorption will happen routinely whereas precipitation will depend on the ion concentration. At low concentrations, many metals are under-saturated with respect to their associated mineral phases so that their mobility/retardation is governed by adsorption/desorption. At higher concen­trations, both adsorption and precipitation may be occurring to take ions out of solu­tion, but it is the dissolution/precipitation processes that will determine the aqueous concentration of the metal.

Advanced First-Order Second-Moment (AFOSM) Method

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The main thrust of the AFOSM method is to improve the deficiencies associated with the MFOSM method, while keeping the simplicity of the first-order approx­imation. Referring to Fig. 4.3, the difference in the AFOSM method is that the expansion point x+ = (xL*, xR+) for the first-order Taylor series is located on the failure surface defined by the limit-state equation, W(x) = 0. In other words, the failure surface is the boundary that separates the system performance from being unsatisfactory (unsafe) or being satisfactory (safe), that is,

{

> 0, system performance is satisfactory (or safe region);

= 0, limit-state surface (or failure surface);

< 0, system performance is unsatisfactory (or failure region).

The AFOSM method has been applied to various hydrosystem engineering prob­lems, including storm sewers (Melching and Yen, 1986), dams (Cheng et al., 1982; 1993), sea dikes and barriers (Vrijling, 1987; 1993), freeboard design (Cheng et al., 1986a), bridge scour (Yen and Melching, 1991; Chang, 1994), rainfall-runoff modeling (Melching et al., 1990; Melching, 1992); groundwater pollutant transport (Sitar et al., 1987; Jang et al., 1990), open channel design (Easa, 1992), sediment transport (Bechtler and Maurer, 1992), backwater com­putations (Cesare, 1991; Singh and Melching, 1993), and water quality model­ing (Tung, 1990; Melching and Anmangandla, 1992; Melching and Yoon, 1996; Han et al., 2001; Tolson et al., 2001).

4.1.1 Definitions of stochastic parameter spaces

Before discussing the AFOSM methods, a few notations with regard to the stochastic basic variable space are defined first. In general, the original

stochastic basic variables X could be correlated, non-normal random variables having a vector of mean ix = (pxi, /гХ2,…, pxK)t and covariance matrix Cx as shown in Sec. 2.7.2. The original random variables X can be standardized as

X’ = D-1/2(X – fix) (4.30)

in which X’ = (X^, X2,…, XK)t is a vector of correlated, standardized random variables, and Dx = diag(o2, a|,…, oK) is an K x K diagonal variance matrix. Through the standardization procedure, each standardized variable X’ has the mean zero and unit standard deviation. The covariance matrix of X’ reduces to the correlation matrix of the original random variables X, that is, Cx> = Rx, as shown in Sec. 2.7.2. Note that if the original random variables X are nonnormal, the standardized ones X’ are nonnormal as well. Because it is generally easier to work with the uncorrelated variables in the reliability analysis, the correlated random variables X are often transformed into uncorrelated ones U = T (X), with T ( ) representing transformation, in general. More specifically, orthogonal transforms often are used to obtain uncorrelated random variables from the correlated ones. Two frequently used orthogonal transforms, namely, Cholesky decomposition and spectral decomposition, for dealing with correlated random variables are described in Appendix 4B. In probability evaluation, it is generally convenient to deal with normal random variables. For this reason, orthogonal transformation, normal transformation, and standardization procedures are applied to the original random variables X to obtain independent, standardized normal random variables Z’. Hence this chapter adopts X for stochastic basic variables in the original scale, X’ for the standardized correlated stochastic basic variables, U for the uncorrelated variables, and Z and Zrespectively, for correlated and independent, standardized normal stochastic basic variables.

The future of the discoveries of the 3rd century BC

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As we have shown, Lagide Egypt undergoes a period of troubles and reduced prosperi­ty from the 2nd century, a situation not at all propitious for development. Ptolemy VIII (called Physcon – i. e. the vain) hunts down the Alexandrian intellectuals in 145 BC and later sends his mercenaries to attack this city that had revolted. Far from being lost, the discoveries of the 3rd century BC reappear in the hydraulic projects that we are going to describe subsequently. They comprise a patrimony shared by the Roman engineers and the scientists of the school of Alexandria from the first centuries of our era – the school poised for another fruitful period under Roman domination.

The implementation of new hydraulic technologies in the Hellenistic kingdoms, from the 3rd to 1st century BC

Even though Pergamon and Alexandria dominated intellectual life, the thread of innova­tion runs throughout the entire Hellenistic world in this period, from Egypt to the Black Sea. The first examples that we will describe are linked to the intensive urbanization that developed in Asia Minor. These are new cities in a mountainous country, and they demand new principles of water supply.

Hellenistic water delivery and the generalization of the siphon

As we have seen in Chapter 4, the Greek aqueducts most often use clay pipes that fol­low the slope of the terrain, as would a free-surface canal. During the Hellenistic peri­od, in the new cities of Asia Minor and Palestine, the technology of inverse siphons is developed to permit an aqueduct to cross a valley and return to a higher elevation. These siphons are schematically in the form of a “U” with depth of from 15 to 75 m (i. e. from the top to the bottom of the “U”.) The portion of the conduit that is under pressure (a “forced main”) is most often constructed from massive stone. Numerous pipe sections of this type have been recovered, often of cubical external shape, and fitted with ferrules so that individual elements can be connected to form a conduit (Figure 5.7). Often the upper portions of these elements have holes in them, probably serving as air vents, clean­ing holes, or perhaps pressure-surge relief valves.

The future of the discoveries of the 3rd century BC

Figure 5.7 Example of a forced main in stone (Laodicee) (after Hodge, 1995)

Inverse-siphon technology made it possible for Hellenistic water-delivery systems to cross valleys without the engineering structures (bridge-aqueducts) that the Romans later used for such crossings. Their development coincides with an improved knowledge of the effects of fluid pressure, as we have seen in the previous section. But it is diffi­cult to say if this knowledge resulted from the technological development, or vice-versa. Table 5.1 summarizes some of the Hellenistic inverse siphons.

Table 5.1. Inverse siphons of Hellenistic technology (Hodge, 1995)

City

Depth

City

Depth

Ephesus

15 m

Apamea Kibotos

28 m

Antioch on the Meandre

15 m

Magnesia

30 m

Blaundos

20 m

Trapezopolis

40 m

Philadelphia

20 m

Prymnessos

40 m

Patara

20 m

Tralleis

75 m

Laodicea of Lycos

25 m

Smyrne

158 m

Akmonia

25 m

Pergamon

200 m (see below)

Antioch on Pisidia

28 m

Ridgen’s method modified by Anderson

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The U. S. method (here called Rigden-Anderson) described in Anderson (1987) stipulates 25 strokes of the 100 g dead weight. Results of the measurements form the basis for calculating the volume of air voids in a dry compacted filler. Only 1.0-1.3 g of filler is needed to conduct the testing. After determining the content of air voids in the compacted filler, the calculation of free and fixed binder may be per­formed (by mass and by volume). The concept of free and fixed binder is presented in Chapter 3.

8.3.2.2 comparison of methods

Rigden’s method (the European procedure) and Ridgen’s as modified by Anderson (the U. S. procedure) produce different contents of air voids in the same compacted [54] filler. This is caused by a lower compacting effort in the U. S. method (25 strokes) than in the European one (100 strokes). Much research, particularly in the United States, has been carried out with the use of Ridgen-Anderson’s method. The results would be very valuable for Europeans, but test conditions differ to such an extent that a simple comparison of results is rather impossible.

Determination of Compacted Filler Air Voids after. Rigden’s and Rigden-Anderson’s Methods

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Rigden’s and Rigden-Anderson’s methods apply to any fine material used as a filler in hot mixes (e. g., bag-house fines and added filler). Filler air voids make up an air volume occurring among grains of filler compacted with a special apparatus by a standardized method. Test methods according to the EN standard (Rigden) and the U. S. procedure (Rigden-Anderson [Anderson, 1987]) differ markedly, which makes the direct comparison of results impossible. The only feature they have in common is their principle—dry compaction of filler.

8.3.2.1 Rigden’s Method after EN-1097-4

The EN method provides for compaction of a dry sample of filler by 100 strokes of a dead weight every second. The mass of sample is 10 g, and the mass of the dead weight is 350 g.

The volume of air voids is estimated, taking into account the mass of the com­pacted sample, its volume, and the filler density. European countries have used the EN 13043 standard for aggregates for asphalt mixes. The most frequently adopted requirement for a filler tested according to EN 1097-4 is the category V28/45, which means the content of air voids should be within 28-45% (v/v).

Techniques SHEATHING A WALL

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WHEN ALL THE walls have been raised, braced, and lined, it’s time to attach the sheathing. On this house, two types of sheathing are used.

1. To provide shear bracing, OSB panels are installed on all corners and every 25 ft. along exterior walls.

2• Foam board sheathing is nailed to the framing between wood panels. It’s easier to sheathe right over window and door openings, then cut out the openings from inside. Foam cuts easily with a handsaw.

Techniques SHEATHING A WALL

Safety on the Job LADDERS

FEW THINGS SCARE me more than working on a ladder. While they are frequently indispensable, ladders must be treated with the same respect as power saws. Here are a few tips to make working on a ladder safer:

ж Don’t buy a cheap ladder. I like the heavy-duty, fiberglass models. Look for one with a 1A rating (the best) on the label. When buying an exten­sion ladder, be sure to select one that is long enough to extend 3 ft. above the height of your roof.

ж Aluminum and wet wood can conduct electricity. It’s best to use a fiberglass model when working near electrical wiring.

Don’t stand on the uppermost rungs. Get a longer ladder instead.

When working on a ladder, you can lose ycur balance by reaching too far to the side. If your reach starts to feel precarious, it probably is.

Get down and move the ladder.

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

Make sure the ladder’s feet are firmly and securely planted on a solid surface before climbing up it. When using an extension ladder, tie it to the building at both the top and the bottom (this is particularly important if it’s a windy day).

Since sheathing panels will he covered with finished siding, they don’t need to be installed perfectly. Earthquake- and hurricane-country sheathing codes are often quite strict, so check with your local building department before you start covering walls. Again, remember to insulate corners, channels, headers, and behind tubs before you attach wall sheathing.

Install sheathing on the corners first

Whether I’m sheathing all the exterior walls with wood panels or just the corners (as we did on this house), I always install sheathing on the corners first (see the bottom left photo on p. 109). To hold a sheet in position while you get ready to nail it, try driving a couple of 16d nails near the bottom of the wall. Keep plywood and OSB ‘A in. away from a masonry

Подпись: SNAPSHOTSПодпись: It's exciting to see an entire wall nailed together on the subfloor . . . We line up and grab part of the top plate to get ready to lift, then up it goes . . . Подпись:Techniques SHEATHING A WALL

At first, we’re not worried about making sure the are plumb or straight—we just keep them up with dio braces. . .

foundation. If the stud layout is correct, the edge of the first panel should fall on a stud 4ft. from the corner. In humid areas, leave a! йі. expansion gap between sheets. If a sheet doesn’t break on the center of a stud, rip the sheet to fit, move the wall stud, or put in an extra stud.

You can sheathe right over windows and doors and cut them out later with a recipro­cating saw. Use scrap pieces to fill in gable ends and underneath windows or to cover rim joists.

1 also sheathe various walls inside the house, though this goes beyond most codes. Ido this because 1 know that a lew extra sheets of OSB might save someone’s life dur­ing an earthquake or a tornado. Sheathing the back wall of a closet, bathroom, or utility room gives the frame extra lateral stability. In areas prone to serious tornadoes, you may be required to create an entirely sheathed and well-anchored safety room in which house­hold members can gather during a storm (see Resources on p. 278).

The nailing schedule for sheathed walls often requires 8d or 1 Od nails at 4-6-12. This means that nails are spaced 1 in. around the perimeters of walls, 6 in. at the joints between sheathing panels, and 12 in. in the field.

Check with your building department for the required nailing schedule in your area.

Install foam sheathing

There are many areas in the country where plywood or OSB sheathing is required only at exterior corners and everv 25 ft. along exterior walls. This allows you to install nonstructural sheathing material everywhere else. On this house, we used [2] -in. foam sheathing. The foam board is light and easy to handle, though it can be damaged by a stray hammer blow or

O j I

by someone stepping on it. Attach foam sheathing with roofing nails. Sheathe right over window openings, then go inside the house with a handsaw and cut out the loam from the openings (see the bottom right photo on p. 109).

If you’ve come this far, vou and vour con – struction crew deserve some heartv congra – filiations and a little time to rest before tack­ling the roof. Getting wa Is framed and sheathed is a huge step forward in the con­struction process, and it demands brainpower for accurate layout and lots of energy to pound nails and raise walls. Make sure you spend some time cleaning up the job site at this point in your project. There are bound to be plenty of offeuts, such as 2x stock, plywood or OSB scraps, and stray fragments of foam sheathing. Remove the debris and get set to raise the roof.

lien we start finding the exact positions with a level к soon as the exterior walls ore up, we start on the

It’s amazing to think that just о short while ago, we had only piles of lumber and a bare floor. . .

This is going to be a great house!

 

… "ШИ II-*• – *’

■ИГГ1 .чи

!!ЇііііЩ#і!

 
Techniques SHEATHING A WALL

Techniques SHEATHING A WALL

CHAPTER

 

WORK SAFELY ON A ROOF

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Keep your wits about you and pay extra attention to what you’re doing when you’re up on a roof—both to keep yourself safe and to ensure that the integrity of the roof is not compromised. To get on and off the roof, use a good, sturdy ladder that extends 3 ft. above the edge of the roof.

■ Keep the roof clean so that there won’t be anything to trip over.

■ Be careful when sawdust is on the roof. Sawdust on a sloped roof can be as slick as ice. To be safe, call out measurements to cutters on the ground and have them clear the board of sawdust before handing it up to you.

■ Never throw anything off a roof, not even a shingle, without first checking to see that no one is down below.

■ In the hot sun, asphalt shingles soften and tear.

Walk gently so you don’t damage the shingles. In hot weather, install shingles early in the morning or late in the afternoon.

■ In bitter cold weather, shingles become brittle and crack. Work carefully, and pray for sunshine.

■ Shinglers who nail off a roof by hand often sit on the roof as they work. In hot weather, try sitting on a piece of foam while nailing shingles. Otherwise, hot shin­gles can literally burn your backside.

Подпись:WORK SAFELY ON A ROOFUnless the trusses were set on the walls at the time of delivery, they must be hoisted onto the walls by hand (see the photo on the facing page). One way to do this is to set good, strong ladders at both corners of the building. If you’re dealing with long trusses, place a 2x in the center, from the ground to the top plate, at the same angle as the ladders. This way, two people can lift a truss, lay it against the ladders and the center 2x, and walk it up to the top. Another person in the middle with a notched pole can push on the truss as needed.

In preparation for installing the first truss (the gable-end truss), I nail a long, straight, tem­porary 2x brace on edge to the wall frame near the center of the end wall. This holds the gable – end truss stable until other braces are installed.

If the truss is not too large, one person on top can drag the truss to the opposite end and lift it up against the temporary brace. Make sure that the eave overhangs are correct and that the out­side of the bottom chord is flush with the outside of the end wall’s top plate. Toenail the bottom chord to the double top plate, driving 16d nails every 16 in.

Подпись: iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii Подпись: GABLE-END TRUSS DETAILSWORK SAFELY ON A ROOF

Подпись: Be aware of wind. Take care with trusses while the wind is blowing. Sheathed trusses can catch the wind like a boat's sail. Even bare trusses can be difficult to control. If it's windy, have extra helpers on hand and use extra bracing to keep installed trusses in place.

Trusses take team­work. A crew of four does a good job of getting roof trusses up on the walls. Us­ing a long push stick, the ground worker helps elevate the truss.

Channel and Shore Protection

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Highways are often located adjacent to streams, lakes, and coastal areas. Channel and shore protection must be provided wherever the need is apparent or the risk is high.

In other circumstances, where the possibility of damage to the roadway or adjacent land is not clear or risk is low, it may be acceptable to delay construction of embank­ment stabilization measures until a problem actually develops.

There are a number of methods of protecting the roadway from damage due to ero­sion. The simplest and surest of these is to locate the highway away from the erosive forces. This should always be considered, although it is rarely the most economical alternative. The most common method used to protect the roadway is to line the road­way embankment with a material that is resistant to erosion such as concrete or rock. Another method is to reduce the force of the water that would cause the erosion. Such bank protection structures retard the flow of the water while at the same time allowing a sedimentation buildup to reverse the trend of erosion and replace material that may have been lost. A final method of protection that should be considered is redirecting the eroding force away from the embankment. This may be done by the use of jetties or baffles, or even by creating a new channel.

Any combination of the above methods may be used to achieve the desired protec­tion. The design of the protective features should be commensurate with the importance of the roadway being protected and with the risks involved. (See Highway Drainage Guidelines, Vol. III, Erosion and Sediment Control, AASHTO; “Design of Riprap Revetment,” HEC 11, FHWA; and “Design of Roadside Channels with Flexible Linings,” HEC 15, FHWA.)

STEP 8 Install and Plumb Door and Window Trimmers

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Many builders—even experienced ones— don’t like to spend time plumbing window and door trimmers. But Lve found that this step really makes a better building. If the door

1. Drive this nail first, then bend it over, embedding the shank and head in the adjacent board. [1]
trimmers are plumb, the doors hinge-side

jamb butts solidly against the trimmer along

its entire length. Thercs no need for shims on

this side of the door. That means vou save

/

time and obtain solid, continuous backing for the jamb that supports the full weight of the door. If the opposite trimmer is also plumb, the shims vou install can share the same thick-

г

ness. There’s no fussing to make shims of dif­ferent sizes. Similarly, window installation benefits from plumb trimmers.

Window trimmers were installed during step 3, when the window assemblies were built on the floor deck. Full-length window trim­mers are firmly attached at the bot:om corners

*

of the rough window opening, but each trim­mer can still be pried away from its king stud to get the trimmer as plumb and straight as possible. Use a straight claw on a framing hammer or a flat bar to pry and a 2-ft. level to test for plumb and straight. When the trim­mer is where vou want it to be, secure it by toenailing through the header with 8d nails. Make sure you toenail from both sides of the wall. To lock a trimmer in straight position, hammer a nail clip into each edge of the trim­mer, as shown in the illustration at left.

It’s best not to install door trimmers until after the walls have been raised and braced. This way, each trimmer can be measured and cut to tit snugly up against the bottom of the header. 1 carrv two straight studs to each opening, hold them in position under the header, and mark them to length. When the trimmer has been cut for a snug lit, secure it to the king stud with a single 16d nail driven near the center. Don’t drive any more nails, because you will need to tap the 2x in or pry it out slightly to get it plumb. Test for plumb with a 6-ft. level. When it is plumb, drive toenails through the header and і г to the

trimmer, then toenail the trimmer to the bottom plate.

Finish by getting the trimmer straight, using nail dips, if necessary. When the sheath­ing is installed, you can lock the trimmers in place by nailing through the sheathing and into the trimmers’ edges.

STEP9 Sheathe the Walls

Hived through the 6.8-magnitude earthquake that hit Northridge, California, in 1992.

Besides nearly scaring me to death, it made me believe in wall sheathing. A 6.8 quake is not even the big one predicted by most seis­mologists, yet a number of people lost their

ives. More lives would have been lost if criti­cal areas in buildings had not been sheathed with plywood or OSH. Serious damage occurred in those buildings, but they didn’t collapse. The buildings that held up best were small, single-story wood-frame houses, such as those built bv Habitat. iVIanv were knocked

‘ 4

several feet from their foundation, but they didn’t collapse on their occupants.

Unlike dryvvall, stucco, and most exterior siding, plywood and OSH wall sheathing pro­vide both lateral (horizontal) and vertical strength. Sheathing helps hold buildings together and makes a house wind proof, which is important if you live in an area where cold winds are a reality.

STEP 8 Install and Plumb Door and Window Trimmers

STEP 8 Install and Plumb Door and Window Trimmers