Category RENOVATION 3

Once limited to building paper, underlayment now includes self-adhering rubberized sheets that replace metal flashing in some cases. Thus you can base your choice of underlayment on climate, composition, and position on the roof.

Weather-resistant underlayment. Traditionally, underlayment has been 36-in.-wide, 15-lb. or 30-lb. felt paper used as a weather-resistant layer with several purposes. It keeps sheathing dry till shingles are installed, serves as a backup layer when water gets under shingles or flashing, and separates sheathing and shingles and so prolongs shingle life. (Without underlayment, shingle asphalt can leech into wood sheathing, or resins in sheathing can degrade the shingle.) Heavy – duty, 30-lb. felt paper is often specified in high – wear, high-water areas such as eaves and valleys. A standard roll of 3-ft.-wide, 15-lb. felt paper covers roughly 400 sq. ft.; the same-size roll of 3-ft.-wide, 30-lb. paper covers only 200 sq. ft. because it’s roughly twice as thick.

Because unreinforced lighter grades of build­ing paper (15 lb.) tear easily and wrinkle when wet, some types are now reinforced with fiber­glass. Moreover, all asphalt-impregnated building papers dry out and become less water resistant when exposed to sunlight, so the sooner they’re covered by shingles, the better. Building paper was never intended to be an exterior membrane.

When installing building paper on a sloped roof, have a helper and work from the bottom up. As you roll the paper out, it will tend to slide down the roof, so be sure to unroll it straight across the roof. The first course of paper should overlap a metal drip-edge nailed along the eaves. Align the paper’s lower edge to the lower metal edge and unroll the paper, stapling as you go. Staples are only a temporary attacher, to help you keep the paper from bunching or sliding. Then nail the underlayment, using the tabbed roofing nails (also called Simplex® nails) shown on p. 57. Along roof edges and where the ends of the build­ing paper overlap, space nails every 6 in., inset­ting them 1 in. from the edge. Elsewhere, drive nails in a zigzag pattern, spacing them 12 in. to 15 in. apart.

For steep-slope roofs (4-in-12 or steeper), overlap horizontal courses of building paper 2 in.

Overlap ends of seams (end laps) at least 6 in. To prevent water backup on low-slope roofs (less than 4-in-12), building codes often specify two plies of 36-in.-wide underlayment, with horizontal seams overlapped at least 19 in. and (vertical) end seams overlapped 12 in. Check your local code to be sure, for it may also specify self – sticking waterproof shingle underlayment along the eaves.

If you’re installing wood shakes or slate, use shake liner: 18-in.-wide rolls of 30-lb. building paper alternated between roofing courses.

Waterproof shingle underlayment (WSU).

WSU is a heavy peel-and-stick bituminous mem­brane that protects roof areas most likely to leak because of concentrated water flows in valleys, ice dams at eaves, or high winds at eaves and rake edges. Many building codes also specify WSU in lieu of building paper where asphalt shingles are installed on low-slope roofs. In addition to being self-adhering, WSU also self-seals around nails, making it a truly waterproof membrane.

Installing WSU along valleys is vastly easier and superior to lining them with unwieldy roll roofing or aluminum flashing. And with WSU,

there’s no need to trowel on 3-ft.-wide swaths of roofing cement between 30-lb. building-paper layers to protect eaves from ice-dam damage. Snap a chalkline to position the WSU. Then unroll and cut the membrane to length, align it to the chalkline, peel off its release-sheet backing, and press the material down. Most manufactur­ers recommend rolling it once it’s down.

WSU is more easily installed with two people, but if you’re working alone, fold the WSU in half, lengthwise, and temporarily staple one edge of the membrane to a chalked guideline. Peel off the release-backing from the unstapled half of the WSU, and flop the adhesive side of the mem­brane over onto the sheathing. Finally, yank free the stapled edge, peel off the backing from the second half, and stick it to the sheathing.

Because WSU is self-adhering, you needn’t nail it; you need to use staples only to keep the sheet from sliding around before sticking it down.

WSU comes in 9-in. to 36-in. widths. Brand names suggest usage, for example, CertainTeed Winterguard™, W. R. Grace Ice & Water Shield™, and GAF Weatherwatch™.

Roof stripping is one of the nastiest, dirtiest, most dangerous jobs in renovation. If you can afford it, hire an insured contractor for this. Most roofing contractors know of tear-off crews that will obtain permits, rip off the old roof, and cart away the debris, or you might be able to sub­contract the job through a roofer. Professional stripping takes at most a couple of days, and it’s money well spent to allow the start of new work.

If you must strip the roof yourself, remove all drain gutters and then minimize the mess by buying a heavy 6-mil plastic tarp to catch shin­gles and old roofing nails. So you won’t be pick­ing shingle shards and nails from the lawn for years to come, lay tarps from the house to the Dumpster as well. To protect plants around the house, place sawhorses or 2×4 frames over them and cover with bed sheets or cloth drop cloths. Caution: Don’t cover plants with plastic or they’ll bake. Finally, lean plywood in front of win­dows so falling objects don’t break them. When the job is done, rent a magnetic roller (also called a magnetic nail broom) and roll the lawn to locate roof­ing nails—before your lawn mower does it for you.

And don’t forget the inside of the attic. Spread plastic tarps over attic floors, especially if there’s insulation between the joists. During tearoff, an immense amount of debris and fine dust falls into an attic.

Unless you catch it in plastic and remove it, you could breathe it or smell asphalt – shingle residue for years.

Other than that, stripping is mostly grunt work. Most strip­
pers use a specially designed tear-off shovel, starting at the top and working down, scooping shingles as they go. Tear-off shovel blades have a serrated edge that slides under nail heads and a fulcrum underneath that pops nails up. Be sure to tear off all old building paper (felt or rosin paper), too.

SHEATHING

Once you’ve stripped off roofing, survey the sheathing for damage and protruding nails. As you pound down nails, be sure to place your feet directly over rafters. Probe suspect sheathing and replace any that’s soft. Cut bad sections back to the nearest rafter centers. For this, wear safety glasses and use a circular saw with a carbide – tipped, nail-cutting blade because the blade will hit a lot of nails. Replacement pieces of sheathing should be the same thickness as the original.

If the old roof was wood-shingled, it probably had skip-sheathing, which is 1 x4s spaced 5 in. on center. Skip-sheathing allows air to circulate under the shingles. If the boards are in good shape, you can nail on new wood shingles after stripping old ones. But many contractors prefer to sheathe over the 1 x4s with J2-in. exterior-grade plywood (for rafters spaced 16 in. on center) or 58-in. plywood (for rafters 24 in. on center). This stiffens the roof and makes it safer to work on, but plywood virtually eliminates air flow under shingles. Consequently, some builders install a synthetic mesh, CedarBreather®, over plywood to increase circulation, before nailing on wood shingles.

Run plywood lengths perpendicular to rafters, centering plywood edges over rafter centers. Nail every 6 in. with 8d galvanized nails. Elsewhere, use H-clips to support panel joints and create Иб-in. expansion gaps. Sweep the roof well and hammer down nail pop-ups.

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

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

WHEN IT’S TIME TO TEAR OFF

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

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

Roof Longevity

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

The roof already has two roofing layers. Two

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

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

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

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

defects, inadequate ventilation, faulty installa­tion, or a combination of those factors. A layer of new shingles won’t lie flat over curling ones. So if shingles are curling—even if there is only a single layer of roofing—tear them off.

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

► Stay off the roof unless you have a compelling reason to be on it. Besides being hazardous to you, walking on a roof can damage roofing materials.

► If you must work on a roof, have a second person within earshot in case you fall or need occasional help.

► Don’t venture up when the roof is wet or near freezing or extremely warm. When wet, most roofing materials are slippery. Cold asphalt shingles are brittle; warm asphalt can stretch and tear. Always wear shoes with soft nonslip soles.

► Position ladder feet securely away from the building about one-quarter of the ladder’s extended length. Never lean sideways from a ladder. If you can’t reach something while keeping your hips within ladder sides, move the ladder.

► When installing a roof, use scaffolding with a safety rail. The most dangerous part of a roofing job—apart from tearing off shingles and underlayment—is applying the first few courses along eaves.

► When walking on a roof, try to "walk on nails." In other words, try to walk directly over the rafters, where the sheathing is nailed. The roof will be less springy over rafters, and you’ll be less likely to break through rotten sheathing.

► Follow the manufacturer’s installation instructions, which often provide time – and money-saving tips. Also, if a material fails after correct installation, manufacturers are more likely to honor their warranties.

EQUIPMENT

Unless you are installing roofing systems that need to be “torched” (heat-sealed with a propane torch) you won’t need a lot of specialized equip­ment or tools. Most of the items discussed here are safety related.

Pneumatic nailers have gauge stops on their bases that you can adjust to the correct shingle exposure. For example, when the gauge stop is snug to the butt of a shingle, the next shingle above, placed on the nose of the tool will be correctly positioned to nail.

Footwear should be sneakers or other soft-soled shoes that grip well on a roof. Old-time roofers prefer boots with thick soles that are less likely to be punctured by stray nails, but such boots are inflexible and don’t grip as well.

Scaffolding can make applying the first few courses along the eaves far safer. After the lower courses are installed, the scaffolding serves main­ly as a staging area for materials and tools.

Roofing jacks enable you to work safely on roofs with a 6-in-12 pitch or steeper. Several dif­ferent roof pitches are shown in “Gutter Lip and Roof Pitch,” on p. 149. Jacks are also indispensa­ble platforms for storing materials. As you work up a roof, install additional pairs of jacks when­ever you must stretch to nail the next course. As shown in the photo on p.65, many roofers leave jacks installed till the job is completed.

Full-body harnesses, also known as personal fall-arrest systems (PFAS), may be required by local building authorities if a roof exceeds a cer­tain pitch or if the eaves are more than a speci­fied height above the ground. If harnesses are required, have someone at the rental company demonstrate correct use.

Kneepads, sturdy ones with integral plastic cups, will spare you a lot of pain. In addition, a Malco Shingle Pad®, an insulated foam pad you can sit or kneel on while shingling, protects shin­gles from abrasion and has a little lip to keep tools from sliding south.

A pneumatic nailer, which you can rent, speeds the job along. Have the rental company recom­mend nails and explain the nailer’s correct use.

Shingling hatchets in the hands of a pro can fasten shingles almost as fast as a pneumatic nailer.

Miscellaneous tools include a utility knife with hooked blades, a straightedge or framing square, a hammer, a chalkline, a tape measure, caulk guns, work gloves, safety glasses, and hearing protection.

A roof is a building’s most important layer of defense against water, wind, and sun. Properly constructed and maintained, a roof deflects rain and snowmelt, and routes them away from other house surfaces. Historically, roof materials have included straw, clay tile, wood, and slate. Although many of these materials are still used, most roofs installed today are asphalt-based composites.

If roofs consisted simply of two sloping planes, covering them would be easy. But today’s roofs have protruding vent pipes, chimneys, sky­lights, dormers, and the like—all potentially water dams and channels that need to be flashed to guide water around them. Then as runoff approaches the lower reaches of the roof, it must be directed away from the building by means of overhangs, drip-edges, and—finally—gutters and downspouts.

This chapter assumes that the house founda­tion and framing are stable. Because structural shifting or settling can cause roofing materials to separate and leak, you should fix structural prob­lems before repairing or replacing a roof.

Roof Safety and Equipment

Among the building trades, roofing is considered the most dangerous—not because its tasks are inherently hazardous—but because they take place high above the ground. The steeper the roof pitch, the greater the risk. If heights make you uneasy or if you’re not particularly agile, hire a licensed contractor.

Although these wood shingles seem randomly placed, the installer is taking great pains to offset the shingle joints between courses and to maintain a minimum exposure of 5 in. so the roof would be durable as well as distinctive.

Wood construction connectors are commonly called Simpson™ Strong-Ties™ after the company that popularized them. For a complete overview of available connectors from Simpson, go to www. strongtie. com. Professionals swear by these ingenious connectors for three main reasons.

►They offer wood-to-wood connections superior to most traditional construction methods. For example, unlike toenailing, metal connectors are unlikely to split lumber ends or loosen under stress. These galvanized steel connectors are strong and durable.

►They greatly strengthen joints against earthquakes, high winds, and other racking forces. They can tie rafters to walls, walls to floor platforms, and the substructure to its foundation.

►Most can be attached to existing framing, a great boon to renovators, and in many cases steel connectors are the only cost-effective way to bolster the existing structure and tie additions to the original structure.

Joist hangers are indispensable in renovation when you want to add joists but can’t end-nail, either because access is limited or because you’re using engineered lumber, which is too thin in cross section to end-nail successfully. (Sawn-lumber joists and I-joists require different hangers.) There are joist-hangers for single joists, double joists, 4×10 beams, joists intersecting at a 45° angle, and so on. You also have the choice of face-mount or top-flange hangers. Top flanges are popular because they effortlessly align the tops of I-joists with the top of a header or beam.

Strap ties come in myriad shapes—tees, right angles, twists—but all help keep joints from pulling apart. Install flat strap ties where wall

plates are discontinuous or where rafter pairs meet at the ridge. Strap ties also keep floor plat­forms from separating, much as shear walling does. Hurricane ties, or twist straps, have a 90° twist to join rafters to top plates, thereby fighting the tendency of roofs to lift during a strong cross­wind. T-straps and L-straps are face-nailed to members joining in a right angle.

Clips vary by function. H-clips are an alternative to solid blocking when installing roof sheathing. They also act as JL-in. spacers so roof sheathing can expand. Drywallclips allow you to eliminate some blocking in corners, but it’s best to use these clips sparingly; solid blocking is much stronger. Deck clips are nailed to deck joists, and then 2×4 decking is driven onto the sharpened

ing gun). You then simply cut the cartridge noz­zle to the desired diameter and squeeze the long pistol-grip trigger to lay down beads of the stuff.

CONSTRUCTION ADHESIVES

Construction adhesives bond to a remarkable variety of materials, including standard lumber, treated lumber, plywood and OSB panels, dry – wall, wall paneling, rigid insulation, concrete and masonry, tile, metal, and glass.

Construction adhesives are a boon to builders. Instead of nailing sheathing every 6 in. around panel edges and every 10 in. "in the field,” build­ers using adhesives need nail only every 12 in. Being flexible, adhesives fill surface irregularities and double as sealants. Structurally, panels bond­ed with adhesive are stiffer and capable of bearing greater loads than panels that are only nailed. Floor sheathing and stair treads so bonded are far less likely to flex, pop nails, or squeak. Drywall ceilings bonded with adhesives do a better job of deadening sound and cutting air infiltration.

A number of considerations should determine your choice of adhesives: the materials being joined, strength, durability, flexibility, shrinkage, conditions on the work site (especially tempera­ture and humidity), workability, curing time, ease of cleanup, and odor.

Most solvent-based adhesives create water­proof bonds and clean up with mineral spirits. Most water-based adhesives create water-resist­ant bonds and clean up with water. Because sol­vent-based adhesives often have strong odors that are problematic for people with chemical sensi­
tivities, there’s a growing selection of solvent – and odor-free adhesives—and whole lines of environment-friendly adhesives.

Fortunately, you don’t need to be a chemist to find a suitable adhesive. Many manufacturers now offer on-line interactive product selectors on their Web sites, such as the Titebond™ company (www. titebond. com). Choose the adhesive fea­tures you want, and the on-line selector will choose the most appropriate product. Once you pick an adhesive, download product specs and study them: particularly application, curing times, cleanup, and safety advice.

A POTPOURRI OF ADHESIVES

Here’s a primer on common adhesives you may encounter.

Polyurethanes are often touted as all-purpose waterproof adhesives, capable of bonding wood, stone, metal, ceramics, Corian®, and so on. Strong, versatile, and easy to use, polyurethanes are favorites with builders and woodworkers. Since they require some moisture to set up, it’s possible to glue up wet wood with polyurethanes. In fact, you should moisten extremely dry wood joints before application.

Acrylics are good for outdoor use. They’re quick drying, strong, and completely waterproof.

Epoxy resins are famous for their strength. Typically mixed from two components, epoxies can bond to materials on which almost nothing else will—that is, when the surface areas to be bonded are small or when dampness is extreme. Epoxy products are especially important in foun­dation repairs and seismic strengthening (for more information, see Chapter 10).

Resorcinol is a strong, waterproof glue used by boatbuilders, among others. Like epoxy, it is a two-part glue that is very difficult to remove once it has set. Wood parts fastened with resorcinol will probably shear before the glue itself does.

Styrene-butadiene is a good all-purpose exterior and interior glue for joining materials of low porosity, such as tile and masonry.

Contact cement is commonly used to bond veneers and laminates to a base material, often particleboard. Once the sheets come in contact with each other, separation or realignment is all but impossible.

Hot-melt glues are applied with an electric glue gun and are excellent for tacking surfaces quickly. However, strength and water resistance are only so-so, because hot glues are applied only as spots. Still, they’re great for building templates out of thin plywood strips (see Chapter 13).

SEALANTS AND CAULKS

As noted in "Sticky Names,” above, sealants and caulks do pretty much the same thing: fill gaps, keep moisture at bay, and reduce air infiltration. Sealants tend to last longer, perform better, and cost more. In this brief section, we’ll look at the strengths and weaknesses of three major types of caulk.

Although caulks aren’t quite so diverse as con­struction adhesives, they do have varying formu­lations and properties. For specifics, go on-line or visit your lumberyard.

Silicones are arguably the most durable and most water resistant of any caulk. They are espe­cially suitable for window glazing and slick bath­room and kitchen surfaces.

► Advantages: Silicones are incredibly tenacious on nonporous materials like glass, glazed ceramic tiles, and metal. There’s little shrinkage, and they can be applied at -40°F. Silicone sealants specified for metal flue pipe function at 500°F. And silicones have the best long-term flexibility, UV resistance, and weather – ability. Also, molds won’t grow on them.

► Disadvantages: Silicones are messy to work with; wear rubber gloves to protect your skin. Once silicones have cured, it’s almost impossible to remove them. Plus, they are bond breakers—that is, because nothing will stick to an area they’ve tainted, think twice about trying them on wood, concrete, or other porous sur­faces they don’t adhere well to. Avoid inhaling acetoxy silicones, and don’t use them on metal because they’ll corrode it. Pure silicones can’t be painted, although siliconized acrylics can.

Polyurethanes are versatile multipurpose caulks but are not as tenacious as silicones.

► Advantages: Because they attach equally well to wood, masonry, and metal, they’re good for caulking joints where dissimilar

materials meet. Polyurethanes won’t corrode metal. They’re easy to work, though polys get pretty stiff as temperatures approach freezing. Shrinkage is negligible. They’re great for sky­light flashing and metal roofs. And they can be painted. Also, they’re easier to work than sili­cones, even though solvent based.

► Disadvantages: Polyurethanes have poor UV resistance, though additives or painting can improve that dramatically. While they are a good all-purpose caulk, they don’t have the durability or shelf life of silicones.

Latex acrylics are a good balance of perform­ance, price, and workability.

► Advantages: Latex acrylics are water based, hence nontoxic, largely odor free, and
very easy to apply (you can shape caulk joints with your finger). They clean up with soap and water. They adhere well to a range of materials, have good UV resistance, and can be painted. Durable once cured, they are best used in protected areas in temperate climates. They are paintable.

► Disadvantages: Expect significant shrinkage (up to 30 percent) and long curing times. Although good as bedding caulk under door or window casing, they’re iffy as exterior caulk or shower and tub caulk. Properties vary widely from product to product. Although some manufacturers tout spectacular per­formance specs, check out on-line contractor chat groups for real-life performance ratings.

30-lb. Live Load 10-lb. Dead Load L/360

If wood is the universal building stock, metal is the universal connector. Nails of many types as well as screws and bolts are discussed in this sec­tion. Specialty plates that reinforce structural members are also described. Later in this chapter is a review of construction adhesives, which, some say, are destined to supplant metal connectors.

NAILS

As they’re driven in, nail points wedge apart wood fibers. The ensuing pressure of the fibers on the nail shank creates friction, which holds the joint together. Nails also transmit shear loads between the building elements they join. Where nails join major structural elements, such as

Nail Sizes

rafters and wall plates, the loads can be tremen­dous; where nails attach finish elements, such as trim, loads are usually negligible.

There are hundreds of different nails, which vary in length, head size, shank shape, point, composition, and purpose.

Length. Length is reckoned in penny sizes, abbreviated as d. The larger the nail, the greater the penny rating. Nails 20d or longer are called spikes.

Heads. The shape of a nail’s head depends on whether that nail will be exposed or concealed and what type of material it’s designed to hold down. Smaller heads—such as those on casing, finish, and some kinds of flooring nails—can eas­ily be sunk below the wood surface. Large heads, like those used to secure roofing paper or asphalt shingles, are needed to resist pull-through.

Shanks. Nail shanks are usually straight, and patterned shanks usually have greater holding strength than smooth ones. For example, spiral flooring nails (with screw shanks) resist popping, as do ring-shank nails. (By the way, it takes more force to drive spiral nails.) Spiral and ring-shank nails are well suited to decks and siding because changes in wood moisture can reduce the friction between wood fibers and straight shanks.

Points. Nails usually have a tapered four-sided point, but there are a few variations. For exam­ple, blunt-point nails are less likely to split wood than pointed nails because the blunt points crush the wood fibers in their path rather than wedging
them apart. You can fashion your own blunt points by hammering down a nail point.

However, the blunt point reduces the withdrawal friction on the nail shank.

Composition. Most nails are fashioned from medium-grade steel (often called mild steel). Nail composition may vary, according to the following situations:

► Material nailed into. Masonry nails are case hardened. That’s also true of the special nails supplied with joist hangers and other metal connectors. Do not use regular nails to attach metal connectors.

► Presence of other metals. Some metals corrode in contact with others because of galvanic action (see "Galvanic Action," on

p. 70). So try to match nail composition to the metals present. The choice of nails includes

Whenever you need to avoid bending nails in dense wood like southern pine and when you’re worried about splitting a joist because you’re nailing too close to the end, simply predrill a pilot hole. There’s no absolute rule to sizing pilot holes: 50 percent to 75 percent of the nail shank diameter is usually about right, letting the friction between nail and wood provide adequate grip.

aluminum, stainless steel, brass, copper, monel metal, and galvanized (zinc coated).

► Exposure to weather and corrosion. Neither stainless-steel nor aluminum nails will stain wood. However, stainless is very expensive, and aluminum is brittle and somewhat tricky to nail. Galvanized nails, which are reasonably priced, will stain only a modest amount where the hammer chips the coating off the head. Therefore, you should seal galvanized nails as soon as possible with primer. Galvanized nails are also specified when framing with redwood
or treated lumber, both of which will corrode common nails. If you’re installing costly redwood or cedar siding, use stainless steel, especially if you’ll be sealing walls with a clear finish.

► Holding power. Nails that are rosin coated, cement coated, or hot-dipped galva­nized hold better than uncoated nails. Vinyl – coated nails both lubricate the nail shaft as you drive it in (friction melts the polymer coating) and acts as adhesive once the nail’s in place.

Sizing nails. Common sense dictates the size of most nails. Generally, length should be about three times the thickness of the piece being nailed down. For sheathing J2 in. to M in. thick, use 8d nails (which are 2J2 in. long). Use 6d nails if the sheathing is ъ/ in. thick or less. Nail points should not protrude through the second piece.

The workhorse of framing is the 16d common, although 12d or 10d nails are good bets if you need to toenail one member to another. Use 10d or 12d nails to laminate lumber, say, as top plates, double joists, and headers.

When nailing near the edge or the end of a piece, avoid splits by using the right size nail, staggering nails, not nailing too close to the edge, blunting nail heads, or drilling pilot holes. Box nails, which have smaller-diameter shanks than common nails, are less likely to split framing dur­ing toenailing.

Pneumatic framing nails. When you’ve got a lot of nailing to do, say, to sheathe an addition, you may want to rent a pneumatic nailer. As noted earlier, it’s best to set nailer pressures so that nail heads stop just shy of a panel’s face ply. Then use a framing hammer to drive each nail flush. Most pneumatic framing nails are vinyl coated to make them hold well. And some pneumatic nail heads are colored, so you know immediately which size you’re loading.

Pneumatic nails differ slightly from common nails, however, so you may want to check your local building code before you rent a nailer. For example, pneumatic nailers load either coils of nails (coil nailers) or nails aligned in diagonal strips (stick nailers). Both work well, but some stick nailers accept only nails whose heads have been partially clipped. (Clipped-head nails pack more tightly.) Clipped-head nails are rarely a problem when nailing 2x lumber together, but plywood secured by the smaller nail heads is more likely to pull through under stress.

Second, pneumatic nail shanks are often thin­ner than those of common nails. In fact, some pneumatic 16d nail shanks are roughly the same thickness as 8d common nails used for nailing by hand.

SCREWS

Screws have revolutionized building. Thanks to a flood of specialized screws, builders can now quickly attach, detach, adjust, and reattach almost any building material imaginable. This is especially important in renovation, when you are scribing cabinets or setting door casing to walls that aren’t plumb—jobs that require patience and test positionings.

Heads. The increased use of cordless screw guns has made slotted screws almost obsolete. That’s because screws with traditional slot-drive heads let the driver blade slip out of the slot when torque is applied, but drive heads with centered patterns completely surround the point of the driver tip, holding it in place. Among the most popular drive heads are Phillips, square-drive, and six-pointed Torx®.

These days, screws are often engineered to specific uses. Trim-head screws have small heads like casing nails so they can be countersunk easily. Drawer-front screws have integral wash­ers so they won’t pull though. Deck-head screws are designed to minimize “mushrooming” of material around the screw hole. Some structural screws have washer heads with beveled under­sides so the screws will self-center in predrilled hinges or connector plates.

Threads. Screw threads are engineered for the materials they join. Traditionally, screws for join­ing softwoods are made of relatively soft metal with threads that are steep pitched and relatively wide in relation to the screw shaft. Screw threads for hardwoods and metal tend to be low pitched and finer. (The steeper the thread pitch, the more torque needed to drive the screw.) If you’re screwing into dense particleboard or MDF, predrill and then use Confirmat® screws, which have thick shanks and wide, low-pitched threads.

Many screws now feature self-tapping tips, in which a slotted screw tip drills its own pilot hole. Another ingenious design is a W-cut thread in which the threads nearest the tip are serrated like tiny saw points, so they cut through wood fiber as they advance. Such self-tapping features make it easy to drive in screws, without compromising holding power.

There are even screws that cut into concrete. Granted, you need to use a hammer drill to predrill an exact pilot hole, but once the pilot is drilled, you can use a 12-volt or 18-volt cordless screw gun, a standard!2-in. screw gun, or an impact screw gun to drive the screw the rest of the way. The threads grab the concrete and hold fast; the trick is not overtightening and breaking screws. Coatings. Coatings matter most on screws used outdoors or in high-humidity areas. Although
galvanized screws do resist rusting and are rela­tively inexpensive, don’t expect them to last much more than 8 years to 10 years on a deck—fewer years if used near saltwater. GRK Fasteners® promises “25 years in most applications” for its Climatek® coated screws. Makers of epoxy-, polymer-, and ceramic-clad screws offer varying life spans. The king of exterior screws is stainless steel—expensive, by far the most corrosion resist­ant, and the only suitable screw to prevent stains after attaching cedar or redwood.