Life Expectancy Depends On Maintenance
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Properly installed and maintained wood siding can last hundreds of years. It seldom does, however, since maintenance is often neglected. As with most sidings, particular attention should be paid to changes in direction or material, and around openings.
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Tight But Loose
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Siding must be tight enough to prevent water penetration and vermin entry, but must be loose enough to dry quickly front and back, after wetting. Good siding has good drying potential.
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Sun Drives Water Into Wood
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Sunlight dries wood, but not the way most people assume. The sun does not simply evaporate the water off the wood surface. It drives the water into the wood, and all the way through if you are lucky. This is why good drying potential (i.e., air movement) on the back of wood siding is important.
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Avoid Vines
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Vines on wood siding will hold water and reduce drying potential. We recommend removal of vines or ivy from wood siding.
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Patterns and Shapes
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Wood siding comes in many different patterns and sizes. Common patterns include the following:
- Bevel (called feather-edge or clapboard in many areas)
- Boards are thicker at bottom than top
- Produces traditional clapboard look
- Common sizes include 1 /2 x 4 to 1 /2 x 6, and 3 /4 x 6 to 1 /4 x 10
- Horizontal only, one inch overlap
- Usually one nail per stud, just above (or just below) the upper edge of board underneath (this is a controversial issue)
- Board and batten
- Vertical planks (boards) with narrower strips (battens) over joint
- Never horizontal
- Common sizes include 1 x 2 to 1 x 12 and 1 1 /4 x 6 to 1 1 /4 x 12
- One nail at every nailing point through boards up to six inches wide, two for eight inches wide and up
- Battens overlap each board by 1 /2 inch, with boards spaced at least 1 /2 inch apart for expansion
- One nail through batten, between boards
- Vertical siding such as this needs horizontal nailing surfaces (1 x 4 strapping) usually placed about every three feet as you move up the wall
- Tongue and groove
- Can be horizontal or vertical
- Common sizes are 1 x 4 and 1 x 10
- For up to six-inch-wide boards, nails are driven in diagonally through the tongue, like hardwood flooring
- For eight-inch boards and up, two face nails are used, three to four inches apart
- Shiplap
- Profile resembles tongue-and-groove boards sawn in half
- Can be horizontal or vertical
- Usually 3 /4 x 4 to 1 x 10
- One nail roughly one inch up from bottom edge at each stud for up to six-inch- wide boards
- Two nails three to four inches apart for boards eight inches wide and up
- Channel and drop (matched)
- Like shiplap, but the notched end of each board that tucks under the other is longer than overlapping end, creating a visible channel
- If the channel is milled to a smooth curve, the profile is referred to as drop siding
- Can be horizontal or vertical
- Common sizes are 3 /4 x 6 to 3 /4 x 10
- Nail-like shiplap
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Note: there are variations to these and there are different names in different areas for the same style.
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Lumber Grades And Species
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There are many different grades and species of woods used in siding. Cedar and redwood are among the best as these species have natural decay-resistant resins. Better grades of lumber with low moisture content and few knots will perform best.
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Narrow, Thick, Rough, Short
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The best performance from wood siding is achieved with boards eight inches wide or less (less shrinkage), thicker boards (less likely to cup and split), rough textured boards (holds finish better) and shorter length lumber (less shrinkage).
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Nails
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Aluminum or stainless steel nails are best for wood. Hot-dipped galvanized nails are better than ordinary electroplate galvanized nails, but even hot-dipped nails will rust and stain the wood over time. Nails may be exposed or concealed, depending on the type of siding.
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Controversy — One Nail or Two?
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Some siding installers use only one nail across the width of the boards up to six inches wide, as we saw earlier. This allows the siding to expand and contract across its grain where movement is greatest, without splitting.
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Two Nails
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Other installers maintain that splitting wood caused by expansion and contraction should not be an issue. They recommend face nailing with two nails at each point, no matter what the board width. The bottom nail, on bevel siding, for example, goes through the top of the underlying board. This provides a good nailing surface. Nailing so that the nail goes above the underlying board may split the top board as it is installed, or the nail is set. Some also maintain that boards are more likely to cup if there is only one nail per point.
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Setting Nails
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Face-nailed siding may leave the nail heads exposed or the nails may be set below the surface of the wood, and the hole filled. Setting and filling may indicate better quality work, but both are acceptable.
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Concealed Nails
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Some siding, usually with narrower boards, has one concealed nail per point. You won’t find any nail heads or filled holes, except at corners and joints. The nails are often round-headed siding nails. The round heads are designed to help promote good drying at the front and back of each board, by keeping the boards slightly apart. The round head holds the overlying board away from the board below.
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Nail To Studs Or Strapping
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Most experts recommend that wood siding be nailed into studs or solid wood strapping (for vertical siding), rather than just into sheathing. Nails need to go into roughly one inch of solid wood. If the sheathing is plywood, nails can go through 1 /2 inch of plywood and 1 /2 inch into a stud. If the sheathing is fiberboard, the nails should go through the fiberboard and one inch into the studs. These rules are often broken, even by installers on new applications.
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Cupping
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Many installers recommend painting or staining the entire boards, front, back and edges, before installing the siding. This helps prevent cupping and prolongs the life of the siding.
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Corners
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There are several corner details that can be used, including –
- vertical corner boards or poles
- metal caps
- mitered joints
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