Part of this process is verifying the acclimation of wood flooring before installing it. The basic process for acclimating wood flooring prior to installation includes:. Even if the wood gains or loses enough moisture to slightly change shape prior to installation, once it reaches EMC, it should stabilize and be fixable.
However, exercise caution when attempting to sand down swollen wood planks—if the humidity conditions change later, it could cause the flooring to become slightly concave where it was sanded down. By making sure the wood is at its EMC value prior to installation, many flooring failures besides warped wood can be prevented.
One of the most common reasons for flooring failures after installation is the presence of excess water in the structure. Moisture intrusion can ruin wood that was at its perfect equilibrium moisture content previously.
In new construction, issues such as burst pipes are rare, but one easily-overlooked culprit is excess moisture in concrete. Newly-poured concrete may have excessive amounts of moisture.
The best way to do this is to use the ASTM F concrete testing method , which uses a thermo-hygrometer with in-situ probes to check the moisture conditions deep in a concrete slab. Why not use a moisture meter? This should give you an idea of how much moisture is deep in the concrete slab, and whether that moisture poses a risk to any wood building materials being installed over the slab. Curious about how to check for moisture in a structure?
Try to locate the wood on a flat dry surface which will not wick moisture. Wood grain — The most difficult is to control where a board is cut from a log. There are three main ways of cutting boards.
Flat-sawn, quarter-sawn, and rift-sawn. I have created a diagram showing how each would be accomplished. Rift-sawn is the most stable but also the most wasteful. It follows the grain of the log always producing boards that are perpendicular to growth rings.
Flat-sawn is the least wasteful but but the most unstable. Lumber is cut flat completely ignoring grain. Despite the instability, flat-sawn in the most common technique. The compromise between the two is quarter-sawn. It gets closer to the grain orientation making it more stable and also is much less wasteful.
Commercial Option: Drying — Wood that is kiln dried will be more stable because the manufactures have much more control over how fast the drying process takes. Surprisingly kiln drying is done more to prevent bug damage. It also allows for more resinous wood to set and become more stable. Even after drying the wood will need to acclimate to whatever environment it ends up in. Wood that quickly regains moisture is much more likely to warp.
How to fix warping While it is not easy, it is possible to fix warped wood. Basic — Spray down the lumber and let the wood absorb the water.
Once it has done so, clamp the board into position and allow to dry. The warp should now be much less pronounced. Ironing — Take a wet towel or paper towel. Place it on the position of the warp. This may be a large area so I would do it in sections. Leave a hot iron on the wet towel allowing the board to steam. This will speed up the moisture uptake and relax the wood fibers quicker. Clamp the board in place and allow to dry.
Repeat as necessary. Different warping shown in the same piece of wood could be a sign of multiple problems related to moisture content. Some species of wood are more stable and less likely to warp or crack than others. The following species are known to be relatively resistant to warping:. Department of Agriculture.
Several factors affect wood warping, some of which are easier to control than others. Different types of warping also tend to be caused by different factors. So being able to link warp types found to particular causes helps in preventing future warping.
Grain patterns can influence the way wood behaves as it adjusts moisture content. Sawing techniques used in processing the lumber can also influence warping. An understanding of these can help you limit your risk of manufacturing warped wood products. For example, in a quarter-sawn board where growth rings are symmetrical, shrinkage will occur evenly and cup-type warping is far less likely. Poor saw maintenance and variation in saw speed can result in boards that are thinner on the ends than in the middle, which can cause bow-type warping.
Sawing so the grain is parallel to the edge of the board can help prevent crooking. The way you stack and store lumber is a major factor for how it will change as it adjusts to EMC. Some best practices for stacking and storage of wood include:. Placing heavy weights on a stacked lumber pile can also be helpful in preventing cupping. The wood also needs proper ventilation, which is best accomplished by spacing the material so all surfaces are exposed to the air.
Store your lumber in a clean, cool, shaded and dry location. If you're storing wood in an area with high relative humidity—80 percent or more—be sure it's wrapped in material that is impermeable to vapor. Of course, moving from dry to damp will cause the board to swell and cup on the heart side. This warping will occur even if the wood is finished on all sides. It will just be slowed a little as the moisture takes longer to get through the finish.
Compression shrinkage The least understood of the three causes of warping is compression shrinkage. This is a phenomenon that occurs usually on the tops of flat surfaces such as tables, decks, cedar shakes, floorboards and cutting boards.
Compression shrinkage explains how screws work loose in wood, and wooden handles become loose in hammers and hatchets. It also explains splits in the ends of boards and checks in the middle of boards in addition to warping. When water enters wood, the cellulose cell walls swell. Each time the handle or the one side is wetted and dries out, it shrinks a little more. Repeated wetting and drying eventually leads to the handle working loose or the one side cupping, and if the cycle continues long enough, the wood splits and checks.
Tabletops come in contact with water when being wiped down with a damp cloth after meals. Decks and shakes are exposed to water on the topside every time it rains. Floorboards are exposed to water when damp-mopped. Cutting boards are wetted during meal preparation and cleanup. Where did it start?
The first mention I was able to find was in the third issue summer of Fine Woodworking magazine page 6. Even here, the instruction was only glancing.
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