Tips for Buying and working with wood Slabs
• Check the %MC and Protect your investment. Never buy a “kiln dried” wood slab without proof of the moisture content. If you are buying from us or from someone else always ask for proof of moisture content, if someone refuses, or say they do not have a moisture meter, then do NOT buy it, because they have no way of verifying their claim that it is kiln dried. A moisture meter is a very basic tool that every legitimate seller of kiln dried slabs should possess. Just like lumber, a slab dried to 6-9% moisture in the middle (NOT on the very end or on an edge of the slab) is generally ready to use. A slab with a moisture content in the upper teens or even the 20s is nowhere near dry enough and will warp and crack if you move it indoors. A slab over 30% moisture can still be considered green. Unfortunately there are people out there that are very dishonest and with the latest wood slab furniture craze there are quite a few millworks that claim to be selling thick kiln dried slabs that were cut only a month earlier. Never assume that a “kiln dried” slab is at the proper moisture content. Do not just take their word for it. Buying a wood slab without verifying the moisture content is taking a VERY large gamble with your money. Demand proof or shop somewhere else.
• A wood slab is generally safe to start working with after it reaches 6-10% moisture. However, just like with lumber, you will want to let it acclimate for at least 1 week per inch thickness before you make it into a piece of furniture.
• Always finish every surface of a slab, both top and bottom. Even if a slab is kilned dried properly, and you acclimate it correctly, if you only finish one side the slab, it will continue to lose moisture and shrink faster on the unfinished side while the finished side will be extremely slower. The result will be a slab that cups or cracks. And no, after a slab dries and warps it will never flatten out like it was before.
• You must allow for seasonal movement of a slab wood top. Wood is like a sponge, it will collect moisture on humid days and release it on dry days. A slab over four feet wide might change in width as much as 3/4″ between summer and winter. If you try to constrain the movement with hard fasteners you could crack your slab. If your slab does have a crack in it already, don’t worry, most slabs have them, but you will want to help keeping that crack from getting bigger. A recommend solution is the use of “butterfly” fasteners or other wood joinery system that allows for seasonal wood movement. While it is then not necessary to put butterfly keys in the cracks, they are a great way to highlight cracks as accents instead of defects.