Optimal Size to Rough Cut for Flooring
Start with a uniform finish thickness, then add allowances for planing, drying shrinkage, and cupping. October 26, 2011
Question
I am currently cutting maple to be used as a 3/4 x 3 1/4 flooring. I am wondering what the optimal cutting thickness should be to allow for shrinkage. Also I am curious if the width should be cut to size before or after drying.
Forum Responses
From contributor M:
Most stock has been cut a little over an inch so that it shrinks to one inch after kiln drying. Cutting into strips will improve yield, but you will lose the ability to rip out a straight piece if it gets sidebent or twisted. You can crosscut the sidebend out but get a much shorter average length in the floor
From Gene Wengert, forum technical advisor:
With the flooring, you want every piece to be 0.75" and not just the average. You must then add a planer allowance, perhaps 3/32", or 0.09", but it might be more. Then add 8% or about 0 .07" for maple shrinkage (more for oak). You could add a few 0.01 for cup. This gives you the minimum thickness. In a good mill, add 0.08" to get the average or target thickness for the sawmill.
From contributor E:
I would start out with " thick wood 4"wide, run it through a kiln first then plane and cut to size and T&G it. Do not cut to width first as when the pieces dry, they will end up different widths.
From contributor H:
Curious as to what kind of equipment and amount of production you wish to accomplish. I should say depending on the equipment you have greatly effects how you will process flooring. I run 3.25” RO clear, select and 2.25” 1Com which both can be ripped from the same size board. 8.75” X 1” is what I saw from a cant and AD for a while before the kiln. All my 3.25” is mainly new construction and 2.25” for remodels and additions to match existing flooring. With any species start with the finished product and work backwards, wider flooring you need to add a little extra width to get a straight as possible piece.
There is nothing like using a four ton frame straighter to install 7.25” white oak that is just a little bowed. Starting from your finished piece, add your allowances for tongue and groove, gang rip blades, and shrinkage. If you do not have a gang-rip or slr for making blanks I would saw 4” to 4.25” boards and make sure you get as much weight on them as possible and condition them. Nothing worse than spending six hours cross-cutting blanks to get semi-straight pieces.
