# Notch joints



## phinbar (Apr 5, 2010)

I am making a sofa using oak that has 6 inch wide, 1 inch thick rails that attach to 2 inch thick posts using notch joints.

Mortise and tenon joints would work, but I like the look of these. 

Won't the 6 inch wide rails expand too much inside the notches?

Here's a link to the sofa that I am basing it on:

http://www.dwr.com/product/living/view-all/frank-lloyd-wright-sofa.do

Thanks


----------



## rrich (Jun 24, 2009)

As a very general rule of thumb...

Starting as 8% moisture content, 12" of wood will expand or contract maybe 1/4" up or down between 3% and 12%. (Oak shrinks 10% from 75%MC to 0%MC.)

So you have 6", and should plan for 1/8" of total wood movement. If you secure the center of the 6" rail, you will have 1/16" wood movement on each side of the rail.

If you use quarter sawn, as FLW probably did, the shrinkage would be about half that. At equilibrium, if you allow for 1/32" on each side of your notch joint, you should be OK. It probably wouldn't be a bad idea to use a loose tenon on the under side of the notch going between leg and rail. Done properly the tenon would be invisible and add significant strength to the joint.

There are some copies of "Wood As An Engineering Material" published by USDA on the web. It is probably the best 65MB you'll ever down load. The information contained there in is more than you'll likely need.

BTW - If you draw plans for that sofa, I would love to see a copy. That sofa is something that I would like to build also.


----------



## cabinetman (Jul 5, 2007)

*WELCOME TO THE FORUM*

That piece/size, may or may not have any movement issues. It might depend on the species, moisture content, temperature, and finish.

Many times after acclimating the lumber, and fabricating the furniture, the wood resides in a fairly controlled environment. Without a lot of swings in temperature and exposure to moisture changes, the movement issue lessens.

You could take steps to minimize the possibility by edge gluing 2 pieces 3" each. Or, even 3 pieces 2" each. Doing that you may decide to even introduce a different species in the middle section to create a different look than the subject piece. Not everything we do has to be an exact copy.


----------



## phinbar (Apr 5, 2010)

This is all good advice which is what I hoped to find here. Thanks for taking the time to reply.

It sounds like I do need to be concerned about the wood expanding in the joint, so I think I'll just use mortise and tenons instead.

What I borrowed from FLW were the cantilevered front and the notch joints. The rest was inspired by a Harvey Ellis design.

Here are my plans:


----------

