Wood movement - should I worry?

Re: Wood movement - should I worry?

Dick Coers

What makes you think an 1/8" of movement wouldn't break something? 1/8" is a LOT! The upright will crack if everything is tight and glued up when the wood is at it's widest in the summer. When the house gets dry, about January around here, I'd expect to hear a pop. The center mortise is tight and glued. That makes each half only move 1/16", but still enough to crack. Outer mortises are dry and pinned through a slot in the mortise. Make it from quarter sawn stock if you don't want to go to the effort with the mortise and tenons.

Re: Wood movement - should I worry?

Don Stephan

I can't think of any reason not to allow for potential wood movement, including your project. I was thinking exactly like Dick - a connection just like a breadboard end.

Use a moisture meter if you have one, comparing the wood you are using to wood that has been at your location for some time - if the walnut was just obtained it might have been stored in a drier environment than yours and thus would expand some now.

Re: Wood movement - should I worry?

Brian Holcombe

You'll certainly have issues, so you might modify your plan a bit.

I don't think they have to be full width mortise and tenons, so you can take up some of that with haunches. I would also consider splitting it into 2 and making haunched mortise and tenons for both, then put a gap in the middle to allow some movement.

Why flat sawn? I would definitely use quarter or rift sawn stock, even if it required (almost certainly it would) a glue up.

Re: Wood movement - should I worry?

Ellis Walentine

Here's a table I made about 40 years ago from a walnut tree I cut down on our property. It's almost identical to the table you're proposing, with a wide-panel trestle leg, a foot and a top rail. I did more or less exactly as you propose: essentially a breadboard construction with a continuous tongue in a half inch deep groove, with two (or three, can't recall) full depth mortises with extra end room for wood movement. No signs of any kind of failure or cracking.

It's important in joint design to be aware of the current moisture content of your wood and the approximate range of relative humidity swings you expect it to have in service. This will help you determine which way the wood will move so you can be sure to leave the expansion space in the right places.

Ellis