Tuesday, April 3, 2012

More about wood movement

This post is an attempt to further explain wood movement and how it relates to furniture building.

While I'm not an expert by any means, I do know some basics of wood movement.

Most of you will have seen, or have in your own homes, cupboard doors, or even interior doors that are made of solid wood.  In many cases, these doors will have a panel in the middle of a frame.  Have you ever wondered why and how it is built?

In most cases, if the the middle part (the panel) is solid wood it is not firmly attached to the outer frame, it's known as floating.  This enables the wood to expand and contract with changes in household humidity. The frame, made with stiles and rails, has grooves in it that the panel sits inside without being glued in.

When the humidity changes (and it will unless you have a precise heating/cooling/humidifier system in your house that can keep the humidity constant no matter what the conditions are outside) the panel will move inside the frame and the door will not crack.

Perhaps you have, or have seen an antique with a cracked door or drawer bottom?  This is usually caused by wood that is expanding and contracting, and is trapped between other pieces of wood.

Now, if the panel is plywood, then you will not have any changes in size and it can be glued in the frame without worries.

One of my readers asked if table tops was one of the biggest issues in wood movement.  It is one of them, but any where that wood is trapped and cannot expand and contract, it will be a problem.  This could occur in the bottom of a drawer, which is often why plywood is used there. It could occur on a headboard, the sides of a bedside table, the back of a cupboard, anywhere really where wood is trapped.

This reader also asked about making the kerf cut in the table apron to hold tabletop clamps that allow the wood to expand and contract. (You can see what she was referring to in my last post here.)

from Lee Valley
I use a tablesaw to make the kerf, but you could also use a router, or a circular saw set to the proper depth.

There are other methods of attaching table tops and this article from Fine Woodworking (an excellent magazine) explains them quite well.

I hope this helps a bit, and I will write more soon.  I was also asked about pocket screws and will write about  that sometime.





4 comments:

  1. Just want to say thanks for these articles about wood movement. I had no idea, and this will improve my building designs for sure.

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  2. Thanks so much for answering my questions! I appreciate it! It will help in my future builds!

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  3. Hi there! I couldn't find your email so I figured I would just post my question on here. I am planning to build this table - http://www.shanty-2-chic.com/2013/09/diy-dining-table.html - and was wondering a few things. Would adding brackets to the plan be enough extra support? If so, where would be a good place to add them? Also, if you would were to build this yourself, what could you see modifying about the plan? I'm wondering if wood glue and brackets would suffice for the bread boards... I am fairly new to furniture making but my brother with a tad more experience will be helping me. I would appreciate any advice you could give! :)

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    1. Honestly, I would never make a table top like that. Those are not bread boards, those are pieces of wood screwed in perpendicularly to other pieces. You are welcome to email me at follow.your.heart@live.ca for further discussion.

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