Wood Movement?

[Greg Crawford]

Whenever attaching solid wood, like a dresser top, to a plywood sub-top, or fastening opposing grains, I make the holes over size or rout slots and use washer head screws or washers with the screws to allow for movement. This is a tradition with a long history, and I’m wondering how important it is today. In just the past 100 years, homes have gone from being heated by fireplaces or other single point heat sources to central heating. Insulation and other weather proofing has improved vastly just in the last 50 years, and central AC has become very common.

With these changes, a home no longer has the tremendous seasonal swings in temperature and humidity. Being in a controlled environment, how much is wood moving in household furniture these days? I know some species, like cherry, are much more prone to change than others, but for more stable woods, are these techniques no longer required?

[Faust M. Ruggiero]

Yes, still necessary. For one thing, the shop you build in may not be part of the same climate control system that keeps your house warm, cool and dry. Secondly, humidity does change from summer to winter. The heating system in your house will still produce drier air in winter than the AC will in summer. Lastly, you are building furniture that will hopefully live for generations, or at least the next one or two. The next owner of your fine piece might not live in the same part of the country or have the same control over their environment. Besides, screwing directly to plywood is just too easy. It would waste all those bits we bought just for that occasion.
fmr

[Tony Bilello]

............ a home no longer has the tremendous seasonal swings in temperature and humidity. Being in a controlled environment, how much is wood moving in household furniture these days? I know some species, like cherry, are much more prone to change than others, but for more stable woods, are these techniques no longer required?

These techniques are still required even though homes have better climate control. Several things can happen such as a bad winter storm or something like another Ike in the summer. These conditions could leave you without heat or AC for several days if not weeks.
Other unforseen events can land your furniture in a garage or mini-storage or even the back of a semi for several weeks. And of course, as previously stated, a geographical move.

[David DeCristoforo]

"...I’m wondering how important it is today..."

Not important at all. Over the years, through genetic engineering, we have made huge advancements in this area. Modern woods do not react to changes in temperature and humidity the way wood did a hundred years ago. Genetic modifications have virtually eliminated the need to worry about wood movement. In addition there are many new "hybrid" woods like the very popular Vinylus Claddus Pressboardus, Fiberboardus MDus and Strandus Lumberus which are almost inert. Of course, there will always be those who insist on using archaic "natural" hardwoods and those people will just have to suffer the consequences of their inability (or unwillingness) to adapt to a changing world.

[Robert Chapman]

If your local supplier can't get you any of Dave's genetically engineered hardwood you might find this website helpful when trying to determine wood movement - www.woodbin.com/calcs/shinkulator.htm (http://www.woodbin.com/calcs/shinkulator.htm)

[Faust M. Ruggiero]

You know there are a lot of people with extensive knowledge and lots of experience that can answer most of the technical questions asked by the rest of us. However, there are only a few with the wit and word prowess to make those answers informative and fun to read. I always look forward to a reply from David DeCristoforo. He has the answers but also has the right combination of humor and wit with a wonderful pinch of well intended sarcasm. I am reminded that the most enduring pearls of wisdom, the ones we remember forever, are usually given to us in a way that makes us smile.
Thanks Dave.
fmr

[Vince Shriver]

You know there are a lot of people with extensive knowledge and lots of experience that can answer most of the technical questions asked by the rest of us. However, there are only a few with the wit and word prowess to make those answers informative and fun to read. I always look forward to a reply from David DeCristoforo. He has the answers but also has the right combination of humor and wit with a wonderful pinch of well intended sarcasm. I am reminded that the most enduring pearls of wisdom, the ones we remember forever, are usually given to us in a way that makes us smile.
Thanks Dave.
fmr

Agree, he's ahead of his mind...uh, time,time.... he's ahead of his time. David definately has a way with words - always enjoy his imput.

[Greg Crawford]

Dave,

I've used some of that! It doesn't stain well, though.

Lots of good thoughts here, things I hadn't considered. I'll keep my bits and templates and keep making slots.

Wish I could have said that with as much wit as Dave's answer.

[Steve Rozmiarek]

I've got a couple walk through doors made of that "wood" that David mentioned in my extreemly well insulated, climate controlled enviroment, and they still get a little "sticky" when the humidity outside goes up....