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When in Tennessee on vacation, I was walking through a house being built by a Mennonite crew. I noticed a framing detail that I thought interesting. On an outside two storey deck, that was framed with pressure treated lumber, the beams did not sit directly on the 6×6 posts. Instead, 5-1/4 x 5-1/4 blocks had been cut from pressure treated 2x material, and two of these were placed between the top of post and the beams– with the grain running horizontal.
I assume that this was done to match the shrinkage of the headers in the interior house framing, so that the house and decks would shrink evenly.
My questions are:
1) Does pressure treated lumber shrink across the grain at approximately the same rate and the same total percent as framing lumber?
2) Are there shrinkage differences between types of pressure treated lumber?
3) Since these “header blocks” are so short, and have so relatively much end grain exposed, should the end grain be sealed in any way to keep these blocks from shrinking faster than the framing headers?
Thanks,
Eric Bott
Replies
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to the best of my knowledge, PT lumber shrinks a lot more than framing lumber. unless it has been kiln dried after treatment.
only my knowledge, ask around.
and of course my locality is a bit away from your's.
good luck
*I'm not sure of the specific detail you refer to. Apicture or drawing would help.But PT definitely shrinks more than typical KD lumber. Upon delivery, a typical 2x8 is 7-1/4" here. PT is 7-3/8" to 7-1/2"
*Eric,Sounds like an unusual detail. Might just be a poor fix for posts that were too short.
*ditto what Mike said.relatedly...I've heard Japanese temple carpenters shim up posts that support crowned beams...and slowly remove layers of shim from beneath the post as the beam straightens over time.(maybe I shouldn't believe everthing I read..)GO
*I appreciate all the responses. It sounds like I might have been giving too much credit to the deck framers!Piffin, your 7-3/8 vs 7-1/4 measurements match my experience for new PT vs new KD. I guess I'll go measure up some 10 yr old PT, and see if there is a typical "end state" dimension for this stuff.
*George, go ahead and believe it. I worked on a Jap frame once. Whole new experience but lots of fun! Had a spot where the housed had to allow seasonal movement and it called for a pair of fir wedges cut from 4x4 with a rounded over heel to push/pull on. Jap strucute is designed to sway with the earthquakes instead of resisting them and falling into splinters, so movement is normal.
*A very interterting observation you’ve made there Eric and while I wouldn’t rule out crediting the deck framers all together for calculating and preparing to match their decks shrinkage to the structures shrinkage I would suggest that a far bettter way to do it would be to calculate the differences and try to match the two systems by cutting the vertical grained deck posts 5/8 of an inch shorter or what have you. The big problem I see with the way that they were calculating for that shrinkage was that it just plain old outright "looks like a mistake". If you absolutly know something is going to shrink or settle "X" amount plan for that circumstance in the dimensions of the matching system.However one of the evidentiary reasons I think what you saw might have just been "a mistake with a real good cover story excuse" is that when we build a deck we plan and build it with a certain amont of pitch in it anyway. The pitch being away from the house to help it shed water and melting snow. A quarter or 3/8’ inch over a four-foot run in a deck is more often than not imperceptible to the naked eye of someone standing on the deck or looking at it from a distance. There are exceptions though so the real trick in our book is to build a deck with pitch built in to it that looks like it’s perfectly level. So my replies to your questions would be:1) Does pressure treated lumber shrink across the grain at approximately the same rate and the same total percent as framing lumber? Answer -Pressure Treated shrinks a little bit more that most framing lumber but the differences are irrelevant considering the uses that are generally associated with pressure treated.2) Are there shrinkage differences between types of pressure treated lumber? Answer - Who cares? It’s irrelevant.3) Since these "header blocks" are so short, and have so relatively much end grain exposed, should the end grain be sealed in any way to keep these blocks from shrinking faster than the framing headers? Answer- Irrelevant, again.Don’t frame at all any more and we don’t build many decks either but we do build and install a lot of curved stairs and railings out of both wood and metal and thinking about and planing for the differences in both shrinkage and expansion and contraction of the two dissimilar materials is vitally important there. But decks? It really does pays to be fusssy, precise, and particular but you still have to consider the value of the diminishing returns for being that picky.As for any stories you may have heard regarding legendary Japanese Joinery. Absolutely believe them. They are that good and that smart. When I was in college I attended a seminar being taught by a Japanese temple builder and in the 23 years since then nothing I’ve seen done has ever impressed as much.
*Mennonite crew?So these guys are "Gods" carpenters and can't make (and then try to correct) a mistake? Maybe the guy who bought the columns ordered them too short? Not on God's crew I guess.I guess that doesn't happen. They have God on their side. So let's just make a complicated justification about shrinkage and lumber camber and such......Give me a break.Excuse me for being cold, but I do live in the big city and have seen most if not all.To be honest with you, the more religious a man claims to be, the less I trust him. However, this is just from experience.The people who follow the Mennonite faith are a fine group of people I'm sure. But they are saddled with the same flaws that the rest of us are. No better, no worse. I'm sure they don't flaunt their religion like the "born agains" that I run into here in the Bible Belt of the USA.But do beware of those who try to impress you by how religious they are. To take the Lords name in vain (like trying to impress someone by telling them just how religious you are) is a sin according to the basics of the Christian religion.A persons religious beliefs does not make a skilled craftsman or an honest man for that matter.Sorry to be so vocal about this......I was recently ripped off by a "Christian" employee. I'm sure he's asked the Lord for forgiveness by now and he feels "forgiven" by his maker. To hell with me I guess.Ed.
*amen Ed
*Ed, you can use my stump anytime you want to preach or rant. Good points.
Ed
I dont think he meant because they were a Mennonite crew all was perfect and flawless. Just as you say being a Christian does not qualify you to be a carpenter. Being a Mennonite also does not qualify you to be a Christian. Only acceptance of Jesus as God's son can do this along with repentance of sin. I am sorry you got ripped off by some one who professed to be a Christian. Although Christians make mistakes there are many people who claim to be Christian just for monetary or other gain. Just as many claim to be carpenters or "good" contractors for the same reasons. I hope and pray you have some good experiences with Christians in the future. We are not all relegious zealots or rip off artists.
Sorry for all this rant but when I read the original post I didnt think about it in a religous context. I just took it the author meant (by saying they were Mennonites )that maybe a different technique was used from their culture just as others discussed Japanese carpentry on other posts.