Replies

1. 
   UncleDunc | Apr 12, 2004 06:20am | #1

   Here's a thread about miter joints in decks. Some builders don't believe in them.

   http://forums.taunton.com/tp-breaktime/messages/?msg=41360.4

   It will be easier to advise you on dealing with your decking if you'll tell us what kind of wood, what size, and what representations, if any, the seller is making regarding moisture content.

2. 
   OneofmanyBobs | Apr 12, 2004 01:43pm | #2

   (I'm a different and original Bob).  Seasonal movement of the wood is a few percent.  The pressure treated lumber is usually very wet and will not dry well by itself.  I've had a stack stickered in a covered location for around 5 years.  Seems to be somewhat more dry than when I bought it.  I'd say it needs to be kilned to get really dry but it would not stay that way for long.  I did a deck a couple years ago with what I thought was pretty dry PT lumber.  Stored covered for a year.  A lot of miters.  I was not keen on the idea, but it was for a friend and he insisted. Looks like hell now.  Whatever you do for a deck has to be designed to allow for the large wood movement.  If there's an intentional gap to allow for movement, you can get away with it.  Tight miters, splined or nailed, no.  I wouldn't recommend it.

3. 
   JohnWW | Apr 12, 2004 04:10pm | #3

   Bob,

   Pressure treated lumber is sopping wet green and you're best to keep it that way until the moment you nail it down.  If you dry it out before you use it you'll lose a lot of the wood to extreme warping and what you can salvage will be much harder to work with.  As others have counseled keep the joinery simple, you aren't making a piano.

   John W.

4. 
   MarkRoderick | Apr 12, 2004 08:50pm | #4

   I definitely wouldn't use miter joints in a deck built from pressure treated wood. No matter how dry you get it now, when it rains it will be sopping wet again, then dry, then wet, etc. The wood will constantly be expanding and contracting. Every time I see a miter joint on a deck it looks terrible because it's nowhere near closed, even though I'm sure it was when they built it. Miter joints are tough enough indoors.

5. 
   YesMaam27577 | Apr 12, 2004 11:31pm | #5

   As mentioned by the ohters who have replied, pressure treated wood will move a lot. It doesn't seem to matter if it's been air dried, or used fresh from the mill.

   I have seen decks built with herringbone patterns in the "floor", using PT lumber. When they're new, they look awesome. Two years later, they look really bad. It's the movement that causes the problems.

   Assuming you nail or screw the decking down (face nailed, or face screwed) the cross-grain movement is restricted by the fasteners. Cracks result. And every one of those mitered ends in the herringbone pattern gets two nails or screws.

   Of course, if you only use one nail or screw, the edges of the board could easily pull up, and the deck looks just as bad.

   These are the reasons that the folks that can afford it, are using other materials. The composites don't have these problems. And there are a few high-dollar exotic woods that really excell for decking -- Ipe being one that is highly sought after.

   Or you might want to look into the Eb-Ty fastener system. It allows each board to float just a bit. I don't know if it helps to avoid the cracks and warps.

   Unless you're the lead dog, the view just never changes.

1. 
   Jimma | Apr 13, 2004 12:52am | #6

   Where you live probably has more to do with shrinkage than an absolute answer. I live in Central Florida where it hardly ever gets really dry, and I have a large, multilevel deck out of mostly 2X6 southern yellow pine treated with CCA -- the old, now illegal stuff. This deck is about 20 years old and has many miter joints, not all at 45 degrees, plus an inside curve with about a fifty-foot radius rimmed with 2X2 treated SYP. In addition, there are benches integral to the decks and a large table with 4X4 legs that are mitered plus openings in the deck for oak trees that have mitered 2X2 trim pieces around them. The plan (view) of the decks is not a rectangle making many joints miter joints. The miters have held up quite well and, even though not furniture grade, are quite acceptable for an outdoor project. Where I do have problems is with end grain rot in about 10 percent of the 2X6 boards where they have been butted up with 2X4 trim pieces. We have very wet summers and the end grain seems to really soak it up where it butts up against edge grain. However, I'm not aware of a single joint failure where it's mitered. If you live anywhere near Orlando, email me for a tour ....

6. 
   JMartinsky | Apr 13, 2004 03:07am | #7

   Dear Bob,

   I would use another type of wood altogether, but if you are stuck with PT, this is what I have done:

   1. Use it wet from the lumberyard.

   2. For 2x6 mitered joint I use four #20 biscuts, for 2x8 use 6 and so on.

   3. Use PL Premium construction adhesive. In the caulk tubes, not the thin stuff.

   4. I use a heavy-duty miter clamp and leave it on at least 48 hrs.

   5. After 48 hrs or better has passed, I drive a couple of six or eight inch screws into the miter.

   That's the only way that I've seen a miter joint in PT hold up more than a season here in CT.

   Good Luck,

   John