I’m building a deck out of #2 treated SYP (2×10 joists). The stuff was real wet.
I crowned all the deck joists 12′ span, but some of them them wound up with a real bad downward crook (of 1-2″ in some bad cases and 1/2″ in some mild cases).
To fix this I’m considering:
- remove joist and turn so it crowns up [plane or cut off top crowns if too much]
- sistering with a 2×6 or 2×4 to take out the crown.
Any advice as to the best way to fix this?
PS: Anybody use butyl tape for deck joist seams? (i.e. to keep the water from sitting between doubled joists or headers)
Replies
How far is the clear span on these joists?
The weather was hot, a-nearly 90 degrees.
The man standin' next to me, his head was exploding,
Well, I was prayin' the pieces wouldn't fall on me.
If I read it correctly he said 2x10's spanning 12'.View Image
One or two INCHES?!?! On a 12' span? Holy moly Batman. I'd call the yard and have them come take a look. I'm assuming you don't have a Volkswagon parked on the deck or something so if not, you really oughta get some new lumber out there.
There's no weight on them yet, I just framed it (you are correct 12' span). I guess they bowed in the sun. I expected a little twisting and bowing, but not that much.
I have not decked it yet. Just framed out the joists between the band and header beam.
it's a big deck across the back of the house (approx 100') and about 3 or 4 joists are crooked down bad enough that I would consider pulling them (or whatever) to fix.
I'd yank 'em dude. Who's to say they're all done moving? On a deck that big it'll stand out like a baboon's azz. With wet PT you gotta expect some warping, checking, etc. But you've got an extreme case there man. It only gets harder to remove them later.View Image
< I expected a little twisting and bowing, but not that much. >Is it a crown or a bow? or both?<G> I asked about the clear span because some decks have joists cantilevered over girders, which changes the fix. A crown doesn't normally change direction 2".I think the tape is a great idea on doubles. Outside of the gates the trucks were unloadin',
The weather was hot, a-nearly 90 degrees.
The man standin' next to me, his head was exploding,
Well, I was prayin' the pieces wouldn't fall on me.
What? Didja install the joists and let them set a year with no deck boards attached? None the less if a joist has sagged down 2", you have a bad joist and it needs to come outa there and be replaced.
Buy your lumber at a place that keeps their lumber covered and dry - true though that sometimes PT lumber is still very wet just from the PT process.
Framed the deck about 2-3 weeks ago, but they warped right away (not decked because I thought it would be ok to let it set a while (my white oak decking is still air drying)).
No one seems to recommend the sistering? what's wrong with that method? It seems easier in the long run (i.e. 2x6 sister)
Do you mean to simply set a 2x6 in so that its top edge is in the correct plane to receive the decking?
That would work. My only concern is that you'd trap moisture between the cheek of the 2x6 and the existing joist. Others here don't seem to share that concern, however, so there may be no downside at all.
A nitpick would be that by offsetting the attachment location of the decking, some screw centerlines would be at 16" centers, while others would be 14-1/2" or 17-1/2". I don't think this is a big deal from a structural perspective, but it might be somewhat noticeable cosmetically speaking. There's also a small chance that by moving the centerlines off of 16" intervals, you might not be able to effectively use boards that were exactly 8' long, etc.
Edited 5/25/2007 12:36 am ET by Ragnar17
OK. Thanks for the feedback. That's exactly what I had in mind with the 2x6 (i.e. "set a 2x6 in so that its top edge is in the correct plane to receive the decking")
On the moisture trapping side I was thinking 2 things: 1) it's a covered deck and 2) I could use butyl tape over the joint.
I hadn't thought about the off-sets on the nailing pattern, however I am planning to use counter sunk and plugged stainless steel screws (5/4 white oak decking; no t&g, just a 1/4" roundover), so the pattern won't be as noticable. Also since the log lengths lengths (from which the boards were cut) were approx 13', I should be able to come out alright with the non typical spacing.
Thanks again,
Roger <><
1) it's a covered deck
LOL -- that little detail definitely changes my concern about the joists getting wet all the time!
Where I come from, that's called a porch. ;)
Good luck with the project.
Ragnar
PS: Anybody use butyl tape for deck joist seams? (i.e. to keep the water from sitting between doubled joists or headers)
The best practice here is to avoid doubled framing members for open decks. For example, use a 4x10 instead of (2) 2x10.
I've been building for 35 years and have never had any issue with double joist on a deck.
When building something out of PT lumber for me, the idea is to get the lumber delivered and then immediately get the thing built ASAP. Once the lumber is all locked together with fasteners the lumber movement is minimized. PT lumber laying around twists up something fearce and boards partially attached to a structure are only a little bit better off. The only exception is re-dried PT lumber which is dry when you get it but still needs to be stacked correctly. This re-dried lumber wouldn't normally be used for framing though - it's more for appearance grade applications; decking boards, railings, etc. If regular PT lumber has to sit around for some reason, I order more than the normal 10 or 15% extra for waste (or returns).
Matt,
Have you ever thought (or tried) to build with something besides PT lumber? Other than the preservative treatment, it really seems to be a crap grade of lumber.
Your profile says you are from the NW. Assuming that is accurate the PT lumber you are using is probably that incised stuff and, yes it is crap.
The PT lumber we use is SYP. Other than its tendency to warp, SYP is really a pretty good wood. It has good strength as indicated by its Fb and E values. In some instances SYP is actually used for finish (paint) grade application like bead-board and S4S. For deck applications we can get #1 PT SYP decking boards, 2x4s, 2x6s and 4x4s. No real framing material though. Further we can get the KDAT (redried) SYP PT.
Generally though, I'll build a deck out of whatever people are willing to pay for - SYP, composits, exotics, whatever. The joists, beams, and posts will still be PT though.
Some cedar is available here but not in framing sized lumber, and further I'm thinking the cedar we get is a little different and not the best as compared to western cedar.
What do you frame decks with?
Matt,
Thanks for the reply.
You're right -- I'm from the NW, and the typical PT we get here is incised hemlock. I don't frame many decks at all -- I primarily do finish work. However, the frustration I've had with PT has got me wondering whether there is a better product out there.
I've thought about using cedar before, and it's much more readily available out here than I think it is in many other parts of the country. My only concern is that it seems to be a fairly soft wood, and I'm not sure about it's strength.
Speaking of which, you mentioned the Fb and E values for SYP. Where did you find those, and do you have any numbers available for TK western cedar? I've got a few books, but the tabulated values for Fb seem to vary wildly and I'm not sure which to assume are accurate.
My book is "Wood Technology in the Design of Structures" by Robert Holyle
It has tables for most conceivable structural woods including SYP and Western Cedar.
You are right. It is complicated and lists values for many different grades and dryness. To find out what you might actually be able to buy at a yard is something that you will have to find out first.
From a practical standpoint you could upgrade to the next dimension up and be perfectly safe. In this case a 2x10 cedar might be adequate as is, a 2x12 or 3x10 would be great.
To find out what you might actually be able to buy at a yard is something that you will have to find out first.
I'm not so sure the guys in the lumberyard would be able to tell me enough information to know for sure! ;)
Thanks for the name of the book -- I'll look it up.
Edit: Oooh. Expensive book. $75 for a used copy. Is it an old college text?
Ragnar
Edited 5/25/2007 2:57 pm ET by Ragnar17
I paid 18.50. The price sticker is still on it. It must be 25 years old and starting to fall apart.
perhaps lots of solid blocking ?
"PS: Anybody use butyl tape for deck joist seams? (i.e. to keep the water from sitting between doubled joists or headers)"
I put 1/4" spacers between anything doubled up so they can dry out.
Mike Hennessy
Pittsburgh, PA
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