Cupping Sill Plates, is there a cure?

[RaysnCayne]

Hey all,

I'm in the midst of building a detached 28x28 garage by myself. It's taking me a good while. I put the 2x8 pressure-treated sills down on the block with anchor bolts about 4 weeks ago now. I've got two walls up and hope to erect a third here in the next couple days.

The problem is, my sills have dried out and are cupping pretty badly. The first wall, went smoothly. But it's to the point that when I was nailing the bottom wall plate on the second wall to the sill, it was pulling the plate down away from the studs, leaving about an 1/8" to almost a 1/4" gap between the bottom of the stud and the top of the bottom plate in some places. It appears the outer most edge of the bottom plate is still in good contact with the studs, but I'm not likin' what I'm seein' on the inside.

Is there any fix for this? Should I even worry about it? Can I put a bunch of weight (cinder blocks, wheels, etc.) along the sill and flatten it out a bit.

 

[A_Pmech]

Wood cups the opposite curvature of the annual rings. Bolt your sill down to the foundation such that the growth rings curve in the form of a bowl towards the sky. Thus, it will actually cup opposite that direction, towards the concrete, where it will be restrained by the bolts holding it to the foundation.

 

[timewarp]

Wood also cups to the dry side if one side drys out faster than the other, the side up and exposed to sun and wind will dry much faster than the side that's down to the concrete. You could try wetting the top of the sill plates that you haven't put walls on, this will make the wood expand and straighten back out some, you could put some rags or old pieces of carpet on top to hold some moisture and just keep them wet for a day or 2 and see if it helps.

 

[5lima30]

I agree with Pmech. You could also try "toenailing" with 3"-4" screwsdown through the stud into the sill plate. Pre-drill your holes to avoid splitting. Good luck!

 

[MP&C]

When you put your outer sheathing on the walls you want about 1/2" gap above the block wall so the sheathing doesn't wick moisture out of the block wall. What we did when building my shop (I think you've seen it ) was to frame up the wall section, square it up (checking cross-diagonal dimensions) and then nail the sheating to the wall section while laying flat, letting it hang down 1" (to tie into the sill plate but also sit 1/2" above the block wall). The sheathing being nailed to the bottom plate of the wall will help to keep it from pulling apart from the studs as you nail it to the sill plate. Now normally once the wall is erected in place on top of the sill, you would nail the wall through the lower plate into the sill plate and then come back and nail the sheathing lower edge to the sill plate as well.

Given the warped boards, I would nail the walls down to the sill, but don't nail so tight that you're pulling the wall lower plate away from the studs. At this time, don't nail the bottom edge of the sheathing into the sill, wait until you have trusses, roof, and shingles in place. This weight should help to settle things down a bit. After the roof is on and complete, then follow up with smacking the lower plate nails into the sill a bit tighter, and then nail the sheathing from the outside into the sill. Hope all that rambling made sense.

 

[Falcon67]

I build my walls in complete sections - top and bottom plate with studs. I pre-drill the bottom plate for the bolt holes, then assemble flat. Square the section, let in a long diagonal brace, then raise the wall. Be sure you use hot dipped galvanized nails into that treated board or your walls will eventually not even be attached to the plate. The treatment eats regular nails. I typically don't sheath with OSB, I just put siding on the studs. Where the wall meets the foundation, I overlap with a 6" wide flashing to keep any siding overlap off the concrete.

 

[Gary S]

I build my walls in complete sections - top and bottom plate with studs. I pre-drill the bottom plate for the bolt holes, then assemble flat. Square the section, let in a long diagonal brace, then raise the wall.

I did mine the same. My treated sill plate is the bottom wall plate. My building inspector saw no reason to use a double bottom plate. All that is needed here is the single treated plate.

 

[RaysnCayne]

Thanks for the input guys.

Robert!?!? What are you doing on here? Sheesh! Do you work at all during office hours? (Guess you realized I'm Zach from Ctalk and Fender Mender fame, right?)

I wish I knew about the ring orientation/cupping before I bolted the sills on. Doh! Unfortunately, I can't flip them over due to the anchor bolt holes ending up in the wrong spots. I suppose I could buy new 2x8s, but that's kind of a drag and money wasted.

I guess I'll try wetting them down and see what happens there. Maybe do some cross-toenailing with screws after the fact.

I did leave every other nail out going through the bottom plate into the sill on one wall. So I guess I'll wait til I see what the trusses do before I go back and nail them down hard. Only problem is, the two side walls where this cupping is pretty bad are the gable ends. So I'll be putting even more weight on the outer edge of the wall and pushing down on the outer edge of that wall and not evenly in the middle so as to push down on the inside of that wall.

 

[70redbee]

Once yoy get all your walls assembled and set and add the roof truss,plywood,shingles it will all settle down from the weight of all the componets. The real problem is the 2x8 sill plate is too wide, a treated 2x4 would have been a better choice but you can't change it now. Don't worry about it, you will be fine and it will settle in a short amount of time. 1/4" to 1/8" difference in framing is not unusual. Good luck on your build, it will work out fine.