Residential Fdn Wall Sill Plate

[SkiisAndBikes]

I looked at a house where the Contractor has used a 1"x4" sill plate on top of the foundation wall instead of a 2"x4" sill plate specified by code. The sill plate is anchored to the foundation wall with anchors at 4'-0" o/c (half the code required spacing) and the floor joists are toenailed to the sill plate. There is no way to retrofit without major demolition.

The only problem I can forsee with the 1"x4" is that the toenailing of the floor joists into the 1"x4" will have less uplift resistance.

Would anybody have any other thoughts on potential problems with the use of a 1"x4" sill plate?

 

[msquared48]

1. It does not have the lateral capacity in bearing to develop the shear from the shear walls that that a 2X plate does.

2. It probably is not treated, yet in contact with the concrete.

3. Technically, toenailing is not allowed in the code to resist anything structurally, especially uplift.

4. What stress grade of lumber did he use for this 1X4 material? Is it form lumber? If so, it's probably pretty crappy material, yielding even less lateral bearing capacity on the anchor bolts.

You could add extra treated 2X blocking between the studs and over the 1X4, installing new chemical anchors, but this would not aleve the treated 1X4 problem. This is probably the cheapest fix, but I do not like it.

If a 2X plate was shown on the plans, that's his problem. He needs to learn to read. Just have him do it right. Maybe next time.... Then again, he is a contractor.




Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[JAE]

Your wall sheathing - which takes all lateral load of the house, would depend on adequate nailing between sheathing and sill plate. You can't nail into a 3/4" edge and meet shear wall capacity requirements.

 

[SkiisAndBikes]

msquared and JAE,

Thank you for your comments. Sill plate is separated from the concrete with a capillary break (poly or sill gasket) as per code.

I agree that adequate nailing between sheathing and sill plate is important and something I had yet to consider in my preliminary thoughts. House is bricked, roofed and has windows in.

I will check if sheathing has been nailed to the rim joist. If so, I may consider providing a metal clip/angle (Simpsons)that can be installed from the inside and connect the rim joist to the top of the concrete foundation wall via epoxy anchors, effectively bypassing the existing 1"x4" sill plate. The additional anchors/clips should provide additional lateral support to the top of the foundation wall as well.

 

[MiketheEngineer]

I think m^2 hit it pretty much on the head.

I suppose you could anchor each joist mechanically into the foundation with chemical anchors or Tapcons - but it would be very time consuming...and would need to be designed. Did he at least provide a rim board?? That might be easier assuming it was correctly attached to the joists..

 

[SkiisAndBikes]

Mike,

I agree with m^2 as well. I have reviewed a Simpsons DTT2Z anchor. Attaching it to the rim joist (1-1/2" thick material) with 8 SDS screws and a 1/2" diameter anchor drilled into the top of the foundation wall provides approximately 2,500 lbs factored capacity. I have yet to do the calcs, however, instinct tells me that 2,500 lbs would replace an awful lot of nails between the sheathing and the side of a 2x sill plate. The rim joist is end nailed into the end of each joist as per the code requirements.

 

[MiketheEngineer]

Yes - something along those lines

 

[msquared48]

JAE:

Thanks. I missed the most obvious point.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com