wood on concrete

Mark Harvey · 10-11-2012, 06:36 PM

I am re-building a front wall on a quonset. The wall is resting on a cement slab. I plan to use pressure treated wood as a bottom plate but have a couple of questions. First, is a sill gasket still suggested? second, because there has been some leakage from rain in the past, is there a suggested caulking/adhesive for this application? thanks. As always, all suggestions are welcome.

joecaption · 10-11-2012, 07:06 PM

Got a picture.
In my mind I'm seeing that front wall almost sitting on grade.
The best way to fix that so water can not get in is to raise it by adding a single row of 8" block with foundation bolts set in concrete every 6 or less ft.
Then build the wall on top of that. The sheathing is run down at least 1" below the top of the block to stop air from getting in.

TheCamper · 10-11-2012, 09:21 PM

A photo would help so that we can see if the slab extends beyond the wall and how high above grade the slab extends. If the re-framed wall is at the edge of the slab and at least 6" above grade then you could use a foam sill siller between the slab and plate. If the slab extends beyond the wall and/or the slab is close to grade, joecaption is dead on and the course of concrete block would be the way to go. I have done block several times in similar situations and it works well for the long term.

Mark Harvey · 10-12-2012, 11:29 AM

Te slab extends outward beyond the foundation by about six feet, with a gentle slope. Being the building is about sixty years old, I am limited as to what I can do without major replacements. This is a community league building and the club has limited funds. I am trying to help but can only do so much. This is why I asked the question in the first place. Personally, I'd like the tear the entire building down and start fresh but this isn't an option. Back to the slab, an extra row of blocks would be great but not in the cards. So, ... I'm thinking just the PT bottom plate to replace the old damaged on and build from there. I will seal the outside seam with silicone or something similar. Again, suggestions are welcome.

TheCamper · 10-12-2012, 09:55 PM

I certainly understand a community organization with limited funds. If you construct using a pressure treated plate with a foam sill sealer, sheathing and a siding, it will last for a while, but it is inevitable that the wood will rot because the bottom of the wall will remain wet. If it lasts long enough to satisfy the organization's needs then it might be the way to go. Try to keep the sheathing and siding, if wood, as high above the slab as possible and otherwise protected. Good Luck.

joecaption · 10-12-2012, 10:22 PM

So they build the wall and a few years down the road there back to square one and have to tare it all down again, or do it one time right and never have to do it again.
Block and morter are cheap.
Penny wise dollar foolish.