DIY Home Improvement, Remodeling & Repair Forum

DIY Home Improvement, Remodeling & Repair Forum (
-   Bricks, Masonry and Concrete (
-   -   Patch/seal a concrete seam in cold weather - how to? (

Quattro 12-17-2007 11:03 AM

Patch/seal a concrete seam in cold weather - how to?
Hi all, I need some help repairing a joint under the top step of the front entryway to my house. The top slab is actually over the corner of the basement, which is odd, but that's another topic.

The issue is this joint between old and new concrete, as seen in the photo below:

The previous homeowner is a mason, and did a lot of concrete and brick work around and inside the house. In 1999, he repaired/resurfaced the entry steps. The concrete under the "lip" is actually the top of the foundation. The concrete in the foreground is the second step. The concrete on top is the top step.

It doesn't look like it from this picture, but cold winter air is entering the basement through this crack/joint. This basically runs the entire perimeter of the top step...and I know this is happening because I'm getting frost in the basement directly on the other side of this concrete.

I need to patch this, asap. Any ideas what will work in the sub-freezing weather? I'll consider anything that is close if something elastomeric or asphaultic comes in "gray", it should work. I just need to stop the air coming in, then I can insulate from the basement side.

Your thoughts are welcome. Thank you.

glennjanie 12-17-2007 04:44 PM

I would use Silicone caulk and use the 'pressure caulk' method. Folks generally drag the nozzle along as they pump the caulk out; to pressure caulk the nozzle should be pushed along at a 45* angle watching to see the caulk come up in front of the nozzle just slightly as you move along. The joint can be tooled after it is applied.
Merry Christmas

ToolGuy 12-17-2007 05:30 PM

Polyurethane caulk will cure better in the cold climate, where as silicone might not cure and just remain sticky forever.

I use that pressure caulking method a lot and definately the right way to do it. But I've always called it pushing the caulk. :)

Quattro 12-18-2007 10:28 AM

Thanks! I'll give it a shot. Then, when it warms up a bit (April, maybe?), I'll do some sort of skim-coat over the whole thing with a concrete-refinisher.

ToolGuy 12-18-2007 01:02 PM

Glad we could be of help, Quattro.

About skimming the whole thing, the crack will come right back through. The new concrete did not bond to the old concrete, which is why it separated and air is coming through. The old and new concrete are moving relative to eachother and there's nothing that can be done about it.

Quattro 12-19-2007 07:32 AM

Hmm, nothing seems to be moving, the guy just didn't do a very good job on the seam. I've heard some "injectable" epoxy may help keep the seam together...which I may try in the spring.

For now, I'm going to tackle the problem from the inside (basement). I'll squirt expanding foam between the top of the foundation and the plywood form that the stoop slab is resting on. Then, I'll use 2" XPS to block off that entire area to help keep the relatively warm basement air from colliding with whatever air might still be coming through the seam.

I'll update.

ToolGuy 12-19-2007 08:32 AM

The foams are sure to make a big difference, probably solve the problem altogether. I'd like to know how that turns out.

Quattro 01-03-2008 12:55 PM

Well, I took the first step and applied Great Stuff in the space between the top of the foundation and the treated plywood form that is under that slab. At first it looked like it stopped most of the air intrusion, but we just got another really cold shot of air, and now there is frost forming around the great stuff, and down the concrete wall in the basement. So...still some work to do. I assume the wood form is just getting cold enough to condense the basement air.

So I've got this 2" thick XPS. Should I put this up first, or a vapor barrier first? Do I even need a vapor barrier with this stuff? Eventually it will be sheetrocked, so I need to be sure the basement air moisture doesn't reach the wood form. I don't want to just cover everything in foam, and have the problem persist behind the foam where I can't see it.

I'll take a picture when I get home tonight and post it here.


ToolGuy 01-03-2008 04:16 PM

XPS first, then vapor barrier. Vapor barrier should always be toward the interior, and any insulation toward the exterior, lest the vapor barrier itself will get cold and collect condensation like a cold window pane. ;)

Quattro 01-03-2008 07:37 PM

OK, that's what I thought. Thanks!

Now, on to the pics. These are taken in the basement, looking up at the underside of that top step. You can see the steel "lintels" used to rest the treated plywood form on. The framing is very "iffy" if you ask me. I'm contemplating removing that framing and putting a load-bearing wall under the lengthwise lintel instead. Thoughts? The house is 20 years old and there doesn't seem to be any issues with the way it is built now, other than the obvious air intrusion (which the Great Stuff didn't seem to stop).

and another view:

I'm thinking more about just framing up a wall that would support the inside edge of that slab. Then I could take out all the iffy framing and build a regular ceiling with the XPS, plastic, and drywall. I could use that space as an equipment closet or something.

Your thoughts?


All times are GMT -6. The time now is 10:09 PM.