# Patch/seal a concrete seam in cold weather - how to?



## Quattro (Dec 17, 2007)

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 color-wise...so 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.


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## glennjanie (Dec 17, 2007)

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
Glenn


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## ToolGuy (Dec 17, 2007)

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.


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## Quattro (Dec 18, 2007)

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.


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## ToolGuy (Dec 18, 2007)

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.


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## Quattro (Dec 19, 2007)

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.


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## ToolGuy (Dec 19, 2007)

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


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## Quattro (Jan 3, 2008)

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. 

Thanks!


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## ToolGuy (Jan 3, 2008)

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.


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## Quattro (Jan 3, 2008)

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?

Thanks!


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## glennjanie (Jan 4, 2008)

Hey Quattro:
It sounds like a plan to me. Is that plywood form holding up a concrete floor? That would be quite a bit of weight for the framing you are showing. I see they used framing anchors but they are attached to a member that is held up to the floor joists with toe nails. That is a dangerous situation and the wall under the preimeter of the form is a very good remedy. I'm all for you.
Glenn


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## Quattro (Jan 4, 2008)

Yes, the plywood is under the concrete slab! My idea is to put a floor jack on it while I remove the existing framing, then build the support wall and then remove the jack. 

Thanks!


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## Quattro (Jan 7, 2008)

Progress report!

I was successful in removing the old 2x4 framing that spanned the plywood form. I built a 2x6" wall to support the ends of the floor joists at the front door, as well as the inside edge of the top step. It's VERY sturdy! I still have to build the short-side wall.

I also placed a cut-to-fit piece of 2" XPS foam against the plywood and steel lintels. I used silicone caulk around the edges to help seal out the air. Next, I'll frame the interior of that new "room", add more foam insulation, a vapor barrier, and finally drywall! I hope I've done things right here...the main concern is to keep the moist/warm basement air from condensing on the cool plywood/lintels. This ought to do it!

I will get a photo up tonight!


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## ToolGuy (Jan 7, 2008)

Congrats Quattro, I think you got it beat. Between the caulk, foam, insulation and vapor barrier, I seriously doubt you'll have any problems. Way to go!


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## inspectorD (Jan 7, 2008)

I agree with Toolguy, Way to go. 
Sounds like you just put a "coozie" around that nice cold soda can.


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## Quattro (Jan 7, 2008)

And, here are the pics! Got the short wall mostly constructed...but it was baby's bed time, so the hammer got put away! 

Overview:






Closer:






A little foam in the gap on the short wall side, then framing on the back and long side concrete, more foam insulation, vapor barrier, then drywall! I'm excited. Oh, and I have to re-route that electrical cable through the joist and down the wall, and the outlet will then be on the short wall.

Thanks for all the support thus far.


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## Quattro (Jan 8, 2008)

Question, do I need a vapor barrier with this XPS? 

I'm getting conflicting info online.


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## ToolGuy (Jan 9, 2008)

Actually, I've used it as it's own barrier, and foam (Great Stuff) in and around all the edges and seams. Can't say whether that was right or wrong, but it worked for me. 

Nice job on the framing, looks rock solid from where I'm sitting.


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## Quattro (Jan 9, 2008)

I have all the seams sealed with silicone caulk, and then taped with packing tape.

Owens Corning's website says this material has a water vapor perm (max) rating of 1.10. But, that's for 1" material. For some reason, they don't give ratings for the thicker material. I have 2" on the ceiling here, and 1.5" on the walls (not in the above pictures). 

So, am I right to assume that the thicker stuff has a lower perm rating? I read that 1.0 or lower is acceptable for residential. I just don't want to have to take drywall down if somehow adding a plastic barrier is going to trap moisture coming through the drywall.

Ugh!


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## ToolGuy (Jan 9, 2008)

I couldn't answer all the technical stuff. But I will say that the packaging tape will dry out over the years and fall off. 

I guess you have to ask yourself how much extra work is it to add vapor barrier. The cost is certainly minimal.


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## inspectorD (Jan 10, 2008)

The technical stuff we could give you will not help anyway. The issue with this is going to be a wait and see. We do not know how much vapor is moving through the area above. You could seal the concrete above and limit the vapor flow also. This area probably does not have to be taped and finished right away anyway. Install what you have temporarilly with no finishing touchs and see what you end up with in the summertime humid months.
Just a suggestion.


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## Quattro (Jan 10, 2008)

That's kind of the plan, I guess (the "wait and see" method). The concrete step outside does need to be refinished and sealed (some exposed aggregate and the seam that needs patching).

However, how will I know if it's working? Wouldn't I have to pull everything off and check the condition of the concrete? That would be a hassle, but not as bad as having to pull drywall down I guess. 

Also ToolGuy, the plastic isn't about the expense or time, it's about whether adding that vapor barrier would trap moisture between itself and the foam. I'm basing this assumption on other things I've read about having 2 vapor barriers on the interior side...

Anyway, thanks for the continued help and ideas. I'm going to spend the rest of the winter getting the rest of the basement insulated in a similar way. Luckily, this is the only place where water was an issue...the rest of the basement is very dry.


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