Foundation wall crack repair

I just found out recently that I still ended up with a crack on my foundation wall. This is a classical case of hairline crack in the foundation wall for poured concrete. It is located right at the window opening, it is vertical and goes straight down.

The crack is very small. On the top you can barely get a knife blade into it. In poured concrete foundation wall, these are typically caused by shrinkage of concrete or caused by settlement. My foundation is poured in Nov 21, 2013. I know that I did not see this crack back in February 2014 when the structural steel is being installed. So this crack is not caused by shrinkage of concrete.

The crack is really narrow, less than a hair width, half way down the wall. As you can see by the time you get to the bottom 1/3 of the picture below, you can barely make out the crack on the wall.

I checked all the photos I have available of my foundation wall. The first time I have a good photo showing this crack is back on April 18, 2014. At that time, it seems the crack is extremely small and only extends about half way down the wall. I believe that this crack has developed over the March/April months. I think initially this is a very small settlement crack that just extends a bit down the corner of the window and does not run down the wall much at all. Over the March/April we had some very bad freeze-thaw cycles in Canada. I think water got into the crack and then freezes and expands to make crack larger and larger. That’s why I don’t see any sign of the crack during February’s freezing weather, but the crack is visible by the end of April. Then I had to dig up the south-west corner of the house twice for plumbing. So that could caused the house to settle downwards in the south-west corner just a little bit and caused this crack to develop a little further.

So what to do with this crack? Structurally there’s no issue. I have rebars every 2′ inside the concrete and it should be holding the foundation wall together just fine. The biggest problem is potential of moisture penetration. The wall should be pretty good from the plastic drainage membrane all the way down to the footing. The water will simply be blocked by the plastic dimpled membrane, forced to travel down, and then will go into the weeping tiles right under the footing. However, there’s some soil back fill above the drainage membrane right now and I don’t know once the drive way is finished, if there are chances where water can meet the foundation wall on top of the drainage membrane. In that case, water will then travel behind the plastic membrane and have a chance to wick through the crack and the foundation wall. Now I will have my basement spray foams. So technically I won’t have to worry about this at all since the spray foam will block any moisture from entering the basement. However, I wanted to go all the way and make sure every single thing is proper. So I decided to fix this so that I don’t have any possibility of moisture penetration inside the basement, spray foam or not.

Epoxy injection is what’s needed to fix this. Used SIKA Sikadur Crack Fix which can be purchased from Home Depot. This is a low-viscosity high strength epoxy resin. Then holes are drilled about 4″ apart from the top all the way to the bottom of the crack a few inches above the finished slab. It comes out to be 17 holes in total. The the holes and cracks are cleaned of dust using compressed air and surface of the wall is wiped clean. Then the full length of the crack is taped up using tuck tape and a tiny opening is cut on the tape where the pre-drilled hole is located. Now start from the bottom most hole, extremely slowly inject the epoxy resin into the hole. You can see the resin rises up due to pressure of the resin being injected and the capillary action that pulls the resin up in the crack. Once the resin reached the hole above the current one and start to flow out, stop, tape up the bottom hole and move one hole up. Keep on doing this all the way to the top. And here’s the end result. Once the resin is cured, I will pull all those tape away and the cracked concrete should now be all bounded and sealed.

How good is this epoxy injection fix? Well once cured, Sikadur Crack Fix claim to be 5 times stronger than concrete. From the product data sheet, the cured epoxy has a compressive strength of over 10,00 PSI and tensile strength of 7,000 PSI. Typical concrete in a foundation walls will only have a compressive strength of 3,000-6,000 PSI and tensile strength of 700 PSI. So yes this epoxy is actually stronger, even though not 5 times stronger as suggested, than the concrete wall it is bounding. And that’s why epoxy injection is a proper way to fix this.

Update 2014-08-20:

Removed the tuck tape and here’s what I got. The dark line marks where the resin has penetrated and bounded the concrete.