Foundation Wall Vertical Crack Repair

I've been writing about my basement insulation upgrade project, which was driven by some air quality issues in my home - such as musty odours during humid periods in the summer. We made the decision to take down all the drywall from the perimeter walls in the basement, remove all the old insulation and vapour barrier, and replace the insulation and vapour barrier with 4" minimum sprayed polyurethane closed cell foam, from the top to the bottom of the walls, including the rim joist area at the top of the foundation wall.

Injecting crack with Sika Crack Fix structural epoxy
Once we got the drywall removed from the perimeter of the basement, we quickly noted three issues - two vertical cracks in our poured concrete foundation walls, and some water entering around a bundle of cables coming through the foundation wall about 2' below grade. We couldn't proceed with the foam installation until the vertical cracks were dealt with - water leaking in behind the foam may be able to force it's way through the foam and find its way into the structure of the wall, causing decay, damage and possibly mould.

Vertical foundation wall crack, running from bottom corner of basement window, to just above the footing
The cracks were quite narrow - about 1mm wide on average, and extended from the corners of two windows in the basement, vertically down towards the foundation footing at the base of the wall. The cracks narrowed in the last foot above the footing. It didn't appear that these cracks were actively leaking, however efflorescence around the cracks seemed to indicate that they had leaked in the past, and that the enormous air movement in the underinsulated walls permitted any water entry to mostly evaporate. There was no evidence of mould or structural damage. I would suggest here that if the cracks are significant, the water ingress is significant, and if there is any damage to the interior walls, etc - it might be a good idea to get the assistance of a professional foundation repair contractor. A foundation crack is significant, and needs to be repaired correctly. Consider professional help with this.

I've been using Sika Crack Fix - a two part structural epoxy - to repair some floor slab cracks in the basement, so I have some experience with its properties. This product ships in the format of a small caulking tube - and is applied using a standard caulking gun. About half of the tube contains usable product, and it uses special mixing tube tips which mix the two parts of epoxy as the product is expelled from the gun. The product is very fluid (non-viscous) - it flows very freely and can infiltrate narrow cracks. It is a structural epoxy, which means that it bonds to both sides of the crack in the concrete - repairing the original strength of the concrete. It is not flexible however, and once the concrete is bonded together with the epoxy, it should resist further movement.

Sika Crack Fix structural epoxy, note the mixing tips on the left that mix the 2 components on application

Sika Crack Fix installed in a standard caulking gun, ready for application
Larger cracks, or cracks that move - may require a different repair product. There are polyurethane foam products like SikaFix PU which are expanding - and that I have no experience with - another good reason to consider the assistance of a crack repair contractor - they should be able to guide you into the selection of the best product / solution for your problem. Finally - I believe that cracks in concrete block walls are a whole other problem entirely due to the voids in the blocks. Again - no experience here - and consider getting in a pro for this type of problem.

So - since the cracks were thin, didn't appear to be active, and should benefit from a structural repair - I decided to do a structural epoxy repair. I've used Sika products in the past, so I decided to use Sika products for this repair - but there are other manufacturers offering similar products that could be considered for this job. I don't have any experience with other products, so I can't make any comparisons.

The datasheet for Sika Crack Fix provides detailed instructions for performing both horizontal and vertical repairs. I followed the datasheet guidelines for the vertical crack repair, which required some other products to make the repair. In short - here are the steps:
  • Clean out the crack with a vacuum or compressed air;
  • Bond injection ports along the crack - spaced out every 6 inches or so
  • Cover the crack using a waterstop repair cement
  • Inject the crack fix epoxy into the injection ports - completely filling the crack from bottom to top
  • Plug the injection ports to avoid losing the epoxy through the lower ports
My first attempt with the first crack was less than perfect - I was in a rush and tried to get the repair done in one evening, the injection ports had not bonded against the concrete, and the waterstop cement had not cured / hardened, and when I injected the epoxy - I ended up with a fair amount leaking out and running down the wall. My second repair went much better - so here's what I learned and how I did it. 

To help with getting the best bond with the injection ports to the wall - I started by using my small 5" orbital sander to clean the concrete wall surface, and take out the small surface irregularities / loose material. I then cleaned the crack and wall surface really well with the Shop-Vac.

Wall surface cleaned and ready for installation of injection ports
I used 5 minute epoxy to bond the injection ports to the wall - a quick set time for this epoxy greatly simplifies installation, and ensures a good bond to the wall. Note that the epoxy will not bond well to the injection port plastic material - so use a bit of extra epoxy at the end to overlap the edges of the injection port to assure a good bond to the wall. This epoxy cures in 8 hours - and I allowed the full cure time to ensure the ports were well installed on the wall - this will make the application of the waterstop repair cement much easier and reliable. Other adhesives can also be used, such as hot melt glue and silicone adhesive - hot melt glue may speed the job by setting up more quickly, and allowing you to move to the next step without delay.

Injection port installed with 5 minute epoxy. 
With the injection ports well bonded to the wall, it's time to apply the waterstop repair cement. Sika recommends Sikaset Plug. It's sold in many different formats at your local home improvement store, 1kg, 5kg and 25kg sizes. For the repair of 2 vertical cracks - about 6 feet long each, the 5kg bag was perfect. This product sets in 2 to 3 minutes - its working time is very very quick. This required some organization to get the best results out of the product, and make an effective repair. I went to the dollar store, picked up 2 sets of plastic measuring cups - so that I could make the mix consistently every time without fiddling with adding a bit more water or a bit more cement. The mix ratio is three parts cement to one part water - and you don't want to make too stiff a mix otherwise it will set even quicker - and give you only about a minute of working time. I was mixing about 1/2 a cup of cement at a time.

Sikaset Plug hydraulic repair mortar - note the dollar store measuring cup to make successive small mixes quickly and consistent.
In addition, I was working behind a 2x4 wall stud - it's important to give yourself enough space to trowel this material onto the wall - taking the time to move the stud out of the way will improve the quality of the finished job. Finally - I took a pointing trowel and bent the tip at 90 degrees - so I could work between the surrounding 2x4 studs, and work the material around the injection ports within the limited space. This was my most important trick for successful application.

Pointing trowel bent to 90 degrees - for working in the wall space between surrounding wall studs
It's important to follow the directions for the Sikaset Plug, begin by cleaning and wetting the wall surface, and keep the wall surface wet - it will improve the adhesion of the Sikaset Plug to the wall. I applied the cement about 1/2" thick, 4" on each side of the crack, with a bit of extra cement around the injection ports, just to ensure the injection ports are well supported by the cement for later when the epoxy will be injected.

Concrete wall surface wet, working the Sikaset plug up from bottom to top
Working Sikaset Plug around the injection ports
With the Sikaset Plug applied from top to bottom of the crack, I allowed the morter to fully cure for 8 hours prior to injection of the epoxy. If you don't give the mortar enough time to cure, the epoxy under pressure will force up the injection ports breaking the mortar, and the mortar will lift off the wall. When it's time to inject the epoxy, set up the cartridge by removing the cap and plug, inserting the adapter and mixing tube, screwing on the retaining ring, and putting the cartridge into the caulking gun. Slow, steady, even pressure and patience to give time for the epoxy to work it's way through the crack is required. I applied pressure for about 2 minutes for each injection port, and waited until epoxy started flowing out the next injection ports above and below before moving up to the next port. Once I injected all the ports, I started back at the bottom and gave each port a second application to ensure the crack was completely filled, and then capped all the injection ports.

Capped injection port
My wall is about 8 inches thick, and the cracks were about 6 feet long. Each crack, about 1mm wide, took about 3/4 of a tube of epoxy each. If your cracks are wider - consider using the expanding polyurethane foam product instead of the epoxy.


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