Replies

1. GBA Editor
   Kiley Jacques | Feb 02, 2022 01:43pm | #1

   I found this recommendation in the Fine Homebuilding discussion forum: Sikaflex. From the builder: “It's a self-leveling concrete sealant. If the cracks are deep, you will need to use some sort of backer rod. Best thing out there. Sometimes if you are lucky, you can find it at Home Depot.”

1. 
   josephny | Feb 02, 2022 03:05pm | #2

   Thanks very much for the recommendation.

   I actually have that stuff and have used it to seal various other (non-concrete) cracks.

   It behaves completely differently than a self-leveling concrete-based filler. One such difference is that it's difficult to make it totally flat and blended/feathered in. But it is indeed good stuff.

2. 
   n2dirt | Feb 02, 2022 09:46pm | #3

   CFS-830 fast set joint filler. Fill the cracks with fine sand then put the product on top. Two part that mixes in the tube.

1. 
   josephny | Feb 03, 2022 12:58pm | #6

   Thank you.

   Is this expensive product really that much better than others?

3. 
   PAUL KUENN | Feb 03, 2022 11:35am | #4

   First, clean with water and wire brush. Then a simple wash with Portland in a bit of water slurry. Then,1 part Portland cement and 2 parts sand to patch all. Feather with a sponge.

1. 
   josephny | Feb 03, 2022 12:59pm | #7

   Thank you.

   Why this and not a sealer-type solution?

4. 
   walta100 | Feb 03, 2022 12:12pm | #5

   Seems to me cracks in a concrete floor are almost 100% cosmetic and an indication the base under the concrete was settled slightly. It seems to me the base is likely to settle more over time making any repair temporary at best. Any repair is unlikely to be invisible unless it is covered paint or floor covering.

   If the goal is to fill the crack keep out radon gas. I would blow the crack clean with compressed air and fill it with a flexible caulking as deeply as possible.

   If you must fill it for some other reason it seems to me cement based products are unlikely to stay in narrow cracks under 1/8 of an inch look at epoxy type products.

   https://www.acehardware.com/departments/paint-and-supplies/tape-glues-and-adhesives/glues-and-epoxy/1325414?store=10672&gclid=CjwKCAiAl-6PBhBCEiwAc2GOVN6K0sG42QCWxDSQI9ePoB_sxdkJIFX36UEmTwftSlfD8dNHlAv3oRoC7JoQAvD_BwE&gclsrc=aw.ds

   Walta

1. 
   josephny | Feb 03, 2022 01:01pm | #8

   So the existence of cracks means it is likely there will be more movement, which would mean a hard and brittle solution would crack.

   And, a hard and brittle solution like a cement/concrete product won't do well in very small cracks to begin with.

   Hence a sealant or epoxy.

   Makes sense.

   Thank you.

5. 
   PAUL KUENN | Feb 03, 2022 01:55pm | #9

   I use the portland mix for most "after 1950s" repairs as you will always have movement and cracking and it's easy just to repatch as needed.