We are having a garage added to our home, and this required a new foundation to be attached to our existing foundation. There were 2 windows in the basement that needed to be filled. The foundation company drilled four large holes (looks like at least 3/4 diameter) and used some strange looking bolts to attach the forms over the windows. I estimate the holes are about 4-5" deep, in an 8" foundation.

Some of these holes will not be covered by the slab, they will be underneath, in the 3/4 gravel. I am worried that these holes will fill with water and create a slow leak or, worse, cause cracking if water gets in and freezes.

I've looked around for a suitable product to fill the holes with myself, as I am almost certain the foundation company is not going to take care of it, and this Monday is the absolute last day I can have them messing about with the foundation.

  1. Should I be worried about filling these holes?

  2. If yes, is QUIKRETE® Hydraulic Water-Stop Cement a good choice?

  • Some pics would help here...
    – Huesmann
    May 7, 2023 at 12:47

2 Answers 2


The best process is to ask the contractors what they plan to do regarding the holes.

They may already have the fill planned in their schedule and you will not need to do anything.


Hydraulic cement is indeed the canonical product for plugging holes in concrete.

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