Discovered this hole today in the corner of my cinder block foundation. Water is pooling there when it rains (another fix I need to do) but for now, I was going to chip out the loose piece, mix instant concrete and fill it. Is that enough to permanently repair it?

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Crucially, this is a cinder block foundation so I was only going to pack about 2” of concrete to leave the center of the block intact for proper water flow. Is that the correct method or should I be filling it in more?

Edit: After reading up, I tried a fix here. I pushed some mesh grating into the block to until it was flush with the core (it's hollow in the middle) and then mixed some dry quickset cement. A few wood forms to hold the corners. Now I need to have the driveway re-graded and maybe a new drainage system near here.

  • 1
    This is a good close-up picture, but you may want to add one a little further back to help with perspective.
    – RetiredATC
    Nov 15, 2022 at 15:41
  • Where is your location in the world ? In most places hollow concrete blocks are not suitable for the foundation of a house.
    – RMDman
    Nov 15, 2022 at 15:49
  • I’m in NY state and they appear very common in this area. Build is 1970s. Added a second photo thanks! Nov 15, 2022 at 16:01
  • @RMDman I'm in Washington State and while not common, they are allowed There are some requirements such as adding a rebar to every other cavity in the blocks and filling it with concrete. Why every OTHER one remains a mystery to me, why not all? Oh well, I'm not an engineer....just thought I'd mention they are allowed. Nov 15, 2022 at 16:02
  • In the first close up picture those blocks look more like cinder blocks than concrete/cement blocks. Repair should be almost the same.
    – crip659
    Nov 15, 2022 at 16:20

2 Answers 2


Make a good faith effort to remove the two bottom broken pieces.

Then fill in with high strength concrete until level with the ground.

Let the concrete sit for couple of hours or so until it sets. Then fill the remaining with more stiff mixture and fill it. After it is completely full, you can just screed it with a trowel nice and square.

As good measure secure it with a little board or what have you just to protect the concrete from sagging.

It is also a good idea to make the grade in that area away from the house since there has been years of water penetration.

There has been no compromise in structural integrity of the house.

Hope this helps.

Take care.

  • 1
    Thank you so much. I did just that and it seems like a decent repair. I'll keep my eyes on it. Thanks for not leaning into the Doomer sentiment of some of these comments, my anxiety can't take it! Nov 17, 2022 at 4:09

The cracks on the pavement indicate there is a settlement problem. I suggest engaging an experienced contractor to solve the problem from the root.

  • The house is perfectly level and the driveway was poorly laid and appears to have eroded (along with the brick) over time with poor water flow. This seems like the nuclear option? Nov 15, 2022 at 16:57
  • Water flow should never cause a block to crack.
    – RMDman
    Nov 15, 2022 at 16:59
  • What? “Water is the primary cause for most crumbling concrete. This substance is known as the universal solvent since it is capable of breaking down almost any compound. Whether from flooding or from repeated rains, water eventually wears down the structure of a cinder block from the outside, causing it to flake off and crumble.” Nov 15, 2022 at 17:06
  • 2
    @podcastfan88 The "universal solvent" moniker is more poetic than practical. I think most of water's bad effects come from freeze/thaw cracking which fits with your NY location. It can soak in, or enter any crack, then as ice it expands, breaking the concrete.
    – Armand
    Nov 15, 2022 at 22:10
  • As is commonly noted, water carved the Grand Canyon, so it can carve out the corner of a cinder block. However, as @Armand noted, it's most likely that a little water sat in the corner between the driveway & this block, froze and started a small crack. Then water got into the small crack, froze and made a bigger crack. Lather, rinse, repeat until what you have here.
    – FreeMan
    Nov 16, 2022 at 1:12

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