DIY Home Improvement Forum banner

Concrete block hole

5339 Views 5 Replies 4 Participants Last post by  algored2deth
I have a hole in a concrete block in my basement. The hole is from previous A/C lines. Would like to patch this but I am really not sure of the best method. Using the right mortar, would it be a matter of filling the hole in half way first (like a half moon) and then finishing off with a second layer? Hole is about 4inches in diameter.


See less See more
1 - 6 of 6 Posts
Plug with Hydro Cement from both sides. You will have to make the first batch stiff enough that it can still be packed into the hole, but not loose enough that it falls apart and drops into the cavity. The last layer, you just smooth over with either a trowel, or wide blade drywall knife.
You can probably stuff crumpled newspapers into the hole as a backe for a pathch since there probably is a cross web under the hole area that will support it. You can just mix up some Type N or Type S mortar and proceed from ones side or both sides depending on accessiblity. Use two applications, the first to fill 80% of the patch depth and then a final application to finish it off reasonably smooth. - Considering the previous workmanship and quality of materials, you do not have to be fussy, after the mortar cures and shrinks, it would be good to apply or force in Hydraulic cement into any deep cracks and voids.

I have no idea what Hydro Cement is, but Hydraulic cement is meant to be forced into cracks and confined spaces and not as a general coating since it relies of expansion to get maximum confinement and will do nothing as a general surface coating.

It looks like there's an opening in the web on top of the block. You could just find a way to cover the holes on each side and grout the block. Just out of curiosity, why is the top set of blocks offset?
The problem with just dumping in from the top, it that there ia nothing to stop the intended slid concrete from going down, leaving a void. The hole is just above a 1" or 1/1/4" wide cross web and concrete can flow around and down. If there is no web, then you just keep dumping concrete in until it finally bridges and settles.

Those blocks were probably made by one of the 3 producers active in Rochester when the house was built. Definitely a bad DIY job of laying the block
I am not sure why the house was built like it was and why there is an offset as cluthcargo asked. This area is specifically in the crawlspace. I have included a couple more pics for more clarity since there seems to be some curiosity to the oddness of it all.

I have had the house for three years. House was built in '64.

You will notice the open "tops" of one row there. In all of the holes, I had put in great stuff foam because there was a lot of cold air leaking into the house. I actually filled the hole with FG batting first then foamed. I had to redo a lot of the brick joint because they were getting bad and allowing air to leak in. It was pretty cold in the crawlspace a couple winters ago. Currently in the process of insulating it all but that is another story for another day. Small gaps are pretty easy to fix with bag mortar. When there is a hole that is 4" across, the approach needs to change.

Just to clarify a bit more: The hole does exist on both sides but the exterior side is still ok for now. Eventually I will do that one but it will be later. Develop my technique here and then do it out there. BTW, just dumping concrete from the top may work but the hole is pretty deep because it channels into other blocks.


See less See more
1 - 6 of 6 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.