# patching hole in 8" concrete block



## Ron6519 (Mar 28, 2007)

BlueBSH said:


> well the geniuses that built the house punched a 3/4" hole in the foundation block to run a Underground feeder electric line out to our lamp post instead of running it through the wood and using conduit, they just ran it right through the sharp concrete hole they punched through... well this line has been moved, now there is just a hole..
> 
> 
> I need to patch this hole, what is the best stuff to use? I don't want to have to mix an entire batch of concrete to do this... the hole may be 3/4" but it of course bevels out due to how they broke it to about 6" in diameter although at the widest point its maybe a 1/8" chip off the block.....
> ...


Are there holes on both sides of the block? Do you have access to both holes? Did they punch through the waterproofing membrane on the exterior? 
I'd use hydraulic cement if the walls of the hole are parallel to one another.


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## BlueBSH (Oct 29, 2009)

Ron6519 said:


> Are there holes on both sides of the block? Do you have access to both holes? Did they punch through the waterproofing membrane on the exterior?
> I'd use hydraulic cement if the walls of the hole are parallel to one another.


yes holes on both sides have access, they are at different levels though, no clue why..... they didn't go through the black coating, because oddly enough they never put any in at this block level, go one down from it and its there


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## BlueBSH (Oct 29, 2009)

BlueBSH said:


> yes holes on both sides have access, they are at different levels though, no clue why..... they didn't go through the black coating, because oddly enough they never put any in at this block level, go one down from it and its there


should add the holes are on different levels, but within the same block... one was at the top the other was at the bottom, its like they tried to get the outside hole as close to on grade as they could


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## SteelToes (Oct 5, 2010)

Well it doesn't really matter what type of cement patch you are going to use.
Hydraulic cement it’s designed to expand and seal.
It works to certain extend on solid concrete foundation walls where there is no voids and it can be packed in tightly. 
I don't know if you've ever worked with hydraulic cement but its sets really fast- in about 5min. You need more time than 5min to fill that void.

Cinder block if not waterproofed on the outside its going to leak regardless if it has a hole in or not.

I would use "precision grout" for this kind of repair and do your best on the outside.


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## jomama45 (Nov 13, 2008)

SteelToes said:


> I would use "precision grout" for this kind of repair and do your best on the outside.


Personally, I wouldn't recommend grout for this. Although it is extremely strong, it's also self-leveling, even when it's mixed extremely dry, and will be a huge headache for a novice to keep in a vertical patch. 

Type M mortar would be my choice and even Type S would be fine. Patch both the interior & exterior. Once the int. is fairly hard, take a scrap of wood, place it flush on the wall, and work it in a circular motion so it looks similar to the block surface.

Tar the outside patch when it's hard, place a little plastic over it so you can backfill w/o damaging the plaster, and fill the hole with dirt.



The reason the tar is likely down one course is because the grade was originally intended to be one course lower than it currently is, and no one really wants to look at exposed black tar.


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