I was wondering if anyone could shed some light on replacing a concrete
block that is in the middle of the foundation. I couldn't find anything
remotely like this problem in the search.
I have a block *shell* there now that was patched. Apparently there was
a pipe that had run through into the basement, then removed and the
hole patched on the basement wall, but not on the outside.
When I took off the patch because of leaking I noticed that they didnt'
patch the outside where the pipe used to come in, all I see is dirt.
Went to home depot to ask some questions and get some a mortar mixing
bucket. They suggested replacing the block.
I bought a block and some mortar repair. I was going to chisel out the
old block and mortar and put the new in.
Seems simple, but wanted to get some pros/cons or better advice.
It is possible to replace it but will almost require being able to get
at it from both sides. My approach would be to use pre-mix concrete.
Block one side with a piece of plywood (if the dirt doesn't already do
it. Block up about 1/2 of the other side and place concret into it and
sloped up to meet the top of the cavity on the other side. Needs a
stiff mix for this. Then, after that sets, It is just a matter of
continueing to fill in the remaining cavity. I did much similar to
block up an old small window in my basement. Another approach is to
get some 2 or 4" block and mortar them in in layers. Trying to mortar a
full 8" block in that situation is verging on the impossible from one
Darn, sounds tough either way.
Unfortunately I can't get to the other side, it's about 8 foot below
the ground and has a concrete slap on the top of the ground serving as
It is feasible to do the concrete mix they way you said, but how do you
get it in the top?
Any other suggestions would be great.
Thanks Harry K.
There is an easy way to do this but you need a little luck.
If the dirt at the back of the hole is very firm you can remove a
little of it and trowel in a concrete mix with a waterproofing
additive. This should fill in a little way on the outside of the wall.
Then with that still wet you trowel on a layer of mortor mix and insert
a new block. It should need to be lightly hammered into the wet patch.
Wait for everything to dry.
To do the concrete patch you can pour some of it as described in the
other post. The last bit you need to push the concrete mix into the
remaining gap, compacting it to the back of the hole, the add some
more. You need a very firm (dry) mix so it does not slump out.
I think that I'm going to combine the waterproofing suggestions, and
then slide the block in.
I will put some waterproofing on the block it's self, let it dry. Then
put some mortar on the rocks with some waterproof additive, then caulk
around that after it drys, and then insert the mortared block in.
Worst case senario is that I have to remove the block and then fill
with concrete with waterproofing.
Thanks for the help guys.
Well, I did it. Took about 6 hours not including drying time.
check out the pictures:
If I was to do it over again, i would go with 4x8x16 blocks, silicone
the one in, then motar the other. or not, this was quite fun. hardest
part was getting mortar in the back and sides, but I did my best. now I
wait for a heavy rain to see if it worked.
How deep below grade level is the hole? You really want there to be
waterproofing on the outside, on the new block, and the mortar joints around
it, which basically means digging a hole outside the house. (Doesn't have to
be a big hole- just enough to expose the block and a few inches around it,
and reach down to brush off the dirt, and brush on the waterproofing.) Did
they dig up the abandoned pipe, or just bust it off and do the patch from
the inside? You want water to stay outside the wall, not leach in through
the naked block and fill up the cavity before it comes through the inside.
If digging up the outside is totally impractical, I would paint the dirt
side of the new block with waterproofing, and run a bigass bead of caulk
around the dirtside edges of the hole befor you mortar the bottom and sides
of the hole , and the top of the new block, and slide it in. The stuff in a
tube meant for driveway cracks should work. It won't be as good as a tar
bucket from the outside, but it may help.
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