Sealing 6″x6″ Holes in Poured Concrete Foundation
Hi-
Currently air sealing the rim joists and when prepping for the job I discovered that the previous owner had covered up/obscured some holes in the foundation where a replaced center beam used to rest. It’s about 6″x6″.
From inside the house in the crawlspace, I can see the squiggly dried glue on the back of the mud board that I now realize was glued to the exterior foundation to cover up the hole. The other hole to the outside actually exits under the poured cement front porch and there is sand and pebble back fill, most of which has already “drained” into the crawlspace.
Any suggestions how how I might these off?
While we are at it, I thought we might also decommission the window.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
I would buy a bag of ready mix concrete and fill them. I'd cover them from the outside with a piece of plywood screwed to the wall with tapcons. On the inside I'd cover the bottom half of the hole with a piece of plywood and then fill and try to pack the concrete in. I'd use a stiff mix. Once the concrete had set I'd take the concrete off and go over it with mortar to make it smooth and flush.
I'd do the same thing with the windows. I'm a fan of decommissioning basement windows. For an opening that size I might drill some holes in the sides and put in short pieces of rebar to bond it all together.
One of my neighbors is 3' away, that means the basement windows on that side look pretty much onto brick foundation. Yet I would still not remove any of them.
I know windows are expensive but they are worth the cost even if you only use the place as the occasional workshop.
The window was covered with plywood that was foam-sealed to the window frame. I just pulled it off and the sudden daylight gave the basement an entirely new feel! So I'm still on the fence about the windows, Akos, but appreciate the advice about the rebar DContrarian if I do go that route. I can practice my concrete skills on the smaller holes first.