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I uncovered a situation where a couple header boards were embedded into the basement foundation. You can see in the photo they punched a hole in the foundation and ran the boards through it.

I can't move the boards, so would like to protect the end grains before putting on a concrete patch.

Is there a good way to seal the wood from the concrete?

foundation 1

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    Those boards appear to be wrapped in masonry already. Sealing the end grain (which is difficult in the first place due to its porosity) won't accomplish much. If anything, dab on some penetrating anti-microbial treatment. – isherwood Oct 8 '19 at 13:30
  • Thanks, I was also thinking it would be difficult to seal and in the end not make much of a difference. Do you have a product example that I could reference for the penetrating anti-microbial treatment? I googled and could not find anything. – OverStacked Oct 8 '19 at 20:18
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The end of that wooden beam will move slightly with humidity and temperature changes, attempts to fill that shallow void with concrete may end in dissappointment.

I'd cut a small rebate using a oscillating tool or grinder and place a piece of fibre-cement sheet over the opening, glue it in-place with builder's filler. then render over it to match the existing footing.

  • That is a good point, being that thin of a coat it would most likely crack. I'll take your advice and chisel out a chunk of the boards before finishing it. – OverStacked Oct 11 '19 at 1:13
  • I would cut the cement board into the concrete so that it finishes flush-ish. – Jasen Oct 11 '19 at 22:25
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You could add a few layers of thin glassfiber net when applying the concrete. This should improve the flexural and compressive strength of the concrete substantially. I personally use insect netting that can be found rather cheap.

There should be no real need to seal the wood when applying the concrete. But applying some oil to the ends of the wood before the concrete should make it not stick together.

For repair jobs where strength is an issue and if you don't need huge amounts. It can be worth looking into high performance concrete. It has superior properties and it bonds extremely well with regular concrete. When using HPC for a repair job its very important that the concrete its being applied on is already saturated with water.

  • I ended up removing about 3/4 of an inch off the end of the boards. Then sprayed some anti mold on the wood and glued a foam sill gasket over the wood. Then used rapid set mortar mix for the patch. – OverStacked Oct 16 '19 at 18:40

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