I've got a fairly common below-grade basement door setup; a doorway thru the poured basement wall into a space enclosed with cemented cinder blocks and a roughly poured floor, containing wooden stairs and covered by overlapping metal doors.

The obvious problem with this setup is that water can find its way through the loose (uncemented) joint between stair enclosure and foundation wall. Especially after a few decades of subsidance have let things shift a bit.

As a stopgap (literally) I've injected urethane foam into the space between blocks and foundation on both sides ... but I'm still sometimes getting a seeping of water thru this space.

If I want to eliminate that, first step is probably to improve exterior grading so there's less water near the foundation. After that, choices seem to be either let it be leaky but put in a french drain, or to dig up and redo the enclosure with a better bond to the foundation, or to dig things out and try for a better injected gasket ...

Any advice for this kind of joint?

  • Dig it out and install your own personal bat-cave and winecellar. ;^> If it was done right it would be poured as part of the foundation, but it so rarely is, and once it's been done wrong it's a never-ending problem... – Ecnerwal Dec 29 '15 at 16:15
  • @Ecnerwal: Don't tempt me on the batcave. My girfriend and I keep muttering about needing a tunnel across the block to connect our two houses... How do folks seal extension foundations to existing foundations? Can it be reliably fixed now if I do rip it out and reinstall? I'd still like an Answer, even if it isn't one I'll be happy about. – keshlam Dec 30 '15 at 15:56
  • Not quite up to "answer" standards, as I can't say it will be reliably fixed. Normal "new concrete to old" is drill holes, insert rebar, possibly these days with diamond saws slice in a V-groove - dovetail would be better but difficult. Maybe etch the old stuff with muriatic acid (be careful, don't become the Joker or the Phantom of the Opera.) Be done with the acid before you start with the rebar. And if you have the thing exposed, waterproof the living <bleep> out of the outside. – Ecnerwal Dec 31 '15 at 0:47

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