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scale of the crack
Thursday, September 9 2004
After Spanish class I turned my attention back to the trench. Realizing that I wouldn't be able to reach the western wall's foundation crack any other way, I started burrowing in from above at the top of the western wall. The western wall is buried for its entire eight foot height behind fill, but there's an added complication. Six inches from the foundation wall is a retaining wall of mortared concrete blocks which hold back earth which rises somewhat above the top of the foundation wall. To burrow in from the top meant dismantling part of this wall. Luckily, the mortar between the blocks is mostly broken up from successive waves of frost heave. Still, even with broken mortar, it's very hard to pull a concrete block out of a mortared wall. It'll give a little and then one of the bumps of clinging mortar will run into something, and there's no wiggle room to get it past. You have to beat on it with a cold chisel or (if you have the strength) pull the wall well out of alignment. I did both of these things and managed to remove a block. For any tier of blocks in a mortared concrete wall, after the first is removed the others are easy. Once I'd cleared four or five blocks that were in my way, all I had to do was dig downward in the general direction of southwestern Australia. At some point I pulled a rounded stone out of the bottom of my hole and there it was, golden light not from the fires of Hell but from the light bulb I had burning down in the existing tunnel.
Much later, I'd cleared out enough of the soil to see the scale of the crack I'd been digging to expose. It ran nearly all the way from the top to the bottom, and at the top there was about an eighth of an inch of east-west displacement. Evidently the weight of the fill soil (with the added burden of roof runoff) had managed to push the wall inward enough to crack the foundation and move a chunk of wall inward an eighth of an inch. It was a pretty serious crack, the kind that might have structural consequences. Indeed, if it weren't for the supporting effects of the floor joists and several framed room walls, the wall might have collapsed a long time ago. And even without structural consequences, a crack of this size would certainly be responsible for a lot of the water coming into the basement. As if to demonstrate this fact, several cloudbursts (the remnants of Hurricane Frances) came while I was working. The drainage system I'd constructed on the ground was quickly overwhelmed and water spilled past the retaining wall and into the narrow gap of soil between the foundation and retaining wall. From there it ran into the hole I'd dug and a good fraction of it vanished into the gaping crack in the wall. Exposing and repairing the full length of that crack is going to be a major job, particularly given the difficulty of maneuvering in such a limited hand-dug excavation. But I've come all this way, why elect Kerry now? Oops, wrong metaphor!
I did some research on fixing serious foundation cracks and found that one of the best methods involves injecting epoxy into the crack. It's a solid repair, but it requires special equipment not available to a DIY neophyte. It looks like I'm going to have to use conventional mortar, at least for the worst parts of the crack. The ultimate goal is to paint the wall with asphalt, cover it with a plastic sheet, install new PVC drain pipes, and bury it all beneath gravel.
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