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DickR · 10-23-2011, 08:30 AM

Building on what Kamper added, in most cases that black spray applied to the outside of a new foundation is just a very thin "dampproofing" layer, intended as a water diffusion retarder. It won't help much against the inevitable cracks that develop over time.

A block foundation inherently has more weak spots, at the mortar joints, and that is where leaks develop. If you go the route of excavating on the outside, There are a few things that could be done then to eliminate the leaking. One would be to have a thicker waterproofing sealant sprayed on. Another would be a peel & stick membrane applied. Either is on the order of 60 mils in thickness and will bridge cracks up to perhaps 1/16" wide. A different approach would be to apply something like Cosella-Dorken's "Delta-MS"
(http://www.doerken.de/bvf-ca-en/prod...eets/index.php) to the outside of the wall.

The best solution will be some compromise between access to the inside or outside of the walls, and cost.

10-23-2011, 08:30 AM	#9
DickR Senior Member Join Date: Apr 2008 Location: Moultonborough Posts: 751 Thanks: 4 Thanked 259 Times in 171 Posts	Building on what Kamper added, in most cases that black spray applied to the outside of a new foundation is just a very thin "dampproofing" layer, intended as a water diffusion retarder. It won't help much against the inevitable cracks that develop over time. A block foundation inherently has more weak spots, at the mortar joints, and that is where leaks develop. If you go the route of excavating on the outside, There are a few things that could be done then to eliminate the leaking. One would be to have a thicker waterproofing sealant sprayed on. Another would be a peel & stick membrane applied. Either is on the order of 60 mils in thickness and will bridge cracks up to perhaps 1/16" wide. A different approach would be to apply something like Cosella-Dorken's "Delta-MS" (http://www.doerken.de/bvf-ca-en/prod...eets/index.php) to the outside of the wall. The best solution will be some compromise between access to the inside or outside of the walls, and cost.