How best to handle wet garage wall ?
I have a free standing garage that has poured concrete walls. The garage is built into a steep hill side that opposes the back of the garage and one side. I intend to convert the garage to a wood shop where I will store lumbar so I am trying to mitigate moisture issues. The garage has a new roof and interior spray foam in the rafter bays. My problem is that an area about one foot wide on the floor adjacent to the back and the hill side wall stays damp and the lower portion of the same two walls is damp for about 18 inches in height. I cannot get to the exterior of the foundation because it is right on the property border on the side and would require a major disruption of my neighbors back yard and hill side. The back concrete wall on my property has a distance of at least 20 feet to the foundation making it nearly impossible to get to.The garage pre dates current zoning laws for abatement explaining how the structure could have been built right on the property line.
I realize that I could install an interior french drain and sump pump to address the damp floor but I question if this would address the wet wall. Is there any way of addressing the damp wall from the inside of my garage? I am not optimistic that any type of applied product to the interior of the concrete wall would solve my problem with the walls. I have tried a water resistant masonry paint and it lasted until the first rain.
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I am just speculating here but...
If the structure does not have perimeter drains or waterproofing on the exterior below grade walls, I think it will always be subject to moisture intrusion. You can probably improve the situation by using gutters and grading to keep the surrounding soils as dry as possible. Even with those steps, you may need an interior drain and dehumidification to create an appropriate work space. I would suggest trying the simplest fixes first.
Xypex- but you would need to remove the masonry paint by sand blasting
Xypex and similar penetrate the concrete and fill pores in it. That might not completely solve the problem, but it would certainly help some.
Gutters and grading should also be used to minimize the water back there, if any of that is possible.
With those done, if you still have a problem, you'd ideally want to excavate, coat the outside of the wall with damproofing, and put in a footing drain. Perhaps you can put down a tarp and/or plywood on the neighbor's lawn to protect it while you (or someone you hire) excavates by hand. Perhaps negotiate with the neighbor and offer something in exchange for permission to do that. (Make them some furniture when the wood shop is up and running?)