I have a problem with water seeping into the corner of my detached, unheated garage and soaking the floor in Spring. It can occur anytime most common in Spring with snow melt and rain. The garage was built for the previous owner, about 2001. I have owned the house since 2002.

The problem is somewhat obvious. The garage lies on a flat slab. The slab is lower than site grading at the high corner. In other words, over time soil has settled so that it lies a few inches above the slab, against the wood sheathing, although the builder did extend the foundation waterproofing over the sheathing in that corner. Water must be getting past seams or cuts in the plastic waterproofing.

My preferred solution, building some kind of retaining wall to hold back soil and thus regrading so that soil never settles above the slab, is not possible. This is because the underground gas line runs about a foot or two away from the foundation on one of the two sides that would need a retaining wall.

I believe my best option would be dig a trench along the length of the two high sides, lining with landscaping fabric, some gravel, putting down perforated drainage pipe with sock along the foundation, feeding into a dry well, and back filling the trench with gravel.

Looking for a sanity check, advice, recommendations, etc.