Thanks for the comments. Would installing a french drain on one side of the garage help? When we moved in we had a big empty muddy clay filled flower bed on one side of the garage. Since we moved in I got rid of that and placed sod down with a slight slope away from the foundation. (advice from a foundation company). We had some sinking in the garage and had piers installed before we closed. Could this have anything to do with my problem?
Yes, a french drain will help a lot. You may need to consult a soils engineer.
I have way more experience with french drains than I ever wanted to have.
The home I currently live in is on a hillside... a custom home that is tiered (it steps up the hill). The General Contractor died unexpectedly about 3/4 of the way through construction, and in the process of picking up the pieces, we discovered a ton of construction defects. Magically, every sub said "I didn't do that; the dead guy came in and did that himself." Yeah, right. 17 lawsuits later... but that's another story.
One of the many things screwed up was the drainage system... I have a pier and grade beam foundation, and water would pool on the uphill side of grade beam intersections. I literally had to put a half dozen sump pumps under the house during the rainy season.
The saturated soil caused the garage slab to heave and crack.
I put in 3 french drains, and magically the water-under-the-house problem was cured. The soils engineer I worked with spec'd the drain a bit differently than most. Because of the high clay content of the soil (tiny particles), we dug the french drain about 3 feet deep (needed to consult with the engineer who designed the foundation to ensure it was OK), and in the bottom on a few inch bed of drain rock he put a perf pipe with the twin perferations facing UPWARD, not DOWNWARD (as is the custom in the area). He said the downward facing perferation implementations have been failing in the area after about 8 years -- it gets clogged. Of course, the perf pipe was wrapped in filter fabric, and the entire trench was also lined in filter fabric.
Here's a suggestion for you to consider... in one location where we couldn't really do a french drain, we did something different that helped a lot. Next to the exterior foundation on one uphill segment I had installed a concrete walkway, with about 12 inches of drainrock underneath. The Concrete is sealed. During the wet months, water from the hill hits the concrete walkway and runs to a surface drain. It has been 16 years and the concrete has never deteriorated.
One other location: in addition to the french drain, in one location we put bituthane (I think) against the grade beam down to about 6 feet.
Good luck -- water infiltration can be a tough problem to solve.
