How to repair small ground level leak in exterior house wall causing water damage in basement?

I would start on the exterior by digging in the area of the leak. You will see the discoloration on the concrete foundation caused by moisture and you can determine if just the area needs to be sealed or the entire foundation on that side of the house and if so have it dug out completely and sealed with any number of quality products you can purchase at your local Home Depot and after sealing it, change the Landscaping outside and have the ground slope away from your home as should be the norm so water will not collect against your foundation. As well as sealing it you can line it with some 8 mil poly to add an extra layer of protection. The drywall problem has occurred because of the moisture coming inside dripping down the concrete foundation and soaking the drywall at floor level. You can cut away three or four inches and put a fan to dry it out, replace drywall where you have removed it, mud sand and paint, and cover with baseboards.

Hello, First step would be to open up the drywall and investigate the water’s point-of-entry. In a best case scenario, you may only need exterior caulking around a window or at other possible building-envelope entry points. Once the suspected water entry point is narrowed down, you can perform water tests on your own, hosing down sections of the exterior of your home, in periodic stages isolating possible entry points. Starting from the lowest point moving up. On the other hand, its possible you may need a waterproofing company specializing in foundation wall leak repairs or concrete epoxy injections, that can expose the exterior foundation walls and then waterproof accordingly, if the water penetration is through your foundation wall. Personally, I would recommend a waterproofing company that can also repair your interior drywall, insulation, vapour barrier, execute possible mold remediation, etc, or a general contractor that can do all of the above. Best regards, Bryan

Your problem has compounded over several years. You now have mold in the wall cavity behind the drywall.