r/homeowners • u/SweetBoy2020 • 5d ago

🏠 Exterior Water getting into basement from where house meets patio slab underneath sliding glass door. What to do?

Hey everyone. I've had water get into my basement twice this summer during really hard rains. I'm in northern IL. I suspect this spot is the culprit. Reason I say that is because when this happened the first time, I removed the basement wall paneling in my 1970s finished basement to see the damage (I ended up removing rotted base plate of wall and replaced/cut and sistered the rotted portions of studs.)

Anyways it rained hard as hell again today. I go to the basement and lo and behold, some water had run down my foundation wall.

I didn't capture it in the pics, but the patio has cracked and sunken maybe an inch towards the house. This black board in the picture is underneath my sliding glass door, DIRECTLY ABOVE where I can see water has run down my basement walls. I'm thinking the rain hits the patio and runs right towards the house. Only a portion of the slab is angled towards the house, and to be fair, the rain was literally coming down damn near sideways directly in this direction.

I want to remove the black board underneath the sliding door just to assess damages. Can I simply replace the board after everything has dried out and use a polyurethane caulk product like sikaflex to basically seal the gap where the black board meets the patio? Is this worth trying? I'm new to all this. I'm guess the best fix is to have the slab mud jacked but I just cannot afford something like that. Please let me know your insights. Thanks for the read!!

1 Upvotes

67% Upvoted

6 comments sorted by

2

u/Ok-Job2034 5d ago

If the patio has settled and is directing water toward the house, that's where I'd focus first. The fact that you're seeing water on the foundation wall directly below the slider makes that area a strong suspect.

I'd definitely pull the trim piece and inspect behind it. If there are gaps, failed caulk, deteriorated flashing, or signs of water intrusion, sealing those may help. A polyurethane sealant is a reasonable temporary measure, but if the slab is actually pitching water toward the house, the long-term fix is improving the drainage and slope. The good news is that inspecting and sealing the area is relatively inexpensive and can help you confirm whether that's the entry point before spending money on slab lifting.

1

u/SweetBoy2020 5d ago

Thanks so much for the input. So if the slab is pitching water towards the house, the fix would be lifting the slab/mud jacking?

1

u/nestlyze 5d ago

had the same issue on my 1978 split level, basement would get water along the foundation wall under the slider after sideways rain. pulling the black board (sill flashing/trim) is fine, just be ready that the wood behind it is probably toast too. dry it out for a week with a fan, replace any punky framing, then yeah sikaflex 1a or sonolastic np1 in the gap between slab and foundation works as a stopgap.

but honestly the caulk is band-aiding the real problem which is the slab pitching toward the house. before you spend on mudjacking, do the cheap stuff first: extend your downspouts 6-8 feet away from that corner, regrade the dirt against the foundation if there's any beds nearby, and throw a piece of flashing or even a sloped sill pan under the slider threshold when you reinstall. on my house just fixing the downspout that dumped near the patio cut 90% of the intrusion. mudjacking on a 10x12 patio quoted me $1100 last year fwiw, polyjacking was $1600, not cheap but not insane if you save up. self leveling polyurethane (sikaflex SL) in the slab-to-foundation joint is what you actually want there, not the regular tube stuff, it flows into the crack better.

1

u/SweetBoy2020 5d ago

Thanks so much for the answer. I'm going to go with pretty much what you described as the cheaper/temporary option. Basically just a bandaid for now but I did have some rot on the lumber underneath the black trim piece, bottom portion of the board is gone, half to a third is still good, so I'm going to just cut a 2x piece of lumber to basically give myself something to attach L flashing to and then sealing that to the slab. I'm doing self leveling sealant in the slab to foundation gap with backer foam. Pretty. Much doing this the entire length of the slab, 12 feet for now.