Water leaking between sill and slab

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Old 10-20-16, 02:04 PM
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Water leaking between sill and slab

Trying to solve a problem on a recently purchased 40 year old home. The basement slab is at the same grade as the patio slab. The patio is 70% covered by a sunroom, the rest by a deck. However given the right conditions of wind and rain, water will make its way under the sill in the basement. You can see in the exterior photo where the previous owner tried to caulk and cut a groove in the patio to channel some water away.

I've exposed the exterior wall and can see where the fiberboard sheathing has previously wicked up water (see photo). So I know I'll have to take off a couple of courses of siding and replace probably the bottom 2' of sheathing.

My big question is how to create a water barrier outside so this doesn't continue to happen. I can't remove/replace the sill - there's two stories of house above it. I can use 1/2" vinyl for the replacement sheathing but that's not going to stop water penetration.

I thought about using some sort of self adhesive rubber membrane behind and under the new vinyl sheathing. Another idea would be to use plywood for the sheathing, tack on some wire mesh and create a dam out of mortar, hydraulic cement or stucco as a barrier. Thought about a concrete lintel that would eliminate the bottom course of siding. Cement them in place then flash over top behind the siding.

But I don't think any of those ideas are great. Does anyone have any better idea on how to create a water barrier? And sorry for the photo rotation - I don't know why they did that.

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Old 10-20-16, 02:57 PM
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The exterior slab should never have been poured at the same level... it should be a minimum of 1" lower. Assuming you wont be tearing it out, but you should.

To flash it, get yourself some Loctite S10 or NP1 sealant, and embed a galvanized flashing in the sealant. (After you replace all the rotten sheathing) Then install a PVC 1x2, then z-flashing, then start your siding above that.
 
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Old 10-20-16, 03:18 PM
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Thanks. Will that Loctite stick to the concrete slab long term? The caulk that the previous owner had used is delaminating and can be pulled up without much trouble.

And just to be sure I have clear what you're recommending, going from the existing sill outwards there would be:

- the sill
- some Loctite or NP1
- "L" galvanized flashing that also angles down and out on the slab
- vinyl 1x2
- z flashing
 
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Old 10-20-16, 03:49 PM
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You would put your sheathing on, keeping it about 1/2" up from grade. Next apply a HEAVY bead of the sealant onto the concrete. Then squish your flashing down into that sealant so that the flashing completely covers it. A WRB should lap over the top of this flashing. Those sealants are MADE to stick to concrete which is why I suggested you use them instead of an ordinary caulk. The concrete needs to be clean and dry. Use a heat gun if you need to dry it off prior to caulking it.

At this point you could put your siding back on. I suggested the 1x2 to keep the siding off the ground... since you have vinyl siding the 1x2 is optional.
 
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Old 10-20-16, 04:52 PM
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Thank you again. That's what I'm going to do.
 
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