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Waterproofing in Existing Structure 1

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phamENG

Structural
Feb 6, 2015
7,621
Existing semi-open structure, looking at a brick wall that is continuous with cast-in-place stairs abutting it. The stairs are exposed to weather, but the owner wants to use the space under them for dry storage. Anyone have any clever ideas for waterproofing that joint apart from a fillet of silicone that gets replaced every 6 months? Whatever the solution is, we can't damage the brick as it's publicly accessible and looks matter. The bricks are of an odd size and replacement is very difficult. So I've shied away from grinding out the edge to recess a sealant.

Sika has a their SikaSwell S-2 sealant, but it seems to require encasement in concrete to work.

It may require a call to Sika to see if they have any brilliant ideas, but thought I'd check here first.

Thanks.

Screenshot_2022-03-25_105122_rjzjqo.png
 
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Maybe Hohmann and Barnard has a suggestion. But I'd say the owner is going to be disappointed. Brick moves different than concrete, so the joint is always going to be stressed.
Can you embed the stairs (partially?)in the brick wall? It's going to be messy for the bricklayers, but the joint will be more waterproof.
 
Install some type of gutter system below the stairs inside the proposed dry storage? This would at least get you away from worrying about looks.
 
Thanks.

Jed - it's existing, so embedding the stairs will be tough.

dauwerda - I'll run that by the architect. Maybe a good 'insurance' option regardless as long as there's a way to get rid of the water.

I did call Sika, and they don't have anything. They recommended 'Mountain Grout' which is an injection polyurea joint filler. They also have a Hydrophobic Polyurethane Chemical Grout that may work.
 
You might look at Sika Silbridge-300 or the originator of the concept, DOWSIL™ 123 Silicone Seal.
It is a pre-cured silicone strip laid into a bed of silicone sealant. The mortar joints would have to be filled with mortar to a flush condition.

Article in Construction Specifier
 
My suggestion will be XYPEX products.
-For the concrete surface waterproof XYPEX coat

- For the joint with brickwall ; one of the repair products acc. to joint width ( Patch'n Plug or FCM 80 )

I have experience with this product ..
 
One could possibly do a "box within a box," i.e., build a water-resistant enclosure under the stairs. Being on the underside of the stairs means minimal sun damage.

Alternately, since the joint is apparently large enough for water to get through the joint, some sort of pressurized applicator might allow you to push sealant into the joint and fill the gap?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
epoxybolt - thanks. It looks like DOWSIL may be available in multiple profiles. If they have an "L" shape it might do really nicely. A good one to explore further.

HTURKAK - thanks. I forgot about Xypex. I've spec'd their admixtures for waterproof concrete before. FCM 80 may be perfect if the joint is large enough to get it in.

IRstuff - that's a doomsday scenario. They really want to stop the water before it enters. If not, they have to manage it after it comes in and that creates a whole new maintenance issue. But if it comes to it, it comes to it. The product that Sika suggested is a 2-part pressure injected foam. Still waiting on pictures of the joint (or an opportunity to visit the site, but it's a hike and I'm not that far along in it yet) to narrow down the repair options a bit more.

Excellent suggestions all around. Thanks, everyone, for your ideas.



 
PhamENG:
That client/Arch. is asking a lot, make it waterproof, after the fact, when those details are actually Arch. details which they usually avoid/ignore, unless we pester them about thinking about them and showing them on their drwgs.. And, trying to deal with that potential differential movement and having it not show is an ask too much. Does the slab slope so it will drain, and is there daylight, a scupper, a down spout someplace to drain it to? I would bond/caulk an ‘L’ shaped flashing to the slab and run it up the wall 6" (several brick courses). This may be a ‘Z’ shaped flashing, and soldered at corners, etc, with the outer vert. leg down and caulked into a saw kerf in the slab, the horiz. leg back to the wall, or sloped up slightly to drain away from the flashing, with small cant strip under it, and then a 6" vert. leg up the wall. Then, a counter flashing can be caulked into an opened bed joint a couple inches higher, and you can from a sloped gutter on its bot, edge, where the drip lip would normally be.
 
Pham-

That one is tough. The geometry is similar to a parapet wall on a building.

How about a nice slip-resistant polyurea coating for the stairs that could wrap up the wall a foot or so?
 
How about adding a curb to the slab and leaving a gap that could be properly caulked. Could also cover it with flashing routed into the brick.
 
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