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tcbailey 12-06-2012 11:54 AM

Creating a water break on flat concrete
We have a covered breezeway between the house back door and the garage. The back of the breezeway is closed, and we would like to close the front to create a mudroom. The challenge is that the breezeway floor is the same level as the flagstone patio area next to the driveway. I would like to create some sort of concrete water break, and build the wall/door on top of that. Here's my plan:

Create 2x2 form where new wall should go, pour concrete along the entire length of the new wall. Attach pressure treated sill plate/wall on top of this new concrete "ankle-wall." Etc - easy enough to finish with wood/plywood/tyvek/siding from there.

- Is a 2x form (1.5" high) good enough here? We never get any standing water in this area, I only expect rain splash.
- How to ensure good adhesion to existing slab? I plan to clean thoroughly, but is there some sort of bonding primer made for concrete-on-concrete? Can I pour the new concrete over partially-sunken tapcon screws to hold it down?
- How best to fix the PT sill plate to this ankle wall -- tapcons, wedge bolts (worried about cracking the ankle wall with these), construction adhesive, or other?

Thanks in advance for your input.


jomama45 12-06-2012 07:08 PM

I wouldn't rely on a "chemical bond" between the old and new, or in other words expect to use bonding agent and have a tiny piece of concrete stay put. Here's what I would do:

- Plan on laying a 4" solid block course instead of using concrete. 4" is the minimum, and any non-pressure treated lumber should be at least 6" above grade.

- Drill anchors at the end of every few block, and simple notchs the blocks out slightly. The anchors will go into the new concrete, extend through the 4" of block, and stick out at least 2" to bolt the sill plate to. Epoxying threaded rod really is the best approach to this IMO.

- Place a product like "Sikaswell S2" of "Voclay" under the block to ensure a water tight seal. Masonry-concrete will not keep water out forever........

tcbailey 12-07-2012 12:06 PM

Thanks JM. Looking through Lowes and HD, I cannot find the siskawell or similar products, so will plan to use normal polyurethane sealer. Tell me if I understand correctly. You suggested to use 4" block, oriented on end like this, with sealant/adhesive on the bottom, and normal mortar between the blocks. My plan at this point is to use both polyU and mortar at the base. I can do the whole section with this, and cut a short opening for the door sill. Okay so far?

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