Hi folks,
I’m in the process of finishing the walkout basement on my 3 yr old home in Atlanta, GA Climate Zone 3a. The builder stubbed out the drain lines for a 3/4 bathroom, but the layout didn’t fit our needs, so I jack-hammered up the 4″ slab and re-plumbed it. I’ve passed my under-slab plumbing inspection and now am ready to patch the hole I created. I have two questions I was hoping to get some input on.
1. The hole is L-shaped, approximately 4’x3′ long, 18″ wide. Is there any benefit in drilling into the jacked edges of the concrete and epoxying in rebar dowels before patching the hole? I don’t have a problem doing the work, but if it is not going to help settling/cracking/strength/etc, then I’d just as well skip it.
2. The house is relatively new, so there was a poly vapor barrier underneath the slab. In the area I jack-hammered, I shredded the vapor barrier. What is best practice concerning the vapor barrier when patching a hole this size? Do I repair it? If so, how? Do I put a layer of poly on top of the slab under the finished floor assembly?
Appreciate any comments,
–Jamie
Replies
We usually run some Tapcons in half way on the sides to give the new concrete a place to bite on the old. Rebar would be fine although probably not needed on a basement floor. Here in FL we have to have termite treatment done anytime we expose the ground and you do need to repair the vapor barrier. We usually try to leave an edge of the VB exposed so we can tape a new piece in place.
Hi Florida,
Tapcons are something I hadn't thought of, and certainly cheaper than using the epoxy (it's around $23 per tube). Do you have any guidelines you try to follow with how much stick-out you look for? Looks like 4" tapcons are the longest readily available, so sinking them in 2" would leave them 2" proud.
Taping a new poly sheet to the existing vapor is going to be difficult, but doable. Any specific tapes you recommend? I've used a 3M 8087 tape before to seal XPS foam sheets, and it seems like a pretty tenacious bond.
Thanks,
--Jamie
2 inches is plenty. You can also tuck the plastic under and run a small bead of foam around to seal it.
I slather on concrete glue on the edge of the existing slab on all patches. Cheap addition. Works on skim patches and certainly doesn’t hurt in this case. Some say it’s the same as Elmer’s white glue.
if the edges are broken as opposed to cut, you will inherently get a better bond between old & new - you can rough up the cut edge also. Bonding agent does also help. slather it in just before pouring. it will moisten the old concrete so the chemical bond can work better between old & new also.
Calvin & Jim,
Thanks for the heads up...I didn't even know concrete glue existed. I'm a belt and suspenders kind of guy, so I think I'll put in some tapcons around the hole perimeter and brush on some of the concrete bonding agent right before patching.
I am happy with how the vapor barrier patching turned out...much better than I expected. Used 6mil poly and Tyvek housewrap tape. Then used caulk on the side that still had some intact vapor barrier.
Tried to upload some photos on that last post but no luck.