Saw a guy in Phoenix use a different underlayment trick for concrete slabs

I was helping a friend on a big commercial job in Phoenix last month, and the lead installer showed me something new. He was putting down a 6mm vapor barrier over the slab, but instead of just taping the seams, he used a specific adhesive called 'SeamLock 200' and rolled it with a 100-pound roller. He said it stops moisture better than regular tape, especially in dry climates. Has anyone else tried a method like this for concrete subfloors?

4 comments

4 Comments

spencer_gonzalez11mo agoOG Member

SeamLock 200 seems like overkill for a basic vapor barrier.

gavin_kim10d ago

Does your cousin ever worry about that happening again with the next slab they pour? I feel for her, man, that's a rough way to learn a lesson about seams. In my experience, what seems like overkill on paper can save a lot of headaches down the road, especially in places with heavy rain or bad ground movement. I've seen tape fail enough times to where I don't blame anyone for going with something like SeamLock, even if it feels like too much for a regular job. Your mileage may vary, but I'd rather spend a little extra up front than deal with a lifted slab later.

the_alex1mo ago

Yeah, that SeamLock stuff is legit. We used it on a data center slab last year where the specs were crazy strict. It's a pain to roll out, but you get a way better bond than tape. In a place like Phoenix, that extra step makes sense to me.

the_jessica1mo ago

My cousin in Tucson had a slab lift two inches after a monsoon season. The contractor blamed a failed barrier seam. I get why someone would want that extra seal now.