That vapor barrier overlap rule finally bit me on a strip mall job near Phoenix

My crew was laying out the vapor barrier under a new slab for a 12,000 sq ft retail build. I told the green kid to just tape the seams and move on. Foreman came back 2 days later and made us pull up 3 sections. Turns out I was overlapping them wrong for years. 6 inch overlap minimum, not just butted together. Cost me half a day and 4 rolls of tape. Anyone else have a basic code rule they never paid attention to until it got called out?

2 comments

2 Comments

the_blair2d ago

Respectfully, inspectors in different jurisdictions often interpret the same rule differently so your mileage may vary.

gonzalez.vera2d ago

Buddy of mine who does commercial roofing got nailed for the same thing on a big box store roof in Tucson. He thought he was saving time by just overlapping the vapor barrier a couple inches here and there. Inspector showed up and made him redo a whole section because the overlap has to be 6 inches minimum with the tape centered. Ended up costing his company like 3 grand in labor and materials. He still gets salty about it when we grab beers.