Dealing with moldy walls made me rethink vapor barrier use.

In wet areas, they can trap moisture and cause rot.

3 comments

3 Comments

Older asphalt felt paper under siding was a classic vapor barrier fail. In my humid area, I've seen it trap condensation against plywood sheathing year after year. That constant dampness just rots the wood from the inside out. Modern breathable wraps are way better because they let the wall assembly dry to the outside. It's a basic principle but so many builders still get it wrong.

martin.elliot6h ago

Man, I feel like my entire knowledge of house wraps comes from watching too many home repair shows. I can spot a vapor barrier fail on TV, but I'd probably still put the siding on upside down myself. It's all theory until you're holding the wrong end of a hammer.

jordanowens1d ago

But what if felt paper actually blocks more wind and rain in harsh weather? Those breathable wraps can get damaged easy by sun or nails, letting water in. In lots of older homes, the felt held up fine because the siding had enough gaps to dry. Maybe the problem isn't the paper, but how tight modern walls are built without enough venting.