GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Blistering Paint

paul_schertz | Posted in General Questions on

Can vapor drive be responsible for blistering exterior paint?  Is this to be expected?  Solutions?

1941 house in Portland, Oregon (climate zone 4C).
Original uninsulated walls, cedar siding and lead paint.
I had the house painted 2 years ago and have had blisters ever since (see photo) primarily on the walls with direct sun exposure.  Painter has returned twice and sanded/repainted the blistered areas.  He stated that this is normal for this type of house and is caused by vapor drive.  He stated that the blistering will continue.
Some blisters contain liquid water.
Internal RH typically ~50%.

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. Expert Member
    NICK KEENAN | | #1

    Blisters full of water doesn't sound to me like vapor drive. What it sounds like is liquid water -- rain -- getting into the wood and working its way out to the exterior. I would think water is getting behind the trim. Flashing the top and painting all six sides might help, but I can't think of anything that wouldn't require reinstalling the trim

  2. Lis77 | | #2

    Is it possible he drove water into the wood by pressure washing and then painted too soon before the siding dried out?

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |