Expert: Bruce E. Johnson - 5/18/2009

Question
We live in a concrete block house built in the 1950's.  We became occupants in 1990.  The exterior remained untreated until several years ago when we painted the exterior.  The back side of our house has a concrete slab patio that butts up to the house.  The backyard slopes downward toward the house.  Once the backside concrete wall of the house was painted, areas of that wall would bubble and peel and the paint would not adhere in spots.  My husband believed it was a moisture problem and sought advice from Sherwin Williams as to what to apply to those "bad" areas of the block before repainting the wall.  The treatment he used lasted for about 1-2 years, but now we are seeing bad areas once again where the paint bubbles and peels.  My husband thinks that moisture is seeping up from the concrete patio that butts right up to the house and is causing moisture to travel up the concrete back wall of our house, causing this problem.  We do not know what kind of ventilation the exterior concrete block walls were constructed with.  Would altering the concrete patio improve the moisture problem in the concrete wall?  Should we search for a better sealant to apply to the blocks before repainting.  Any advice you can offer would be greatly appreciated.

Answer
Hi Debbie, it could be a combination of things but I would opt for the rain bouncing off the patio and hitting the wall as being the larger culprit.  This is a common occurrence and will involve a routine maintenance every 2-3 years or even less if these same areas get a lot of UV exposure from the sun..There are a lot of waterproofing products out there that may prolong the process another year depending on how much rain you get in your area.  Whatever brand paint you have been using?  Use their waterproofing products if possible.  This will guarantee compatibility.  Or if you change products get complimentary paint and waterproofing materials.  Epoxy paints work well in wet areas but check for UV protection when using epoxies. I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com