Besides the stucco shrinkage and besides the block shrinkage we also have to deal with shrinkage of the mortar joints themselves from imperfect mix proportions of sand, water and cement.
Besides the stucco shrinkage and besides the block shrinkage and besides the shrinkage of the mortar joints, other documented problems start with the initial installation of the vapor barrier between the framed second floor and concrete block first floor. Discontinuous membranes, under-lapped membranes and the lack Z flashing allow water to run behind the stucco veneer until it runs into an electrical outlet or your baseboard.
Other common moisture intrusion areas are around poorly sealed windows and inconsistent/improper window installation, electrical/cable guy/dryer vent/bath vent/mechanical/plumbing/gas line and other decorative wall penetrations. The one I really love is when I find bare block around and behind electrical panels. Bare block sucks, water that is.
According to this UCF study and their researchers, waiting and loading strategies are advised if ya got the time. The Portland Cement Association apparently suggests waiting a full 28 days before applying any paint to new stucco. Happens lots huh?
Next, let's look at remedies and actions we should take to help minimize moisture intrusion for stucco veneered walls. I say minimize because some construction techniques already exist and may be vulnerable to moisture intrusion by nature. Remember, before you throw your builder under the bus, a house is a house. It's not a swimmin' pool, it's not a submarine and it's not a frog's butt. If you hold the house under water or subject it to conditions similar to…it'll eventually leak. So let's deal with what we've got. If you're building a custom home and have the luxury of dictating methods (or even if you're not), I encourage you to check out the below referenced web sites. The Dr. Joe (Building Science) article reads like a conversation, plain understandable language we can really identify with.
So what in the world do we do with our existing housing issues? A line I have coined is “the better we caulk/seal/paint, the better the house performs” works for me. We all agree that a good “breathable” elastomeric or acrylic paint be applied. This will help keep the water out while still allowing the wall to breathe and can be purchased from all major manufacturer's. In a two story home where the initial intrusion may be occurring at the block/frame transition, reflashing may be necessary which of course is more expensive. Just two token pieces of advice...1)don't buy cheap caulk or paint and 2)when you recaulk your windows, don't caulk the weep holes! Focus on the corners, not the little holes or areas that let water back out. I quote the UCF study…
Paint:
Use a premium, high build, acrylic coating with the following characteristics:
- Meets Federal Specifications for resistance to wind driven rain (TT-C-555B).
- Allows water vapor transmission (high perm rating) permitting water to evaporate from the wall to the exterior.
- High flexibility/elongation to cover existing and new cracks.
Service:
Near the end of the warranty period, repair all visible cracks and apply a second coat of paint. Cracks should be repaired with an elastomeric waterproof sealant patching compound. The method will depend on crack width and the sealant product, but might typically include:
- Less than 0.4 mm (1/64 inch) - apply a brush grade compound with a small brush.
- Between 0.4 mm (1/64 inch) and 0.8 mm (1/32 inch) - apply a knife grade compound.
- Between 0.8 mm (1/32 inch) and 6.4 mm (1/4 inch) - route out crack ¼ inch wide by ¼ inch deep; apply two coats of knife grade compound.
My personal experience…DO NOT GOOP CAULK on/in stucco cracks no matter how strong the urge and how careful you are. It “flashes”, looks like caca and generates love letters and heckling from neighbors/HOA associations.
If you need to hire a contractor for repairs use common sense. You can check out licensed contractors at the Better Business Bureau or the National Home Builder's Association. Make sure the contractor has insurance or you could be liable. Get a written estimate and contract. If you get a guarantee, it should be in writing and state who is responsible for repairs and maintenance and for how long. And finally, don't give up your final payment until the work is complete and you have obtained all necessary release of liens. If a building contractor has not paid their subs and leaves with your money, you may be paying the subs again!
