Building Homes or Extensions/Stucco
I'm planning to build an outside gazebo-like structure to match the style of my existing Spanish Colonial house. The structure will be built on poured concrete footings(below grade), next will come about 6 courses of 6" concrete block (reinforced w/ grouted cells) and on top of that I will stick-frame the remaining height of the walls an the roof.I plan to sheath the wood framed walls with 1/2" plywood and then I want to cover the entire outside( concrete block on bottom and wood framed on top) with a 3 coat stucco finish. My objective is to have a finished surface that is uniform, i.e, you would not be able to see the transition between concrete block and the wood framed portion. I am concerned that over time there will be some movement along the junction between the sill of the framing and the block wall below resulting in cracking of the stucco. Is there any way to prevent/minimize this from happening? Should I extend the wire mesh (stucco mesh fastened over plywood) to cover part of the blocks, say 12"? If so how do I fasten the mesh to the blocks? Any help you can offer is appreciated.
BTW, project is located in frost-free Southern California.
You will have to waterproof the plywood as much as possible. You can use 2 layers of grade D Building paper or two layers of Asphalt felt paper to cover the plywood. You will need an air gap over the felt or building paper to provide air circulation between the stucco and plywood. They are called drainage mats or Dimpled Membrane. To completely water-proof your plywood siding, you need at least two more layers of building paper or asphalt felt over the Watermat or Dimple Membrane. This should prevent any cracking where the plywood meets the concrete block of anywhere else.
On the concrete block I would not extend the wire mesh from the plywood area. Us RibLathe instead of wire mesh on the concrete blocks. They sell special fasteners for the RibLath to attach it to concrete. Be sure to pressure wash the concrete block very well before applying any stucco. Then apply a bonding agent.
There is an option. There are products that are called Flexible Stucco that have acrylic in them to make the flexible and prevent cracking. They claim it will last 30 years. Two companies that make them are StucoFlex & Tess.
I have seen these products put right over concrete and cement block and it looked great. I saw a demonstration of one of these products at a trade show. A concrete block was coated with flexible stucco. When it dried, the company rep hit the concrete block with a small sledge hammer and cracked the concrete block. The flexible coating actually held the two pieces of block together. As far as using the flexible stucco on plywood, would have to check with the manufacturer on it's application.