Stucco: Southwest Siding

For the owner builder back east, stucco is probably not even an option. He or she will be thinking brick, lap siding, cedar shakes or maybe vinyl. But for the owner builder in the Southwest, 9 times of 10, it is the siding of choice.

Why is stucco so popular? It provides a hardened exterior that can be manipulated and textured to suit the owner's preferences. It also provides an air barrier, moisture barrier, and insulation while allowing the house to breath. Basically everything a owner builder would want to help a house be healthy and perform better. In addition, it is a cement based product and fire resistant. That's a big bonus in the dry Southwest.

The Process

After framing is complete, windows are in, electrical wiring and plumbing are run and the house is dried-in, the lath can begin.

The lathing process is composed of several tasks. Initially, the subcontractor will set a weep screed at just below finished floor level around the house. Weep screed is a metal seat that has small holes in the bottom. The holes allow any water that may get behind the exterior, to drain out. This keeps the exterior walls from holding water.

They will then roll black lathing paper, very similar to roofing felt, starting at the bottom around the house. Each roll should lap 4" over the roll beneath it. The paper is stapled to the studs. This creates a water shedding plane beneath the "mud",lath metal and foam.

The next step is to set lathing foam ( usually 1/2 to 1 inch in thickness) over the paper. The foam acts as an insulation for the building and along with lathing metal is the base for stucco application.

Lathing metal is the final piece of the lath assembly. It acts as a base for the scratch coat or brown coat to cling to. Without metal, the mud would simply fall off the structure. It is important that the metal is stapled to studs and is fairly tight. If it is loose, it will lead to pockets in the stucco and cracking.

Checking the Work

One area I constantly had to verify by personal inspection was the sealing of the lath paper on the inside. Crews attempt to fasten paper, foam and metal directly to the studs of the exterior wall. Unfortunately, sometimes they miss. It is an unpopular chore to go back and caulk the interior of the paper wherever there is a tear or break. This must be done. I don't encourage doing the work yourself, but it is something I found myself doing from time to time. Be aware, if there is a lot of caulking work to do, the subcontractor needs to return and add staples to the studs that they missed.

An inspection of the lath is usually required before any mud is applied. The building inspector will check to see how the metal is attached, if it is actually fastened to a stud or just hanging on the paper. He or she will inspect the tightness of the metal and for vertical seams in the foam. The foam should be staggered to prevent long seams. They also look for breaks in the foam and caulking around exterior outlets, fixtures and plumbing. For some inspectors, this is their time to put the hammer down. It is important that your stucco contractor do it right the first time.

Two Coat Vs. Three Coat Stucco

There are a two main methods of applying the stucco. The three coat method consists of a "scratch" coat, a 1/2 inch base coat, a brown coat, and a texture coat. This is extremely solid, heavy and a more expensive method of stuccoing your home.

The two coat method skips the scratch coat and starts with a thick brown coat. The texture coat is the final coat with this application. Most production builders use the second method because it is faster and less expensive. If done properly and wetted down for several days following completion, it holds up fairly well. However, there is definitely more tendency to crack with the two coat method vs. the three coat method.

Discuss options with your subcontractor.

Popouts

Popouts are accents set around windows or on corners etc., to add a look of depth to the exterior of a home. There are different methods and products available to add popouts to the owner builder's project.

Traditionally 2-4 inch foam was cut and set over top the base foam and was metalled with the rest of the building. Today, however, new products are available. A product that we used recently is a prefabricated foam/cement product. It is installed after the browncoat and then blended in during the texture phase. Of course, nothing is perfect. The issue with it is that the stucco isn't applied to metal over the product. The foam becomes exposed very easily because the manufactured finish is thin.

Consult with you subconstractor about the methods they use and are willing to use. Ask about the pro's and con's of any product.

Things To Be Aware Of

Both lathing and "mud" application are messy endeavors. When the lathing crews start working, they have a tendency to leave their foam all around the job site daily. If the wind kicks up, your neighbors will be picking foam from their rose bushes. Make sure your lath contractor agrees to daily clean-up, Especially during the lath phase.

Insist on protection for the street and on your window when the crews start applying stucco. Both cement AND the lath metal can scratch your windows, Protect them. Stucco washout in the street is a serious SWPPP violation.

Scaffolding and Safety

Your plastering contractor will set up scaffolding around the house so his crews can access the higher areas. Be certain they have constructed the scaffold correctly and safely. There should be ladder access to the top levels of the scaffold. Workers should not have to climb up the side to get to the top. Guardrails must be up and all sections are required by OSHA to be double planked.

Signs indicating that there are falling hazards and that hardhat construction personnel are the only ones allowed in or out should be posted.

In this era of litigiousness, the owner builder needs to act like a general contractor and protect themselves. If a person goes onto the jobsite and gets hurt, the owner builder could be held liable.

Finishing Up

The next step is to wet down the walls with a hose. This helps the hydration process. Stucco is a cement based product and needs to cure properly. Do not paint the exterior until a minimum of 3 full waterings on different days have been completed. Consult with your painting contractor and your stucco contractor before you proceed.