How do you mix a scratch coat for stucco?
Scratch coats are mixed at 1 part cement to 2-1/4 to 4 parts sand, brown coats are mixed at 1 part cement to 3 to 5 parts sand, and finish coats are 1 part cement to 1-1/2 to 3 parts sand.
How thick should a scratch coat be for stucco?
3/8″
The scratch coat should be 3/8″ thick. Force it through the wire mesh so that it fills the ΒΌ” gap between the mesh and wall completely. 3. Smooth the scratch coat with the trowel.
How thick should scratch coat be?
The normal thickness is between 3 and 5 mm. On soft or weak background use 1:2 or 2:5. Successive coats must be weaker than this coat. The thickness of the first coat depends on the nature of the background and the overall thickness required of the render.
How long does stucco scratch coat need to dry?
Cure Time: The scratch coat should be allowed to moist cure for a period of 3-5 days. This allows the cement to become hard enough to gain most of it’s strength before the brown coat is applied. Cure Time: The brown coat requires a lot more time to cure (28 days is recommended).
What is a scratch coat for stucco?
The scratch coat is a base coat and the first one to go on the wall. It is applied with a hawk and trowel and a scratcher. The cement is spread evenly among the surface at a depth of about 3/8 of an inch thick.
What is the scratch coat for stucco?
Next comes the scratch coat, which is a base layer of field-mixed Portland cement, sand, lime, and water with a series of horizontal lines scratched into it. Then comes the brown coat. This layer is applied with a darby, or long trowel, to make sure the cement is applied evenly.
Do you let the scratch coat dry?
17. Let the scratch coat dry before going on to the next step. Drying time will depend on temperature, humidity and airflow, and could take anywhere from 2 to 24 hours. You’ll know its dry when it turns a light gray color.
Do you let scratch coat dry?
How long do you leave a scratch coat?
The first coat is a scratch coat where thats laid on and then scratched to create key for the next coat. Once thats dried usually about 24-48hours you can apply the top coat, after laying on its important to use a derby or a straight edge to rule the wall flat.
Should I wet the scratch coat before applying brown coat?
It is also recommended to pre-wet the surface of the first or second coat before installing the brown or finish coat; this will improve bonding between the layers and improve the scratch coat’s long-term strength gain.
What kind of stucco do you need for a scratch coat?
Depending on how much stucco you need to make for a scratch coat, choose a large container. If using a wheelbarrow, be sure to scrape and rinse it first. The formula to make stucco is one part Type 1 Portland cement, two to four parts sand, one-quarter part hydrated lime and enough water to make a slurry.
What’s the best way to make a scratch coat?
This is a basic recipe and is the simplest and fastest way to mix a decent scratch coat up. There is a few more variations of stucco recipes out there that call for lime, fiberglass, acrylic and other elements but a basic recipe will suffice.
What is the formula for scratch coat mix?
Stucco Scratch Coat Mix, A Simple Recipe. The stucco scratch coat mix is a simple recipe that really consists of sand, cement and water. There are other formulas that you can use but in its simplest form it is merely a 3 to 1 ratio of sand to cement.
Can a scratch coat be applied over cement?
Applied Over: Typically, the scratch coat is applied over lath (paper and wire fastened to wall) but can sometimes be applied to a cement based substrate like cmu block, bricks, etc.