How to Apply Stucco with the Stucco Sprayer By Herb Nordmeyer
Start in an area where mistakes can be made while standing on the ground. Mask all windows, doors, soffits, and other areas. Spraying stucco is messy and the air blast can remove masking.
With the Mortar Sprayer hooked up to the air line, pull the trigger and count seconds. If the air blast continues for 10 seconds before the tone of the blast changes, there is sufficient air for operating the sprayer. If the tone changes after 5 seconds, there is sufficient air to operate if care is taken. The change in tone is related to the drop in air pressure at the gun. It indicates that more air is being used than can flow through the line from the air compressor. If you waited to do this test until you had stucco mixed up, grin — you should be on Candid Camera.
Put on safety goggles. You are about to learn about stucco rebound.
Fill the hopper on the Stucco Sprayer. If stucco flows out of the nozzles before the sprayer is triggered, send word to the mixer to thicken the mix. With the nozzles about 12 inches from the wall, and aimed so the flow of stucco is perpendicular to the wall, trigger the Stucco Sprayer. Repeat about once per second or two. Note how the stucco sprays. After a few hoppers-full, you will learn the optimum trigger pull, the optimum time to hold the trigger, the optimum time between trigger pulls. Keep the Mortar Sprayer moving. Consider that you are doing a slow dance with the Mortar Sprayer. No fast movements, but never stop moving. Keep the nozzles 12 inches from the wall and keep the mortar sprayer perpendicular to the wall. If stucco does not flow out of the nozzles, the mix is too thick. Send word to the mixer to loosen up the mix and add a little water to the wheelbarrow and do a little hand mixing.
While spraying, the hopper must be filled about every 10 seconds. This is a full-time job for a person. The ideal filler is a modified shovel. Next best is a one-gallon dipper. By maintaining the slow dance step, the filler can judge where you are going to be and do his job easier. If there is clutter, problems will develop. The wheelbarrow should be placed about 6 feet away from the sprayer and slightly further from the wall than the person operating the sprayer. If everyone is right handed and the wall is a long wall, the wheelbarrow should be placed to the right of the person operating the Mortar Sprayer.
If you don’t have the luxury of an extra person to fill your hopper, no problem, simply place the wheel barrow closer to your sprayer area and scoop directly out of the wheel borrow. Mason’s wheel borrows are the best wheel borrows with steel handles and body to make it easier to lift heavy weights.
After you are comfortable using the Mortar Sprayer, pass it off to someone else to use.
I am over 6 feet tall and can spray up to about seven feet in height. Straw walls are never just 7 feet in height, so arrangements need to be made to elevate the person operating the Mortar Sprayer. Do not stand on buckets, chairs, or boxes. The ideal solution is a scaffold on wheels. Lacking that, a substantial stepladder is the next best option. If the stepladder is placed between the person operating the Mortar Sprayer and the area being sprayed, the person can lean into the ladder for added stability. The person with the Mortar Sprayer should not be moving the ladder.
If the stucco starts to run when you are spraying, you blew it. You should have moved on just before it started to run. If sufficient depth of stucco is not applied with the first pass, depending on the stucco mix, after a few minutes a second pass can be made. If after a few minutes the shape of the lath or mesh can be seen in the stucco, it is an indication that the stucco is sagging. Reduce the depth of the stucco.
The crew consists of the person spraying, a second person filling the hopper, and a third person moving the ladder and the wheelbarrow. Troweling Stucco
After stucco has been applied to an area, it should be lightly troweled. This troweling is to cut down the high points and fill in the holes. If it is not troweled before it stiffens, the wall will not be as smooth as it could have been. While troweling on a straw wall, straw will stick out. Don’t worry about the straw that is sticking out. Do not slick the wall down. If a steel trowel is used and the wall is slicked, the fines (cement) come to the surface. As they dry and hydrate, shrinkage occurs and cracks show up. Trowel as little as possible at this point. A wood or manganese trowel will leave a rougher surface.
After an area has been troweled, check the set periodically. If you believe in scratching a wall, or if the code officials require that the first coat be scratched, do so before the initial set. If you do not believe in scratching the wall, as the initial set is starting, back drag the wall with the edge of a steel trowel. If there are high points on the wall, they can be cut down with the trowel (grains of stucco will come off rather than mud). This removes any high-cement areas and provides a surface that the next coat of stucco can bond to.
As soon as the initial set has taken place, any stucco that needs to be scraped from the floor, the casing bead, or other areas should be scraped. Any masked areas that received a blast or a splatter of stucco should be cleaned. Scrape with the edge of a trowel first and then go back with a large sponge and water.
It can be helpful to have extra people to help keep up with the troweling.
More information on Stucco.