Directions for Use

[photo: a lime plaster hopper sprayed onto scrap board.]

The Mortar Sprayer By Herb Nordmeyer

The Mortar Sprayer, if used right, can be a major labor-savings device. This document is written to help you get the most from your Mortar Sprayer. This document is broken down into the following sections: System Requirements --Mixing Mud --Preparing to Spray --Spraying with the Mortar Sprayer --Following with the Trowel. --Notes from Nolan

This is not a treatise on how to stucco. It is hoped that the user of the Mortar Sprayer has some background in stuccoing. As an introduction to stuccoing, go to the website www.isgproducts.com and download Handbook of Stuccoing for Builders. This document contains a list of trade-offs and a troubleshooting guide that are valuable for a person stuccoing. My forthcoming book on straw construction will contain an extensive chapter on stuccoing on straw. This book has been forth coming for five years so it may take a little longer to be published. Whenever it happens, Nolan Schied will know about it.

System Requirements

A Mortar Sprayer uses a lot of air. We have found that a two horsepower air compressor furnishes sufficient air. Air pressure can be a problem. Air at 80 psi takes up half of the space of air at 40 psi. If there are restrictions in the air delivery system, it may be necessary to use a higher air pressure to obtain adequate air.

40 psi air pressure at the sprayer appears to be adequate. Depending on the hose diameter, the number and type of connections, and the length of hose, the pressure at the air compressor may need to be substantially higher. If the total volume of air produced by an air compressor is not sufficient to operate the Mortar Sprayer, increasing the pressure will not help. Increasing the pressure is effective only if the air transport system (hose, quick connects, etc.) is undersized. There will be less of a load on the compressor if the air transport system is resized.

Most 2 horsepower air compressors come with a *” npt (national pipe thread) connection. Use a bushing to increase the size to 3/8” and pass the air through a filter/water trap if desired. (Note: a filter/water trap is not needed if spraying gray stucco is the only function of the line leading from the compressor.) From the filter/water trap, use a minimum of 3/8” hose to the Mortar Sprayer. If the hose run is to be over 50 feet, increase the size of the hose to *” for all except the last 50 feet. Running air compressors on extension cords reduces the life expectancy of the air compressor. If you do not have appropriately-sized electrical outlets where you will be spraying (most people do not), use a longer air line.

Note from Nolan: Normally I recomend a compressor capable of 90psi at 7 cfm. This will let you spray stiffer mixes at full speed.

Back to Herb: The Mortar Sprayer comes with a male 3/8” quick connector. We have found that this fitting is not readily available in all home supply super stores. Remember, there are several varieties of quick connectors. To obtain a matching female quick connector, one may need to go to a hose supply store. An alternative would be to directly attach a 3/8” hose to the Mortar Sprayer. A *” quick connector close to the Mortar Sprayer will not pass sufficient air to operate the Mortar Sprayer. The hopper of the Mortar Sprayer is small and takes 10 seconds or less to empty. It can be dipped into a wheelbarrow of stucco to fill, but it becomes a messy process.

If one is working on a ladder, one must descend and re-ascend each time the hopper is filled. That is a lot of work (about 25 times for a wall 8 feet high, 10 feet long, and receiving a stucco coating *” thick if the hopper is filled completely each time). That is a job for young people in training. After 30 minutes, it is like running the bleachers. The hopper can be filled with a 5-gallon bucket, but that becomes a major job for the bucket carrier. A one-gallon dipper or a modified shovel works better. With a square-nosed shovel, weld on 3” side boards on the front, back, and one side of the shovel. On the dump side of the shovel, weld sufficient brackets to guide the stucco into the hopper. With such a shovel, an operator can dip or scrap in a wheelbarrow to fill and then easily fill the hopper when the hopper is 6 feet off the ground. This means that the person operating the sprayer can stay on the ladder. This means the job gets done sooner. A scoop works well, but is more work for the person on the ground than is the shovel.

Mixing Mud

Do not attempt to mix the stucco by hand when using the Mortar Sprayer. It would require ten wheelbarrows and ten people mixing to keep up. A two-bag mixer (also called a 6-cubic foot mixer) is the appropriate mixer to use. These mixers usually come with a 5- to 8-horsepower gasoline engine. Most stucco requires one cubic foot of cement (Portland cement, blended hydraulic cement, masonry cement, plastic cement, hydrated lime, fly ash), three cubic feet of plaster sand (coarser than masonry sand), and from four to seven gallons of water.

Cement comes in 1 cubic foot bags. Masonry cement usually ranges from 70 to 78 pounds. Plastic or stucco cement usually is 80 or 94 pounds. Portland or blended hydraulic cement is usually 94 pounds. Some companies make “half-bags” of cement. A 47-pound bag of Portland cement is not a cubic foot, but a half cubic foot. Lime is usually packaged in 1.25 cubic foot bags which weigh 50 pounds.

Three cubic feet of loose, damp sand fill four 5-gallon buckets level full.

With the first batch of stucco to be mixed, you will not know the amount of water that will be required. If the stucco is made too wet, it is often easier to throw the batch away rather than to try to salvage it. Even though you have a two-bag mixer, your first batch should use one bag of cement. Fill one bucket with water to about 1.25 inches from the top (this is 5 gallons). Fill a second bucket half full (this is about 2.5 gallons).

--Clean out the mixer, including chipping off loose material.

--Lock the mixer drum in the upright position.

--Start the mixer, put it in gear, and speed the engine up to a very rapid idle.

--Add about 3.5 gallons of water from the fuller bucket. Insure that your helper does not refill the bucket as it is set down.

--Add 2 buckets of sand.

--Break the cement down into two buckets. Add one of the buckets slowly.

If the mix remains soupy, proceed with adding the remainder of the cement. If the mix becomes stiff, add additional water. After all of the water is added, the mix should have the consistency of toothpaste. Mix until there are no lumps remaining.

Add the remaining sand. As the sand is added, the mix will become stiffer. Add additional water as needed to maintain a mix that rolls freely off the mixer blades.

When the mix appears correct, take the mixer out of gear and reach into the mixer with a long-handled cup (if you are going to put your hand into the mixer with the mixer running and in neutral, please buy extra insurance before you do so) and obtain a sample. First test is to place the sample on a steel plastering trowel and then tip the trowel. If the mix slides off before the trowel is at a 40 degree angle, it is probably too wet. Second test is to apply stucco to the substrate that you are applying stucco to. If it sticks well, it is a good consistency. If it peels away when the trowel is removed, it is probably too wet or too dry. Adjust the water and retest.

Determine the amount of water that was used for the one-bag mix. In the future, add 75% of this amount of water to the mixer if making a 1-bag mix or 150% of that amount if making a 2-bag mix.

After the mixer is dumped, add the water for the next batch and let the mixer run for a few minutes. This keeps the stucco from hardening in the mixer.

The second and later batches are much easier to mix. Be sure and measure the sand and water for the next batch while the previous batch is mixing. With the mixer running:

Add 75% of the water needed.

Add half of the sand.

Add cement.

Add remaining sand and remaining water.

Mix for 4 minutes after all components are in the mixer.

Persons using the stucco should report to the mixing crew with recommendations for adjusting the water and the sand concentration. Usually it takes a crew of four people mixing and wheel-barrowing to keep up with the Mortar Sprayer.

Spraying Stucco

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 Mortar 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 Mortar Sprayer and release. 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 every 10 to 15 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.

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.

The first coat of stucco is designed to embed the lath or stucco netting. Do not attempt to build much beyond this level.

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.

Two people are needed to keep up with the troweling.

Cleaning the Mortar Sprayer

Before using the Mortar Sprayer, ensure that it is clean and the orifices are open. If they are not, use the supplied tool to clean them. It is easier to keep them open than to have to dig stucco out after it has set.

It is helpful to keep a 5-gallon bucket * full of water where you are spraying. When the mortar sprayer is not in use, set it in the bucket.

When the Mortar Sprayer hopper is empty and you are not going to be using the Mortar Sprayer for a few minutes, shoot a couple blasts of air to ensure that the ports are open and set the Mortar Sprayer so stucco will not flow into the ports.

Twice a day, use a green scrub pad and scrub off any stucco that has set. If you allow it to set longer, it will probably never come off. Curing the Stucco

Allow the stucco to cure for at least 48 hours before adding the second coat. This will prevent any plastic shrinkage cracks that may form in the first coat from passing through the second coat.

Stucco needs to be moist-cured. This is accomplished by misting the stucco with a “Hudson-Type” sprayer periodically for 48 hours. If one is located in Las Vegas, the misting may be needed every 2 hours around the clock. If one is located in Seattle, one misting per day may be sufficient if the humidity is high and the wind is not blowing.

Notes from Nolan

Thank you Herb for taking the time to put together a set of directions to help get people started with spraying. I truly enjoy using these sprayers and seeing the possibilities they open up for builders.

Normally I recommend people use a 5 horse power 220 volt compressor for full speed spraying. This is the size I use when in fast production. The manufacturer recommends at least 7 acfm (actual cubic feet per minute) @ 90psi as the minimum requirement. People have reported using less but I don’t want someone to be disappointed by not having enough air to do the job. The pressure used can vary widely by the mix used. For Papercrete, I would use lower pressure around 50psi. For stiff mortar mixes I prefer about 100 psi.

With enough air power, the sprayer can empty a wheelbarrow faster than a second wheel barrow can be delivered from a mixer. We use the sprayer to scoop directly out of the wheel barrow for increased speed. We use 2 all steel mason’s wheel barrows. The mason’s wheel barrows can be recognized because they are narrower than a regular contractor’s wheel barrow and have steel handles. These flex less when running up ramps with large loads of material. If anyone needs a picture for a description, I can email one. Please write to sales@mortarsprayer.com .

To start the day with a sprayer, I apply a light coat of LPS3 spray to the unit. This leaves a thin waxy layer on the hopper that aids in clean up latter. When I don’t have LPS3, I use a light coat of WD-40. I pay particular attention to preventing material from setting up in the air jets. I keep the cleaning rod handy for the jets. Hardened mortar in the jets can be close to impossible to clear. The other area I keep an eye on is the air valve. I don’t let material harden on the shaft that can damage the O-rings inside. Every now and then, when I am doing a thorough cleaning, I will disassemble the air valve and grease the inside parts. I have occasionally replaced the o-rings which I purchased from a local supply store.

If you have comments or suggestions for using the sprayer, please send them to me. My goal is to help as many people as possible expand their construction possibilities.

Best regards, Nolan Scheid

sales@mortarsprayer.com

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		SPRAYING WITH THE TIROLESSA