Stucco Recipes for the Mortar Sprayer

Stucco Recipes for the Mortar Sprayer
August 28, 2013
Sammy

Choosing the right tools can help a project for speed and ease, We have the correct stucco recipes & variations for the Mortar Sprayer. As a stucco sprayer can be many times faster than the old hawk & trowel. Read more

By Herb Nordmeyer

Each method of application of stucco requires a little fine tuning of the formula to get the optimum results. Here are some starting formulae for using the Mortar Sprayer for several different stucco applications. Sand is variable, and you have to live with what is available, thus these are referred to as starting formulae. The best blended stucco mix I have ever worked with is the Magna Wall Brand, but it is not available in many parts of the country. This document deals with products that are available.

Most stuccos have a water/cement ratio of about 0.55. With most mixes FritzPak Supercizer 7 (a dry water=reducing agent) can be added to reduce the W/C ratio to about 0.4 and increase the strength. If FritzPak Supercizer 7 is not available, use FritzPak Supercizer 5. The down side is these agents have a limited working time in the stucco (about 20 to 30 minutes). FritzPak Supercizer 7 comes prepackaged in 2.5 pound (40 ounce) bags. Recommended dosage rate is from 4 to 12 ounces per bag of Portland Cement. Polycarboxolate water-reducing agents have a much longer working time, and can reduce the W/C ratio down to about 0.32, but they are harder to find in small quantities and tend to make the mixture slick. This necessitates spraying a number of thin layers.

Fibers Stealth or Stealth imitator fibers (6- to 7-deneir polypropylene fiber) are the most efficient fiber to use. Normal dosage rate is 1.5 ounces per bag of Portland Cement for normal stucco applications and not more than 4 ounces per bag for FerroCement and Panel mixes. Higher dosage rates can reduce the compressive strength.

Stucco Sprayer for Walls

The Tirolessa USA Stucco Sprayer can be used for applying plaster, shotcrete, papercrete, earthen mixes, plastering a stucco house, traditional one coat or three coat stucco, GFRC, stamped concrete, stucco fences, organic sculptures, and more! learn more

Scratch Coat Stucco on Lath

  • 1 bag Portland Cement 94 lbs
  • 0.33 bags Type S Hydrated Lime 16 lbs
  • 4 cubic feet of loose damp plaster sand 5.33 5-gallon buckets

This will produce a 2,700 to 3,200 psi mix. Moist cure for 48 hours before adding Brown Coat.

Brown Coat Stucco on Lath

Use the Scratch Coat Stucco formula and increase the Hydrated Lime and the Sand by 10%. This will make a weaker mix so as it dries, it will not crack the scratch coat. Moist cure for 48 hours and dry cure for 5 days before adding the finish coat (reduces the tendency to effloresce).

Finish Coat Cementations Stucco – Traditional cement stucco mix

  • 1 bag White Portland Cement 94 lbs
  • 0.5 bags Type S Hydrated Lime 25 lbs
  • 5 cubic feet of loose damp sand 6.67 5-gallon buckets

Depending on the texture desired, different gradations of sand may be used. Pigment may be added. Add pigment with the initial water and sand so it can disburse evenly in the mix.

Panel and Dome Construction

  • 1 bag Portland Cement 94 lbs
  • 1 oz Liquid KelCrete Admixture 1 oz
  • 3 cubic feet of loose damp sand 4 5-gallon buckets

This will produce a 3,500+ psi mix, but it will not be as workable as the stucco mixes above. Crushed sand will produce greater strength and will not be as workable.

FerroCement

  • 1 bag Portland Cement 94 lbs
  • 1/5th bag Type S Hydrated Lime 10 lbs (Or 1 ounce of KelCrete)
  • 12 ounces of FP Supercizer 7
  • 3 cubic feet of plaster sand 4 5-gallon buckets

FerroCement is applied to an armature of 5 or more layers of wire or mesh. To get good penetration, it needs to be sprayed into the mesh and worked from one side until the armature is full of stucco and then worked from the other side until that side of the armature is full of stucco. If gaps are left in the armature, there will always be a weak spot. Mix should be as thick as possible while being able to work it into the armature.

Carving Plaster

  • 1 bag Portland Cement 94 lbs
  • 0.5 bags Type S Hydrated Lime 25 lbs
  • 3 cubic feet of loose damp 60 mesh sand 4 5-gallon buckets

This is a high-build, high-plastic stucco. As it dries, it can be carved. Adding most additives will shorten the working time. This stucco weighs 1.5 pounds per square foot per 1/8 in thickness.

Light-Weight Carving Plaster

As per Carving Plasters instructions, but perlite can be used to replace up to 100% of the sand. If you can find it, use perlite that is approximately 60 mesh. With full perlite substitution, this stucco can weight as little as 0.375 pounds per square foot per 1/8 in thickness.

Back to the Stucco information page.

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8 Responses to “Stucco Recipes for the Mortar Sprayer”

  1. john says:

    I am going to be starting construction of about 10 straw bale structures on our new self sustaining ranch in southwest Missouri. Most of the structures will be small overnight villas made for a wellness center as well as several single family homes, a hay barn and several other “outbuildings”.

    I need to know a mix that I can use that will be strong but will set up quick enough to do multiple coats as well as finish coats. I also need suggestions on the purchase of an entire spray system and compressor system. This will not be the only structures we install so i need a spray system that will last for multiple jobs. thanks

    • Nolan says:

      Hello John,
      Ten straw bale structures sounds like good fun! Please keep us in the loop and send pictures of your progress.
      There are two different paths that bale builders take when it comes to plastering. Some of our customers prefer cement based stucco mixes others prefer to batch local earthen plasters. Do you know which direction you want to go?

      If you go the natural plaster route, please consider your local weather. In Missouri, I would guess that you are in an area that gets good hard rains. Designs with generous roof overhangs are a good idea. Also a splash barrier on the lower couple feet of the wall can help a bunch.

      Typically people with whole houses to plaster will use one of the 4 hole sprayers. Either the wall sprayer or combo sprayer. If you have 220V electricity, a 5 hp electric is my favorite for less maintenance and less noise. If you are going with a gas powered compressor, please use a 5.5 hp or larger compressor ( I prefer 6-8 hp for gas). I normally look for used compressors on Graig’slist or Ebay.
      One of the best brands I have found for durability in the gas powered compressors is Rolair.

      Please let me know if I can help with any more details.
      Best regards,
      Nolan

  2. Cindy says:

    We live in a “Log Cabin” style home in Georgia. The outside of the home is built with cedar boards and has”chinking” between each board. It’s time to replace the chinking and I was thinking about using a more durable material like Stucco. What do you think?

    • Nolan says:

      Hello Cindy,
      I would not use cement stucco as chinking. It will be too brittle and rigid. More flexible is a good idea between logs. I have heard of people using blends of papercrete as chinking. The extra fiber of the papercrete can help reduce cracks. There is a great group of people at the Yahoo Group called Papercreters. I would suggest posting a question there for the latest advice on PC and chinking.
      Good luck with your project.
      Nolan

  3. Bob says:

    I have purchased your mortar sprayer (but not actually used it yet). I am going to be using to spray lime plaster on a straw bale structure. Does adding chopped straw to the lime plaster (for the scratch coat) create a problem for the sprayer? It seems like the straw would cause stoppages or flow problems through the nozzles of the sprayer. If so, is there some other “fiber” which could be used? Thanks.

    Bob

    • Nolan says:

      Hello Bob,
      I hope your straw bale project goes well. lately we have been receiving emails from SB builders in growing numbers from around the world. I think the idea is finally taking hold.

      The secret to using straw fiber in the mix is in the preparation. Chop the straw in a metal garbage can with a weed eater. Then soak the straw in water for a day or two before spray day. This will soften the fiber enough to pass through the sprayer. Also, some balers screen the chopped straw to help eliminate the longer pieces. If I can help with anything more, please don’t hesitate to call or write.
      Best regards,
      Nolan

  4. Jeff Green says:

    Nolan,

    I love your combination sprayer! I am very pleased with the quality of construction and how easy it is to use!

    My question is fairly simple; I am getting ready to build my first concrete domes (10ft dia. Storm shelter and 26ft 2br monolithic design home) and I am looking for the highest strength mix that will also spray well and stick with minimum rebound. You list a 3500lb mix and monolithic lists one that they claim is about 8000, both use Kel-crete to replace lime and reduce the water needed, I could use some guidance to help find a starting point. I have purchased basalt fibers and basalt rope and plan to incorporate both in my projects and would like your opinion on these as well.

    Thank you for your help!

    Jeff Green – Branson Missouri

    • Sean Maxwell says:

      Hi Jeff, thanks for the positive comments. It is always fun to hear from people that are enjoying our tools.
      The compressive strength will be determined by your design loads. The 3500 PSI mix is probably a realistic number for most designs. Since you mention adding fiber and making your own mix, the only real way to know what results you are getting is with testing. Find a local lab that can help out. Often there is a basic quality control lab at local ready mix plants. If your project is interesting to them you might be able to get a few samples crushed there. Otherwise, send the samples to an official test lab. For bulk testing of dozens of samples you can set up a hydraulic press with a very precise digital gauge. The Parker Service Junior is a good gauge for basic testing. You can test with this as you zero in on the optimum mix and then confirm the final results at a lab.

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