Exterior application over Frame Construction

Many plaster crews refuse to install color coat directly into a scratch coat.  Traditional scratch / brown / finish coats are steps with time honored success.  Good results are had using our material and the traditional scratch brown finish.  The problems arise when the installers drop below a minimum ¼” thickness. 
Our plaster will fail if installed less than ¼” thick.
We specify a heavy deep scratch using fiber stucco and brown with our own material.  
Our finish works well as a double back over the filled scratch coat.  
This method allows the clay plaster to gain better depth and richness. 
Be sure to fill and cover the scratch coat with enough plaster, ¼” above the top of the scratch, to hide the scratch coat.

Exterior Application over Frame Stucco

Follow normal code compliant lath requirements through lath inspection.  
Apply ASTM approved one coat fiber brown coat over the lath 3/8” thick.
Use a plaster scratchier to score the soft wet stucco horizontally ¼” to 3/8”deep.
Begin water curing for a week minimum, lightly spraying the stucco daily.
Fill any cracks ASAP with same material to seal building envelope.
Allow the crack less deeply scored brown coat to cure for 28 days.

Installation of Clay Plaster:

Wet the area to be installed with a light garden hose spray.  
Mix plaster in a mechanical mixer for minimum 10 minutes.
Mix to consistency of loose brownie mix.  Not too wet, not too thick.
Allow the plaster to “Slack” (set still) in the wheelbarrow for 30 minutes before use.  
Slacking allows the clay plaster to thicken up in the wheelbarrow.
Apply a thin coat filling the deep scratch to a flush wall profile.
Wait for up to an hour until the material is still tackey and trowel on the topcoat ¼” thick.
Smooth finish will be 90% achieved and we again wait up to an hour.
When still tackey, spray a light mist on the plaster and finish trowel the clay plaster to a hard finish.
This will cause increased color variegation (mottled effect).
Begin water curing after three hours and continue lightly misting the plaster for two days.
In direct hot sun and windy conditions water the material as needed to prevent damage caused by 
drying out too fast.

Exterior / Exterior application over ICF Block 

We recommend 100% coverage with #30 lb felt with 10/20 self furring lath then stapled over the felt.  
We have had echoing glue joints cracking through the fiber brown coat and finish clay color coat.
Allow weep holes at the bottom of the plastered walls for water to escape.

Exterior / Interior application on Concrete Cinder Block

Use fiber brown-cote stucco to coat the 8x8x16 cinderblock before applying our plaster.  
Use a plaster scratcher to score the stucco with horizontal lines ¼ ”deep.  Some installers prefer to float the stucco to leave a rough sandy finish ready for our clay color coat.
Exterior application uses a ¼”minimum deep horizontal scratch into the fiber brown coat.
Water cure the brown/scratch coat for a week by spraying with a garden hose to cure the material.
Fill any deep large cracks with more same stucco ASAP.
Failure to brown the wall will cause “flashing” to occur when rain wets the wall. (Visible bricks behind the plaster).
Allow a month to dry the stucco slowly.

Installation over previously painted surfaces, PRIMUS APPLICATION

We recommend a Primus mixture basecoat over painted surfaces. 
Use a mixture of 1 part Primus (Drivit Corporation Product)
1 part Portland Cement
½ part silica sand
Add small amount of water to attain a soupy mix that can be installed 1/6” thick.
Trowel or roll it on with a paint roller.  Most people will trowel it on and then float it with a sponge float to bring the sand to the surface as a key for the plaster to bond to.
Wait a day and apply the Clay Plaster a minimum ¼” thick using the double back method.

Installation over Clay Plaster PRIMUS APPLICATION

Always use the Primus Application when going with our clay plaster over itself.  The clay will not bond well to itself, the service life is limited to a few month to a couple of years.  Always use the primus when re applying or changing color.

Installation over Drywall.

Primus application OR PVA Emulsion
Elmers glue (100%PVA) works well and is considered by some to be less messy.
Use the thick emulsion 100% PVA glue and allow to set over night.
Apply a thin (1/16”) watery coat over the glue to allow the PVA to re-wet. 
Apply second thin coat to the still tacky plaster and trowel to smooth finish.
Water trowel the finish (light mist spray) when tacky again to increase motteling.

General Rules for Installation of Clay Plaster

Cracks will occur in our material.  We seal the building envelope first with ASTM stucco brown coat and we specify all cracking on that brown coat should be repaired prior to installation of our “Clay Color Coat”.
Allow a month for a natural 28 day cure to happen with the stucco brown coat substrate we specify for frame buildings.  Patience.
If our clay plaster cracks don’t worry, we have mitigated for them and reduced them to a design flourish.  Sometimes we have zero cracking but usually a few areas will have hairline cracks.
It’s very unusual to see larger open cracking that will usually indicate other problems with the substrate preparation.  Expansion joints can be used however it’s difficult to control the cracking and we elect to allow it to do it’s own thing 99% of the time with great results. Expansion joints are ugly
Please start slowly and work into the confidence required to stride through a big project.

This plaster is earthen based.

Never plaster over dry cured (even using glue) clay plaster because it won’t stick well enough for a good service life.
Wet the surface lightly before installing over stucco brown coat.
As a General Rule our plaster always installs best using a “Double Back” application.
Apply the first thin coat 1/6” of an inch to 1/8” of an inch thick then wait…..
After up to an hour, when the material is still tackey, apply the top thin / finish coat.
The material will bond well to itself only when installed into a tackey stage of dryness. The glues we use need that. 
Water trowel to increase the interesting variegation of color.
Don’t over wet the material when water troweling it. 
It’s worth the effort as you will be rewarded for the learning curve with 
a really nice finish.
Water cure the plaster for 48hrs with a light misting to a heavy spray depending on conditions.
Exterior Installation of Stabilized Clay Plaster

Our mix design is very stable / tough when installed per instructions.
Our material looks better with age; the clay weathers and looks better as it is battered and rained on etc.  
Get the substrate right and all else follows smoothly!


The San Tan Adobe Company

Queen Creek, Arizona

​(928) 231-2926