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Application Method

A. Substrates

1. Limestone High Performance Cladding that is principally used to protect external surfaces from water penetration, but its use internally is not excluded.

a. Applied in one pass and one coat as a basic finish, with two or more passes depending on the thickness, type of substrate or desired finish, but always in one coat.


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Approved substrates:


  • Concrete blocks
  • Poured in place concrete
  • Tilt wall
  • Sheathing and lath, base coat
  • Light weight blocks including Autoclaved Aerated Concrete (AAC)
  • Insulated Concrete Forms (ICF)
  • Clay Bricks


  • Bricks
  • Blocks
  • Stone

3. Unacceptable substrates: Specifically excluded are the following substrates:

  • Gypsum (Interior Grade)
  • Wooden boards
  • Lath (without a scratch coat)
  • Cob, adobe
  • Frozen masonry units
  • Over saturated
  • Waterproofed (unless adequate key has been provided)
  • Pre cast units with presence of de-molding oils
  • Painted, unless paint has been removed


Substrate preparation and types

1. For all substrates: the application surfaces must be clean. No dust, traces of other materials, paints, salts, organic growth etc... should be present.

- Concrete surfaces should be brushed and washed. Traces of materials such as building finishes should be scraped off if they are over 1/3 of the proposed finish thickness.

- Wetting/Dampening: Thermocromex must be applied on a correctly dampened substrate. As a rule the substrate should be damp on the surface. Dampening must take into account the overall substrate suction and the climatic conditions at the time of application and should be done about half hour before application. Thermocromex should be dampened in hot weather conditions, in the presence of strong drying wind and on high suction substrates. Do not apply materials over saturated surfaces (when water runs off it after wetting) or on previously waterproofed surfaces unless these have been keyed properly.

- The suction of the walls must be uniform throughout.

2. On very smooth and non suction surfaces including tilt wall and poured in place concrete:

- apply a coat of Thermocromex with added bonding agent (Check with SPE for list of current approved bonding agent) or sand the surface to create a key

- surfaces should be free of any de-molding oil. If not, this has to be done by sanding or high pressure washing (min. 5800 psi)

3. For Concrete Masonry Units (CMU):

- new masonry units should not have Thermocromex installed as a finish for at least 1 month after the initial installation to be sure that these units have dried out and that most of the shrinkage has taken place.

- when installing on masonry units with vertical joints not filled, the joints should be floated smooth.

4. For sheathing substrates:

- apply two layers of building felt to allow for differential thermal movement between the substrate and Thermocromex

- mechanically attach/fasten the lath per ASTM E 1063 over the two layers of building felt

- apply base coat over the lath at 1/2" thick per ASTM C 926/apply OCS (see box below).

- allow base coat to cure a minimum of 3-5 days before applying the finishes or until the initial shrinkage has occurred

5. Before installation of Thermocromex, ensure all flashing, trim accessories and any other miscellaneous required materials have been installed.


Check the individual project specifications to see which one has been specified over lath, scratch coat or OCS. If it's a residential project, use OCS as this will satisfy the local building codes for the ICC, UBC and IRC.



B. Application Method


There are 2 major application methods:

  1. Thermocromex is easily applied with machines such as Putzmeister or any stator or piston type pump.
  2. Manual application (small areas only - Less than 100 SqFt). Please note: Thermocromex is made for spraying and could present some "stickiness" when applied manually.


When using spraying equipment it is essential to respect the mixing instructions of Thermocromex on the water addition and mixing time. It is also essential, as for all plastering work, that the substrate is correctly prepared.


This is achieved when the finish thickness is at a minimum of 3/8 inch (10mm). Use a depth gauge or equal to measure thickness.

Coat(s) Thickness

Do not apply in coats over 3/4 inch (20mm). If a thicker coat is required, apply in 2 or more passes at 48 hour intervals. In cold weather 40oF (4oC) to 50oF (10oC), this interval should be one week. The maximum overall thickness should not be over 1 1/2 inches (40mm).

Thermocromex over CMU and AAC Blocks/Panels

Apply Thermocromex at 3/8" thick directly over clean and properly prepared CMU block or AAC Blocks/Panels at 3/8" thick.

The suction of the walls must be uniform throughout.

Thermocromex over sheathing, lath and a base coat/OCS

After sheathing, lath and a base coat (ASTM C 926)/OCS, apply Thermocromex at a minimum 3/8" thick. Allow base coat to cure 3-5 days or until initial shrinkage has occured.

On very smooth and non suction surfaces including tilt wall and poured in place concrete

Check with SPE for current list of approved bonding agents. 


The main finishes are:

  • as sprayed or rough cast
  • partly smoothed roughcast
  • scratched
  • floated, smooth
  • blended
  • textured
  • custom

These finishes have been specifically designed to maximize speed of application to shorten completion. Normally sprayed, they can be supplied in a range of colors using inorganic pigments (See color chart). This eliminates the need for painting or re-coloring. Thermocromex is weatherproofed, but also retains high breathability and elasticity and vibrant custom color finishes.

- When applied. Thermocromex should be immediately straightened with a straight edge or a feather edge.

- Where the humidity is less than 80%, apply a light water mist at least twice a day to adequately cure the work for 48 hours after application.




C.  Judging Exterior Plaster Finishes

The expected surface finish of plaster products used on exterior applications has for many years been a mystery.  This is clearly seen by the differing opinions expressed by architects, designers, applicators and clients when viewing the surface finish on walls.

In most applications, small but noticeable changes in plane are left when a float or trowel is applied to a surface and visually it can appear as a mark free finish. It never is a truly level, smooth or trowel mark free surface. These same imperfections will appear much more significantly on larger panels and should be expected. Another variable in the appearance of an exterior finish is
the type of texture used as the smoother a finish is, the more variations you will see.

A modest amount of finish and color variation is considered a part of the character of exterior plaster finishes in showing its natural ability. These products are finished by hand which will show the characteristics of the craftsmen applying it under varying environmental conditions, not by a machine in a controlled atmosphere.  Having clear communication, approved samples and mockups along with hiring qualified contractors will go a long way in meeting everyone’s expectations. For additional information regarding critical light issues, judging the finished product etc., please contact us at 800.780.7731 or 972.424.8280 or by email at info@thermocromex.com.

This document is published to supply general information and recommendations only. Specifications should be site specific and issued by the Specifiers. No responsibility can be accepted by Southwest Progressive Enterprises for specifications issued by third parties or for bad workmanship.

* For further guidance, contact Southwest Progressive Enterprises.

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