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Expert Assessments of
Historic Masonry

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Many historic brick, stone, and adobe exterior walls have been covered with a variety of stucco materials. Some of these finishes were applied as part of the original construction, while others were applied later in the life of the building. Stuccos and renders were applied as weathering and decorative treatments. As these materials fail, the quest for more permanent or "maintenance free" treatments has left a sad legacy of accelerated deterioration. This is usually caused by using incorrectly formulated stucco material, poor workmanship, or failure to control the curing conditions after application. Properly repairing, matching, or replacing an existing stucco/render that will endure the test of time presents significant challenges.


Historically, stuccos and renders were often applied to protect underlying masonry.

This failed stucco was formulated excessively hard, and was applied over an improperly prepared surface.

If your stucco is cracked like this wall, it may be allowing water in. Water penetrating stucco into the masonry will likely cause a host of unseen problems.


Frequently Asked Questions
about Historic Stuccos & Renders:

Question: What caused my existing stucco/render to crack, deteriorate, or otherwise fail?

Answer: It is likely the failure was caused by one or more of the following:

  1. Incorrectly preparing the substrate for application of the stucco materials.

  2. Incorrectly formulating the stucco mix. Formulating an appropriate mix is a function of a) the environmental conditions the stucco/render will be exposed to, and b) the mix's compatibilty with the background substrate it is applied to. Your stucco mix may have been formulated to be excessively hard and brittle, or it may be lacking in water vapor permeability. A sound understanding of historic masonry materials science is essential. Contact us for assistance.

  3. Lack of appropriate detailing in vulnerable areas. Flashing and similar materials must all be correctly installed and working properly.

  4. Failing to follow good on-site working practices when the stucco/render was applied.

  5. Failing to correctly control the working environment and curing conditions after installation of the materials.

  6. Naturally occurring environmental forces acting upon the stucco/render over time, such as rain, snow, ice, wind, building settlement, etc.

  7. Lack of implementing an effective and regular maintenance strategy.

  8. Efflorescence (the appearance of soluble salts).

  9. Movement and/or cracking of the materials behind the stucco.

See Deteriorated Masonry for more specific information on the causes of deteriorated masonry.










This example shows Pebble Dash, an external stucco system that fully exposes the aggregate.


Question: What are some of the other terms used for "stucco?"


  • Render — an external plaster system.

  • Harling — a thrown-on or cast-on finish usually composed of lime and various aggregates.

  • Wet Dash — another name for roughcast or harling. More commonly used in English practice.

  • Roughcast — another name for wet dash or harling. More commonly used in English practice.

  • Pebble Dash — an external plaster system that fully exposes the aggregate. The aggregate may vary in size, be rounded or angular in shape, or any color.

Question: Why should I consider repairing my existing stucco/render?

Answer: Any failing stucco surface left unrepaired allows accelerated and advanced deterioration to take place in both the remaining stucco and the materials the stucco is applied to. The forces of wind, water, ice, etc. are then allowed access to the substrate materials. Repairing this additional deterioration is much more costly than simply repairing the stucco itself.

Sometimes the best and most cost effective way to properly repair an existing stucco/render is to completely remove it from the wall and apply a new, properly designed stucco system.

Question: Can you create a stucco/render that will match the color, texture, and aggregate I desire?

Answer: Yes!

At Abstract Masonry Restoration, our hands-on experience and technical expertise with historic stuccos and renders assure you the best approach performed right the first time. Contact us for assistance with your historic stucco needs.

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