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The following is a recommendation for Crazing, the Care and Maintenance of Cast Stone Material.


Careful quality assurance and control of cast stone on-site are important as well as proper installation, preventing of puddling of water on the face of the cast stone, and use of sealants to prevent or control crazing of the cast stone.


Even with careful control, handling and installation, crazing may occur. Crazing can best be described as a spider web or map cracking effect. Fine lines randomly appear along the surface of the cast stone, horizontally, vertically, and diagonally in any shape. Without proper care and sealant, dust lodges within the fine cracks, making the crazing more visible. Thus, one questions the integrity of the stone when there is no actual failure of the stone.


There are many different views of why and how crazing happens, yet it has no structural or durability impact, and does not constitute rejection of the cast stone material. Crazing appears to be caused by a differential contraction of the surface and innermost sections of the cast stone. Generally, all concrete, many natural stones, and cast stone are frequently subject to crazing because of moisture, temperature, installation, inadequate curing, or improper manufacturing.


Manufacturers must be aware of the moisture content, the compaction techniques, and curing methods. Masons and contractors in charge of installation must familiarize themselves with the design and proper installation techniques of cast stone to minimize and prevent crazing from appearing. Common errors found to cause crazing are:

Proper use of washing with a mild (5%, maximum 25%) acid solution can remove the crazing. Keep in mind that proper rinsing is required with a hose (not pressure washed or sand blasted). Proper monitoring of water drainage is required so water does not pool at the base of the cast stone, especially water with too much acid mix, thus, discoloring and change in texture may result.


Deeper cracks may require a siloxane sealer to prevent dirt from penetrating the cracks making them more visible.


Note that careful planning at the start will assist in eliminating disappointment for any homeowner or commercial designer at the completion of the project. Proper design at the start of the project can provide the proper drainage control, moisture control, ventilation, and allowances for movement.


Manufacturers must carefully monitor moisture content, compaction, curing, and storage of material. Installers must carefully review the plans and specs to ensure they conform to the designer’s allowances for proper moisture control, ventilation, and movement. They must ensure they have properly inspected the material, verifying that the cast stone matches the setting plans and all flashing, ventilation, and joint considerations have been considered.


Additionally, while on the job site, all cast stone must be stored properly, out of the way of heavy traffic and properly covered (with non-staining materials) so water cannot sit on top of cast stone for any length of time.


There is so little one can do to change the appearance of cast stone after installation if it is not properly cared for and sealed, therefore, we strongly suggest that careful consideration and planning are executed from the start.




The information within this and all our bulletins has been provided as a guideline and based upon statistical data and prior uses. We always suggest that you consult with your engineer, architect or contractor for the best design and use of cast stone for your project. Our design team is always available to answer any of your questions. We do not accept any liability from damages resulting from your interpretation of the data contained within.