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TECHNICAL BULLETINS—SEALANTS

 

The following are design tips for the use of sealants relating to whether one uses mortar with pointed joints or sealant joints when using cast stone material:

 

Soft Sealant Joints allow for movement at vertical joints. A professional designer or engineer should be consulted for proper joint design and function with:

Sealant joints are not designed to bear weight, use plastic setting pads, or lead shims when setting the stone on a soft bed joint. It is not intended to adhere to the foam backer rod. Sealant joints are to be designed to adhere to parallel surfaces only. The foam rod should be placed to a depth equal to the width of the joint.

 

Since sealant joints allow for vertical movement, it is recommended that you follow these rules of thumb:

Mortar Joints are recommended for the following and should have a professional designer or engineer review for proper joint design and function as well as verify pointing:

There are two most common types of sealants, specified under section 07920; one-part moisture cure and air cure. There are two–part systems available that require mixing of materials to allow for, and chemically induce proper curing.

 

Silicone Sealants are excellent sealant materials providing superior weather resistance over a range of temperatures. The advantage to using silicone sealants is that they are easy to apply, have a low shrinkage rate and can accommodate high movement. They are flexible and durable. They are preferred over organic materials as they tend to crack, dry up, become brittle, and can even revert with age.

 

Two–part component polyurethane sealants are tough and elastic in nature, allowing movement up to fifty percent of the joint width. They are flexible, durable and form a water-tight bond with most building materials.

 

According to many manufacturers, two–part applications offer weather tight seals in caulking joints today for up to twenty years, and ten years in severe conditions.

 

Allowances for thermal and other movement should be within twenty–five percent of the joint size. A normal three–eighths inch joint should be expected to compress to approximately a quarter inch and expand to approximately a half inch.

 

It is important to note that careful planning at the start will assist in eliminating disappointment for any homeowner or commercial designer at the completion of the project. There is so little one can do to change the appearance of cast stone after installation and the application of sealants, therefore we strongly suggest that careful consideration and planning is executed from the start.

 

DESIGN TIPS — SEALANTS (PDF)

 

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.