National Gypsum - Construction Design News

PermaBase® BRAND Cement Board As A Substrate
For Masonry Veneer Installation Systems (MVIS)
By Scott Hughes

What comes to mind when you hear the words PermaBase® BRAND Cement Board? Most likely you think of a tile backer substrate, right? This is correct. It’s the best choice for that application, and here is why.

PermaBase Cement Board is a rigid substrate made of portland cement, aggregate and glass mesh that provides an exceptionally hard, durable surface that withstands prolonged exposure to moisture. Using EdgeTech® technology, PermaBase allows for closer fastener application of nails or screws without crumbling or spinout due to the reinforced edge. PermaBase resists the growth of mold, achieving a panel score of 10, the highest score possible, per ASTM D 3273. This is all great stuff, but there’s more.

National Gypsum’s PermaBase Cement Board is the best substrate for MVIS as well. Here are the advantages of specifying and installing PermaBase in this exterior application:

PermaBase Exterior Advantages

Factory produced substrate consistently manufactured to ASTM C 1325 standards
Time and labor-saving alternative to field applied metal lath and scratch coat substrates
Less affected by job-site weather conditions
Score and snap PermaBase for a quick installation
Qualifies for multiple-year system warranties

Think of the time that is saved by installing 4' x 8' sheets of PermaBase Cement Board in place of metal lath and scratch coat. Humid or damp weather won’t delay the installation of the substrate, and this saves time and money for your client.

So, how do you install MVIS? Tony Fuller, at our 800-NATIONAL Technical Department, walked me through it step by step.


	Scott Hughes Construction Design Manager 484.678.6132 Mobile Email Technical Info: 1-800-National

Installing PermaBase Cement Board

Cement Board Installation

For either horizontal or vertical application
Use galvanized roofing nails or flat wafer head cement board screws through sheathing and water-resistant barrier into wood or metal framing.
1. Fastener spacing: maximum of 6" o.c. along perimeter and intermediate framing
2. Fastener heads: driven flush with face of cement board
3. Joints in cement board: treat with 4" wide alkali resistant fiberglass mesh tape imbedded in polymer modified adhesive mortar

Waterproofing

Apply liquid waterproofing membrane with a paintbrush, heavy napped roller or sprayer in two coats over the PermaBase
Allow to dry between applications
Now, you’re ready for the stone or thin brick

Mortar And Masonry Installation

Prior to installation, ensure the back of masonry units are clean of debris that could impede bond, including dust, laitance, loose concrete crumbs and excess film
Moisten back of masonry unit and cement board substrate
Use trowel to key a thin coat of mortar, covering entire back of masonry unit
Spread additional mortar on the back of skim-coated masonry unit. Completely fill the space between masonry unit and substrate when compressed against substrate
Press mortar-covered back of masonry unit against substrate at desired final position
Slide unit roughly 1" diagonally from desired final position and back into desired position

Pointing Mortar

Allow installed masonry units to set for minimum of 12 hours
Verify that joints are free of debris, dirt or spacers
Brush dust and dirt off veneer face
Mix pointing mortar to a smooth, slightly fluid consistency by hand or with slow speed mixer
Fill joints by forcing pointing mortar into joints to desired depth, ensuring mortar has filled all voids. May use grout bag
Mortar should be "thumbprint" hard
Smooth the mortar—your final step

For details, check out our website to see a short installation video, then go to the PermaBase Exterior Applications Guide. A short article on a MVIS project installed at Cedar Park Center in Dallas, Texas, is available online. PermaBase Cement Board was the exterior substrate in this MVIS installation. Please give us a call to discuss your next MVIS specification.