Webinar Q&A

Cement board: innovative exterior applications

Attendee questions

Cement Board: Innovative Exterior Applications Webinar on April 7, 2022
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Does the cement board application work with large pieces of marble?

Yes, large pieces of stone, like marble, can be adhered to cement board in both interior and exterior applications. The maximum weight per square foot is 15 lbs. for exterior and 25 lbs. for interior applications.

What type of adhesive is needed for large pieces of marble or stone applications?

Several manufacturers sell a polymer modified adhesive and require that to be used for warranted work. Check out this website and this website.

Does this type of cement board have any inherent fire resistance when calculating the fire rating of an exterior wall?

For standard PermaBASE® Cement Board the surface burning characteristics are Class A and the ASTM E84 results are 0 Flame Spread and 0 Smoke Development. For the PermaBASE CI™ Insulated Cement Board the ASTM E84 results are Flame Spread less than 25 and Smoke Development less than 450. Refer to the UL Evaluation Reports for both products including the NFPA 285 testing with the PermaBASE CI Insulated Cement Board. UL Evaluation Report PermaBASE Cement Board, UL Evaluation Report PermaBASE CI Insulated Cement Board.

Is there an ASTM reference standard to cite for the cement board masonry veneer system and the direct applied stucco system?

The ASTM “Standard Practice for Application of Direct-Applied Exterior Finish Systems” for cement board direct applied stucco is ASTM C1516. The ASTM “Standard Practice for Installation Methods for Cement-based Adhered Masonry Veneer” is ASTM C1780.

How heavy is a 4’x8’ sheet of cement board?

PermaBASE Cement Board and PermaBASE CI are available in different thicknesses. 1/2” PermaBASE is 2.9 lbs. / sq. ft., 5/8" PermaBASE is 3.65 lbs. / sq. ft. 1" PermaBASE CI is 2.2 lbs. / sq. ft., 2" PermaBASE CI is 2.4 lbs. / sq. ft. and 3" PermaBASE CI is 2.6 lbs. /sq. ft.

Where is the weather resistant barrier installed; on the exterior sheathing or on the cement board product?

The weather resistant barrier is typically applied over the exterior sheathing, but it can be applied over the cement board if the system is designed that way. If a weather resistant barrier is installed in both places, the outer layer over the cement board is for bulk water management and extra insurance against water penetration. Check the appropriate weather barrier placement with the systems manufacturer for warranty requirements.

Is 1/2" thick cement board still the recommended thickness for interior applications?

1/2” PermaBASE Cement Board is appropriate for both interior and exterior applications. Studs must be a maximum of 16” o.c. for tile applications over cement board or gypsum board tile backer substrates.

How do you detail expansion and control joints in the direct applied stucco systems over PermaBASE CI?

The EIFS manufacturers have details on their websites for both expansion and control joints.

Is the cement board discussed in the webinar (cement board with insulation) the same as structural magnesium oxide board?

Cement boards are considered non-structural and are to be considered substrates for finish application. Magnesium oxide boards are not approved for the same applications as cement boards like PermaBASE Cement Board.

What is the advantage of a cement board stucco system with CI over an EIFS with CI?

The Cement Board Stucco Systems (CBSS) with continuous will give you increased durability, multiple finish options, faster installation, and increased impact resistance over EIFS. From the impact resistance perspective only, think of the golf course setting and stray golf balls hitting the walls of a house or building.

Can cement board with CI be installed over CMU walls?

Yes, PermaBASE CI can be installed over CMU and concrete walls. To learn more, click here.

Are there any limitations to installing thin brick or stone over cement board in an exterior soffit application?

Thin stone and thin brick can be adhered to cement board as a masonry veneer in a soffit application, but the mortar and finish must be less than 10 lbs. / sq. ft.

Can PermaBASE be used in a conventional stucco application? If so, how does conventional stucco adhere to the PermaBASE?

PermaBASE and our cement board stucco systems are developed to be a lighter weight and more durable alternative/replacement to traditional stucco. You can use PermaBASE as a sheathing behind traditional stucco, but you will still need to apply a metal lath to support the stucco application.

Cement board is heavier than typical sheathing. Please comment on any problems with installation.

Typical 5/8” gypsum sheathing is 2.5 lbs. / sq. ft., whereas 1/2” PermaBASE Cement Board is 2.9 lbs. / sq. ft., so it is slightly heavier. There really are no problems with installation compared to gypsum sheathing. In most instances, PermaBASE Cement Board is approved as a sheathing substrate.