Top-10 design and construction FAQs from 2024 answered

The 1-800-NATIONAL^® Construction Services team, construction design managers and field sales representatives answered a wide variety of questions from architects, contractors, installers, dealers and specifiers in 2024. Topics ranged from fire resistance and drywall finishing to STC ratings and solutions for mold and moisture resistance.

This blog post answers 10 construction FAQs from the past year, plus a bonus question on a topic that consistently stumps newcomers to fire-rated assemblies.

1. How do you build fire-rated wall assemblies from one side to achieve 1-hour and 2-hour fire ratings?

Whether you’re renovating a retail space in a shopping center or repurposing an old mill building into condominiums, you’ve certainly run into situations where you can access only one side of a wall. The 1-800-NATIONAL Construction Services team created multiple fire-rated design solutions to meet this challenge. Learn more about these UL designs and how to construct them.

2. What are the five levels of finish for gypsum board?

We receive many questions about the Gypsum Association’s GA-214 “Levels of Finish for Gypsum Panel Products,” from architects, general contractors and drywall finishers seeking clarity on the differences between each level of finish.

The five levels of finish for gypsum correspond to the aesthetic of the room:

• Level 0 is used in temporary construction or wherever final decoration has not been determined.

• Level 1 is specified as joint treatment to meet the minimum requirements for smoke barriers or areas not in public view.

• Level 2 is required when gypsum board is used as a substrate for tile or in spaces such as garages and warehouses where the surface appearance isn’t important.

• Level 3 is specified in areas that will have heavy- or medium-texture finishes before final painting or that have heavy-duty, commercial-grade wallcoverings.

• Level 4 is designated for areas that will have smooth wall designs decorated with flat paints, light textures, noncontinuous textures or standard wallcoverings.

• Level 5 is used in critical lighting areas or those decorated with nonflat paints, glossy or decorative finishes, or dark- or deep-tone paints.

View the steps to achieve each level of finish or download our simplified visual guide.

3. What drywall products are mold and moisture resistant?

A building’s longevity is connected to its ability to resist mold and moisture damage. PURPLE^® XP^® and PURPLE^® eXP^® products manufactured by Gold Bond Building Products, LLC, an affiliate of National Gypsum Company, offer solutions for long-term mold and mildew resistance and weather resistance during construction.

• PURPLE^® XP^® family of products: Specially treated, mold- and fire-resistant paper-faced gypsum board includes a core encased in heavy 100% recycled mold-, mildew- and moisture-resistant purple paper on the face.

• PURPLE^® eXP^® family of products: Coated fiberglass mat facers provide excellent resistance to the elements and a 12-month exposure warranty.

Find out why PURPLE is the color of confidence.

4. What can be changed in a wall assembly to increase its STC rating or value?

Sound Transmission Class ratings are affected by six variables, ranging from the materials used to build the assembly to the construction method. They include:

1. Mass
2. Cavity absorption
3. Cavity depth
4. Stiffness
5. Decoupling
6. Damping

Read our blog post “6 variables that affect STC ratings” or watch our science of sound video to learn about the role each plays in reducing sound transmission.

5. Can I use waterproof cement board to eliminate the need for an additional waterproofing membrane?

Yes, PermaBASE WP^® Waterproof Cement Board has the same strength as standard PermaBASE^® Cement Board but includes a waterproof core. When installed, waterproofing/sealant is required only at the joint seams, fastener heads/penetrations and exposed edges, instead of over the entire wall, saving the installer time and money.

Learn more about waterproof cement board.

6. What’s the difference between Type X and Type C gypsum boards?

Type X gypsum board is defined by ASTM C1396, Standard Specification for Gypsum Board. The following qualify as Type X gypsum board:

• 1"-thick shaftliner panels that provide a 2-hour fire rating when installed in a double-layer, non-load-bearing H-stud area separation wall assembly.

• 5/8" gypsum board that provides a 1-hour fire rating when installed vertically to each side of 2-by-4 wood studs spaced 16" o.c. with 6d nails spaced 7" o.c., with board joints centered over the studs and staggered on each side with fasteners spotted and joints covered with tape and compound.

• 1/2" gypsum board that provides a 45-minute fire rating when installed vertically to each side of 2-by-4 wood studs spaced 16" o.c. with 6d nails spaced 7" o.c., with board joints centered over the studs and staggered on each side with fasteners spotted and joints covered with tape and compound.

Type C gypsum board is not defined by an ASTM standard. Rather, Type C gypsum boards are Type X products with special additives that increase fire resistance. Type C gypsum board can be used to reduce the number of gypsum board layers in a floor-ceiling assembly or the overall thickness of a wall assembly.

Get all the details and a list of Type X and Type C products manufactured by Gold Bond Building Products by reading our blog post “Comparing Type X vs. Type C gypsum board.”

7. Are Gridstone Gypsum Ceiling Panels available in black?

Yes, Gold Bond^® Gridstone^® Gypsum Ceiling Panels now come in black, allowing architects to create an elevated look for restaurants with the practical benefits of straightforward installation and low maintenance. Gridstone panels, also available in white, come with a 15-year limited warranty, a noncombustible gypsum core and a 2-mil. vinyl laminate finish for easy cleaning.

8. How are shaftwall assemblies constructed?

Created as a lighter and more economical alternative to masonry shaft enclosures, gypsum board cavity shaftwall assemblies make it possible to provide fire protection in elevator shafts and stairwells in high-rise buildings. Cavity shaftwalls are built from one side using shaftliner panels that are friction-fitted into metal shaftwall studs. They are non-load bearing and can be built with fire ratings ranging from one through four hours.

9. What are some innovative solutions for designing facades in mixed-use retail and residential developments that also offer energy efficiency?

Mixed-use retail/residential developments continue to be popular, and that means architects are looking for new ways to design facades that visually break up storefronts and lend a residential vibe. Available in four thicknesses with R-values of R-4, R-6, R-10, R-16 and R-22, PermaBASE CI^® Continuous Insulation Cement Board combines streamlined installation of adhered veneers with the energy-efficiency benefits of continuous insulation.

10. How do I create a fire-rated horizontal ceiling membrane?

National Gypsum has tested horizontal membrane systems to achieve fire-ratings where it isn't feasible or necessary to construct a loadbearing floor- or roof ceiling assembly. Use these 1- and 2- hour rated ceilings to provide fire ratings at unrated floors and roofs, duct enclosures, or to enclose elevator and stair shafts that terminate below the roof.

Bonus Question: How are fire-rated shaftwall corners constructed?

There is no standard fire test method for corners, and they are not addressed in UL designs. It is up to the design professional to determine how wall components intersect at corners. Best practices for the design of corners include providing continuity of the gypsum board around the inside and outside of a corner. This can be tricky with shaftwall systems due to how the shaftliners are installed within the framing. Pages 68-79 of The PURPLE Book^® provide guidance for maintaining the continuity in 1- and 2-hour shaftwall systems.

National Gypsum Company aims to provide architects, specifiers, contractors and installers with technical insights and innovations that help the industry build better. Reach out to 1-800-NATIONAL Construction Services or your regional construction design manager with your questions, project challenges and construction needs.

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The color Purple is a registered trademark of Gold Bond Building Products, LLC.