TECHTALK Technical Insight from the Roof Board Experts

- * continues on reverse Roof Board 5/8” (15.9 mm) minimum 5/8” (15.9 mm) for 24” (610 mm) ® metal stud spacing • 24” over wood framing, maximum stud spacing ** Fastened 8” (203 mm) o.c. • 1/2” (12.7 mm) for 16” (406 mm) metal stud spacing • ion eck D ime

al r r r Insulat P o u d Flashing oar eck ed Foam B Struct ensD igid R Any Roof DensDeck D Coping Membrane Adher for exposure to normal weather normal weather to for exposure parapet wall parapet in vertical conditions Industry’s first 90-day limited warranty warranty limited first 90-day Industry’s applications (1/2” and 5/8” only). Go to (1/2” and 5/8” only). applications www.densdeck.com for warranty details. for warranty www.densdeck.com Sheathing on vertical surfaces. Sheathing on ® Brand products for roofing applications, and DensGlass and applications, roofing for products Brand ® membrane, you’re putting a component into the roofing into the roofing membrane, you’re putting a component the agencies that assembly that hasn’t been evaluated by Sheathing give approval and certification. With DensGlass Some apply. not may warranties system roof substrate, a as bonds say, “If the membrane roof system manufacturers a as Sheathing DensGlass accept we’ll satisfactorily, substrate, but we won’t warrant it.” membranes DensDeck may be used above vertical Most roofing membrane manufacturers require that the membrane come up the wall at least eight inches above and sealed is membrane the of edge The plane. roof the on another finish may have the wall of and the rest flashed rest the finishing for appropriate is Sheathing DensGlass it. of the vertical surface above the membrane, but DensDeck Roof Board could also be used, so there’s only one substrate material to deal with. Sheathing is not certified in membrane roofing systems. Sheathing is not certified in membrane behind a vertical So if you put DensGlass Sheathing Testing and warranties between DensDeck Roof Boards and Much of the choice in parapet wall applications centers DensGlass Sheathing and roof-system warranty. on testing, certification have industry roofing the and Gypsum Georgia-Pacific all types of DensDeck and DensDeck aggressively tested test standards as Prime Roof Boards to UL, FM and other TPO, PVC, EPDM, including systems roofing for substrate a mastics. The test SBS torched and modified bitumen cold certifications results and product properties have earned component infor DensDeck Roof Board as a non-structural many membrane roofing systems. verti for designed is board Sheathing DensGlass contrast, In component in cal applications. It has been tested as a EIFS with brick veneer,and exterior insulation systems, and also barrier or secondarywhere the DensGlass Sheathing is a fire Gypsum weather barrier behind the facing. Georgia-Pacific other the of any or Sheathing DensGlass tested not has Dens

. rred vs. DensGlass prefe oard Nailer Nailer B

te a oof r R bst u ime S r P ® Wall

t Minimum 1/2” (12.7 mm) eck e Parapet Walls: When is a Wall a Roof? When is a Wall Parapet Walls: p a r a Concrete Masonry Unit (CMU) Some discussion to clarify the use of DensDeck Some discussion P DensD DensDeck Prime Roof Boards** Sheathing. But if the But Sheathing. back side of the ® Prime Roof Board. ® * Information presented in this * Information presented in this systems roofing concerning article and assemblies is presented as illustration for guide a general purposes only. Please consult the appropriate system manufacturer or design authority for system specifications and instructions for assembly.or system specific any Georgia-Pacific Gypsum does not provide roofing design services. In some cases, a wall isn’t a wall. A parapet wall projecting In some cases, a wall may be a part of the roof. According above the roof plane protectto railing or low wall “a is wall parapet Webster, a to roof or bridge.” Laly’s The Science the edge of a platform, Systems Roofing Modern and Traditional of Technology and building walls of exterior an extension is “generally says it about three feet or party- and fire-walls that usually extend or less above the roof.” Why do we have parapet walls? One of them is Parapet walls can serve several purposes. the roof plane, fire protection. By extending the wall above a of the exterior up coming flames prevents wall parapet a roofing combustible a igniting immediately from building membrane. Wind- resistance. wind-uplift improve can wall parapet A start when induced catastrophic roofing failures typically back the entirewind forces lift the roof edge, and then peel wind elevated prevent helps wall parapet A system. roof roof edge. pressure from compromising the vulnerable provided vapor In older masonry buildings, parapet walls vapor can’t passpressure relief for the building. Since water its way to the roof through the roofing membrane, it finds the parapet, which edge and exits through the back side of bricks. is typically finished with permeable clay function. It A parapet wall can also perform an aesthetic apparent the increase may or equipment rooftop hide may height of the building to improve the proportions. parts Parapet wall designs may have several finish of the On frame-construction buildings, the exterior front of the parapet wall will usually be similar to the rest of the exterior walls. But the sheathing used on the roof side of the parapet wall will be dependent on the surface treatment. If the front of the parapet wall is EIFS (Exterior Insulation Finish Systems), brick veneer, stone or metal, then the sheathing be DensGlass could parapet wall is to be covered with roofing membrane to to membrane roofing with covered be to is wall parapet help keep water out of the building, that surface actually becomes part of the roof. Then shouldsheathing the be DensDeck TECH TALK continued from front

Fire ratings require tested substrates to push the membrane away from the substrate. DensDeck The membrane could go over the top of the wall, be covered Roof Board has been tested for peel bond strength, which with a cap and finished off on the outside. (See diagram on is critical in membrane to substrate bonding. front.) In this case, the entire inside of the parapet wall is a Construction decisions can pose dilemmas vertical roof, and you need to deal with it as a roof. In the real world, the substrate choice can be complicated. Fire ratings on vertical surfaces may require non-combustible When a building is built, the contractor will sometimes put substrates such as DensDeck® Roof Boards. If there’s a com- DensGlass® Sheathing on the vertical inside face of a parapet bustible surface such as plywood or OSB behind a vertical wall. When the roofers arrive on the job, the wall already has membrane, it may not have a fire rating, because of the slope DensGlass Sheathing on it. Now the roofers have a dilemma: limitations on combustible decks. If you put in a component Is the DensGlass Sheathing acceptable? that has not been approved for fire resistance, you may lose In some cases, the roofers may apply a layer of DensDeck the fire performance for the whole roof system. Roof Board over the DensGlass Sheathing so they’ll have an Bond strength matters on vertical surfaces acceptable substrate for the membrane. They may even Another issue in the vertical wall is the strength of the bond remove the DensGlass Sheathing and replace it with DensDeck of the membrane to the substrate. When the membrane Roof Board. But if the installers attach the membrane directly comes up just eight inches, it’s virtually self-supporting. But to the DensGlass Sheathing, the building may not have a if the membrane goes up the vertical surface two, three, five, fire-rated roof. even ten feet, some manufacturers require additional attach- On any roof assembly, designers should consider factors of ments, such as rails or plates. That’s because, on a vertical moisture gain, proper ventilation and allowances for conden- surface, the weight of the membrane tends to pull it off the sation. For example, if a brick wall has deteriorated and is substrate. If the substrate isn’t tested for that application, being refaced with a non-permeable membrane, the designer the whole roof may be in jeopardy. should allow for proper venting between the brick and the Bond strength is also tested by pressure differentials that DensDeck Roof Board substrate. try to separate the membrane from the wall. Wind turbulence GP support can help with choices may tend to pull the membrane away from the vertical surface. For all these reasons, the appropriate board behind a vertical Direct wind forces that come through defects in the wall, or roof membrane is DensDeck Roof Board, not DensGlass building air pressure that comes up inside the wall may tend Sheathing.

U.S.A.– Georgia-Pacific Gypsum LLC

Canada – Georgia-Pacific Canada LP 1 • Guidelines for installation: ⁄2” (12.7 mm) DensDeck can be applied to 5 Sales Information & Order Placement vertical studs with up to 16” (406 mm) center spacing. ⁄8” (15.9 mm) U.S.A. 1-855-6GP-DECK DensDeck can be used on vertical studs with up to 24” (610 mm) (647-3325) centers. Screws to be installed on 8” (203 mm) centers. CANADA Canada Toll Free: 1-800-387-6823 • Guidelines for installing DensDeck in a parapet wall appear in the Quebec Toll Free: 1-800-361-0486 Georgia-Pacific Gypsum brochure titled DensDeck Roof Boards. Technical Information Georgia-Pacific Gypsum Technical Hotline • Parapet wall framing and fastening guidelines are available online at U.S.A. and Canada: 1-800-225-6119 www.densdeck.com, in the DensDeck architectural specifications. www.DensDeck.com

TRADEMARKS DENS, DENSDECK, DENSGLASS and Georgia-Pacific are subject to our Terms of Sale Use a dust mask or NIOSH/MSHA approved respirator the GEORGIA-PACIFIC logo are trademarks owned by available at www.gpgypsum.com. as appropriate in dusty or poorly ventilated areas. or licensed to Georgia-Pacific Gypsum LLC UPDATES AND CURRENT INFORMATION FIRE SAFETY CAUTION Passing a fire test in a WARRANTIES, REMEDIES AND TERMS OF SALE The information in this document may change without controlled laboratory setting and/or certifying or For current warranty information for this product, please notice. Visit our website at www.gpgypsum.com for labeling a product as having a one-hour, two-hour, go to www.gpgypsum.com and select the product for updates and current information. or any other fire resistance or protection rating and, warranty information. All sales of this product by CAUTION For product fire, safety and use therefore, as acceptable for use in certain fire rated information, go to www.buildgp.com/safetyinfo or assemblies/systems, does not mean that either a call 1-800-225-6119. particular assembly/system incorporating the product, or any given piece of the product itself, will neces- HANDLING AND USE–CAUTION This product sarily provide one-hour fire resistance, two-hour fire contains fiberglass facings which may cause skin resistance, or any other specified fire resistance or irritation. Dust and fibers produced during the protection in an actual fire. In the event of an actual handling and installation of the product may cause fire, you should immediately take any and all actions skin, eye and respiratory tract irritation. Avoid necessary for your safety and the safety of others breathing dust and minimize contact with skin and without regard for any fire rating of any product or eyes. Wear long sleeve shirts, long pants and eye ©2015 Georgia-Pacific Gypsum LLC. All rights reserved. assembly/system. Originally published 8/05. Rev 2/15. GP-TM Lit. Item #053010. protection. Always maintain adequate ventilation.