Lightweight High Temperature Performance
Select HT is a unique, lightweight and easy to apply, self adhered underlayment capable of meeting the high temperature resistance requested by contractors in hot climates. The underlayment is composed of two waterproofing materials—a high temperature rubberized asphalt adhesive, backed by a layer of high density cross laminated polyethylene film.
The product is 25 mils (0.64 mm) thick making it lightweight and easy to handle and apply. The unique, advanced rubberized asphalt formulation allows the membrane to meet industry standards for fastener sealability equivalent to products that are often significantly thicker and heavier.
The rubberized asphalt is backed by a paper release liner that protects its adhesive quality. The release liner is easily removed allowing the rubberized asphalt to be bonded to the roof deck.
The membrane comes in a 195 ft2 (18.1 m2) roll, and measures 36 in. (914 mm) wide. The Ripcord® embedded in the adhesive provides the applicator a “split release on demand” feature, making it easier to apply in detail areas.
Features & Benefits
- High Temperature Adhesive — Unique formula can withstand high temperatures up to 220F.
- Lightweight — The 195 ft2 roll weighs only a fraction of what competitive materials weigh making transport and handling easier.
- Self sealing — The membrane meets key building code standards for nail sealability of self-adhered roofing underlayments.
- Easy to handle and apply — The membrane is easy to reposition, easy to install, bonds to the roof deck and forms high quality laps.
- Slip resistant surface — The slip resistant surface maximizes traction for safety without compromising the water integrity of the laps. The surface film is resistant to scuffing and tracking oil in hot weather.
- Ripcord — Split Release on demand feature makes Select HT underlayment easier to apply. Faster application of the membrane in the straight-aways, as well as ease of membrane positioning in detail areas (valleys, around dormers, etc.).
- Reroofable — Unlike granular surfaced membranes, Select HT membrane will not adhere to the underside of the exposed roof covering making reroofing easier and less costly.
- Application expertise — Select HTcomes from the makers of Ice & Water Shield® , the original and best in class self adhered underlayment, and is backed by local technical support personnel.
Guidelines for Use
Select HT membrane can be used as a sloped roof underlayment to resist water penetration due to wind-driven rain and ice dams. The membrane is designed to meet code based standards of protection against leaks, while being thermally stable at high temperature service conditions.
Sloped roofs protect structures by shedding rain water but they are not waterproof. Storm-driven winds can cause sloped roof coverings to lift. Rain can be easily driven under the roof covering directly to the unprotected deck where it causes leaks and damage to the interior of the structure. Select HT membrane that is applied beneath the sloped roof covering prevents wind-driven rain from entering the structure. For wind-driven rain protection, full coverage with the membrane is recommended. Since Select HT membrane is a vapor barrier, the roof construction must allow for proper ventilation in full roof coverage applications.
For ice dam protection, Select HT underlayment should be adhered at the edge of the roof deck along the eaves. The product should be applied to a point on the roof deck above the highest expected ice dam. Several variables influence the height of ice dams and the membrane coverage required. Local building codes should be consulted for specific requirements. Many variables influence the height of ice dams including climate (particularly the annual snowfall), slope, overhang, valleys, how well the structure is insulated and ventilated, and exposure (sun vs. shade). In addition to placement along the eaves, the product can be used to help prevent roof leaks in danger zones including valleys, rake edges, around chimneys, and skylights
Install Select HT underlayment directly on a clean, dry, continuous structural deck. Some suitable deck materials include plywood, wood composition, wood plank, metal, concrete, and gypsum sheathing. Prior to membrane application, remove dust, dirt, loose nails, and old roofing materials. Protrusions from the deck area must be removed. Decks shall have no voids, damaged, or unsupported areas. Wood planks should be closely butted together. Repair deck areas as needed before installing the membrane. (Refer to Tech Letter #5, Chemical Compatibility, when installing over wood plank decks).
Prime concrete, masonry surfaces and DensGlass Gold® with Perm-A-Barrier® WB Primer. Prime wood composition and gypsum sheathing with Perm-A-Barrier® WB Primer if adhesion is found to be marginal (refer to Technical Letter 12, Use on Oriented Strand Board (OSB) Roof Sheathing). Apply Perm-A-Barrier® WB Primer at a rate of 250–350 ft2/gal (6–8 m2/L). Priming is not required for other suitable surfaces provided that they are clean and dry
Precautions & Limitations
- Slippery when wet or covered by frost.
- Consistent with good roofing practice, always wear fall protection when working on a roof deck.
- Release liners are slippery. Remove from work area immediately after membrane application.
- Do not leave permanently exposed to sunlight. Maximum recommended exposure is 90 days.
- Place metal drip edges or wood starter shingles over the membrane.
- Do not fold over the roof edge unless the edge is protected by a drip edge, gutter or other flashing material.
- Do not install on the chamfered edges of wood plank.
- Do not install directly on old roof coverings. For more information, refer to Technical Letter 5, Chemical Compatibility.
- Provide proper roof insulation and ventilation to help reduce ice dams and to minimize condensation. Select HT is an air and vapor barrier.
- Repair holes, fishmouths, tears, and damage to membrane with a round patch of membrane extending past the damaged area 6 in. (150 mm) in all directions. If fasteners are removed leaving holes in the membrane, they must be patched. The membrane may not self-seal open fastener penetrations.
- Do not install fasteners through the membrane over unsupported areas of the structural deck, such as over the joints between adjacent structural panels.
- Due to its slight asphaltic odor, do not apply where the membrane is exposed to interior living space. Refer to product literature for more complete information.
- Refer to product literature for more complete product information.
- Not recommended for roofing in alpine climates.
- Not compatible with EPDM or TPO; use Ultra™ underlayment for tie-ins (refer to Technical Letter 5, Chemical Compatibility).
- Not compatible with polysulfides, flexible PVC, or high concentrations of resin (pitch) found in some wood plank decks. For more information, refer to Technical Letter 5.
Select HT meets the following standards:
- ICC ESR-1677 approval according to AC-48 Acceptance Criteria for Self-Adhered Underlayments to be used as an Ice Barrier
- Underwriters Laboratories Inc. Class A fire classification under fiber-glass shingles and Class C under organic felt shingles (per ASTM E108/UL 790)3
|Roll length||65 ft (19.8 m)|
|Roll width||36 in. (914 mm)|
|Roll size||195 ft2 (18.1 m2)|
|Roll weight||32 lbs (14.5 kg)|
|Rolls per pallet||25|
|Thickness, membrane||25 mil (0.64 mm)||ASTM D3767 method A|
|Tensile strength, membrane||250 psi (1720 kN/m2)||ASTM D412 (Die C modified)|
|Elongation, membrane||250%||ASTM D412 (Die C modified)|
|Adhesion to plywood||3.0 lbs/in. width (525 N/m)||ASTM D903|
|Permeance (max)||0.05 Perms (2.9 ng/m2s Pa)||ASTM E96|
|Material weight installed (max)||0.14 lb/ft2 (0.7 kg/m2)||ASTM D461|
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This document is only current as of the last updated date stated below and is valid only for use in the United States. It is important that you always refer to the currently available information at the URL below to provide the most current product information at the time of use. Additional literature such as Contractor Manuals, Technical Bulletins, Detail Drawings and detailing recommendations and other relevant documents are also available on www.gcpat.com. Information found on other websites must not be relied upon, as they may not be up-to-date or applicable to the conditions in your location and we do not accept any responsibility for their content. If there are any conflicts or if you need more information, please contact GCP Customer Service.
Last Updated: 2018-11-29