BUR — Modified Bitumen — Cap Sheet

Problem

Application Issues:

- If the asphalt is heated to an improper temperature, blistering and slipping of felts can occur, accelerating the aging of the roof system.
- Overheating asphalt can result in burns and fires in the kettle and on the roof.

Common Problems:

As oils leave the asphalt, the dark colored substrate becomes dry and brittle. The roof is less flexible and less able to expand and contract as it heats up and cools down during the day. As a result, the following problems occur:

Alligatoring: Cracking of the roof substrate, sometimes severe − looks similar to the skin of an alligator.

Seam Failure: The asphalt based seams are unprotected from UV, causing cracking from severe temperature changes and thermal shock.

UV Weathering: The roof substrate breaks down from wind, rain and UV exposure, as well as expansion and contraction from changing temperatures.

High Roof Temperatures: Dark colored roofs can reach 180+ degrees, which absorbs and transfers the heat inside the building.

Solution

Why SRM over a BUR/Cap Sheet/Modified Bitumen Roof?

SRM will restore and extend the life of your roof.

SRM protects the seams and substrate from the UV attack and weathering, offering the ultimate protection to the weakest parts of the above systems.

SRM is a liquid applied directly to the roof system, covering every crack, gap and patch with a silicone product designed specifically for that part of the roof.

SRM provides a monolithic roof membrane, eliminating all the seams, which eliminates all the leaks!

SRM in white will take a hot roof and make it cool.

SRM eliminates costly tear-offs and landfill waste.

WDG Products needed:

  • 601 Butter Grade to seal the cracks in substrate seams
  • WDG Polyester Fabric (if needed)
  • KGF 1000 to seal around drains or scuppers
  • HSS 535 Flashing Grade on walls, skylights, parapets, ect.
  • HSS 535 Coating on the roof

Always perform an adhesion test prior to application of WDG SRM. 211 Primer may be required.

How to apply SRM to a Cap Sheet/Modified Bitumen roof?

Power-wash/Clean Roof Substrate
Address details and required repairs (sealants/535 coatings/embedded fabric)
Single-coat application of HSS 535 Solvent-Free Silicone

Note: Always refer to WDG Specifications for application instructions. 211 Primer may be required.

BUR – Modified Bitumen – Cap Sheet

Built up roof membranes, referred to as BUR or "tar and gravel" roofs, are composed of alternating layers of bitumen and reinforcing fabrics that create a finished membrane.  The bitumen typically used in BUR roof systems is asphalt, coal tar or cold-applied adhesive. The asphalt or coal tar is heated in a kettle or tanker and then applied by mop or mechanical spreader. Asphalt is a petroleum product refined from crude oil; coal tar is derived from the distillation of coal. Cold-applied adhesives typically are solvent-based asphalts that do not have to be heated in a kettle or tanker.

Modified bitumen membranes, SBS or MBS, combine the features of a built-up roof with polymer modifications.

Cap Sheet is the top layer of the BUR/Modified Bitumen system.

click image to enlarge

Before

Before

After

After

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