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4' x 50' roll

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Polyguard Underseal Underslab Membrane is used as a waterproofing membrane/vapor barrier to virtually elimnate water and vapor transmission through concrete slabs on grade.


Product Data Sheet


In addition to protecting floor finishes and indoor air quality, Underslab Membrane also acts as a barrier to methane gas and radon gas.

Product Features

  • Creates a continuous seal underneath the concrete slab.
  • Forms a strong mechanical bond when the concrete, at time of pouring, intermingles with the fibers of the nonwoven geotextile.
  • Creates a strong adhesive bond when the static load of the concrete slab causes the sealant/adhesive compound to “cold flow” throughout all remaining voids between the fabric and the underside of the concrete slab. (See the McGraw-Hill Dictionary of Architecture and Construction for a definition of cold flow). The Underslab System has been tested to ensure no water migration occurs between membrane and concrete.
  • Underslab Membrane has a puncture resistance of 220lbs., which is 64 times higher than current Class A Vapor Barrier requirements (2200 grams, or under 5 lbs). A higher puncture resistance is critical to the vapor barrier underslab system due to abuse caused by construction methods, i.e. concrete truck routes, motorized-equipment contact with rebar during concrete applications, normal foot traffic, and regular vibration.
  • Features fully-adhered, watertight laps and other details.
  • Acts as a barrier against toxic contaminants, including methane and radon gas, which may attempt to enter the structure through concrete cracks.
  • May qualify for L.E.E.D. certification via these credits:

- IAQ Credit 5 - Indoor Chemical and Pollutant Source Control (below-grade toxin barrier)
- SS Credit 3 - Brownfield redevelopment
- ID Credit 1 - Innovation in design

Composition & Materials
Underseal® Underslab Membrane is a strong sheet membrane with a double-thickness, cross-laminated, high density polyethylene (HDPE) backing laminated to a thick
layer of proprietary waterproofing adhesive compound integrated into a high-strength, nonwoven geotextil fabric. Total membrane thickness is factory controlled at
85 mils.

On the fabric side, a 4" wide lap of waterproofing adhesive compound is left exposed along one edge with a removable silicone-coated release sheet. Expose this adhesive just prior to the installation of the adjacent roll to create a 4" wide self-adhesive overlap seam.

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