Underseal® Underslab Membrane

U.S. Patent No. 7,488,523
U.S. Patent No. 7,686,903

Underseal® Underslab Membrane is a tough, 85-mil pre-concrete pour waterproofing membrane/vapor barrier designed to virtually eliminate water and vapor transmission through concrete slabs on grade. In addition to protecting floor finishes and indoor air quality, Underseal® Underslab Membrane also acts as a barrier to methane and radon gas.

Underseal® Underslab Membrane provides a continuous seal underneath the foundation slab. A strong mechanical bond is developed between the membrane and concrete at the time of pouring as the concrete intermingles with the fibers of the nonwoven geotextile. Underseal® Underslab Membrane is typically installed horizontally over a prepared subbase such as compacted soil, mud slab or #57 stone. 85 mil Underseal® Underslab can also be used in vertical applications.


  • Superior Protection: 3-layer composite membrane
  • Superior Puncture Resistance: Higher than current Class A Vapor Barrier requirements (2200 grams, or under 5 pounds)
  • Superior Resistance to Water Migration: Eliminates water and vapor migration by forming a strong mechanical bond to the concrete
  • Superior Adhesive Bond: Creates a strong adhesive bond when the static load and thermal reactive heat of the concrete slab causes sealant/adhesive compound to have an intimate contact with the concrete surface
  • Superior Adaptability: Flexible material that adapts to job site irregularities for ease of installation
  • Superior Joints: Fully-adhering, watertight laps
  • Superior Crack Protection: Stress-absorbing and elongation properties to maintain a watertight seal to the structure if cracks develop in the base material or the slab
  • Superior Barrier: Acts as a barrier against toxic contaminants methane and radon gas, which may attempt to enter the structure through cracks in the concrete

Photo Gallery

Product Resources

Data Sheet (PDF)Download 
Guide Spec (PDF)Download 
Guide Spec (WORD)Download 
Materials List (PDF)Download 
Features & Benefits (PDF)Download 
SDS (PDF)Download 

To obtain a DWG detail, you must:
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PGArch Detail US11 Underslab US Inside Corner Detail 07052018Download 
PGArch Detail US17 Underslab Preformed US Outside CornerBoot Concrete Column 01182018Download 
PGArch Detail US21 Underslab Pit Top Corner Boot 10012014Download 
PGArch Detail US22 Underslab 650 Membrane Boot For Underslab Inside Corner 06052018Download 
PGArch Detail US23 Underslab Outside Corner Field Cut 07032019Download 
PGArch Detail US24 Underslab Field Made Outside Corner Boot 07032019Download 


PGArch Detail US10 Underslab Sump Or Elevator Pit Overview 03182014Download 
PGArch Detail US13 Underslab Carton Form Detail 03182014Download 


PGArch Detail US15 Underslab Penetration Detail Profile 1and2 06132016Download 

Repairs / Patches

PGArch Detail US6 Underslab Saw Cut Slab Through Underslab Membrane 06142018Download 
PGArch Detail US19 Underslab Repair Patch Less Than 2Download 
PGArch Detail US20 Underslab Repair Patch Greater Than 2Download 

Seams / Laps

PGArch Detail US2 Underslab EndLapSeam 03182014Download 
PGArch Detail US12 Underslab Side Lap Selvedge 03182014Download 
PGArch Detail US18 Underslab PreApplied Seal Of Vertical Leg Turn Up From Underslab Membrane End Lap 03182014Download 


PGArch Detail US3 Underslab Pile Termination Profile1 03182014Download 
PGArch Detail US4 Underslab Pile Termination Profile2 03182014Download 
PGArch Detail US5 Underslab Termination To Existing Concrete Wall 03182014Download 
PGArch Detail US7 Underslab Post Concrete Pour Termination Of Underslab To Face Of Footer Structural Slab 03182014Download 


PGArch Detail US1 Underslab Tie In To Blindside 11152019Download 
PGArch Detail US8 Underslab 650 Membrane TieIn To Post Terminated Underslab Profile1 03182014Download 
PGArch Detail US9 Underslab 650 or PRM membrane TieIn To Embedded Underslab Profile2 03182014Download 
PGArch Detail US14 Underslab 650 or PRM membrane TieIn To Embedded Underslab Showing Polyflow 15or15P 03182014Download 

Product Submittals

For a job-specific submittal package, please contact Polyguard for Product Submittal Requests. Click here to find your area’s field representative.

Companion Products

(Where Applicable)
606 Tape High strength double-sided tape comprised of rubberized asphalt.
650 LT Liquid Adhesive Used to prime all structural concrete, masonry, or wood surfaces prior to membrane installation.
California Sealant Used to seal all porous portions of Underseal® geotextile surface and promote adhesion of Polyguard sealants.
Detail Sealant PW™ VOC/HAPS-free high-performance solvent-free sealant.
Detail Tape Use as detail strips on corners, penetrations, joints, and for patching damaged areas of the membrane.
LM-85 SSL Self-leveling flood coat waterproofing membrane.
LM-95 Two-component fast cure urethane waterproofing membrane.
Polyflow® 15 / 15P Sheet molded drain for vertical application with a compressive strength of 15,000 psf.
Polyflow® 18 Sheet molded drain for horizontal application with a compressive strength of 21,000 psf.
Underseal® Fabric Tape Use around pipe penetrations and at end laps for patching damaged areas of the membrane.
Underseal® Inside Corner Boot To be applied in the inside corner to reinforce and seal the corners of the Underseal® Underslab membrane.
Underseal® Outside Corner Boot To be used in the outside corner to reinforce and seal the corner.
Underseal® Pit Top Corner Boot Preformed corner boot used to reinforce and seal the Underseal® Underslab Membrane and Underseal® Blindside™ Membrane.