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CoverShield WaterStop Primer – An Exterior / Interior Waterproofing Primer For Concrete, Masonry & Wood


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Location : Interior/Exterior
Task : Oil Stop Primer
Application : 3/8th Nap Roller
Surface : Concrete
Base : Solvent Based
Drytime : 3-12hrs
Coverage : 200 sq.ft/Gal.
Finish : Black

Frequently Purchased Together

CoverShield WaterStop Primer Water chasing primer and vapor barrier for concrete and wood – Exclusively for Contractors

WaterStop Primer

WaterStop Primer is unique penetrating water chasing primer that uses hydrophilic technology to react with moisture deep inside any porous surface. WaterStop Primer forms a dense waterproof barrier that prevents the passage of water and moisture vapor through concrete, wood and other porous substrates.


  • Works internally to seal all porous surfaces
  • Chases water > 60 mils into the surface
  • Reduces Moisture Vapor Emission (MVE)
  • Waterproofs (holding back a hydrostatic head)
  • Increases bonding of polymer top coating (including polyurethanes, epoxies, mastics, etc.)
  • Retards pitting, dusting and efflorescence.
  • Can be used on Green (2-day old) concrete.
  • Works on all concrete, wood, masonry and many porous substrates
  • Increased resistance to freeze-thaw and salt attack
  • Can be coated over, and will accept concrete topping or adhesives for floor tile, etc.

Main Uses

  • Water and vapor barrier
  • Moisture tolerant primer
  • Deep seal saturated concrete
  • Flood restoration
  • Above, below or on grade waterproofer
  • Concrete treatment before coating—polyurethane, floor levelers, adhesives, polyurea, epoxy, vinyl flooring

Surface Conditions

The surface must be completely free of oil, grease,

curing compounds, other coatings, water repellants and

any other foreign material that may inhibit the primer penetrating into the surface

Any non-moving cracks or pock holes should be filled with CrackFiller epoxy before the application of WaterStop Primer.

Surface Preparation

All moving cracks, joints, and seams should be filled with a high elastomer material after priming. CoverFlex J45 HD, or similar product is recommended. Avoid acrylic caulks or any compound with silicone.

Cement Based Toppings

Note: Cementitious underlayment and patching should only be installed after priming with WaterStop Primer.

For cement-based toppings, underlayment, thin-set tile mortar, adhesives, etc., it is necessary to double prime and then broadcast sand. Apply 2nd coat WaterStop Primer within the recoat window (1 to 12 hours at 77°F) then immediately broadcast #50 – #70 sand directly over the WaterStop Primer while still wet. If the subsequent cement coating requires a primer over concrete, it should also be used over the sanded surface.


Mix ratio is 1 Part A :1 Part B

Condition the material to a minimum temperature of

60°F (10°C). Add the hardener ‘Part B’ in to the base

‘Part A’ and mix using a slow speed drill (350 to 500rpm)

and paddle for 3 minutes until both components have fully dispersed and are uniform in color. Be sure to rotate the mixer throughout the pail.


Apply in a single coat at the specified application rate (see above) thickness using a long-notched squeegee. Then use a 3/8th nap non-shed roller to achieve uniform coverage. Apply any topcoat or resin floor as soon as the primer is tack free (2 to 4 hours after application depending on temperature).

Top coat or recoat

Primer OS can be top coated with epoxy and /or urethane systems  within the recoat window (3 to 12 hours at 77°F). We recommend 1 coat of Primer HS and 2 coats of CoverShield U270 (see separate data sheets and color chart for color options). If different topcoats are desired, contact CoverTec for application details before proceeding. Proposed intermediate and topcoat selections should be evaluated for adhesion and compatibility.  A representative sample patch should be applied for this purpose.

This product is exclusively for contractors.

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Frequently Asked Questions

CoverShield Primer OS Photos

CoverShield Primer OS Videos

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