LinkedIn Youtube Facebook Twitter Sales Rep Locator Document Search

Stone Mason® U-Seal Cement Based Waterproof Coating

Product Description
Installation and
Technical Literature
Application Tips
and Instructions

Stone Mason® U-Seal Cement Based Waterproof Coating is a breathable, heavy-bodied, cement-based waterproof finish that penetrates into the pores and voids of concrete and masonry to become a part of the surface to which it is applied. U-seal protects against water penetration, yet allows walls to breathe. Tested and proven safe for use on potable water containment surfaces.


  • Becomes a part of the surface to which it is applied
  • Easy to mix, use and apply
  • Will last as long as the structure to which it is applied
  • Safe for potable water containment


  • Available in white and pearl grey


  • A 22.7Kg (50 lb) bag covers 22.7 m2 (225 sq ft) at 1 kg/m2 (2 lb/sq yd)
  • For severe water conditions, two coats applied at the above rate are normally sufficient
  • For deep-below grade applications, it may be necessary to increase amount of material applied per m2 (sq yd)


  • Available in 22.7Kg (50 lb) bags

SDS Sheets

Stone Mason® U-Seal Cement Based Waterproof Coating Gray SDS Sheet Download PDF      
Stone Mason® U-Seal Cement Based Waterproof Coating White SDS Sheet Download PDF      

Surface Preparation

To ensure good, long-lasting results, apply only to clean, structurally sound surfaces. Remove all dirt, grease, oil, efflorescence, laitance, paint, loose mortar or anything else that may impair good bonding. Repair all cracks or holes larger than 0.8 mm (1/32”) using U-Plug to stop running water leaks. Use Vinyl Patch to repair dry cracks and holes in walls and floors. If time constraints exist, use UP 2000 to repair and patch holes and cracks in walls and floors.


In a clean mixing container place 6 litres (1 1/2 gallons) of mixing liquid (1 part Acryli Bond to 3 parts clean potable water) and slowly mix in powder U-Seal until a rich creamy consistency is reached. Allow material to soak for a minimum of 5 minutes and then re-mix, adding more mixing liquid if required. Under normal conditions each 22.7 Kg (50 lb.) bag requires 7 1/2 to 8 litres (2 gallons) of mixing liquid. At higher temperatures more mixing liquid will be required.


Dampen previously prepared and cleaned surface immediately ahead of application. Lay on a heavy coat of U-Seal at a rate of 1 Kg/ m2 (2 lb./sq.yd.), using a stiff brush or broom. Level out application of U-Seal to achieve a uniform thickness and appearance beginning at the top of the wall and continuing down and onto the floor. Continue to work across the wall in this manner until application is complete. If the wall becomes dry or the U-Seal starts to pull during application, dampen the wall again with a fine mist of water and continue with the application of U-Seal. Allow to dry overnight and apply a second coat to achieve maximum waterproof protection.

Above Grade

Normal water conditions: Apply one coat of U-Seal at 1 Kg/m2 (2 lb/sq.yd.) and the second coat at 1/2 Kg/m2 (1lb/sq.yd.) Severe water conditions: Apply two coats of U-Seal, both at a rate of 1 Kg/m2. (2 lb/sq.yd.)

Smooth finish

Apply first coat of U-Seal at a rate of 1 Kg/m2 (2 lb/sq.yd.). Allow to set and apply a trowel coat of Stone Mason® Plaster Mix at a rate of 4.9 Kg/m2 (9 lb/sq.yd.) or sufficient material to bring surface true, level and float smooth.

Exterior Foundations

Clean surface of wall to remove form release agents, dirt, dust, efflorescence, grease, oil or loose mortar. Clean top of footer and apply cove of mortar at intersection of wall and footing. Fill any holes in masonry or concrete prior to applications. Apply two brushcoats of U-Seal each at a rate of 1 Kg/m2 (2 lb/sq.yd.) ensuring that application extends down onto the footer.

For below-grade exterior applications

Apply a base coat of U-Seal at 1 kg/m2 (2 lbs.per sq.yd.) and allow to cure for 5 to 7 days. Then apply a top coat of Stone Mason® Plaster Mix at 6.5 kg/m2 (12 lbs. per sq. yd.). A steel trowel finish is recommended. For both below-grade interior and below-grade exterior applications it is recommended to cut out and place a U-Plug cove at the wall/floor junction prior to the application of the U-Seal base coat.

Over Parge Coat

Brush apply one coat of U-Seal at a minimum rate of 1 Kg/m2 (2 lb./sq.yd.), ensuring that the application extends out over the footing.

Interior of Perimeter Basement Walls

Repair all cracks or running water with U-Plug. Brush on two applications of U-Seal each at a rate of 1 Kg/m2 (2 lb./sq.yd.).

To Achieve a Finished Plaster Surface

Apply a brush coat of U-Seal at 1 Kg./m2 (2 lb./sq.yd.). Allow to set and apply by trowel a coat of Stone Mason® Plaster Mix at a rate of 6.5 Kg./m2 (12 lb./sq.yd.) hiding all form marks and other construction faults. Bring surface to true and even lines with sand float finish.

Swimming Pools

Remove all foreign materials from surface of pool. Repair cracks and areas of disbonding. Brush apply two coats of U-Seal each at a rate of 1 Kg/m2 (2 lb./sq.yd.), and float smooth before material hardens. Water cure the finished surface with a fine mist of clean water until the pool is to be filled. Allow 7 days curing, before filling with water.

Cisterns and Reservoirs

Repair all cracks and holes, dampen the previously cleaned surface and apply two brush coats of U-Seal each at a rate of 1 Kg/m2 (2 lb./sq.yd.). Allow U-Seal to harden for 48 hours and then wash down all surfaces with a brine solution (12.5% salt in water). Leave damp brine solution on walls and floors overnight and then rinse with clean water to remove free lime left on walls and floors. Repeat until final rinse water is completely clean and clear.

Sewers and Tunnels

Repair all running water leaks with U-Plug. Patch spalled areas with UP2000 Patching Cement. Brush on two coats of U-Seal each at a minimum rate of 1 Kg/m2 (2 lb./sq.yd.). If a smooth, true surface is required, replace second coat of U-Seal with a trowel application of Stone Mason® Plaster Mix at a minimum rate of 6.5Kg/m2 (12 lb./sq.yd.).

Back Plastering

Prior to placing the back-up units, apply one heavy coat of U-Seal to the interior of the exterior wall surface. Completely fill and seal all mortar joints, pores and voids.

Parapet Walls

Prior to placement of the coping on parapet walls, install one heavy uniform brush coat of U-Seal at a rate of 1.5 Kg/m2 (3 lb./sq.yd.). Be sure to cover the entire surface on the roof side from the top of the roof flashing to the top of the wall.

Finishing Concrete

Strip forms, clean wall surface, fill snap-tie holes and severe honeycomb with UP2000 Patching Cement. Brush apply the first coat at a minimum rate of 1 Kg/m2 (2 lb./sq.yd.). Allow to set and apply second brush coat at the same rate as first coat. When second coat has set, float it to a smooth uniform finish.


Expansion or control joints must be maintained or placed as necessary in a structure to which U-Seal is to be applied. After the U-Seal has cured, these joints can be filled with an appropriate caulk or sealant. Do not apply U-Seal to frozen or frost-filled surfaces. Do not apply when temperature is below 4°C (40°F). Do not apply in rain. Protect fresh finish from rain. Do not use in enclosed areas without adequate ventilation.


Corrosive. May cause eye injury. If product gets into eyes, flush repeatedly with water and seek medical attention promptly. Avoid skin contact. If contact occurs, wash exposed skin with water. Protective eyewear should be worn. Avoid contact with eyes.

First Aid Treatment

Cement when mixed with water results in a solution of calcium hydroxide. If splashed in eyes or skin, flush thoroughly with water.


Silica sands which may cause lung cancer.

The consumer shall satisfy themselves of the suitability of this product for the intended purpose. Weather, applicator's skill and surface conditions are beyond manufacturer's control. We, therefore, limit our liability to replacement of defective material only, within one year of proof of purchase.