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Stone Mason® Instant Waterstop/U-Plug

Product Description
Installation and
Technical Literature
Application Tips
and Instructions

Designed to stop active water leaks in concrete and masonry surfaces, Stone Mason® Instant Waterstop/U-Plug expands to fill cracks quickly and permanently.


  • Mixes easily with just water
  • Sets in 3–5 minutes
  • Suitable for interior/exterior use


  • 1 Kg will fill 600cc, or a crack 19mm x 19mm x 1.5m (1 lb will fill 17 cubic inches or a crack 3/4" x 3/4" x 30")

Required Tools and Materials

  • Chisel and hammer
  • Putty knife or trowel
  • Mixing pail
  • Stir stick
  • Rubber gloves

Data Sheets

Stone Mason® Instant Waterstop/U-Plug Data Sheet Download PDF      

SDS Sheets

Stone Mason® Instant Waterstop/U-Plug SDS Sheet Download PDF      

Surface Preparation

Chisel crack open to minimum 3/4" wide by 3/4" deep, to create a greater surface area for bonding with cement. Always undercut or cut square and do not use a V shaped cut. Clean all loose material from crack or hole.


Place a small amount of Instant Water Stop cement in mixing pail. Add water, and mix into a putty like consistency.


Using a trowel or hand, form cement into a cone-shape. Beginning at the top, force cement in crack and hold in place until set.

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.