Durable Portland Underlayments

PBU — a Portland cement-based, non-structural floor underlayment — is mixed on site using PBU, Portland cement, sand, and water. Pumped into place, it forms a high strength yet lightweight cement topping, perfect for use in commercial, multi-family, residential, institutional, and light industrial projects. PBU combines the excellent durability of concrete with lightweight, crack-resistant, sound-insulating, and fire-resistant qualities. Cost-effectiveness, proven performance, toughness, and speed of installation make PBU ideal over cast-in-place concrete, pre-cast concrete, and plywood sub-floors. In fact, up to 25,000 sq. ft. can be installed in one day!

Portland Underlayments Being Installed


Do not apply PBU when the temperature is below 40° Fahrenheit (or 4° Celsius). The structural floor must support design loads with maximum L/360 deflection. If application thickness exceeds 4" over wood, consult Northwest for technical advice.

Technical Data

  • ASTMC 109 Modified
  • Compressive Strength: 3,500 psi to 6,500 psi
  • Dry Density: 105 lb/ft3, 1.7 g/cm3
  • Weight: 4.0 lb/ft2 @ ½", 18.5 kg/m2 @ 12mm
  • Flame Spread: 0
  • Fuel Contributed: 0
  • Smoke Developed: 0