Fluid-applied membranes include polyurethanes, polymer-modified asphalts, PMMA and polyureas. They form a continuous skin with no laps, follow complex shapes and penetrations, and are measured in wet and dry mils. Thickness control, substrate dryness and preparation of bugholes and cracks decide performance, because thin spots and pinholes become leaks.
Fluid-applied on the plaza, 60 mils dry, so pull wet mil readings every hundred square feet.
Inspectors trust a wet mil gauge reading taken during application far more than an estimate based on the number of pails used.
Also heard as
- liquid membrane
- fluid-applied waterproofing
- LAM
Related terms
Sheet membrane
Waterproofing supplied in rolls of factory-made sheet with a controlled thickness, joined at overlapping laps.
Bugholes
Small surface voids in formed concrete left by trapped air bubbles against the formwork.
Holiday
A gap, pinhole or thin spot in a membrane or coating where it fails to cover the substrate.
Detail coat
An extra reinforced layer of membrane at corners, cracks, drains and penetrations before the main coat goes on.