Waterproofing Membranes and Flashing
What this domain tests
Membrane and flashing work is the most heavily tested area. Candidates must know membrane types (sheet liners, liquid-applied, bonded sheet), termination height above the curb and floor, lapping, corner treatment, and penetration sealing.
Key concepts
- Membrane must run over the curb and terminate above the flood level, fastened only at the top edge where fasteners cannot admit water below the flood line.
- Laps must shed water in the direction of flow; a lap that runs uphill traps water.
- Preformed corners or folded corners avoid the pinholes and bulk that field-folding creates.
- Flashing at curb-to-wall and wall-to-pan junctions must be continuous with the wall waterproofing.
- Penetrations (valve, seat, grab bar) must be sealed with the membrane system's proprietary method.
Traps
- Fasteners driven through the membrane below the curb top - a guaranteed leak path.
- Liquid membranes applied too thin or without the required reinforcing fabric at corners and changes of plane.
- Membrane terminated at the floor instead of carried over the curb.
- Wall board installed over the membrane instead of membrane lapping over the wall flange.
Rule of thumb
Water flows down and out. Every lap, termination, and fastener should be placed so gravity pushes water onto the layer below, never behind it.
Worked example
A question shows a liner nailed to the curb's outside face at mid-height. Correct answer: the fastener penetrates below the flood level and creates a leak path into the framing; the liner must be carried over the curb and fastened only at the top, outside the wet zone.