The barrier behind the cladding
Codes call it a water-resistive barrier; many in the trades still say water-resistive barrier or simply building paper. Its job is to stop water that gets past the cladding and direct it down and out. Common types include asphalt-saturated felt, Grade D building paper, housewraps, fluid-applied barriers, and self-adhered membranes.
The principle is simple: every upper layer laps over the layer below, like shingles. Window and door flashings, penetration flashings, and roof-to-wall flashings must be woven into that sequence. A reverse lap anywhere in the wall can send water inward instead of out.
Behind cement plaster over wood-based sheathing, codes have generally called for a barrier that performs at least as well as two layers of Grade D paper. The outer layer is commonly described as bonding to the plaster while the inner layer remains a drainage path.
Common installation defects
Many barrier failures are sequencing errors. Common findings include head flashings set on top of the barrier instead of beneath it, sill flashings tucked behind the barrier below them, and laps that run the wrong direction. Tapes and sealants that are incompatible, or applied to a dirty or damp surface, can also let go.
Damage before the cladding goes on is another source. Tears, unsealed fastener holes, and exposure to sunlight beyond the manufacturer’s limits can weaken a barrier that looks complete. Gaps at the base of the wall, at weep screeds, and at transitions to other materials leave water without a path out.
Because the barrier is covered soon after installation, these conditions are rarely visible until damage appears inside the wall. Staining, decay, and mold on sheathing are often the first evidence.
Investigating barrier installation
Barrier conditions can only be confirmed by looking at them. Investigations typically select inspection openings at windows, doors, roof-to-wall intersections, and the base of the wall, where problems concentrate. Each layer is photographed as it is exposed so the lap sequence is preserved in the record.
Water testing at an opening can show whether a suspected path leaks before the wall is disturbed. The pattern of findings across many openings helps show whether a condition is isolated or repeated.
We take field samples to store at our office in case they are needed at trial. If a barrier, tape, or flashing product appears to have a manufacturing defect, we are aligned with several laboratories that test and analyze product failure.
Reports and repair scopes
Our field reports, photo documentation, conceptual repair scopes, and cost estimates describe what was found at each opening and what repair would address it. Because barrier repairs require removing cladding, clarity about the extent of the work matters to every party.
Gregg de Haan specializes in plan reviews as they relate to waterproofing above and below grade. We also perform construction document plan and detail analysis for constructability and code compliance.
Common warning signs
- 01Stains or damp spots on interior walls below windows
- 02Decay or mold on sheathing found during repairs
- 03Exterior stains that track down from window corners
- 04Persistent dampness at the base of exterior walls
- 05Rusted lath or fasteners visible at cracks
- 06Musty odors in rooms along exterior walls