How cement plaster and siding are meant to work
Exterior cladding is not the only barrier against rain. Cement plaster, wood siding, and composite siding shed most water at the surface, but some always gets behind them. The wall depends on a water-resistive barrier, flashings, and drainage paths to carry that water back out.
Traditional cement plaster over wood framing is applied in coats over metal lath, with building paper or another barrier behind it. At the base of the wall, a weep screed lets water that reaches the barrier drain to the outside. Over wood-based sheathing, codes have generally called for a barrier that performs at least as well as two layers of Grade D paper.
Wood and composite sidings follow the same logic with different details. Laps, joint flashings, clearances to grade, and fastening patterns come from the manufacturer’s instructions and the code in force when the building was permitted.
Where stucco and siding failures usually begin
Most water intrusion through cladding starts at an interruption: a window, a door, a roof-to-wall intersection, a deck ledger, or a penetration for pipes and fixtures. These are the places where the barrier and flashings must be lapped in the right order. A single reversed lap can direct water into the wall instead of out of it.
Cracking in cement plaster has many sources. Shrinkage cracks are common and often cosmetic. Cracks that radiate from window corners, follow framing lines, or reopen after patching can point to movement, missing control joints, or lath and attachment issues.
With siding, problems often appear at the bottom of the wall and around trim. Inadequate clearance to soil or paving, unsealed cut ends, missing joint flashings, and overdriven fasteners are frequent subjects of investigation. Composite products carry detailed installation requirements from their manufacturers, and departures from them are often at issue.
How a cladding investigation proceeds
A typical investigation starts with the documents and a visual survey of every elevation. Investigators map cracks, staining, and past repairs, take moisture readings, and note where interior damage lines up with exterior conditions. The pattern usually narrows the question before any wall is opened.
When the parties agree, small inspection openings show what the finish hides: the barrier, the lath, the flashings, and the condition of sheathing and framing. Water testing at selected locations can confirm whether a suspected path actually leaks. Each step is photographed so the record can be reviewed by everyone involved.
Our associates are active in the building trades and familiar with current building materials. If a material appears to have a manufacturing defect, we are aligned with several laboratories that test and analyze product failure. We also take field samples to store at our office in case they are needed at trial.
What the findings support
Our field reports pair photo documentation with clear descriptions of each condition. Where repairs are in question, we prepare conceptual repair scopes and cost estimates, so the parties can weigh options on the same information.
Cladding questions often involve the building code, product literature, and, for many California homes, SB800. We are educated on past and current building codes, SB800, and building product performance testing. Findings can then be read against the requirements that applied when the work was done.
Common warning signs
- 01Cracks that reopen after patching or radiate from window and door corners
- 02Staining, efflorescence, or streaking below windows, sills, or roof edges
- 03Bulging, soft, or hollow-sounding areas of plaster
- 04Siding that is swollen, cupped, delaminating, or decayed at laps and cut ends
- 05Cladding in contact with soil, paving, or roofing without the required clearance
- 06Interior stains, damp baseboards, or musty odors along exterior walls