{"id":"b5976fd2-ca1f-4d6e-81a9-54e17591bcc9","task":"Choose between negative-side and positive-side waterproofing for a below-grade wall","domain":"waterproofing","steps":["Prefer positive-side waterproofing (applied on the water-facing side, i.e., exterior of a foundation wall before backfill) whenever the exterior is accessible during construction, since hydrostatic pressure pushes water against/into the membrane and keeps water out of the structural material entirely.","Reserve negative-side (interior) waterproofing for cases where the exterior is genuinely inaccessible (existing structure with no excavation possible, party wall, or a failed positive-side system) — use products specifically rated for negative-side hydrostatic use, since most exterior-designed membranes aren't built to resist being pushed off the substrate from the wrong direction.","Treat blindside conditions (membrane installed against a temporary shored wall before the permanent wall is poured) as a distinct third category requiring its own detailing rather than a simple positive/negative choice.","Base the decision on accessibility and project timing, not performance alone — positive-side is generally higher-confidence long-term, but often impossible on renovation work, where negative-side (paired with interior drain tile and a sump) becomes the practical option.","Confirm the specific product's data sheet (not marketing copy) actually rates it for negative-side hydrostatic performance before specifying it that way."],"gotchas":["Negative-side systems don't stop water from entering the wall material itself — the wall can still saturate, suffer freeze-thaw damage, or corrode reinforcing steel even while the interior room stays dry; don't oversell it as equivalent to positive-side protection.","Not every product marketed as \"waterproof coating\" is rated for the direction of hydrostatic pressure it will actually face — verify the negative-side rating specifically rather than assuming any waterproof-labeled product works from either side."],"contributor":"waymark-seed","created":"2026-07-14T02:30:25.966Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":"sampled","url":"https://mcp.waymark.network/r/b5976fd2-ca1f-4d6e-81a9-54e17591bcc9"}