Short answer. Water visible near a Therma-Tru sill does not by itself identify a failed door sweep. The 2017 manufacturer water-leak table separately lists the sill/subfloor sealant, sill-to-jamb joint, damaged weatherstrip, distorted sill, saddle/bulb condition and damaged door bottom as possible causes. source The practical first task is locating where moisture first appears, without assigning a cause by guesswork.
Three observation zones, not three diagnoses
| First observed moisture | Record it as | Candidate the document prompts you to consider |
|---|---|---|
| At or beneath the stationary threshold | Under-sill region | The manual includes insufficient/broken-down sealant between sill and subfloor. source |
| At the jamb-to-sill meeting point | Sill/jamb corner | A broken joint seal is another independent row. source |
| At the moving door-bottom interface | Door-bottom/contact region | The manual also lists damaged door bottom or sill distortion and damaged saddle/bulb contact. source |
These locations help organize photographs; they cannot prove the actual concealed path. The same table includes damaged or painted weatherstrip as a separate candidate. source
A non-destructive leak log
- On discovering moisture, avoid exposing electrical fixtures or continuing use where water may create a hazard. Keep a dated note of rain or washing conditions rather than reproducing a damaging water test.
- Record the first visible wet edge before wiping it; include a wide frame photograph for orientation. If the area is already dry, write “source not observed.”
- Photograph both threshold ends, the entire door bottom, and the jamb weatherstrip. Show any distortion without manipulating the sill.
- Keep a two-column list: observed (location, time, condition) and possible (which 2017 table row might apply). Do not merge the columns.
- Escalate damp structural material, recurring ingress or an unlocated source for a qualified inspection rather than applying a blanket adhesive or replacing a sweep first.
How to interpret the result
Under-sill or joint evidence: prioritize inspection of original sill sealing/installation details. Visible bottom or saddle damage: investigate the matching door-bottom or adjustable-threshold assembly. No unique clue: keep all candidate routes open. The 2017 table offers different repair references, not an exact proof test or a promise that any one change makes an assembly watertight.
Primary sources and claim locator register
- — Therma-Tru original, 2017 Site Manual — SITE 4, US; p.4.4, sill/subfloor sealant. Publisher document.
- — Therma-Tru original, 2017 Site Manual — SITE 4, US; p.4.4, sill/jamb broken joint. Publisher document.
- — Therma-Tru original, 2017 Site Manual — SITE 4, US; p.4.4, damaged/painted weatherstrip. Publisher document.
- — Therma-Tru original, 2017 Site Manual — SITE 4, US; p.4.4, depressed/humped sill beyond sealing capacity. Publisher document.
- — Therma-Tru original, 2017 Site Manual — SITE 4, US; p.4.4, damaged saddle and wrinkled bulb. Publisher document.
- — Therma-Tru original, 2017 Site Manual — SITE 4, US; p.4.5, damaged door bottom. Publisher document.
Evidence and safety boundary
In Therma-Tru’s 2017 SITE 4 manual (printed p. 4.4), leakage near a door sill may involve the below-sill joint rather than only the door-bottom seal. Note whether moisture appears beneath the threshold, at a corner joint, or along the moving bottom edge; avoid diagnosing from a wet floor alone. Document the assembly and ask the installer or manufacturer for the appropriate inspection path before buying a sweep.