What is a roof jack? The pipe collar that often leaks first
A roof jack is a small part with a big job: sealing the spot where a pipe pokes through your roof.
A roof jack is the flashing around a pipe that passes through the roof, most often a plumbing vent. It is also called a pipe boot or vent flashing. It has a flat flange that sits under the shingles and a collar, usually rubber or neoprene, that grips the pipe.
Why the roof jack is a common leak point
The metal or plastic base lasts for decades. The rubber collar does not. Sun and temperature swings crack it, and once it splits, rain runs down the pipe and into the ceiling below.
It is a small part that fails early. That makes it one of the first places to look when you find a stain and cannot see any other cause.
What a failed roof jack looks like
From the yard, with binoculars, look at each pipe on the roof.
- A cracked, split or shrunken rubber collar.
- A gap between the collar and the pipe.
- A flange lifted at one edge, or shingles lying unevenly around it.
- Rust or staining running down from the base.
Inside, the clue is a stain on the ceiling or wall near where the pipe runs down. In the attic, look at the pipe itself with a flashlight. Dark streaks or damp insulation around it point to the jack above.
Not every stain near a pipe is the jack
Condensation on a cold vent pipe can drip and mimic a leak. If the stain shows up in cold weather and not after rain, suspect condensation. If it shows after rain, suspect the collar. A roofer can tell the difference, and so can you if you note when it happens.
Why we stop at looking
We do not give steps for replacing a roof jack or sealing around one. That means walking the slope to a pipe and working at the shingle edge. Replacement is a short job for a roofer, so hand it over with good photos and a note of when the stain appears.
For the wider picture of metal at roof penetrations, read what is roof flashing. For tracing a stain back to its source, see flashing leaks.
Frequently asked questions
What is a roof jack used for?
It seals the opening where a pipe, usually a plumbing vent, passes through the roof. The flange sheds water over the shingles and the collar grips the pipe.
Is a roof jack the same as a pipe boot?
Yes, in most cases. Roof jack, pipe boot, vent flashing and plumbing vent flashing all describe the same part.
How do I know if my roof jack is leaking?
Look for a cracked collar or a lifted flange from the ground with binoculars, and a ceiling stain or damp insulation near the pipe. A stain after rain points to the jack.
Can I replace a roof jack myself?
We do not publish steps for it, because the work is done on the roof slope. Document the damage from the ground and the attic and have a roofer replace it.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- NRCA. National Roofing Contractors Association
- US OSHA. 1926.501 — Duty to have fall protection (OSHA)