How to Install Lead Pipe Flashing on a Plumbing Vent
A lead boot outlasts rubber, but it needs careful forming, correct lapping and sensible lead handling.
- Advanced
- 45 to 90 minutes
- Updated
The short answer
Lead pipe flashing is a pre-formed lead sheet boot with a tapered collar that is folded down into a plumbing vent pipe, instead of clamping around it. Slide the flange under the shingles above and over the shingles below, nail only the upper corners, then form the collar down inside the pipe with a wood dowel. Wash hands after handling lead and keep it out of rainwater drainage where possible.
Rubber pipe boots crack from sunlight in a decade or so. Lead pipe flashing is the long-lasting alternative. A lead boot is a sheet of soft, dense metal with a formed collar. It does not crack in UV light, and because it is malleable, it is pressed down into the pipe rather than relying on a rubber gasket. Many lead boots last for the life of a shingle roof or longer.
It has downsides. Lead is soft and can be chewed by squirrels and other animals, and it is a toxic metal that has to be handled with care. Lead also adds a small amount of metal to rainwater runoff, which is a consideration near rainwater collection. The install is otherwise similar to a rubber pipe boot.
Read this guide with the lapping rule and roof flashing types. For gas vents and metal flues, see B-vent flashing.
Tools
- Flat pry bar
- Roofing hammer
- Hook blade utility knife
- Smooth wood dowel or rounded wood block for forming the lead
- Tin snips
- Tape measure
- Nitrile gloves
Materials
- Lead pipe flashing of the right size, with a tapered collar and a flange about 12 by 12 inches or as needed
- Roofing nails, 1-1/4 inch
- Sealant rated for lead and shingles, for exposed nail heads only
- Replacement shingles as needed
- Ice and water shield, for low slopes
Safety first
- Lead is a toxic metal. Do not eat, drink or smoke while handling it, wear nitrile gloves, and wash your hands and face before food or drink. Keep lead sheet and offcuts away from children and pets, and do not sand, grind, torch or burn it.
- Do not cut lead where dust or shavings will fall on a surface people use. Collect all offcuts and recycle them as scrap. Follow local disposal rules.
- Work tied off. WorkSafeBC requires fall protection at 3 metres (about 10 feet) and wherever a fall could cause serious injury. See walking a roof safely.
Step by Step
Step 1: Identify the pipe and choose the boot
Lead boots come in sizes for 1-1/2, 2, 3 and 4 inch pipes, often with a single tapered collar or one that is trimmed to fit. The collar should stand at least 3 to 4 inches above the roof so that it can be folded down into the pipe, and the pipe should have a clean open end. Ask the supplier for the boot size suited to your pipe.
Step 2: Remove the old flashing and prepare the roof
Work gently, since cold shingles crack. Clean the deck of old sealant and stray nails. Replace any soft decking. On a low slope or where the old boot leaked, add a square of ice and water shield around the pipe, leaving the pipe opening clear.
Watch out: Do not cut or scrape old lead flashing in a way that creates dust. Lift and bag it, and recycle it as scrap.
Step 3: Check the pipe top
A rough pipe edge can cut the lead. Smooth it gently with a file if needed. The pipe should stand above the deck high enough to fold the collar down by at least 1 inch, but not so high that the collar cannot reach.
Step 4: Slide the boot over the pipe
The flange is shingled in: the upper half slides under the shingles above and the lower half lies over the shingles below. This is the lapping rule, and a reversed flange will funnel water into the roof. See the lapping rule. Lift extra shingle tabs if the flange does not slide easily, and never cut the flange to squeeze it in.
Step 5: Nail the upper flange corners
Lead is soft, so do not over-drive the nails. Seat the head flush and stop. Any nail that stays exposed should have a dab of sealant over the head. Keep nails out of the collar and out of the lower flange.
Step 6: Form the collar down into the pipe
Start by gently folding the collar inward with your gloved hands, then use the dowel to press it against the inside of the pipe all the way round. You want a tight, even fold with no sharp creases that could split the lead. A gap at the fold is a path for water. The fold should be at least 1 inch below the pipe rim.
Take your time. Lead work hardens slightly as it is folded, and repeated bending can crack it.
Step 7: Replace shingle tabs and check laps
Press the tabs flat and re-nail them outside the flange area. Replace any cracked tabs. See how to replace a damaged shingle.
Step 8: Clean up and wash
Wash work clothes separately from household laundry if they have lead residue. Keep children and pets away from offcuts and the work area until it is clear.
Lead Handling Hygiene
- Wear nitrile gloves and wash hands and face before eating, drinking or smoking.
- Never cut, sand, grind or heat lead in a way that creates dust or fumes.
- Collect all scrap and offcuts. Do not leave them on the roof or in the yard.
- Keep lead away from rainwater collection and garden beds, and do not let lead sheet hang over a rainwater catchment roof.
- Recycle old lead as scrap metal, and follow local rules for disposal.
- Wash work clothing separately and change before going home or into a vehicle.
Animal Damage
Squirrels, raccoons and rats gnaw on soft lead collars and sometimes chew the fold open. If animals are common around the house, use a rigid lead boot with a thicker collar, add a short metal collar or wire cage over the fold, or consider a different type of flashing. See pipe boots for the rubber alternative.
Fraser Valley Notes
Lead resists UV and moss better than rubber, which suits shaded roofs under firs and cedars. On a wet climate roof, check the fold each fall for gaps or animal damage, and keep needle debris from collecting around the base.
Common Mistakes
- Not folding the collar down into the pipe, leaving a gap at the top where water runs down the pipe.
- Cracking the lead by bending it sharply or repeatedly in the fold.
- Reversing the flange lap, with the lower half tucked under the shingles below.
- Handling lead carelessly, eating or drinking without washing or leaving offcuts around.
- Ignoring animal damage, allowing chewed collars to leak unnoticed.
- Over-driving nails and puncturing the soft flange.
When to Call a Professional
If the pipe is on a steep or high roof, if the deck is damaged, or if animals have damaged the flashing or the attic, hire a roofer. If there is any doubt about lead exposure or disposal, ask a professional to handle it.
If your roof collects rainwater for drinking or gardens, think twice about lead, and consider another flashing material. A roofer can suggest an alternative.
Fraser Roofing does free roof inspections across the Fraser Valley, from Hope to Abbotsford. See our Roof Repair service or the towns we cover.
How to Install Lead Pipe Flashing: Questions
What is lead pipe flashing?
Lead pipe flashing is a sheet lead boot with a tapered collar and flange, used to seal around plumbing vent pipes on a roof. The flange is shingled into the roof, and the collar is folded down inside the pipe and pressed flat. It resists sunlight and does not crack like rubber, so it often lasts as long as the roof or longer.
Is lead pipe flashing better than a rubber boot?
It usually lasts longer because lead does not crack in UV light. Rubber collars commonly fail in about 10 to 15 years. Lead is softer and can be chewed by animals, it needs careful handling because it is toxic, and it costs more. Many roofers choose lead for long-life repairs on roofs with shade or heavy moss.
Is it safe to handle lead flashing?
Yes, with sensible precautions. Wear gloves, do not eat, drink or smoke while handling it, and wash hands and face afterwards. Never sand, grind or heat lead, and collect all scrap for recycling. Keep offcuts away from children and pets. Sheet lead on a roof does not usually pose a risk once installed, but rainwater collection is a consideration.
How do you fold lead flashing into a pipe?
Slide the boot over the pipe, nail the upper flange corners, then press the collar inward by hand and finish with a smooth wood dowel so it lies flat against the inside of the pipe all the way round. Fold it in at least 1 inch below the pipe rim. Avoid sharp creases, since repeated bending can crack the lead.
Do squirrels chew lead roof flashing?
Yes, squirrels, rats and raccoons sometimes chew soft lead collars, opening a path for water. If animals are a problem, use a thicker lead boot, cover the fold with a small metal collar or wire guard, or choose a different flashing. Inspect the collar each season, and call a roofer if you see bite marks.
Related Guides
All Flashing Details guides|The full How-To Library
This guide is general education. Always follow the product manufacturer's installation instructions, the BC Building Code and WorkSafeBC requirements, which take priority over anything written here.
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