What damages a Butynol roof?
Punctures. A dropped tool, a fallen branch, a chair leg on a deck, or sharp grit trodden in.
Lifting laps and corners. Where two sheets join, or the membrane folds into a corner or an outlet, the bond can let go over the years.
Upstands pulling away. Where the membrane turns up a wall or meets a door sill, movement and sun work at the edge until it opens.
The deck underneath moving. BRANZ says Butynol normally needs no maintenance provided the substrate doesn't move significantly. Splits running along plywood joints often point to movement below.
More foot traffic than it was built for. BRANZ specifies 1.0 or 1.2 mm Butynol for roofs and lightly used protected decks, 1.5 mm for walk-out decks and 2.25 mm for heavy-duty areas. A roof that has quietly become a deck wears faster, so ask what thickness yours is.
How a roofer patches Butynol
First comes the search: outlets, laps, corners and upstands, and sometimes wetting one section at a time to see where water shows inside.
Then the damaged area is cut out and a patch bonded over it. E2/AS1 notes that coloured butyl contains EPDM and is harder to adhere to, so ask what membrane they think you have and what they'll bond the patch with.
ARDEX and Viking both say their butyl membranes should be laid by installers they've approved. If your roof is still under a product warranty, ask whether the repairer is approved for that membrane.
A good repair also fixes the cause: clearing a blocked outlet, or adding the overflow or second outlet E2/AS1 calls for.
When a patch isn't enough
If the plywood feels soft or spongy, water has been getting in for a while and the ply needs replacing before any new membrane goes down. If laps are failing all over the roof, or water ponds because the falls are too flat, patching just moves the leak. BRANZ expects Butynol to give at least 20 years with proper maintenance, so an older roof with several problems is usually due for a rethink. Our page on flat roof repair covers fixing falls, and membrane roofing covers replacement.
Stay off the roof to hunt for the leak
A flat roof feels safe, but wet rubber is slippery, many edges have no barrier, and WorkSafe lists skylights and clear roofing as brittle surfaces that won't hold a person. Look for the leak from inside and from a window, and leave the roof to the roofer.
Your part, and the roofer's
You can
- Photograph ceiling stains and note what kind of rain brings them on
- Keep a deck's outlet grate clear and lift pot plants that sit in water
- Dig out any paperwork on who laid the membrane and its warranty
- Tell the roofer whether the membrane is black or coloured, if you know
Leave to a roofer
- Getting onto the roof
- Tracing the leak, including water testing
- Cutting out damage and bonding patches
- Replacing plywood or adding outlets and overflows
What we'd do about a Butynol leak
Book a repair as soon as you see a stain, rather than waiting for a dry spell to see if it stops. Ask the roofer for photos of the damage and the finished patch. If they find soft plywood or failing laps right across the roof, ask for a quote to replace the membrane alongside the repair quote, so you can weigh one against the other.
Want a roofer to take a look?
Tell us the job and your postcode. We match it with a Find My Roofer certified roofer who specialises in that kind of work, and they call you to quote. Your number goes to them alone.