Why slates slip and crack
Slate is split natural stone, and the stone is rarely the first thing to go. The nails are. When they rust through, slates slide out of line, which slaters call nail sickness.
Slates also crack from foot traffic, falling branches and hail. The NSW Government's heritage inspection schedule gives slate roofs a life expectancy of 50+ years and suggests a check every 7 years for slipped, cracked, broken or porous slates.
How a slater repairs a slate roof
Refix slipped slates
A slipped slate is pushed back and held with a small metal hook or a copper or lead strip called a tingle, because the original nail can't be reached without disturbing the slates above.
Replace broken slates with a match
Colour, thickness and size all vary, so a slater matches from stock or reclaimed slate. A mismatched slate stands out for as long as the roof lasts.
Renew flashings and valleys
Lead or copper flashings and valleys wear out on their own schedule. On an old roof, these are often where the water gets in, not the slate.
Re-slate when the problem is everywhere
If nails have failed right across the roof, the slates are stripped, sorted and relaid on new battens with new fixings, reusing every sound one.
Heritage homes, parapets and box gutters
Melbourne terrace designers deliberately hid the roof behind a decorative parapet. That usually means a box gutter (a gutter built into the roof behind the wall), a classic leak point on older houses. Our page on box gutters explains why.
Heritage overlays control changes to the outside of a home. Albert Park, Fitzroy, Carlton, Parkville and East Melbourne are under strict overlays, and in parts of Ballarat the controls restrict the extent of external works. Perth's heritage rules are run council by council across its 30 local government areas.
Like-for-like repairs are the simplest path, and the NSW heritage schedule advises against replacing original roof coverings unnecessarily, or combining materials that react with each other. In Ballarat, ask about the council's low-interest Heritage Loans Scheme.
Fake slate can be asbestos
ASSEA, the national asbestos agency, says asbestos cement 'slates' and shingles about 4 mm thick were made in Australia from the late 1800s to the 1980s, often to replace real slate while keeping the look. Those made between the mid 1950s and 1968 might contain blue asbestos, and gutters under them are likely to hold asbestos debris. Only a NATA accredited laboratory test can confirm it. Don't let anyone walk on, drill, cut, water-blast or clean them until a sample has been tested.
Leave the roof itself to a slater
You can
- Note slipped or missing slates from the ground, and photograph them
- Check with your council whether a heritage overlay applies
- Keep any slates that fall, because they help with matching
Leave to a roofer
- All work up top, because slate breaks underfoot and is slippery
- Refixing, replacing and re-slating
- Lead, copper and box gutter work
- Arranging a test on shingles that might be asbestos cement
If we were deciding
We'd look for a roofer who has actually worked on slate, and ask to see a previous slate job. We'd want repairs done like for like, with matching slate, and the flashings and box gutters checked on the same visit, because that's where old roofs tend to leak. When you send us your job, say it's slate or heritage, so the roofer knows before they call.
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.
