Short answer. Metal tile can go over asbestos-cement sheeting, on two conditions: a roof pitch of 14° or more — the minimum for Classic — and sound rafters. The old sheeting is not stripped; counter-battens and new battens are fixed over it. If the rafters have rotted, metal will not rescue the situation, and money spent on a roof over an unsound structure is money lost.
When laying over the old sheeting is acceptable
| Condition | Why it matters |
|---|---|
| Pitch from 14° | the minimum for Classic. Below it, water climbs the horizontal overlap by capillary action |
| Rafters free of rot and sagging | the extra load is small, but it finishes off a structure that is already failing |
| The old sheeting lies flat across the plane | counter-battens even out small steps but do not correct sagging |
| Ventilation under the roof is possible | air has to move between the old sheeting and the metal, or condensation has nowhere to go |
If even one condition fails, the old covering is better stripped. It costs more in labour and cheaper than relaying the roof a second time.
Why the old sheeting is usually left in place
The reasons are practical. Stripping means labour, haulage and disposal: asbestos-cement cannot go out with ordinary building waste and needs a site licensed to take it. And while the old covering is off, the roof is open, and rain at that moment costs more than any saving.
Left in place, the old sheeting acts as an extra layer: it holds no water, but it is no obstacle either, provided there is ventilation under the metal.
What goes over it
| Layer | Purpose |
|---|---|
| Counter-battens along the slope | create the ventilation gap and even out the plane over the corrugations |
| Battens across | what the metal is fixed to. Spacing for Classic follows the 350 mm wave pitch |
| Metal tile | working width 1,100 mm, sheet length cut to the slope |
Batten spacing under metal tile is stricter than under profiled sheeting: it is tied to the wave pitch, because the screw has to land in the step of the wave rather than on its crest. That is geometry, not preference.
What we can state precisely and what we cannot
Precisely: the minimum pitch for Classic is 14°, the wave pitch is 350 mm, working width 1,100 mm, and we roll the length to the slope. That is enough to tell whether your roof qualifies at all.
We cannot say whether your rafters will carry it, whether the boarding under the old sheeting has rotted, or whether strengthening is needed. That comes from inspecting the structure, and we do not visit sites or design roofs.
How to order
Step 1. Find out the pitch
Below 14°, Classic is out and profiled sheeting is the answer: T35 works from 9°, T57 from 6°.
Step 2. Measure the slopes
Ridge-to-eaves length and width along the ridge for each slope. We roll the sheet to the slope length so there are no horizontal joints.
Step 3. Place the order
Call (067) 077-56-77, Mon-Fri 08:00-17:00. Production 1-2 days, delivery a further 1-5 days.
What we do not do
We do not inspect roofs, assess rafters, calculate loads or install. We do not haul away old sheeting. We roll the sheet to your dimensions and deliver it.
FAQ
Is metal tile heavier than asbestos-cement sheeting? No, lighter. But the exact difference for your roof should be worked out by whoever assesses the structure, not by us.
Will rain be noisy with the old sheeting underneath? The old layer damps the sound a little but does not replace insulation. In a habitable loft the answer is insulation, not the old covering.
Can profiled sheeting be used instead? Yes, and on shallow roofs it is the only option. T35 from 9°, T20r from 12°.
Where does stripped sheeting go? To a site licensed for asbestos-containing waste. Not a question for us, but one to settle in advance.
How long is the wait? Production 1-2 working days, delivery a further 1-5 days.