Short answer. Asbestos-cement slate is four times heavier and that is exactly why it is quieter — by the mass law the difference works out at about 12 dB in its favour. Steel is lighter, goes on a shallower pitch, and covers a slope in one sheet with no transverse joints. We sell steel and do not trade in slate, so what follows is numbers rather than persuasion.
The comparison in numbers
| Measure | 8-wave asbestos-cement slate | T35 profiled sheeting, 0.45 mm |
|---|---|---|
| Sheet | 1,750 × 1,130 × 5.8 mm, 26 kg | length to order, working width 1,080 mm |
| Mass per m² of roof | 16.6 kg | 4.1 kg |
| On a 4 × 9 m slope (36 m²) | 596 kg | 148 kg |
| Minimum pitch | from 22° | from 9° (T57 from 6°) |
| Transverse joints on a 4 m slope | 3 courses, so 2 lines of joints | none |
| Noise barrier | +12.1 dB | — |
| Colour | grey, or painted on site | factory coating, warranty from 20 to 50 years by steel class |
Where the mass comes from: an 8-wave slate sheet weighs 26 kg and covers 1.57 m², so 26 ÷ 1.57 = 16.6 kg per square metre of roof. Profiled sheeting at 0.45 mm is 3.5 kg/m² of flat steel plus about 15% for the developed width of the profile, so 4.1 kg/m².
Where slate objectively wins
Noise. The insulation of a solid barrier follows surface mass: 20 · log(16.6 ÷ 4.1) = 12.1 dB. That is a lot, and no steel thickness closes it — 6 dB costs a doubling of mass. If there is a habitable loft under the roof with no thick insulation, slate will be noticeably quieter. The mechanism is in the roof noise article.
Material price. Slate is usually cheaper per square metre. We do not put a figure on it: we do not sell it, and a number lifted from someone else’s price list would be invention.
Where steel wins
Weight and rafters. A 449 kg difference on one 4 × 9 m slope. That is not abstract: under slate the rafters and battens carry four times the dead load, and on a light extension or a garage that changes the timber section directly.
Pitch. Slate needs 22° or more; our T57 starts at 6°. This is not taste: on a shallow roof slate cannot be used at all, and steel can.
Joints. Slate sheet length is fixed at 1,750 mm. Allowing for the head lap the effective length is about 1.60 m, so a 4 m slope needs three courses and two lines of joints across the full width. We roll steel to the length of the slope: no joints at all.
Colour. Slate is grey, and site painting lasts exactly as long as paint lasts on a porous surface. Steel colour is applied at the mill, under a polymer, with a warranty.
Asbestos: what to know
Asbestos-cement slate contains chrysotile asbestos bound in a cement matrix. An intact sheet in good condition does not release dust. The problem starts when it is cut with an abrasive, broken, or left to weather — that is when fibres get into the air.
In practice: do not cut old slate with an angle grinder, do not smash it and do not burn it. In many countries asbestos-containing waste is collected separately from ordinary construction waste — check the rules with your local operator, they differ.
If you would rather not strip it, there is the option of covering old slate over. When that works and when it does not is covered separately.
What we do not do
We do not sell slate, strip old roofs or remove waste. We roll steel sheet to the length of your slope and fold flashings from the same coil.
How to order
Step 1. Look at the pitch
Below 22° slate rules itself out. Above that, it is a choice between mass and weight.
Step 2. Decide what is under the roof
A habitable loft with no insulation — noise matters. A cold attic — it does not.
Step 3. Order sheet to the slope length
Call (067) 077-56-77, Mon-Fri 08:00-17:00. Production 1-2 days, delivery another 1-5 days.
FAQ
What about metal tile against slate? The same arithmetic: 4.1-4.5 kg/m², so slate keeps its noise advantage. What separates metal tile from profiled sheeting is the 350 mm module, not the weight.
Which lasts longer? Slate does not rust but crumbles at the edges and grows moss on a north slope. Steel lasts as long as its polymer coating.
Can steel go on the old battens from a slate roof? Slate batten spacing is different, so usually no. Spacing is set by the profile.
Slate is heavier — does that mean the wind will not lift it? Wind lifts things past their fixings, not past their weight. A light sheet fixed properly holds just as well.