The short answer
You can’t be 100% sure without testing
Materials can look identical whether they contain asbestos or not. If you suspect asbestos, don’t disturb the sheets and arrange professional advice/testing.
Step 1: Check the age of the garage
Asbestos was used widely in building materials for decades, and it’s far more likely in older garages.
Age clues (helpful, not proof)
| Garage/roof likely fitted… | Asbestos likelihood |
|---|---|
| Before the 1990s | Higher likelihood |
| 1990s to early 2000s | Still possible |
| Modern garage / recent roof | Less likely (but still don’t assume) |
HSE diagrams and guidance show asbestos cement roofing as a common historical external use.
Step 2: Look at what the roof sheets look like (from ground level)
Most asbestos garage roofs are corrugated asbestos cement sheets.
Common “suspected asbestos cement” visual clues
| Clue | What it suggests | How reliable? |
|---|---|---|
| Grey corrugated sheets (dull, weathered) | Often matches asbestos cement roofs | Medium |
| Moss/lichen on old grey corrugated sheets | Common on older cement sheets | Medium |
| Sheets feel “solid” like cement (not plastic) | More like cement-based sheet | Medium |
| Fixings are bolts/nuts through the sheet (older style) | Common on older sheet roofs | Low–medium |
| Sheets are brittle/cracking at fixings/edges | Ageing sheet roof (asbestos possible) | Medium |
HSE includes asbestos cement roof locations in its diagrams/guidance on where asbestos can occur.
Step 3: Check for markings (if safely visible)
Some older corrugated sheets have markings. If you can see a stamp/marking without climbing onto the roof, it can help.
“NT” marking clue (useful but not definitive)
Some council guidance notes that grey corrugated roofing not stamped “NT” is more likely to be asbestos cement (with “NT” often used to indicate non-asbestos).
Important: Markings vary by manufacturer and age. Treat markings as a clue, not proof.
Step 4: Don’t confuse asbestos cement with other corrugated roofs
Several materials can look similar from a distance.
| Material | Typical look | Common on garages? | Common leak points |
|---|---|---|---|
| Asbestos cement (suspected) | Grey, dull, cement-like corrugations | Very common on older garages | Fixings, overlaps, cracked edges |
| Metal (steel/iron) | Often shinier (or rusty), thinner edges | Common | Fixings, rust holes, overlaps |
| Bitumen sheets | Usually darker/blackish, lighter feel | Common | Fixings, brittleness, overlaps |
| Plastic / GRP sheets | More translucent or glossy | Seen on some outbuildings | Fixings, UV degradation |
If you’re unsure, describe it as “corrugated cement sheets (possibly asbestos)” in your quote request.
What NOT to do if you suspect asbestos
These are the actions most likely to release fibres or spread contaminated debris.
Avoid these completely
- Don’t drill, cut, sand, scrape, or break the sheets.
- Don’t pressure wash the roof.
- Don’t climb on the roof — asbestos cement roofs are often fragile and can’t bear weight safely.
- Don’t dry sweep debris/dust if sheets are damaged.
The safest way to confirm asbestos
Option A: Asbestos sampling & lab test (best for certainty)
A competent professional takes a small sample safely and sends it for lab analysis. (This is the only way to confirm.)
Option B: Asbestos survey (useful if you’re planning work)
If you’re refurbishing, converting, or doing major work, a survey helps identify materials likely to be disturbed.
If it IS asbestos cement: what are your options?
If confirmed (or strongly suspected), homeowners typically choose one of these routes:
| Option | Best when… | Why people choose it |
|---|---|---|
| Leave it and manage | Sheets intact, no planned disturbance | Avoids unnecessary disturbance |
| Repair (specialist method) | Minor damage only | Can be appropriate with correct controls |
| Encapsulate / coat | Weathered surface, you want to reduce fibre release risk | Seals/locks down surface (method matters) |
| Remove & replace | Leaks, cracks, upgrades, conversions | Long-term solution; controlled removal & disposal |
What to write in your quote request (copy/paste)
- Postcode
- “Corrugated cement garage roof (possibly asbestos)”
- Single/double garage (or rough length × width)
- Condition: intact / cracked / leaking / debris present
- Access notes (tight driveway, attached garage, height issues)
- What you want: testing advice, removal only, or removal + replacement roof
- Preferred replacement: steel / bitumen / “not sure — advise”
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FAQs
Can I tell if it’s asbestos just by looking?
No. Visual checks can only indicate suspicion. Confirmation requires sampling and lab testing.
My roof is grey corrugated — does that mean it’s asbestos?
Not always. Grey corrugated sheets are often asbestos cement on older garages, but metal and fibre-cement alternatives exist. Treat it as suspected asbestos until confirmed.
Is asbestos cement “lower risk” than other asbestos materials?
Asbestos cement is more tightly bound than some other asbestos products, but damaging or disturbing it can still release fibres, so safe methods matter.
Can I clean moss off a suspected asbestos garage roof?
Avoid DIY cleaning, especially pressure washing. If cleaning is needed, it should follow the correct controlled method.
What if I’m planning a garage conversion?
If you’re planning work that could disturb the roof, get professional advice/survey first so you don’t accidentally disturb asbestos-containing materials.