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Leaking asbestos roof
What you may legally do about it. Updated 18 September 2026.
A leak means a sheet has cracked, weathered through or broken — and a damaged sheet is the point at which an asbestos roof stops being low risk. The waterproofing products on the shelf will not fix it, because preparing the surface is the part the regulations prohibit. Here is what is actually allowed, and what it costs to put right.
Leaking now? Send a photo of the sheet on WhatsApp. You'll get a straight answer on whether it's one sheet or the whole roof.
Is a leaking asbestos roof dangerous?
The honest answer has two halves.
An intact asbestos cement roof, left alone, releases very little. That is why the regulations deal with asbestos in place rather than ordering every roof off. It is disturbance that turns a roof into a risk.
A leak means the disturbance has already happened. Decades of sun, hail and thermal movement have broken the cement matrix that holds the fibres, which is why water is getting through. The same weathering releases fibres into rainwater, into your gutters and into the soil below the drip line.
So a leaking roof is not an emergency to flee, but it is not something to leave for another five years either. It is the signal that the roof has reached the end of its life.
What makes it materially worse is what people do next: climbing up, scrubbing the area clean, wire-brushing the crack, drilling a screw through the sheet to hold a patch. Each of those releases far more fibre than the leak itself, and each is prohibited.
Can you waterproof or seal an asbestos roof?
The rules turn on two words: surface preparation.
| What you want to do | Who may do it |
|---|---|
| Paint it, with no surface preparation at allType 1 work. No registration needed, and no fibres may be released. On an old, dirty roof this is hard to do well, because paint makers want a clean surface and the cleaning is the banned part. | Anyone |
| Seal, encapsulate or repair itType 2 work, even where no surface preparation is involved. This covers every waterproofing membrane, sealant coat and crack repair sold for roofs. | Registered contractor |
| Clean or prepare the surface firstScrubbing, wire-brushing, sanding or pressure-washing asbestos cement: regulation 24(b). | Nobody |
| Cut, grind or drill itAngle grinders or any fast-moving power tool: regulation 24(f). This rules out screwing a patch over the crack. | Nobody |
That second row is the one that catches people. Painting without prep is free to do; sealing is not, whatever the tin says. More detail on the painting side in can you paint an asbestos roof?
Why the sealant won't solve it anyway
Set the regulations aside for a moment. A waterproofing coat bridges a gap; it does not restore strength. The sheet cracked because the cement matrix has degraded across its whole area, not just at the visible line.
So a sealed crack holds until the sheet flexes again — the next hailstorm, the next hot afternoon — and then it fails beside the patch. People end up recoating the same roof every season and paying more over five years than a replacement would have cost.
Encapsulation done properly by a registered contractor is a different product from a tin of sealant, and it can buy real time on a sound roof. It is not a fix for one that is already leaking.
What to do about the leak right now
- Deal with it from inside. Catch the water, move what's underneath, and photograph where it comes through. That costs nothing and breaks no rules.
- Stay off the roof. Old asbestos cement is brittle and people fall through it. A weathered sheet will not carry your weight, and walking on it cracks more sheets.
- Don't clean, brush or drill anything. This is the moment the risk actually changes, and all three are prohibited.
- Photograph it from a ladder at the edge, or from inside the roof space. That's enough for anyone to tell you whether it's one sheet or the whole roof.
- Check your gutters. Sediment below a weathered asbestos roof carries fibres. Leave it wet, don't sweep it dry.
Repair one sheet, or replace the roof?
It depends on whether the roof failed, or one sheet did.
| Situation | What it usually means |
|---|---|
| One sheet broke after hail, the rest looks soundRemoving the broken sheet is type 2 work, but under 10 m² and not repeated within six months it can fall under type 1. A matching fibre cement sheet goes back in its place. | Single-sheet replacement |
| Sheets are failing in several placesWeathering is roof-wide. Patching buys months, not years, and each patch is another disturbance. | Strip and replace |
| Full removal and disposalRegistered contractor, notice to the Department, air monitoring, hazardous waste site. | R150–R250/m² |
| New roof over the topFibre cement, IBR or corrugated steel, or tile. | R500–R1,000/m² |
These are our own market figures for Gauteng, not a published tariff. The full cost breakdown has worked examples, and you can check any contractor against the Department's register.
Questions people ask about a leaking asbestos roof
Is a leaking asbestos roof dangerous?
A leak means the sheet has cracked, weathered through or broken, and a damaged sheet is exactly when an asbestos roof stops being low risk. An intact asbestos roof left alone releases very little. The danger comes from disturbance, and the weather has already done the disturbing.
Can I waterproof an asbestos roof myself?
Not in practice. Every waterproofing product needs a clean, sound surface, and cleaning asbestos cement by scrubbing, wire-brushing or pressure-washing is prohibited under regulation 24(b). Painting without any surface preparation is type 1 work and needs no registration, but sealing or encapsulating is type 2 work and needs a registered contractor.
Why can't I just put sealant on the crack?
Two reasons. Applying it properly means preparing the surface, which is the banned part. And a sealed crack is still a cracked sheet: the sheet has lost its strength, so it will keep failing around the patch and the next hailstorm finds the same weakness.
Can I climb up and look at the leak?
Be careful. Old asbestos cement sheeting is brittle and people fall through it. Beyond the asbestos question, a weathered sheet will not reliably carry your weight, and walking on it also cracks more sheets. Look from a ladder at the edge or from inside the roof space instead.
Can a roofer patch it with a new sheet?
Removing the broken sheet is type 2 asbestos work, so it has to be a registered asbestos contractor, not a general roofer. The exception is type 1: under 10 m² of asbestos cement, not repeated on the same site within six months. One or two sheets can fall inside that.
Is it worth repairing, or should I replace the roof?
If one sheet failed after hail, a single-sheet replacement makes sense. If sheets are failing in several places, the roof has reached the end of its life and patching buys months, not years. Removal runs R150 to R250 per square metre in Gauteng and a new roof R500 to R1,000.
Find out if it's one sheet or the whole roof
Send the address and a photo of the leak. You get an answer on what you're dealing with and what it would cost, before anyone comes out.