Your building inspection flagged the roof. Here's what it means and what to do
You ordered a building or pest inspection, probably because you're buying or selling a home, and the report came back with a paragraph about the roof that you needed a dictionary to read. Fretting. Chemical delignification. Perished battens. Efflorescence. Hairy timber. It sounds alarming, and the report rarely tells you what to actually do about it.
This page does. We'll translate the terms into plain English, explain what each one means for the roof over your head, and walk through the real decision: repair, treat, or replace. We'll also be straight with you about something the companies selling roof treatments tend to skip over.
The short version. Most of these terms describe an old tiled roof reaching the end of its life. Some flagged roofs genuinely just need a repair. Others are past the point where patching makes sense, and a few of the "treatments" on offer in Perth address the symptom while leaving the actual cause in place. Knowing which situation you're in is the whole game, and that's what this guide is for.
What the report is actually saying
Here's what the common terms mean, why they show up on Perth roofs specifically, and where each one points on the repair-versus-replace question.
Fretting tiles
Fretting is the slow death of a terracotta or, less often, concrete tile. The fired surface erodes, the clay underneath goes powdery, and the edges flake away. You'll see crumbling tile faces and reddish grit in the gutters. It's the most common end-of-life signal on older Perth roofs, and terracotta tiles can start fretting from around 30 to 40 years old. It's worse near the coast, where salt air speeds it up, but you'll find fretting tiles well inland too, because an ageing tile also turns porous and leaches its own minerals. Isolated fretting on a handful of tiles is a repair. Fretting across the whole roof, where a tiler cracks more tiles than they fix just by walking on it, means maintenance has become impossible by definition. We cover this in detail in the fretting guide.
Chemical delignification (also called "hairy timber", "furry battens" or defibrosis)
This is the one that worries people most, and it's worth understanding properly because there's a treatment industry built around it. Delignification is the breakdown of the timber battens that hold your tiles up. As terracotta tiles age and turn porous, they leach salts and minerals; near the coast they pick up airborne sea salt on top of that. Those salts wash down into the timber when it rains and crystallise as it dries. That repeated wetting and drying breaks down the lignin, the natural glue binding the wood fibres together. The timber surface turns soft and furry, loses its strength, and in advanced cases the battens, and then the rafters, can no longer safely carry the roof. It's common across Perth, more so near the coast but found well inland. We go deeper in the delignification guide, and there's an important point about treatment further down this page.
Perished or rotten battens
Battens are the horizontal timber strips the tiles hook onto. Delignification is one way they fail; ordinary rot from long-term moisture is another. Either way, perished battens are a structural conversation, not a cosmetic one, because they're what stops your tiles ending up in the ceiling.
Efflorescence and salt staining
The white, crusty or powdery deposits an inspector notes on tiles or timber. It's the visible salt, the same salt that drives delignification. On its own it's a warning sign rather than a defect, but it tells you the process that damages battens is active.
Sagging or uneven roof lines
Visible dips or waves along the ridge or gutter line. Often the outward sign that the timbers or battens underneath are tired, sometimes after decades carrying heavy tiles. Worth taking seriously.
Asbestos cement roofing
If the home was built before 1990 and the report flags asbestos or "fibro" roofing, that's a different category again. Degraded asbestos roofing isn't a repair candidate, because working on it safely is so heavily regulated in WA. It's a replace decision with a strict legal removal process, covered in the asbestos guide.
Repair, treat, or replace: how to actually decide
A flagged roof falls into one of three buckets. Most reports don't tell you which, so here's how we'd think it through.
When a repair is the honest answer
If the damage is localised and the rest of the roof has years left, repair it and move on. A storm-damaged section, a cracked valley, a few fretting tiles on an otherwise sound roof: that's maintenance, not replacement. Anyone pushing a full re-roof for localised damage is selling, not advising. Our signs guide sets out the cases where keeping your money is the smart call.
When the roof is genuinely finished
Widespread fretting, battens failing along the whole roof, repeated leaks that keep moving, sagging lines, or asbestos that's degrading: these are end-of-life signals. At this point repair money buys months, not years, and it compounds. If a roof is past 25 to 30 years old and the running repair total is heading past a quarter of what a replacement would cost, the roof has already told you its answer.
The treatment question, and the part that often goes unsaid
For delignification specifically, you may be offered a chemical treatment that hardens the affected timber so you can avoid replacing the roof. It's marketed in Perth as a way to get a sale across the line or buy peace of mind. It can have its place on a roof that's otherwise sound. But there's a logic problem worth sitting with before you spend the money.
Treating the battens doesn't remove what's attacking them. As terracotta tiles age they turn porous and start leaching their own minerals and salts, and near the coast they pick up airborne sea salt on top of that. Those salts wash down into the timber below every time it rains, which is why you see delignification well inland and not just near the water. So the tiles sitting above your battens are themselves a salt source. Treat or replace the timber and leave those same porous, ageing tiles in place, and the salt keeps bleeding into whatever timber sits underneath. A treatment can slow or arrest the damage in the timber it touches, but on a roof where the tiles are already fretting and 50-odd years old, you're chemically defending the battens while the thing feeding the problem stays on the roof.
So the honest framing is this. If your tiles are sound and delignification is early and localised, a treatment or targeted timber repair may genuinely be the right, cheaper call. If your tiles are already fretting, brittle and near end of life, and the battens are furring up underneath them, then treating the timber is treating the symptom. Replacing the roof, tiles and battens together, with a new Colorbond or tiled roof, removes the salt source and the damaged timber in one go. We're not going to tell you to replace a roof that doesn't need it. We're also not going to let you spend on a patch that leaves the cause sitting on your rafters.
If this is happening at the point of a sale
Most of these reports land during a purchase or sale, which adds time pressure. A roof defect can stall a settlement or knock the price around. Advanced delignification is a structural issue, not a cosmetic one, which is exactly why it spooks buyers and lenders. A realistic replacement cost in hand, rather than a vague worry, is often what gets a deal moving again, whether you're the buyer negotiating or the seller deciding how to present the home. If that's your situation, a price indication gives you a number to plan around without committing to anything.
The sensible next step
If your inspection flagged the roof and you're not sure which bucket you're in, the cheapest move is to get a realistic sense of the replacement cost before anyone tries to sell you a treatment or a re-roof. From there you can weigh a repair, a treatment, or a full replacement with actual numbers instead of jargon. Our Perth replacement cost guide shows the ranges and what drives them.
Holding a report and unsure what to do with it? Request a free price indication and paste the roof section of your inspection into the notes. We'll tell you honestly whether it reads like a repair, a treatment, or a replacement, and give you a realistic range either way. If it's a repair job, we'll say so. That happens often and nobody's ever minded hearing it.