Slate is one of the longest-lasting roofing materials there is. On the Victorian and Federation terraces of Paddington, Surry Hills, Darlinghurst and Glebe, a lot of the original slate is still doing its job well over a century later. So when a slate roof leaks, the slate itself is rarely the whole story. The question is whether the parts holding it together are failing in one spot or everywhere.
What usually goes wrong with a slate roof?
- Slipped slates: each slate hangs on nails, and when those nails corrode the slate slides out of position. This is often called nail sickness.
- Broken or cracked slates, usually from someone walking on the roof, a fallen branch or hail.
- Failed flashings where the roof meets a parapet, chimney or party wall, often old lead or mortar fillets that have cracked.
- Rusted or blocked valleys and box gutters that push water back under the slates.
- Deteriorated battens, the timber strips the slates are nailed to, which can rot after years of small leaks.
- Earlier repairs done with the wrong materials, such as cement slabs, roofing silicone or slates of a different size.
How do you know if the roof can be repaired?
If the problems are local, it can almost always be repaired. A few slipped or broken slates, a cracked flashing or a rusted valley are all fixable without disturbing the rest of the roof. We replace individual slates and secure them with a small copper clip, sometimes called a tingle, so the surrounding slates stay put. Flashings and valleys can be renewed on their own.
A slate in good condition gives a clear ring when tapped and does not flake or crumble at the edges. If most of the slates on your roof pass that test, the roof is worth keeping.
When is re-slating the better option?
- Slates are slipping all over the roof, not just in one or two places. That points to nails failing everywhere.
- The slates themselves are delaminating, flaking or turning soft.
- The battens are rotten across large areas.
- The roof has been patched so many times that repairs are causing as many problems as they solve.
Re-slating does not always mean new slate. Where the existing slates are sound, a common approach is to strip the roof, renew the battens and sarking, and re-hang the good slates on new fixings, topping up with matching slate where needed. That keeps the look and character of the house while fixing the cause.
Slipping slates in one area usually mean a repair. Slipping slates across the whole roof usually mean the nails have reached the end of their life everywhere, and that is when re-slating starts to make sense.
Can slate be replaced with tiles or metal?
Sometimes, but on a terrace it is worth thinking carefully. Many terraces in central Sydney sit in heritage conservation areas, where changing the roof material is likely to need council approval and may not be supported on the street-facing side. Slate also suits the steep pitches these houses were built with. If you are weighing it up, check with your council first, and talk to us about what a like-for-like approach would involve.
Why do slate repairs need a specialist?
How often should a slate roof be checked?
A slate roof that is in good order does not need much, but it does need someone to look at it now and then. We suggest a check every few years, and after any big storm or hail. The things we look for are slipped or cracked slates, the state of the flashings and valleys, and any sign of water in the roof space. Catching a few slipped slates early keeps the battens dry, and dry battens are what let a slate roof keep going for decades more.
Slate is brittle underfoot and unforgiving to work on. Walking on it the wrong way breaks more slates than it fixes, and a slate that is cut or fixed badly will slip again. The repair needs matching slate of the right size and thickness, the right fixings and an understanding of how water moves across the laps. Our slate roof repairs page covers what we do, and we work on slate roofs across Paddington, Surry Hills and the surrounding suburbs.
What should I do if slates are falling off?
Keep people away from below the roof edge, because a falling slate is heavy and sharp. Do not climb up to push it back. Call us, and we will secure the area, check whether it is one slipped slate or a sign of a wider problem, and quote the fix.
