The short answer
Yes, it matters. Copper, aluminium and silicon-bronze head the British Standard's list of metals for a slate roof meant to last, and stainless steel is widely used as well. Plain iron and thinly galvanised steel nails rust through, and the slate then slips out of its course. Fixings are the part of a slate roof that most often decides its life, which is why a quote should name them. A line stating the metal, the length and the gauge costs the roofer nothing to write.
Why the nail decides the life of the roof
A natural slate roof can outlast a century, yet each slate hangs from a nail or two driven into a batten, a timber lath running across the rafters. Everything the slate does for the house depends on that small piece of metal staying sound. If it fails, the slate drops, and the gap lets water onto the timbers beneath.
A Northern Ireland historic environment technical note on roofs observes that galvanised steel nails live far shorter lives than the slates they hold. Stirling City Heritage Trust describes the outcome: iron or poor galvanising rusts away, the slate slides, and the trade calls the fault nail sickness. MyBuilder's guide warns that slate fixed badly may be failing before its tenth year, whatever the grade.
That is the reason we treat the nails as part of the material choice, not an afterthought. A good slate on weak fixings is a short-lived roof.
Which metals are right for slate
The British Standard for slating ranks copper, aluminium and silicon-bronze highest where longevity is the aim. HomeBuilding goes a little further and says all fixings must be non-rusting, naming copper, silicone bronze and stainless steel.
- Copper. The traditional choice. It does not rust, it is soft enough to drive cleanly, and it has a long record on period roofs. It can be less stiff than steel, so the nail gauge and length need to be right.
- Silicon-bronze. Harder than copper and very durable, and often the choice where a stiffer nail is wanted.
- Stainless steel. Strong, non-rusting and widely used. It is sound for slate when the grade is suitable for the setting, and it suits exposed roofs where a stiffer nail helps.
- Aluminium. Named in the standard, though some roofers avoid it near damp lime mortar or in contact with other metals.
Avoid mixing metals on the same roof where you can. Lead, copper and steel in damp contact can set up corrosion that eats one of them.
The metals to avoid
Plain iron or mild steel nails, which were common on older roofs, rust. As the metal rusts it swells and stains, and then it weakens until the slate tips down. Galvanised nails are better, but a thin coating wears through over time, especially in the nail hole where water sits.
The danger is that the slate looks fine. A roof can show no loss for years and then begin to shed slates after a storm or a hard winter, because the nails across the whole slope are failing together rather than one by one. This is why one slipped slate on an old roof is worth looking into. It may be a single accident or the first sign of a roof-wide fault. Our answer on slate hooks covers another fixing method, which has its own rules.
Brown streaks running down a slate usually mean the iron in the nail, or in the slate itself, is rusting. They are worth investigating rather than scrubbing off.
Getting the fixing right on the day
Metal is only one part of a good fixing. A slate is nailed twice, through holes near the head, or once at the centre, depending on the roof and the exposure. The nail must be long enough to bite into the batten without splitting it, and it should be driven so that the head just touches the slate rather than crushing it. Over-driving a nail cracks the slate. Under-driving lets it rattle and lift in wind. A careful roofer checks a sample of nails by hand on a re-fixed slope before carrying on, since a poor habit repeated across a roof is expensive to unpick.
The size of the slate sets the batten gauge and the headlap, which is the overlap between courses. BS 5534 and the slate maker's data give the figures for your exposure, and a roofer should work to them. Cupa Pizarras, for example, publishes headlap tables by pitch for the main slate sizes.
If you are comparing quotes, ask what nail is specified, in what metal, and what length. A quote that says nothing about the fixings is leaving out the part that matters most.
Re-fixing instead of replacing
When an older roof is showing nail sickness, the fault is the fixings, not the slate. In many cases the slate can often be lifted, graded, and relaid over fresh battens using non-rusting nails, with any gap filled by matching new or reclaimed pieces. The roof keeps its appearance and gains a fresh working life.
The cost is set by the area, the access and how much of the slate is reusable. Typical UK ranges reported by MyBuilder (2026) are £100 to £180 per square metre for slate installed, which is a guide, not a quote. Our page on slate roof cost sets out what moves the price, and stone-tiled houses face a similar question, treated in the answer on matching stone tiles.
To judge your own fixings, book a free survey through our slate roofing service. We look at the nails and battens, record the roof with photographs, and send you a written fixed price. If many nails have rusted through but the slates themselves ring sound when tapped, refixing is usually the better use of your money.
