Everybody knows slate costs more than tile. Fewer people know why, and the reason is mostly arithmetic — how many separate pieces a roofer has to lift, place and nail.
"Slate costs more than tile" is true and unhelpful. The interesting question is why, because the answer tells you which decisions on your roof actually move the figure — and several of them are not the ones people focus on.
Most of it comes down to how many separate pieces have to be lifted, positioned and nailed.
A large concrete interlocking tile covers a substantial area in one piece and is single-lapped — each course overlaps only the one below. A slate is much smaller and is double-lapped, meaning each course overlaps the two courses below it.
The consequence is that a slated roof takes several times as many units per square metre as an interlocking tiled roof of the same area. Every one of those units is lifted, positioned, aligned and nailed by hand.
That is the cost gap, and it is a labour gap rather than purely a materials one. Natural slate is also the more expensive material, but on many roofs the labour difference is the larger part.
Slate comes in a range of sizes. A larger slate covers more area per unit, so fewer units, fewer nails and less handling — which generally makes a larger slate cheaper per square metre to lay, even though each slate costs more.
It is not a free choice, though, because size interacts with the next two factors.
Headlap is the amount by which each slate overlaps the slate two courses below it. Increase the headlap and each slate covers less exposed area, so you need more of them — which means more material and more labour for the same roof.
Headlap is not arbitrary. It is set by the pitch of the roof, the size of the slate and the exposure of the site, working to BS 5534:2014+A2:2018. The principle is straightforward: the lower the pitch, the greater the lap, because water moves more slowly down a shallow roof and wind can drive it further back up under the slates. Exposure increases the required lap independently of pitch.
Which is why two roofs of the same measured area, covered in the same slate, can need noticeably different numbers of slates. A shallow, exposed roof needs more headlap, which needs more slates.
Slate is cut around hips, valleys, dormers and chimneys, and cutting slate is slower and more careful than cutting tile. On Warrington's inter-war hipped semis this is a real factor — every course cut on the rake down both sides of every hip.
Where the existing slates are being kept, they are sorted and graded as they come off, the unsound ones discarded, and every survivor re-holed because the new batten gauge will not match the old holes. Everything is handled twice. That is worth doing for appearance and continuity — it is not a way of making the job cheaper.
Older slated property tends to carry more abutment and valley detailing than modern tiled roofs, and every junction needs lead. On town-centre Warrington property with several chimney stacks, this is a significant share of the work.
| Material cost | Laying speed | Appearance | Service life | |
|---|---|---|---|---|
| Natural slate, new | Highest | Slow | Best | Very long |
| Reclaimed slate | High | Slow — sorting and re-holing | Best for matching | Unknown remainder |
| Fibre cement slate | Moderate | Faster — uniform units | Fair | Shorter |
| Slate-effect tile | Lowest | Fastest — large units | Poor at close range | Moderate |
Within natural slate, the grading matters more than the country of origin. Producers declare performance under BS EN 12326-1 for water absorption, thermal cycling and sulphur dioxide resistance, and 1 is the best grade in each — so W1 T1 S1 is the best specification available. Ask which slate is being quoted, by producer and product name, and for its declaration of performance.
Worth understanding, because it decides whether you are buying a new covering or relaying an existing one.
Slate itself is extremely durable. What fails is the fixings: every nail on the roof went in at the same time and has sat in the same conditions since, so they corrode together. The symptom is slates slipping in unrelated places over several years with no storm to explain them, and once that is general there is no repair for it — the slates either side of the one you refix are on the same clock.
So on Warrington's Victorian and town-centre stock, a failing slate roof often has a perfectly sound covering. Stripping, renewing the battens, underlay, fixings and lead, and relaying the original slates is a genuine third option between patching and buying a new covering. It is worth having priced alongside a new roof rather than assumed either way.
A like-for-like re-slate is not development at all under section 55 of the Town and Country Planning Act 1990. Warrington has no Article 4 direction, though it has conservation areas including Bewsey Street and Bridge Street — so if you are changing the covering, check with Warrington Borough Council first.
Building regulations apply: renewing the covering renews a thermal element under regulation 23 of the Building Regulations 2010, with Approved Document L Volume 1 giving 0.16 W/(m²K) for a roof in an existing dwelling.
We will tell you the slate size, the headlap and what that means for your roof.
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Because there are far more pieces. A large interlocking tile covers several times the area of a slate, and slate is double-lapped so each course overlaps two below it. The difference in the number of units a roofer handles per square metre is the single biggest reason for the cost gap.
Generally yes, per square metre — fewer units to handle and fewer nails. But slate size interacts with pitch and exposure through headlap, so it is not a free choice. A larger slate on a shallow or exposed roof may need a headlap that erodes the saving.
Headlap is how far each slate overlaps the one two courses below. Increasing it means more slates per square metre, because each one covers less exposed area. Lower pitches and more exposed sites both require greater headlap.
Somewhat. The units are uniform in size and thickness, so there is no sorting and less adjustment, and it is generally quicker. It is still a small-unit covering, so it does not approach the speed of large interlocking tiles.
Apex Roofing covers Cheshire and the surrounding area for complete roof replacement, new slate and tiled roofs and re-roofing.
Apex Roofing Cheshire · 105 Fence House, Fence Avenue, Macclesfield SK10 1LM
Tell us about the property and the roof in Warrington, and we will come back to you — usually the same day.
Prefer to talk? Call 07377 461095 · WhatsApp +44 7465 861265 · Email apexroofing14@gmail.com
