Can I change my roof from tiles to slate?

Re-covering in the identical material normally stays outside planning control. Switching to another material is less clear-cut, because the roof reads differently from the pavement. Under the Town and Country Planning Act, upkeep and alteration that leaves the outside look of the building materially unchanged is not development, and whether tile to slate passes that test depends on the street, the house and the colour and texture of the slate you pick.

Protected places are firmer. In a conservation area, or where an Article 4 direction withdraws permitted development rights, the council can insist on an application. On a listed home, listed building consent is required before any work that would alter the special interest of the building. Our page on tiled roofs in conservation areas covers that route, and Swindon Borough Council's planning team can say whether your address falls under any of it.

Ask the council before you order a single slate. A brief email carrying a photograph and the proposed slate often settles the question, and that is far cheaper than stripping a new roof off again. Keep the reply, because it is useful if you sell the house later.

Weight matters because the rafters were sized for whatever covering went on originally. Natural slate is often lighter than concrete tile, which can ease the load, whereas reconstructed stone-effect slates can be heavy. Marley lists its concrete plain tile at 73.8 kg/m² on a 100 mm gauge, and Bradstone gives about 84 kg/m² for its reconstructed Cotswold-style slate at an 80 mm headlap. For any real product, the maker's data sheet supplies the number to use.

The Planning Portal asks for approval where a new covering is 15 per cent heavier or more, and under Approved Document A a load rise of more than 15 per cent counts as a significant change. Approval also applies if the new covering behaves very differently in a fire. Re-covering alone does not normally need a building control application where under 25 per cent of the total building envelope and under 50 per cent of the roof is affected, though a full strip generally passes those limits.

We explain what consent applies to your roof, and on notifiable work the Building Regulations notification is ours to handle. If the timbers raise doubts, a structural engineer is called in before the slate is ordered.

Slate needs a steeper roof than many interlocking tiles. Cupa Pizarras, a slate producer, reads BS 5534 as setting a 20 degree minimum for natural slate, using a 500 mm slate and a 115 mm headlap in moderate exposure. Its table gives nothing below 25 degrees for 600 by 300 mm and 500 by 250 mm slates, and it advises against hook fixings on any slope under 25 degrees.

That means a low-pitch roof with interlocking tiles may be too shallow for slate. A porch roof at 17 degrees, for example, suits some interlocking tiles but not slate. Our page on roof valley types is relevant too, since valleys are where changes in covering and pitch meet and each needs its own lead or trough detailing.

Measure each slope before you plan anything, from the loft rather than the roof. Our guide to measuring roof pitch shows how.

Measure each slope again if the roof has several parts. A single roof can mix angles, and the shallowest part governs the choice for that area.

Slates are laid to a different gauge from tiles, so the old battens cannot simply be reused. The strip-down exposes the timbers, and any that have rotted come out. Our page on rotten roof battens shows what we look for, and the layer beneath is covered on the torn roof felt page.

New underlay goes over the rafters, new battens at the slate's headlap and gauge, and the slates are fixed with nails, or with clips and hooks where the pitch and the product allow. Lead flashings and valleys are renewed to suit the new, thinner coursing. Ridge and hip details change too, and the new ones are held down with metal fixings as well as mortar.

If the old tiles are to be kept elsewhere, for instance on an outbuilding or a repair to a neighbouring roof, say so at the start. Mixed coverings on the same roof or a terrace can look odd, and matching tiles is its own task, discussed on our page about matching old roof tiles.

MyBuilder's slate roof guide (updated August 2026) gives £100 to £180 per m² installed for a slate roof, with Welsh slate at £140 to £180, Spanish at £100 to £130 and reclaimed at £110 to £150. These are national guides for the slate work, and the price for your house will also reflect the roof's area, the scaffold, the state of the timbers underneath and the amount of lead.

A swap also adds the work of removing the old tiles and taking them away. Ask every contractor whether the figure they give includes scaffolding and VAT, since that often explains a gap between quotes.

Our survey records the pitch and condition of each slope, and you receive the photographs and a written quote. Our guarantee on workmanship lasts 10 years and is written down. Our pitched roofing hub has the other tiled roof pages, and we recommend only the work the roof genuinely needs.