The short answer
Often yes, but not as a simple swap. Building Regulations approval is required if the new covering is at least 15 per cent heavier than the old one, and the Planning Portal advises getting a structural opinion beforehand. The roof pitch must also suit the new tile, and listed status or a conservation area gives the council a say on appearance too.
Changing concrete tiles for slate or clay starts as an engineering question and only then becomes a matter of taste. Here is what to settle before you buy anything.
Why weight is the first thing to settle
Every roof structure was sized for one particular covering. Rafters, purlins and walls were chosen for the tiles that went on, plus snow and wind. Change the material and the load changes, sometimes up and sometimes down. A thin natural slate can be lighter than an interlocking concrete tile, while a heavy clay tile or a thick stone slate can weigh more. The maker's data sheet gives the weight per square metre, and that figure is where the conversation starts.
Estates built in the post-war boom were tiled in concrete on timbers never intended for anything heavier, so a grander covering can overload them. Warning signs of an existing struggle include a sagging ridge, bowed rafters or a dip across a slope, and our answer on sagging roof causes explains what those mean.
Do not order tiles on the strength of a brochure. Ask the roofer to work out old and new weights from the data sheets and put both figures to the building control body, so the decision rests on arithmetic rather than a hunch.
What the regulations ask of a heavier covering
The Planning Portal sets its line at a new covering carrying 15 per cent extra weight or beyond. Approved Document A, the structural volume, treats loading that rises by more than 15% as a significant change. Those two wordings differ at the margin, so when your chosen product lands near the line, ask building control which test it applies.
The Portal adds a second trigger: approval is also needed if the replacement would behave in a fire in a significantly different way to what is there now. That seldom bites with slate or clay, but it is on the list. For any weight question it recommends an opinion from a structural engineer or surveyor ahead of the work.
That advice protects you. An engineer may confirm the roof carries the extra load as built, or specify strengthening that goes into the price. Building control then signs the work off. Which team that is depends on your address, so put the question to your own council's building control team, not a neighbour or a supplier.
Planning permission is a separate matter, and the next section takes it on.
Pitch, planning and conservation limits
Each tile carries a minimum pitch. Marley's published list runs from 12.5 degrees for its Mendip 12.5 concrete tile up to 40 degrees for its Canterbury clay tile. For natural slate BS 5534 indicates 20 degrees as the lowest pitch, and slate hooks should stay off anything shallower than 25 degrees. A shallow roof built for interlocking concrete may simply be too flat for the covering you have in mind.
On planning, the Town and Country Planning Act 1990 (section 55(2)(a)) places works that leave a building's external appearance materially unchanged outside the definition of development. Swapping concrete for natural slate or clay does alter how a roof looks, so put the question to the council's planning team before assuming an exemption. In a conservation area, under an article 4 direction, or in a National Landscape or National Park, speak to them early.
A listed building is a further layer. Works touching its character need listed building consent. The South Downs National Park Authority notes that regular maintenance and like for like repairs do not. Changing the material takes you outside like for like. Our natural vs man-made slate answer covers the look and cost of slate.
Cost, lifespan and the sensible order of work
Checkatrade's October 2026 installation guide gives typical UK figures of £120 to £230 per m² for plain tiling and £160 to £275 for clay. Its June 2026 repair table lists concrete at £90 to £120, plain clay at £110 to £160 and Spanish natural slate at £150 to £220 per m², before VAT, for small areas. These are yardsticks. Any strengthening the structural check calls for sits inside the one written total, which follows the survey.
What the change buys is longevity and character. Well-maintained natural slate is described in one roofing guide as lasting 100+ years, and for clay Marley points to a 60-year minimum life expectancy, though neither figure is a promise. A long-lived covering only pays off if the structure beneath stays sound and the fixings follow current practice.
The sensible order is: gather the roof's pitch and loft details, get the structural view, ask the council about appearance, then choose the tile. Pass on the pitch if known, a snap of the slope and the tile you fancy. We check the pitch and the timbers first, then say whether the idea works before you spend anything. Our pitched roofing page lays out the wider options.
More on this in Pitched Roofing Services in Crawley
Two more covering questions
Do I need planning permission to put slate on a house with concrete tiles?
Usually not on a house. A new material changes the look, so it counts as development, but the general right covering roof alterations normally applies to a house. Flats, article 4 directions and listed status add limits. Ask the council's planning team with a photo and the product name before ordering, and keep their reply in writing.
Is a lighter covering always safe to fit?
Lighter does not remove the other checks. The pitch must still suit the tile, the fixings should follow BS 5534, and the wind loading needs checking for the new product. Building control and the maker's data sheet are the places to confirm that the whole combination works on your roof.