Question answered
What is the main disadvantage of a slate roof?
The short answer
The main disadvantage of a slate roof is cost. MyBuilder's slate roof guide (updated 21 August 2026) puts a slate re-roof at a typical £100 to £180 across each square metre of roof. Slate is also heavy, breaks if walked on, needs a minimum pitch and skilled fixing, and the nails that hold it can fail long before the stone does.
For most owners the main drawback of slate is the price of getting it laid. The others are weight, brittleness when walked on, and fixings that age faster than the stone does.
Cost is the first hurdle
In MyBuilder's slate guide (updated 21 August 2026) a full slate re-roof comes out at a typical £100 to £180 for every square metre. For repair work rather than a whole roof, Checkatrade's repair guide (table updated June 2026, before VAT) prices natural slate at £150 to £220 per m², against £90 to £120 for concrete and £110 to £160 for clay.
The reasons are plain. Slate is quarried and cut, and each slate is fixed by hand with nails through punched holes. The work is slow, and a roofer who can lay slate properly is working to a more demanding standard than for machine-made concrete tiles. Access, scaffold, roof pitch and slate size all move the total.
It helps to set that cost against the roof's life. A covering that lasts for many decades can come out cheaper per year than a cheaper one replaced twice, though that argument only holds if the roof is looked after.
Weight and what the roof structure must carry
Slate is a dense stone, and a slate roof loads the rafters, purlins and walls more than a lightweight metal or single-ply covering would. For an existing slate roof this is not a problem, because the structure was built for it. It matters when you change the covering.
Replacing slate with something heavier can be a structural question, and the Planning Portal says that a heavier covering may bring Building Regulations into play where the new covering is 15 per cent or more heavier than the existing one. Going the other way, from slate to a lighter material, alters how the roof looks and may need planning permission in a conservation area, on a listed building or where an Article 4 direction applies.
If your rafters have sagged or the ridge has dipped, tell your roofer at the start. Heavy coverings and weak timbers are a pairing that should be assessed before any work begins.
Brittle underfoot
A slate will carry a lot of rain but little point load. Step on one and it can crack, often invisibly, and the crack opens later as water finds it. This is the drawback that catches homeowners by surprise, because damage can be done by somebody who only came to clean a gutter or fix an aerial.
It makes maintenance on slate more careful than on tile. Roofers use ladders laid on the roof, roof ladders or crawling boards to spread their weight, or work from scaffold or a tower so they never need to stand on the slates. Be sceptical of any quote that does not say how the roof will be reached.
If a person has walked over your slates in the past, a loft inspection can find daylight at cracked ends and wet marks on the underlay. Replacing a few broken slates is a modest repair, as long as it is done before damp reaches the timbers.
Pitch, fixings and nail sickness
Slate needs a steep enough slope to shed water. Slate supplier Cupa Pizarras reads BS 5534:2014+A2:2018 as setting a 20 degree floor for natural slate in moderate exposure (a 500 mm slate with a 115 mm overlap), and advises against hook fixings below 25 degrees. A low roof, a porch or a dormer cheek may fall short, so the pitch must be checked before slate is chosen for them.
The other long-term drawback is the fixing. Slates are held on by nails that go through the slate into a timber batten. When the nails corrode and snap, slates slip down, one at a time at first and then in runs. This is called nail sickness. The stone is often still sound, but the roof is not. See why slates slip for the causes in more detail.
Repairs are possible, and a skilled roofer can strip and refix a slope, reusing the good stone with new fixings.
Weighing the drawbacks fairly
Slate has costs, but it also lasts. Published guides put a well-installed slate roof at 80 to 100 years or more, which is covered on our page about how long a slate roof should last. So the sensible question is not whether slate has drawbacks, but whether they matter for your house.
For a Victorian terrace or villa near the Worthing seafront, with Welsh slate and a tall chimney stack, the case for keeping and repairing slate is strong, because it suits the building and can last for decades more. For a newer house with a low pitch and a complex roof, a different covering may fit better. Compare options with the help of the Welsh against Spanish slate guide, and look at what small repairs cost in what a roofer charges per slate.
Pictures of the roof itself come first, and a written quote with a single total follows, so you decide from what is really up there. Our slate roofing page lists the work we take on. For fuller costs, see roof slate prices.
Slate drawbacks: two more questions
Is slate a poor choice for a roof by the sea?
Not by itself. Slate has a long record on exposed roofs, and the question is how it is fixed and maintained. Wind loosens slates that were poorly nailed, so the fixing method and the battens matter more than the stone.
Is it safe to inspect a slate roof by climbing up?
It is better not to. Slate breaks under a footstep, and a fall is a real risk. Use binoculars from the garden, or look in the loft for daylight or damp, and leave the close inspection to a roofer with proper access.
Tell us about your roof
Describe what is happening and we will call you back to arrange a visit.
- Photographs of what we find
- A written quote with one total price
- Or call 01903 299063
10-year workmanship guarantee, in writing.