Slate itself needs no sealing, painting or treatment. What wears out are the things around it: the nails that hold each slate, the lead that seals the junctions, the valleys that carry concentrated water, and the gutters that take it away. Maintenance is mostly the business of catching those items early, while a repair is still a small one.
This guide sets out a sensible routine, the faults to look for at each part of the roof, the work an owner can reasonably do from the ground, and the work that should go to a professional. It does not cover moss removal in detail, which has a page of its own on moss on slate roofs. Our slate roofing page gives the wider service, and typical costs below are national figures from published guides.
A routine that fits a slate roof
There is no official inspection interval for domestic slate, so what follows is our own practice, offered as a sensible default rather than a rule. Look at the roof from the ground twice a year, perhaps in spring and autumn, using a pair of binoculars where you own some. Look again after any named storm or spell of very high wind. Arrange for a roofer to inspect close up at intervals that suit the age and condition of the roof: more often for an older roof or one with a history of slipped slates, less often for a recently re-slated one.
What to look for from the ground
- Slates that have dropped out of line or left a visible gap.
- Slates lying in the gutter, on a flat roof below or in the garden.
- Sagging, dipping or bulging in the roof line.
- Staining on ceilings or walls below the roof, which points to water getting in.
- Moss, algae or plants growing at the edges or in valleys.
- Ridge pieces that look out of line, or mortar crumbling at the ridge.
What an inspection costs
MyBuilder's roof inspection guide, updated 21 August 2026, gives £150 to £250 for a standard inspection, £200 to £400 for a drone survey and £300 to £500 for a thermal survey. Those are national ranges, nothing to do with our own pricing. A survey of a slate roof also gives you photographs of the slopes, which are useful for comparing from one year to the next.
Slipped and cracked slates: replace them early
A single slipped slate is the commonest slate fault and one of the least expensive to fix. Ignored, it admits rain to the battens and underlay, and a small gap becomes a leak, then rotten timber. MyBuilder's slate roof cost guide prices replacing a single slate at £60 to £120, and five to ten slates at £150 to £350. Those figures are the reason to act promptly: one visit now costs less than several later.
Why slates slip
Natural slate is normally fixed with nails or hooks. On older roofs, the nails corrode or loosen over the years, and the slate then slides down until it catches on its neighbours or falls. When one slate slips, its neighbours are often fixed in the same way and are at risk of following. That is why we check the fixings around a slipped slate, not just the slate itself. Our page on slate roof repairs sets out how a repair is made and when it is better to re-slate.
Do not walk on it
Slate is brittle. Walking on a slate roof can crack several slates at once, and the damage may not show from above. If a slate must be replaced, the roofer uses a ladder or a roof ladder that spreads the load, and works from boards rather than directly on the slope. This is one reason we advise owners to leave repairs to a professional.
Flashings and lead details
Flashings are lead (occasionally another metal) dressed into the joint where a slope butts against a chimney, a gable wall or a dormer cheek, closing a gap that slates alone cannot. These junctions are weaker than the open field of the roof, and they are where a leak is more likely to start than in the slates themselves.
What the lead tells you
Lead is sold in codes that set its thickness. For everyday flashing work Leadworx names Code 4 as the usual choice, and lead flashing can last for more than 80 years when correctly fitted, according to MyJobQuote, last updated 22 September 2026. That is a long time, but it is not infinite. Look for lead that has lifted from the wall, cracked at a fold, slipped down its slope, or been patched with sealant, which is a poor long-term fix.
Costs to expect
MyJobQuote gives £150 to £250 for a chimney flashing patch and an average of £570 for a full replacement. Checkatrade, updated October 2026, prices lead flashing repairs at £50 to £70 per metre and stepped flashing at £80 to £120 per metre, excluding VAT. Stepped flashing is the sawtooth strip that follows a roof slope up a wall.
Chimney stacks also carry mortar joints and flaunching, the sloping mortar at the top of the stack that holds the pots. These are different jobs from slating but are part of the same inspection, and our chimney repairs page covers them. A flashing repair also usually involves lifting nearby slates, so it is cheaper to do while a roofer is already there.
Valleys, ridges and hips
A valley forms along the inside corner of an L-shaped or intersecting roof, and it collects run-off from both slopes. On a slate roof it is usually lined with lead, or formed in slate cut to shape. Because so much water runs down it, a valley is where blockages, cracked lead or a missing slate show up fastest.
What to check in a valley
From ground level, look for debris or leaves that have lodged in the valley, a visible gap at the sides, or staining beneath. Valleys fill with leaves and moss, which can back water up under the slates. Clearing debris from a valley means reaching it, which is not a safe ground-level job for most houses, so it falls to a roofer.
Ridge and hip pieces
Ridge pieces sit along the very top; hip pieces run down each outside corner of a hipped roof. These are usually capped with ridge pieces, and the cost of looking after them is modest. In MyBuilder's figures, a re-bed or replacement of ridge tiles is £300 to £600 and £200 to £400 for repointing a ridge or hip. A dry ridge system, which holds the pieces with fixings rather than mortar alone, is priced by MyBuilder at £40 to £60 per metre. BS 5534:2014 stopped treating mortar alone as a sound hold for ridge and hip pieces, hence mechanical fixings in a re-bed. After a storm we look at the ridge mortar early, since crumbling there is a warning.
Gutters, downpipes and the roof edge
Gutters are part of the roof's drainage, and a blocked or leaking gutter sends water to places the roof was not built to take it: behind the fascia, into the eaves and down the wall. Slate roofs shed water fast, so a gutter that is undersized or choked overflows readily.
Clearing and checking
Clear leaves and debris at least once a year, and again in autumn if there are trees nearby. Look for gutters that sag, joints that drip, and downpipes with stains or damp patches around the base of the wall. Gutter falls matter: makers usually ask for a slight run towards the outlet, roughly 1:600 to 1:350 by system, with bracket spacing set in their instructions. Water standing in a gutter after rain suggests the fall has slipped.
Fascias and eaves
For uPVC fascias MyBuilder suggests an inspection roughly every five years, and prices guttering at £30 to £70 per metre and fascia at £80 to £150 per metre. Rot behind the fascia often starts as a gutter leak. Our guttering, soffits and fascias page covers renewal.
If you can only do one maintenance job each year, clear the gutters. Blocked gutters cause damp at the eaves long before the slates show any fault.
Working on gutters means a ladder at height, so use a stable ladder with a second person, or leave it to a professional. A scaffold is only needed for larger jobs, and MyBuilder prices one for a re-roof at about £1,125.
Moss, algae and cleaning
Moss and algae grow on slate, mostly on shaded or north-facing slopes. They do not hurt the stone quickly, but thick moss holds moisture against the slates, can lift their edges, and can choke gutters and valleys when it falls. A light film of lichen is usually harmless.
What owners can do, and what they should not
From the ground, a long-handled soft brush on a safe reach can remove light growth. Climbing onto the roof is not something we recommend. Scraping and chemical treatments need care: MyBuilder prices manual scraping at £5 to £10 per m², soft washing at £15 to £20 per m² and pressure washing at £10 to £15 per m², with a caution about pressure washing and fragile tiles. Slate roof cleaning overall is quoted at £500 to £1,000.
A hard jet can drive water beneath the laps and scour the face of the slate, so it is not our method. Moss removed from a roof can also block gutters further down, so plan to clear the gutters straight after. The detail of moss treatment, and when to leave it, is on the moss page linked above.
After the clean
Cleaning is a chance to inspect: with the growth gone you can see cracks, slipped slates and failing flashings that the moss was hiding. That makes the survey after cleaning the most useful one of the year.
Safety, and when a repair should become a re-slate
Falls from roofs and ladders are a real risk, and a slate roof is slippery and fragile. Our advice is to keep your own work on the ground: look, photograph, clear gutters you can reach safely from a proper ladder with someone footing it, and call a roofer for anything that means stepping onto the roof.
When maintenance stops being enough
Repairs have a limit. Slipping slates spread over a wide area, rotten battens exposed when slates are lifted, or flashings and valleys failing in several places all point towards re-slating rather than a series of small visits. Our re-slating guide explains the process and what each stage involves. Re-slating a whole roof normally exceeds the Planning Portal's 50% roof limit, so Building Regulations approval comes into play; the notification is ours to handle where it applies.
What to send us
Not sure your roof needs attention? Send photographs from the ground and a note of where you have seen staining or fallen slates. We give priority to leaks and storm damage, and a leaking roof gets made safe before anything else. The quote that follows a survey is in writing, and the 10-year workmanship guarantee is in writing too. Rubbish leaves with us.