Do Slate Roofs Need Maintenance?

What actually wears out on a slate roof

Good natural slate is an exceptionally durable material, so the covering often outlasts everything fastened to it. The parts that fail first are the fixings. Iron nails rust and let slates slip, and that is the commonest reason an old slate roof needs work. Lead flashings around chimneys and valleys fatigue and split as they heat and cool. Ridge pieces and their mortar crack, and gutters block with silt and moss, sending water into the eaves. The underlay beneath, if the roof has one, can perish. Our page on how long a slate roof lasts gives the wider picture.

Some slates fail on their own. Poor-quality stone can delaminate, flaking into layers, and thin pieces crack when hit by falling branches or ice. A maintenance routine finds these early, while they are single-slate repairs and not a section of re-covering.

A yearly check you can do from the ground

Pick a clear day and look at each slope with binoculars. You are looking for slates that have dropped out of line, gaps, broken or missing pieces, lifted or stained lead, a ridge that has shifted or lost its mortar, and gutters sagging or overflowing. Check the garden and the gutters for fragments. Inside, look at the loft with a torch for daylight at the eaves, damp patches on the boards or rafters, and stains that dry then reappear. Take a photo each year from the same spot so you can compare.

Resist the temptation to climb. Our guide on walking on a slate roof explains the risk to both you and the slates.

What a roofer adds every few years

A roofer can get close to the covering with a ladder, tower or scaffold and look at the nail fixings, test the slates by touch and check the lead and ridge. Small repairs are usually done on the spot: replacing a cracked slate, refixing a slipped one with a clip or tingle, re-dressing a lifted flashing, rebedding a loose ridge tile. Typical UK ranges reported for a single slate repair are £100 to £250 for labour plus £5 to £25 for the slate, with an access tower or scaffold adding £300 to £800. Your fixed quote follows the survey.

Moss and lichen are treated differently. A light covering is cosmetic on slate, but a thick mat holds moisture against the surface and clogs the lap between courses. Hand-cleaning with a biocide is the usual approach, and typical UK ranges reported by one cost guide run from about £748 to £978 depending on roof size. High-pressure washing is not recommended on slate because it can damage the surface and drive water under the laps. We look at the effects in does moss damage slate roofs.

When maintenance becomes repair or replacement

If slates keep slipping across a wide area, the fixings have probably failed and patching will chase the problem around the roof. The same goes for widespread delamination or if many slates break when lifted. At that point, a survey that compares repair and re-slating is worth having. Our guide to whether it is worth repairing a slate roof lays out the decision. Very often a roof that looks tired has years left once the fixings and flashings are put right.

Listed buildings and conservation areas have their own expectations for materials, and like-for-like repairs are usually fine while changes may need consent, so speak to the council's conservation officer before departing from the existing slate.

Keeping a record

A simple log pays for itself. Note the date of each inspection, what the roofer found and what was done, and keep the photographs with it. When you come to sell the house, a buyer's surveyor will ask what the roof has had, and a tidy record answers the question and shows a covering that has been cared for. It also helps you spot slow trends, such as one slope that needs attention more often than the rest, which can point to a drainage problem, an overhanging tree or a ventilation fault in the loft below.

The parts people forget

Gutters, fascia boards and soffits are part of the roof system and affect how well the slates cope. A gutter that overflows soaks the eaves courses and rots the batten ends. Cracked or slipped valley lead sends water sideways under slates. Chimney pots and flaunching, the mortar cap around the pot, can crumble and drop onto the roof below. Cover these on the same visit as the slates and the survey will save repeated scaffold costs.

We assess slate roofs openly, with pictures of each fault, and we say plainly when repair is enough. After the survey you get a written price that does not move. The rest of what we do with slate is gathered under our slate roofing service.