Reclaiming and Reusing Old Slate Tiles

By Choosing the Right Underlay for Slate Roofing Projects
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23 Sep 2026

Reclaiming and Reusing Old Slate Tiles

Why reclaimed slate is worth the effort

Slate quarried before the First World War was split by hand, graded thick, and expected to last a century. Much of it has. Welsh slate from the Penrhyn and Blaenau Ffestiniog beds, Delabole slate from Cornwall and the green Westmorland stone around Borrowdale is routinely stripped from roofs at 100 to 140 years old in sound enough condition to be laid a second time. That is why a decent reclaimed slate still commands a healthy price, and why conservation officers so often specify it for work in conservation areas and on listed buildings.

There is also the matter of appearance. New slate arrives flat, uniform and a little cold in colour. Reclaimed slate carries its history: softened edges, a weathering that shifts from grey-blue to silver, lichen traces and the odd iron stain from an old fixing. On a heritage roof that reads as authenticity rather than shabbiness.

Grading a salvage pile: what to look for

Never buy a tonne of mixed slate and hope for the best. Sort before you commit, and sort again when the pallet lands.

Soundness. Hold each slate by one corner and tap it with a fingernail or small hammer. A clear ring means good stone; a dull thud usually means a hairline crack or a delaminated layer. Reject anything that sounds flat.
Thickness. Old roofs were laid in graded courses of similar substance. Mixed thicknesses on one plane give you a rippled roof and uneven laps, so grade into roughly 5mm bands.
Size. Imperial sizes are the working language — 20x10, 18x9, 16x8, 14x8, 12x8 and the small 10x6 duchess. Count what you have and match it to the courses you need.
Condition. Look for broken corners, worn heads, torn or enlarged nail holes, and signs of pyrites decay — pitting with rust-brown staining. Cornish Delabole, in particular, suffers from iron pyrites faults.

Expect to lose between 10 and 30 per cent of a salvage pile to breakage and rejects. Price that in from the start.

Cleaning, de-nailing and re-holing

Resist the pressure washer. A jet of water at 150 bar will open up laminations, drive moisture into the body of the slate and strip the very surface you were hoping to preserve. A stiff hand brush, a scraper and patience will remove moss, lichen, old mortar and bitumen far more kindly.

Remove nails with a proper slate ripper, or punch them out from the back with a drift; levering from the face splits slate along the cleavage. Where the old holes are sound and line up with your intended lap, reuse them. Where they are torn, or sit wrong for the new headlap, punch new ones — two per slate, set in from the side edges, at a gauge that keeps the fixing well covered by the two courses above.

Re-holing weakens a slate, so keep it to a minimum. Slates with holes in the wrong place for one job will often suit another with a different lap.

Storing and sorting for the job ahead

Reclaimed slate left in a heap on wet ground will not survive a winter. Frost creeps into the laminations and splits it, and the weight of a flat stack crushes the slates at the bottom.

Stack on edge, like books on a shelf, never flat.
Keep off the ground on timber battens — not on soil or bare concrete.
Keep stacks below about a metre high.
Cover against rain and keep clear of frost; a dry, ventilated store is ideal.
Sort into labelled piles by size and thickness, with separate piles for cut-down stock and scrap.

A 20x10 with a broken corner will often cut down to a 12x8 and go back into service, while whole slates too far gone for a roof can be sawn into peg slates for the next project.

Blending reclaimed with new slate

Mixing old and new on the same plane is the classic mistake. Fresh slate is usually thinner, sharper-edged and a different tonality, and a patch of it on an old roof reads as a repair from the ground.

Where the budget will not stretch to all reclaimed, use the salvaged material on the slopes visible from the road and new slate on rear pitches or hidden valleys. Sort reclaimed into colour groups and spread the weathered slates through the courses rather than clustering them. Note that Westmorland green is markedly heavier than Welsh slate, so check rafter and batten capacity before you commit, and think about fixings — copper nails outlast galvanised in most situations.

Beyond the roof: secondary uses for tired slate

Not every slate needs to go back on a roof, and the damaged ones have real value elsewhere. Sawn slate makes excellent hanging pegs, copings, hearth surrounds, worktops, window sills, floor tiles, garden paving, plant labels and wall cladding. Whole courses can be used for dry-stone wall coping, and crushed slate fines make a superb top dressing for paths and borders.

Whatever the end use, the principle holds: grade honestly, prepare carefully, and treat the material with the respect it has earned. Old slate is not a cheap substitute for new — handled properly, it is better.

Restoration

A Beginner's Guide to Slate Roof Restoration

Improve warmth and energy efficiency by understanding insulation options that respect the ventilation needs of a traditional slate roof.

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5 Comments

Robert Sonny says Jul 21, 2024 at 10:00am

I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system
Reply
- John Abraham says Jul 21, 2024 at 10:00am
  
  I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system
  Reply
  - Robert Sonnysays Jul 21, 2024 at 10:00am
    
    I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system
    Reply
Robert Sonny says Jul 21, 2024 at 10:00am

I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system
Reply

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