Roof tiling and slating in Peterborough

The coverings, and what each is actually good at

Concrete interlocking tile

Cheap per square metre, fast to lay, and structurally heavy. Commonly quoted at 40 to 60 years. Its real weakness is not strength but surface: the coloured coating weathers off, the tile goes porous, and a porous concrete tile holds water and grows moss. Colour fade is cosmetic. Delamination, where the surface flakes away and the aggregate shows through, is the end of the tile.

Concrete and clay plain tile

Small format, double lapped, and a much better looking roof. Clay holds its colour where concrete fades, and it comfortably outlasts it. The penalty is quantity: six times as many tiles per square metre means six times the handling and fixing, so the labour line goes up sharply even before the material does.

Clay pantiles, the S-shaped profile, sit somewhere between the two on coverage and turn up on a scattering of older properties around the city and the villages.

Natural slate

The longest lived of the mainstream coverings and the standard on the Victorian railway terraces. A well laid slate roof outlives the fixings holding it, which is why the classic failure is nail sickness rather than the slate itself wearing out.

Not all slate is equal. Welsh slate and good imported Spanish slate are different products at different prices, and cheap imported slate with high pyrite content can rust and split within a couple of decades. Ask for the source and the grade in writing, not just the word slate.

Reconstituted and fibre cement slate

Manufactured products designed to look like slate for considerably less money. From the ground, a good one is convincing. They are lighter than natural slate, easier to lay, and they come with manufacturer guarantees worth reading properly, because the length of the guarantee and what it actually covers are two different questions.

In a conservation area or on a listed building they are usually not acceptable, so check before you fall in love with the price.

Collyweston stone slate

A fissile Jurassic limestone quarried at Collyweston in Northamptonshire, roughly 12 miles from Peterborough, and historically used on almost every building within about ten miles of the quarries. That takes in Wansford, Thornhaugh, Barnack, Pilsgate, Southorpe, Ufford, Bainton, Helpston, Castor, Ailsworth and Marholm.

It is laid in diminishing courses, largest slates at the eaves and smallest at the ridge, double lapped, traditionally pegged to riven laths with lime mortar torching underneath. When one of these roofs fails it is almost always the fixings, the pegs and the laths, rather than the stone, which means a careful strip and relay reusing the original slates is often the correct repair.

The wrong repairs are cement mortar, spray foam and bituminous coatings. All three trap moisture and all three prevent the slates from ever being reused. The full story, including why the material nearly disappeared, is in the Collyweston stone slate guide.

Matching existing tiles, which is the hard part

On a repair or a single elevation re-cover, finding tiles that match is frequently harder than the roofing. Profiles get discontinued. Manufacturers change their colour ranges. A tile that has sat on a Bretton roof since 1972 has weathered into a colour that no new tile will ever be.

There are three honest routes and one dishonest one.

1. Reclaimed tiles. Salvage yards hold old profiles and the weathering matches because they are the same age. This is the best answer for a visible elevation. Check the reclaimed tiles are sound, not just old.
2. Borrow from the back. Take matching tiles from a rear or hidden elevation for the visible repair, and put the new tiles where nobody sees them. Standard practice and completely legitimate.
3. Nearest current equivalent. Accept that the repair will show for a few years and will blend as it weathers. Fine on a rear elevation, less good on a front.
4. Painting the new tiles to match. Not a route. It looks wrong within two winters and it is a marker of a firm cutting corners.

If a roofer tells you the profile is obsolete and the whole elevation has to come off, that is sometimes genuinely true and sometimes a convenient upsell. Ask what they searched, ask whether reclaimed stock exists, and get a second opinion before agreeing to a re-cover you were not expecting. The guide ranges on the roof repair cost page and the scope of a proper repair on the roof repairs page will tell you quickly whether you are being sold a bigger job than you have.