SLATE ROOF TILES

A natural slate roof offers a timeless natural appearance and is often the go-to roofing solution for many building projects. Rebecca Foster considers what you need to know

A slate roof is a popular roofing choice because of its impressive service life, excellent durability and timeless appeal. One of the first things to check before laying a slate roof is the origin of your slates. Plus, with such varied quality levels available, how do you know whether the slate product is up to the task? Installation and maintenance are also crucial.

Roof slates come in an array of textures, thicknesses and colours, some of which are inherently linked with certain geographical regions of the country. “When it comes to slate quality, the country of origin isn’t as important as the specific quarry you source it from. Slate varies hugely from quarry to quarry, and even between different veins of rock,” says Ahmed El-helw, managing director at SSQ. “For the best slate, you need to find a well-established, widely respected quarry with excellent quality control, regardless of what country it’s in.”

Welsh slate is known for its bluer tones, while Westmoreland is celebrated for its green-grey hue. Imported slates offer a cheaper alternative, although units sourced from overseas have been subject to some bad press over recent years. However, providing you check your slates meet the required quality standards, they can be a smart purchase.

ASSESS THE QUALITY

Like many building materials, cost is a pretty dependable gauge in terms of quality — cheaper slates do not typically offer the same durability. “Look for accreditation — quality slate will always carry one. If slate hasn’t been tested to BS EN12326 standard and it doesn’t have CE marking, it doesn’t meet UK Building Regulations and shouldn’t be installed,” says Ahmed El-helw. Another key area to investigate is the rate of water absorption, where lower rates are better. “Regulations require that slate has a water absorption rate of less than 0.6%,” says Ahmed. “However, that’s only recently changed. The standard used to be 0.3% or less, and many in the industry would argue this is still the mark of excellence.”

Double check the carbonate content, too — slate that has been graded S1 is the best as it has a carbonate content of no more than 20%; more than this could reduce the durability of the slate.

Slate comes in a variety of thicknesses and textures, so it’s vital for your roofer to sort the slate into at least three categories to guarantee a uniform look across the whole slate roof. Natural slate can be cut into any shape for installation on your slate roof, although rectangular units are the traditional option in the UK.

HOW MUCH DO THEY COST?

As a premium natural product, a slate roof isn’t cheap. “Roughly, prices range from £26-£35/m2,” says Yasmin Herfegar from Cupa Pizarras. Slates quarried in Wales, Cornwall and Cumbria can cost more than £40/m2.

“For a 150m2 roof, the lowest you should pay for budget natural roofing slates would be about £6,300,” says Ben Fernandez from Iconic Slate. “For a higher quality grade you would be paying approximately £7,800, plus VAT.”

Factor in installation costs, too. “The lowest would be in the mid £20s/m2 for the whole roof, with the highest in the mid £40s/ m2, based on a traditional method of fitting,” adds Ben.