Slate, clay or fibre cement? How to choose roof tiles for your home
Natural slate is a deeply respected, heritage material that can be used on a modern home. It can survive for a century when well cared for, and even reused on a different roof. File picture
In familiar colours of leather and heather, and riven by millions of years, natural hand-split slate is a beautiful material, its sustainability only marred by the cost and petrochemical price of taking it out of the Earth and transporting it. Itâs estimated that concrete tiles create 0.19kg of carbon dioxide per kilogram and natural slate. Throw in their longevity and this might offset that extra up-front costs if youâre a green-spirited buyer.
Its advantages include complete fire resistance and durability that allows it to be saved and reused. Hundred-year-old roofing slate is a relative youngster, while a fibre-cement roof of 25 years old may be showing its age and physically struggling if it's not well maintained. On the flip-side, slate is brittle, and hefty and must be handled with supreme skill. Despite being cut to size, it will still require expert âgradingâ on the ground for size, colour and condition before itâs ever taken aloft.
Compared to fibre-cement or box-profile steel sheeting, slate is heavy (around 38kg per square metre of typical 250mm x 500mm Spanish slates). It is lighter than concrete (add another 25%), but the roof structure will need to be up to support it. In a renovation, this could cost tens of thousands to strengthen the roof structure or even replace it, and weeks of extra work.
Up on the roof, it wonât respond well to heavy jack boots of other trades, for example, a clumsy installation of a PV-solar system. Being more expensive, replacement and repair will be a bigger spend. When hiring a roofing contractor pick the guy or gal known for their superb touch with slate, and ask to see examples of their work. They should be proud to provide images and references.
Slate requires the same attention as fibre cement â checks for lifted, shattered or slipped slates, and the removal of algae and moss build-up. Moss can spoil the roofâs appearance and larger cushions of moss can push the slates out of position.
Harsh winter conditions can work moisture between the layers that make up natural slate, freezing and then shattering them here and there. Keep the roof in good order and in 100 years it will be intact when fibre-cement, clay and concrete alternatives have hit the landfill.
Irish, Spanish, Cumbrian and Welsh slates are on offer. The colour variety covers everything from olive green shades from the English Lake District to rich Iberian purples, many with century guarantee as standard. Depending on your needs, slates come in fixed sizes and formats, random widths and sizes replicating the available materials used on heritage buildings in the past.
To look left and right of real slate for something with an elegant, traditional finish â include interlocking, fade-free clay tile if your planning permission will allow you a colour choice (and even if it doesnât as it can also play slate in black or grey).
Also referred to as klinker tiles, these products are fired to a high temperature and carry a UV-resistant glaze. They can outlast fibre-cement and are 100% natural.
Clay tiles fit tightly together, are suited to very shallow 10-degree pitches, and acute pitches (refer to your supplier here) and come in larger formats, which can make laying them faster in the right hands. Do they carry higher architectural credentials than fibre cement? Yep â afraid so.
Clay is heavy (not as heavy as concrete but heavier than fibre cement). However, these tiles absorb less water than cheap, concrete tiles - 6% compared to untreated concreteâs 13%, meaning they wonât suffer in wet weather or add damaging weight to the roof when wet.
For more information go to sig.ie for a good selection of clay tile, and supplier details nationwide. In terms of the environment, clay tiles are fired, and this does have a high carbon price, with kilns burning 24/7.
In terms of imposter materials, fibre cement does a superb job of playing all natural. With a wide choice in thickness, widths, colours and richly textured surfaces, it does take a second look to spot a composite over real stone. Itâs been around for over a century.
Does it carry the same prestige as a natural slate? Never. Laid artfully you can mix up colours, patterns and with a CAD visualiser you can put the tile on the roof to see how it marries with other materials and the wider landscape.
Fibre cement-like concrete is getting a second look these days and is growing in popularity as a sleek, modern, vernacular, not just in roofing, but for cladding new builds and flips. Look up the products at Swisspearl.com, formerly Cembrit. Its green CV? Fibre cement has a low carbon footprint of 16 CO2 per sq m and can (in theory) be recycled.
Fibre cement doesnât suffer the same cold-weather problems of natural slate, but it does provide a perfect growing environment for a variety of wind-borne plant seeds and spores. It is fire-resistant and in a good product, highly impact-resistant.
Its composition and factory-set uniform size means itâs both lighter and easier to install and repair â so potentially cheaper overall. In terms of weight, youâre looking at 20kg-23kg per square metre, much lighter than concrete which is notorious for ingesting rainwater, making it even heavier.
If you are replacing faux-slate with slate, have the roof surveyed by an engineer before going ahead, and ensure you know the weight per metre, together with the minimum/maximum pitch and recommended lap of your chosen slate.
So, cheap and straight-forward to install, whatâs the cons of going synthetic? Well, in my prejudiced view, itâs simply longevity. Fibre cement can last up to 60 years, but by that time it will be soft, stained with efflorescence and likely quite a mess.
At 25 years on my roof and having replaced all the ridge tiles, itâs the first thing I would heave-ho if the Lotto fairy alighted on my life. Cedral describes the changes in an ageing fibre cement roof as âmore of a visual flaw than damageâ but without cleaning for a heavy build-up of bio-muck, it can look unsightly.
Doing your sums for new roofing covering, take the following into account â weight, durability, looks (wet and dry), and sustainability. Look at this roof as a 50-year investment. Then key in the price per metre of natural slate, clay and fibre cement (presuming youâre going for that slate appearance). Tot up the installation costs.
Imagine replacing the tiling in 25-30 years or having repairs done for the life-time of the building with a natural slate or clay product.
Donât forget the outliers like box-metal sheeting when building or replacing a roof â these materials can sit oddly well in the Irish countryside in particular, are lightweight and increasingly affordable, and could make a self-build or extension with a little creative tension to your otherwise slated roofs.
