Building in Stone

Architect Neil Turner explores the re-emerging trend for building in stone and answers the key questions to get your stone-clad home out of the ground

Stone is experiencing a renaissance but there’s a lot to consider when specifying this material for your new home, renovation or extension, as architect Neil Turner explains

I’ve been working on four projects recently —

all different in scale, shape and architectural interest, but with one key similarity: they are all clad in stone.

This to me suggests that there’s a resurgence in the popularity of this most traditional of building materials, but why is it happening now? Stone has inherent characteristics of quality and durability, but it’s also particular to areas of the country and gives an immediate identity. From the rich yellow limestone of the Cotswolds to Glasgow’s red sandstone, regional stone anchors projects to their locale and bestows homes with a distinctive character that ties them to the history of the area. That’s to say nothing of the fact that builders through the centuries have often used stone to imbue houses with a sense of prestige and to show the wealth of the homeowners.

the choices

Modern techniques of construction allow stone to be used more creatively than in past years. In many ways, stone has been re-invented as a cladding material rather than being seen only as a loadbearing material. This means it is now increasingly used on both traditional and contemporary-style projects.

The choice of stone, its detailing and even the mortar will therefore directly affect the style of the house you are creating. So, there are some key decisions you and your team (your architect and perhaps builder) will need to make, including:

Stone type — do you opt for a regional stone to match the area or pick a contrasting stone to make a statement? If you are buying from out of your area expect the costs to rise.

Size — historically, larger stone sizes were used on the grander houses and often on the estate houses to match the main manor house. Typically, the larger the stone module the greater the price.

Finish — the look of the stone can be altered by different finishes. A common one is dressed stone, which gives a precise, highly uniform finish; other effects include sand-blasted or riven.

Laying pattern — think about how the stone will be laid. Options include coursed, uncoursed, random rubble, dry stone and flint pattern. Does the building demand a coursed stone like a Georgian house, or is the aesthetic more agricultural? In this latter case, an honest and an uncoursed or rubble façade would be more suitable. These latter finishes can be cheaper and more appropriate to a more basic architectural form, but they can work equally well on modern buildings when contrasting with a sharper modern material (see page 195 by way of example).

Mortar choice — This is a huge subject in its own right. Random rubble will have more visible mortar to cover the irregularity of the stone compared to dressed stone. A dry stone wall will ideally have no mortar (or hide the fact it does with skilfully placed mortar at the back of the construction). Don’t forget to think about the colour, too. Pick with real care and take your time to trial some — or live with the error for a long time.

A lot of the design decisions will depend upon the aesthetic of the building and the architectural style of the house. When renovating a listed building, the local authority conservation officer will impose conditions on what stone can be used — this will usually be to match the existing. Otherwise it typically falls to the architect or client (or in rarer cases, the builder) to specify the stone and style.

I like to think it’s the architect who has the best aesthetic judgement, and on projects I’ve worked on it’s usually me who decides on the type of stone, size and mortar colour. Of course, sample panels are there so everyone involved will be able to give their opinion and tweak the final design. These panels are usually a necessity of planning too, and the planners will often insist on signing off on the materials used.

stone innovations

Over a century ago, stone would have been used in a solid wall construction as the loadbearing wall. A stonemason would have carefully selected the best stone for the external face of the building, with the cheap stone and rubble used inside the solid wall.

As buildings developed cavities from the Edwardian period onwards, the use of stone developed in a manner similar to brick construction, with metal ties used to tie the outer stone leaf to to the inner leaf of blockwork.

With modern construction methods, such as SIPs, steel and timber frame buildings, stone remains popular, but as an outer skin or cladding. When used this way, the designer needs to think about how to connect this heavy material with the lightweight structural system.

One method I have used successfully is an offsite system in which the stone is fixed, in a factory, to concrete panels. These are then delivered to site and bolted onto a steel frame. This method is often used on commercial buildings, but can be replicated on smaller-scale projects and with a variety of fixing systems. Some of the new systems have a full stone panel or stone tile bonded to a granite backing, allowing the stone face to be a larger size tile. These are then fixed on metal carrier/hanging rails hidden behind the stone tile, which can be fixed to the main structural system of the house.

It’s not always a cheap option: the systems start from £120 for the stone and £50+ for the structural system. It’s generally specified when there are large areas to cover, or on difficult sites where the speed of erection that comes with this method

is a major bonus. Remember, though the upfront costs might be high, the labour cost is massively reduced as the site work simply involves bolting it all together.

the costs

Stone is expensive. There’s no way around it. Even with a shortage of skilled bricklayers, the cost of brick will still be about half that of stone. When estimating the costs of using stone you have to factor in the price of the raw material and the skilled labour of laying it too.

The labour costs reflect the time-consuming nature of laying this material, and it’s a false economy to spend on a beautiful product and cut costs by getting a non-expert to lay it. Each stonemason has a slightly different style, adding to the texture of the building appearance, and their skill, expertise and knowledge will benefit a project. Each area of the country has companies that specialise in their stone of the local vernacular (I’m working with TA Law of Kirkby Stephen for a slate project currently) so take the time to find them — it’s worth it.

Putting up a limestone wall will cost around £150/m2, which is slightly more expensive than sandstone. A slate wall may cost closer to £200/ m2, and will be even more expensive if you’re further away from its natural habitat in places like the Lakes. This is true of any stone, so it usually pays to stick to materials common in your region.

To save costs, it may be worth combining stone with brick, timber or render. Timber has always combined well with stone and continues to look good — cedar cladding, for example, is around £20-£50/m2. Render (£80-£140/m2) can also be used to give a sharp contrast and is used on many contemporary buildings. Obviously, the amount of stone can be reduced to feature panels, as render and cedar is cheaper than the stone.

how to source stone

If you are looking to match a stone, for example when renovating or building an extension, it can be a difficult process. There are several avenues available to you, however: l Speak to local stone suppliers and quarries about what is available.

l Speak to the planners and conservation officers. If they are stipulating certain materials then they can advise where it can be sourced.

l A recent client of mine approached demolition contractors and bought the stone from three different buildings. The stone was then mixed up in the field next to them and the result is a lovely weathered natural random stone for their new farmhouse.

l Specialist society groups, such as the Society for the Protection of Ancient Buildings (SPAB), Historic England and local architectural societies, can offer guidance.

l Accredited conservation architects have undergone additional training and some will have specific skills, experience and knowledge of stone and stone repair.