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

Homebuilding & Renovating - - CONTENTS -

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.

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