Diary Of An Eco-Builder

'With stone tiles, no further firing is needed beyond that completed millions of years ago'

I'm standing in the rain on a fell in Cumbria, watching clouds curl round the cliffs. Scree spills down the hillside; sky, rock and land are united in the distinctive grey-green tones of the Lake District. The scene ought to be elemental, but the sight of an earth-mover high on the fell suggests all is not what it seems.

I'm standing in the rain on a fell in Cumbria, watching clouds curl round the cliffs. Scree spills down the hillside; sky, rock and land are united in the distinctive grey-green tones of the Lake District. The scene ought to be elemental, but the sight of an earth-mover high on the fell suggests all is not what it seems.

I am climbing up to the quarry on the Kirkstone Pass, as a guest of the manager, Nick Fecitt. I'm here to check out the environmental credentials of one of the key materials in the palette of Tree House: Kirkstone slate.

We are off to a good start, for the hillside is actually a restoration - an old quarry scar filled with stone waste then seeded to blend in with the surrounding fells. Given its location in the middle of a national park, this work is essential to sustaining a long-established industry in an area where tourism now has first priority.

Kirkstone slate is principally used for high-quality tiles and for work surfaces. The 'Silver Green' slate is the most distinctive - every tile is patterned with bands of grey and green, seemingly cut against the grain of the rock.

At the top of the quarry, where boulders are being dragged out of the mountainside and split by the earth-movers, Nick explains their origin. The stone was formed by a series of volcanic eruptions that created layers of mineral and ash deposits.

Then, in the collision of the islands that preceded Scotland and England, this rock was thrust up and compressed against the grain of the original sedimentation. Consequently, the rock now cleaves at right angles to the volcanic layers, exposing the early geological history of the rock on every tile.

The beauty and strength of slate are its core eco-credentials. Like wood, most stone suffers little from the vagaries of fashion, so typically enjoys a long life once installed. This is only possible because it is so hard-wearing; even if your floor does get ripped up by future inhabitants with dubious taste, the stone will hopefully achieve a long life via the reclamation yards.

Nick shows me the progression of the slate from cliff-face to consumer product, through a series of bleak sheds where huge circular saws cut and hone the rock, first into blocks and then into tiles or slabs.

Although the transformation is remarkable, I am struck by how simple the process is, requiring relatively little energy and no toxic extras. This is a major environmental advantage of stone: the tough part of the manufacturing process has already been done by Mother Earth. Unlike concrete, bricks, ceramic tiles and synthetic finishes, no further firing is needed beyond that completed several million years ago.

As we drive back to the company office in the valley below the pass, Nick draws my attention to the buildings. Although slate still defines the character of the Lake District, its ubiquitous use in earlier buildings is not matched in many recent constructions, where concrete roof tiles and rendered block walls are also in evidence.

The UK building industry has long departed its local roots, to the extent that using British (let alone local) stone is exceptional. Unfortunately, the eco-profile of stone drops dramatically as soon as you start importing it, given the energy required to transport it. South London may not be Windermere, but a truck on the M6 is a relatively small eco-cost to pay compared to ships from the south seas.

Kirkstone isn't cheap but it is gorgeous: I am confident that its unique character will pay long-term dividends. If you're in the market for a high-quality, durable finish, think twice before you shell out for Indian sandstone or Italian travertine, and consider buying a slice of an English national park instead.

Kirkstone: 01539 433296, www.kirkstone.com.