Farms and architecture with a capital ‘A’ rarely go hand in hand, but one cowshed’s dry mix concrete colonnade is a notable exception, writes Felix Mara. Photography by David Grandorge
ainstream architecture and farms are connected by two-way traffic; in Palladio’s villas and follies such as Squire Barry of Fyling Hall’s classical pigsty, they meet. A more recent example of this overlap, Stephen Taylor Architects’ cowshed at Shatwell Farm evokes classical stoas, while its dry mix concrete arches and columns contain local crushed aggregate.
The first stage of the farm’s revitalisation, the cowshed, with capacity for 350 cattle, is the largest building within a group; its stoa announces one’s arrival at the farmyard at the end of the ‘valley walk’ route from Hadspen House. This bespoke concrete stoa with arches at each end of its central axis adjoins the large, slat-gabled, prefabricated steel cattle enclosure on the opposite side of the ‘feed line’.
‘It’s an off-the-shelf shed, tweaked a little,’ says project architect Sam Holden. ‘We used three types of concrete: a dry mix for the in situ circular columns and arches; a more standard C35 concrete for the in situ gutter beam and precast, pre-stressed pilasters, rafters and beams.’
The architects worked with the shed supplier to develop these pre-stressed components, cast on steel beds and stressed by high-tensile wire, as variants on its precast wall panels, designed for cattle loads. Like the panels, the pilasters and beams have cast-in M16 threaded sockets, used to clip them to bolted plates fixed to the shed’s portal frame.
‘Only a small amount of water was added to the concrete used for the columns and arches - less than normally required for placing and compacting - and it had to be dug out of the mixer,’ says Holden. ‘It was mixed on site, with six parts aggregate to one part Portland cement by volume.’
Construction management procurement, with client, structural engineer and contractors amenable to experimentation, enabled the practice to work empirically, seeking the right consistency and mix of sand, clay and aggregate. ‘We wanted a rich, warm colour, similar to Bath stone, but more yellow,’ says director Stephen Taylor. A soft golden limestone from Hadspen quarry was chosen, screened and crushed to give a 0/40mm ‘all in’ aggregate.
The contractor built sample columns trying different mixes and lifts, even mixing earth from the ground with cement. Excessive lifts would have made the concrete compact under its own weight. In the end, the columns were cast with 450mm lifts over consecutive days and the WBP plywood formwork, treated with polyester resin and a release agent formwork, was ‘slipped’ up the column with a slight overlap to avoid misalignment. The concrete was placed by hand and tamped manually without mechanical vibration, so day joints are visible. With modelling increasingly used in construction, it’s a tonic to see more empirical approaches.
‘The circular columns are big, fat, with no steel,’ says Holden. ‘We worked closely with the structural engineer to establish a diameter we were both comfortable with.’ Almost Doric in proportion and in the way they meet the tamped plinth with no articulation, their texture is rich, like travertine. ‘The columns were hit and miss but, when they missed, they were fine,’ says Taylor.
The arches needed more complex formwork with traditional centring; there is simple reinforcement at their heads and where they spring from the columns. Above the point where the concrete was contained in a top shutter, the top edge of the arch was trowelled to follow the line of the formwork.
Peter Zumthor’s use of rammed earth construction is well known but Taylor references Breton farmhouses, whose concrete resembles rammed earth. Could previous work with rammed concrete enthusiast David Bennett have inspired a devil-may-care approach to concrete design, rather than choosing a specific technique? The best architects learn from consultants, rather than just delegating to them.
From some angles, the arches seem uncomfortable appendages to the shed’s massing and the gables feel two-dimensional. But these arches, with the gutter beam, are immensely sculptural. The beam has cage reinforcement and its concrete was formed in a single pour. Pumped and mechanically vibrated, its top surface was trowelled and coated with waterproof slurry. Its smooth blue-grey finish emphasises the yellow of the colonnade and its simple, bold sectional profile neatly fits the skilful assembly of pre-stressed components tidily integrated with the shed roof build-up above. Along with the linear site organisation, the cowshed’s formal architectural qualities complement its rustic in situ concrete’s terroir.
AJ Buildings Library
See images, drawings and data for Shatwell Farm by Stephen Taylor Architects