Wilkinson’s Brook, Dublin
Case study Proctor & Matthews has revived a traditional form of settlement with a modern method of construction
At Wilkinson’s Brook, architect Proctor & Matthews has looked to the past of Irish housing to transform its present. The practice has taken inspiration from clachans – traditional settlements clustered around a communal focal point – to create a neighbourhood of “own door” homes centred on green spaces connected by a network of shared-surface streets.
The 69-home development has won plenty of admirers for its compact formal arrangement, which moves cars off the street into integrated carports and provides private outdoor space on generous multi-level terraces. Earlier this year, it won a Royal Institute of the Architects of Ireland Award, with the judges praising it for “enhancing the living experience of its residents”.
But it is also notable for the way it was built. The use of insulating concrete formwork (ICF) created a highly efficient thermal envelope, while speeding up the programme, taking watertightness off the critical path and reducing site waste. The house types – of which there are seven variants across the development – were not specifically designed as ICF structures.
“There was a certain flexibility,” says Stephen Proctor, founding director of Proctor & Matthews. “We were asked to design something that could be built either traditionally or with MMC [modern methods of construction] – whether timber, panellised or ICF.” The key advantages of the latter system were that it could be supplied locally, built very quickly, and was cost-effective – an important consideration with nearly a quarter of the homes being made available under Ireland’s Affordable Purchase Scheme.
The chosen ICF system uses interlocking hollow blocks of graphite-enhanced expanded polystyrene (EPS) insulation, with integrated cross-ties made from recycled polypropylene and spaced 150-200mm vertically. The blocks – castellated top and bottom like Lego – were stacked directly on strip foundations, ready for the concrete to be pumped into the cavity in half-storey pours. The resulting walls are 300mm thick with two 75mm leaves of insulation around a 150mm concrete core.
The proprietary system included a corner block and an insulated rebated window reveal, which simplified detailing around openings, as well as integrated reinforced lintels. This was particularly useful because of the unusual typology, with the setback terraces and parking incorporated within the building footprint. “It could have been a very big, complicated hybrid structure, with lintels and steels to go over the carport,” says Proctor.
Where additional reinforcement was needed, the system allows for two courses of rebar to be supported on the cross-ties. “It was just very straightforward,” adds Eamonn Doran, of executive architect Doran Cray. “A nice, uniform concrete structure. The structural engineers loved it.”
Because the structure is completely enclosed in insulation, ICF virtually eliminates thermal bridging. Combined with rooftop photovoltaic panels and air-source heat pumps, the thermally efficient envelope has helped the homes to secure an A1 under Ireland’s Building Energy Rating scheme.The system also offered aesthetic benefits. “It gave us the opportunity to do lots of interesting patterns with brick that would have been more expensive and added time with traditional methods,” says Doran. A variety of brick slips, including some striking vertical bonds, and coloured renders were applied directly to the outer layer of formwork.
There was another practical advantage, particularly relevant in the Irish (and British) climate. “The terraces couldn’t be waterproofed until the building was nearly fully up, with the roof on,” says Doran. “With a timber frame, you would need to tank and seal the terraces, but here there was no water damage to the structure at all. “To me, that’s the biggest advantage of ICF with this typology – it can be rained on.”