Green and gold

After a barrage of complaints from local residents, the London Borough of Barnet decided that the time had come to polish up Gold Lane. It approached Notting Hill Housing Group about demolishing the garages and using the site for housing.

The brief was not promising. The land available to build on was only 9 m wide, and lay within the Watling Estate conservation area, a 1930s suburb built to house the thousands moving away from London's East End. Conservation status meant that any new homes would be restricted in height, and would have to blend in with the bricks and tiles of the surrounding council homes.

Notting Hill Housing Group selected English and Konu Architects to rescue the site. "We were asked to come up with a landmark scheme. They were being tongue-in-cheek – the site was dilapidated," remembers Sue Konu, a partner at the practice.

What English and Konu came up with exceeded all expectations. Its design of eight green-roofed houses won a RIBA Housing Design Award in 2002. RIBA called the designs "a textbook piece of regeneration benefiting both new and existing residents."

But coming up with the award-winning design was the easy bit. The challenge for English and Konu was to make sure that the design was implemented without sacrificing the host of sustainable features that were part and parcel of it.

According to partner Audley English, the practice was aiming for a "very good" or even "excellent" EcoHomes rating. But if build costs started rising – not unknown on awkward brownfield sites – then the clever design features and innovative sustainability measures would be the first to go.

Almost immediately, disaster struck. "The NHBC inspected the site and said it wouldn't provide a warranty unless we went down another metre on the foundations," explains Konu. The extra expense of digging deeper put pressure on the budget, and the practice realised that compromises would have to be made on design and specification. But fortunately, the consequences were mitigated by using a partnership contract that established common goals and allowed the contractor, project manager and architect to design out cost-risk factors at a very early stage. "As a partner, we looked at ways of making savings as we went along rather than there being an almighty claim at the end," says Konu (see "Like minds", below).

The homes' designs are unashamedly modern and unlike anything else in the area. For a start, the eight houses have sedum roofs (see "Roots for roofs", page 10) by Sarnafil, which greatly improved the view from the flats above the parade of shops opposite, and helped persuade the planners to give the buildings consent. The planners were also impressed by the monopitched butterfly roofs, as they helped to restrict the roof height while still providing two-storey houses. Traditional two-storey homes with pitched roofs would have blocked out light for nearby homes.

The facades of the two- and three-bedroom homes also bring vibrancy and colour to the site. White render, western cedar cladding and bright yellow rainscreen panels give the homes a bright and sunny air even on cloudy days. The floor-to-ceiling windows and dome rooflights also ensure that the interiors get a generous splash of natural daylight.

The provision of light was especially important as the northern brick facades are windowless. Because the new homes are only 18 m away from the existing ones, the northern facade doubles up as a new boundary wall, preserving the existing residents' privacy. For this reason, English and Konu could not specify a timber frame structure as originally intended. The scaffolding for the timber would have to have been erected in the neighbours' gardens and, says Konu, this promised too much disruption. In any case, the buildings' EcoHomes rating was completely unaffected by the specification of medium density blockwork over timber frame (see "Point scoring", below).

Close collaboration between the partners allowed costs to be shaved in several areas of the specification. For example, by working closely with window subcontractor Arden, English and Konu managed to avoid specifying costly custom-designed frames. As Arden was involved from the outset, it could judge whether bespoke window designs would be cost effective. On a number of occasions, Arden suggested that the architect could change the size of the windows to match standard components, which helped rein in the budget.

Discussions with Eternit about the resin-based Lamina cladding panels were also fruitful. Lamina rainscreen panels are usually found on commercial buildings, but were specified by English and Konu because of their strong colour and low maintenance requirements. Eternit offered to prefabricate the Lamina panels in the factory to ensure a precision finish, making one less trade on site. Three large panels of Lamina tiles were prefabricated for each of the three-bedroom homes.

More money was saved by altering the facade designs to include more Lamina panels at the expense of the more costly western red cedar cladding. These changes were made with the blessing of the architect, although Konu acknowledges that including any more panels would have spoiled the look of the building. "It was as far as we could have gone before we lost the correct proportions," she says.

What was left of the western red cedar cladding also underwent some compromise. The architect originally wanted to stain it the same colour as the timber windows, but collectively the project team decided that money could be saved by leaving the cladding untreated. Savings were also made on the specification of the timber soffit. As the soffit is less prone to weathering than the vertical cladding, tongue and groove timber boards were specified instead of the more expensive and thicker western red cedar.

Another key construction saving came from using quarried stone to fill the gabion walls. The architect had wanted to use recycled hardcore from the original site but the contractor, Bugler Developments, argued that the costs were prohibitive. Other savings were made in the homes' interiors such as the kitchen units, which were downgraded from solid timber to laminate finish.

Effective cost cutting ensured that all the major design elements appeared in the final build. The green roof was the greatest triumph, and although it required an extra cash boost from client Notting Hill, it was not prohibitively expensive.

Louise Reddin, project manager at the housing group, believes that green roofs and perhaps solar panels will be feasible on future projects if NHHG forms partnerships with suppliers and contractors. "If firms have guarantees of demand they will reduce their costs. With partnerships you can repeat things you have learned on previous projects," she says.

The transformation of Gold Lane from eyesore to oasis is remarkable. Once the haunt of fly tippers and vandals, it is now a pleasant, secure street.

The new homes have even sparked a localised regeneration as landlords opposite have started tidying up their yards and refurbishing their properties.

Konu offers a piece of evidence from one tenant that the transformation has made residents take more pride in their area. "She told me she used to come down to 'the garages' 30 years ago for a fag. But now if she sees any kids hanging around on the street, she tells them to clear off."