Transforming a dilapidated sliver of suburbia into award-winning, sedum-roofed housing was easy enough on paper. The hard part was pruning the specification to preserve the eco-friendly design – within budget.
Gold Lane, in Burnt Oak, North London, must have been one of the most unpromising brownfield sites in the capital. It is a narrow scrap of land sandwiched between the neglected backyards of a tatty parade of shops and the gardens of a large housing estate. Two years ago it was in a desperate state, a no-go area of vandalised lock ups and smashed up gates and fences. It was also a security concern, as the garage roofs offered a perfect jumping off point into people's back gardens.

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."

Like minds: Debut of a partnering contract

Notting Hill Housing Group used a PPC 2000 partnering contract for the first time at Gold Lane. The contract was drawn up by law firm Trowers & Hamlins, and is designed to reduce construction costs and build times, and to improve value for money by encouraging a team-based approach to procurement. PPC 2000 emphasises that the contract comes first and that all members of the team, by entering into the partnering contract, agree to work towards the goals of the project. Louise Reddin, Notting Hill’s project manager, said the contract helped everybody understand what the other parties wanted from the project. “There’s no suspicion between parties, it’s an open process. You have to understand that not everybody has the same aims in the project. You have to respect everybody’s goals and work towards them harmoniously.” Notting Hill Housing Group is serious about using partnering contracts in the future. “We really want to do something about partnering – it’s not just about paying lip service. We want to involve consultants, designers and suppliers.” Reddin thinks one of the main benefits of partnering is the ability to negotiate discounts for repeat purchases from partner suppliers or subcontractors. “You can repeat certain features from site to site, therefore it is possible to build contracts with suppliers and subcontractors,” she says.

Point scoring: The pursuit of excellence

“Our rating was 10 points short of an “excellent” rating, but to get that we would have needed to do so much,” says Susan Konu, referring to the EcoHomes measure of sustainability. Devised by BRE, the system scores homes according to how green they are. Environmental specifications earn “Ecopoints”, which are totted up to determine whether the scheme gets an EcoHomes rating of “pass”, “good”, “very good” or “excellent”. The architect’s pursuit of the “excellent” rating was probably doomed as soon as the NHBC insisted on digging the foundations be 1 m deeper. This squeezed the budget, which meant some environmental measures had to go. For instance, the solid wood kitchen was downgraded to a laminate one, and the bike stores in the three-bedroom homes were taken out entirely. English and Konu managed to pick up easy Ecopoints by installing rotary driers in the gardens, which meant energy-hungry tumble driers could be omitted, and installing extra phone and electrical sockets in the living room. Enabling home-working means that tenants are less likely to drive to work. However, Konu questions some elements of the EcoHomes scheme, such as the fact that the system forced the team to drop the cycle storage it planned to provide. “We would only have gained an Ecopoint if we included them in every home, but there was no room in the two-bedroom homes. It meant there was no Ecopoint to be gained even by including bike storage in the five three-bedroom homes,” says Konu. As specifying them would have eaten into the overall budget, the team decided not to include any bike stores.

Roots for roofs: The sedum specification

Sedum is a hardy, grass-like plant that grows in rocky terrain and requires very little attention. Architect English and Konu specified a sedum roof for two reasons: to enhance the view from flats overlooking the site, and to improve the environmental credentials of the scheme. The planners were impressed with the introduction of natural spaces in an area short of greenery and the roof specification helped English and Konu gain planning permission in this conservation area. The specification of the green roof also gained the architects an Ecopoint, and helped them towards their EcoHomes “good” rating. The green roof has a number of environmental plusses. It saves on energy costs as the soil provides extra insulation. Green roofs also improve air quality. Supplier Sarnafil says that over a year, 1.5 m2 of green roof generates the equivalent of one person’s annual oxygen requirement. The plants also reduce carbon dioxide in the air from car fumes and other pollutants, and their foliage traps 85% of dust and air particles, further improving air quality in the local environment. English was also impressed by the lifespan of the roof. The soil and vegetation helps protect the roof membrane from UV, thermal shock, physical damage and winds; Sarnafil says this can double the life of the membrane. The ability to absorb 75% of rainfall also attracted English, as this natural form of stormwater management greatly reduces the risk of flooding and sewage overflows. It was the first time English and Konu had specified a green roof, and English did a lot of research into what was available before opting for Sarnafil. “We looked at other providers but it was the only one that could provide a one-stop service,” says English. Not only did Sarnafil provide the entire roof build-up, from profiled metal roof to sedum, it also supplied all the rooflights and guttering, as well as a 30-year warranty. The grass roofs give Gold Lane a genuine lift, even if not all the tenants have quite grasped the concept. When a Sarnofil employee called by to check the condition of the grass, the tenant thought he had knocked on the wrong door. “Grass roof? What grass roof? I haven’t got one,” he said. But at least the third-floor flats opposite appreciate the specification.