How we did it ... Grocery roof becomes biodiversity showcase

Project: A scheme to create a brown and green roof on an existing building, the Unicorn Grocery.

Living roof: insulation plus bird habitat
Living roof: insulation plus bird habitat

Background: The roof is part of a Manchester-wide project called Make Room for Black Redstarts, which aims to create habitat "stepping stones" for this bird species, now rarer than the golden eagle.

Who is behind it? The Greater Manchester Biodiversity Project, the Unicorn Grocery, the SITA Trust, the BTCV, Outerspace Garden Design and Living Roofs.

Project aims: As well as creating wildlife habitat, the roof covering would improve insulation.

Skills involved: Architecture, landscaping, biodiversity expertise and green roof design.

Organic grocery Unicorn first considered installing a green roof for purely practical reasons. Located in a completely uninsulated building, workers were forced to wear hats and gloves at the tills all through winter.

"We looked at getting it insulated, but the quotes were astronomical. So we thought that if we were going to spend that much money, we might as well do something a bit different," explains Leah de Quattro, one of the shop's co-operative members.

Unicorn approached Manchester City Council, which put it in touch with the Greater Manchester Biodiversity Project. Biodiversity manager Graham Jones was just starting work on an initiative to boost numbers of the black redstart by creating a habitat for the species. The small bird only breeds in cities and widespread regeneration had resulted in a massive loss of habitat. There are only around 100 breeding pairs in the UK.

Most of the 520m2 space on top of the Unicorn building is a brown roof, which differs from a green roof in that it does not have any sedum. This is partly due to the weight limit that the building can take, but it is also the best habitat for the bird which likes poor vegetation.

The roof is believed to be the first in the UK to incorporate a pond. The 50m2 of water draws midges, which supply the birds with food, and also attracts bats. By diverting rainwater coming off a higher roof from going straight down the drain, it also helps prevent flooding.

The project received £25,000 funding from the SITA Trust and volunteers were brought in from the BTCV. Permission was not a problem, as Jones explains. "Green roofs are the in-thing in Manchester, so there were no issues with planners."

Outerspace Garden Design owner Iain Weguelin designed the roof and managed the construction. The biggest challenge was getting all the materials on to the roof, he says. As much as 30 or 40 tonnes had to be hoisted up.

"We had to have a crane in the neighbouring building's car park. This belongs to British Telecom, which only gave us two days even though the company barely uses it. The short time frame focused us, but it was fraught with problems. This is something people need to think about when putting a living roof on an existing building. It's much easier on new developments," he says.

Once the materials were on the roof, however, it was easier than landscaping on the ground, Weguelin says. Jones agrees: "Once you've done the nitty-gritty working out the load capacity, putting the roof on couldn't be easier." Construction and landscaping took just 12 days. Three or four people worked permanently on the site, with varying numbers of volunteers each day.

The project has been a success all round. Jones is planning to use it as a showpiece to demonstrate to planners and local authority staff what can be achieved by similar projects. Manchester City Council is including living roofs in its climate change strategy and biodiversity action plan, which forms part of its bid to become the greenest city in England.

De Quattro comments: "We paid a little less than for a conventional roof, but ended up with something that's doing a lot of good. It's being colonised already and it's great to see it changing every day. And it's much less cold in the shop."

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