Colin Viebrock’s garage is very cool. It’s custom made with stylish wooden slats on its exterior walls and a workshop inside. Plus it has a garden on the roof.

The pretty mixture of sedum, lavender, chives and other low plants lowers the surrounding air temperature — very cool — in summer, and helps insulate the garage in winter.

Viebrock, 38, had no intention of being on the cutting edge of green innovation when he sold his share of a downtown Toronto Internet company back in 2005. “I decided I wanted to build something real as opposed to things that weren’t really real.”

He didn’t know what that was, but he’d always loved architecture and design and knew the design program AutoCAD. His garage was about to fall down and he called around trying to find someone to help him put a green roof on it. No one would work in such a small space.

So he spent the summer of 2006 rebuilding the garage and equipping it with a roof garden — the roof tilts slightly so he can see the greenery from the third floor of his house.

The blog he wrote about the project garnered interest. So that winter he took some home renovation courses at nearby George Brown College and then launched Green Garage and began installing green roofs on everything from sheds to houses.

For existing buildings, Viebrock starts by having an engineer assess the structure to see if it can withstand a minimum of three inches of soil. (When Viebrock designs the building, he makes it tough enough to take six inches.)

Viebrock then builds up the garden in layers, including a waterproof membrane, small rocks or gravel (for drainage) and an irrigation drip line.

Then comes a special lightweight soil that’s a mix of compost and crushed stones and brick, which he carried up on the roof by hand using a ladder.

Finally, Viebrock puts in the plants — he’s always experimenting to find a bigger variety that will grow on roofs.

He returns for a few visits after an install to check on the roof and do some weeding. Within about two years, garden fully fills in and needs little maintenance.

For small jobs, Viebrock will work alone using a rented van, but he’ll hire a team for larger projects.

He can build a roof garden almost any time of year, but the final planting happens in just the fall and spring.

In the winter, Viebrock keeps busy doing interior designs and renovations.