Rather than the tight, dark entry hall typical of century-old row houses, Bernier and Thibault’s three-story-high stairwell is flooded with sunlight that illuminates surprising architectural details and an open-plan interior. Bernier, an architect, and Thibault, a lawyer specializing in alternative dispute resolution, managed to renovate and expand their home for about $100 per square foot by using affordable materials, forgoing extravagant hardware and finishes, and taking on much of the work themselves. Bernier tells us how it came together.

I bought this house in 1993. It’s a hundred years old but had been cheaply renovated with vinyl windows, mirrored closet doors, and carpet. Still, I saw lots of potential. I was alone and I had a small budget, so I slowly did a little work by myself. Then, in 1998, Joëlle moved in.

In Montreal, the yards are usually behind the houses, and everybody can see into each other’s property. In our case, our yard is on the side, wrapped by other buildings, and it’s very private—–that was the main thing that drew me to the house. There was a building there, but it collapsed in the ’70s, when the Plateau was a really poor neighborhood and the buildings weren’t well looked after. Our garden is very lush, and the walls of our house and the neighboring place are covered with greenery, which really absorbs the sounds of the city. You notice the difference in the fall when the leaves drop, and all the hard surfaces become exposed—–suddenly, you hear the noise.

When our older son Edouard was two and Victor was on the way, we decided to expand. We were tripping over the kids’ toys. So we designed two additions: a playroom and an office. They are two boxes, each about 264 square feet, one in the garden and one on the roof. Our objective was not only to gain some more space but also to make the house lighter and brighter. We moved to an apartment across the street for about six months during construction, and I served as the general contractor.

We decided to site the playroom at the end of the garden, and keep it at one story, to allow sunlight to come into the yard—–around three p.m., when there’s sun, there’s a big ray of light that streams in. We put a green roof on top to absorb heat and sound and to extend the lush feeling of the yard. We had to work around the silver maple tree—–the wall comes in to make way for it, and I installed windows so you can see the trunk.

I really like that the house now runs around the garden and embraces it. In the summer, it’s cooler there than on the street, and we move from the living room to the outdoors to the playroom, as if it’s all just part of the house. We love having family dinners out there.We also put an outdoor shower in the corner of the garden, hanging from a tree with no enclosure. On hot days, the kids like to run under it in their bathing suits, and sometimes we use it for a quick shower before bed because it’s more fun.

For the office, which is on the roof, our addition had to be invisible from the sidewalk, because the city has designated our block as a two-story street. I set it back and lowered it partially into the existing building, so you can’t see it. That’s why the city accepted my proposition. It has large windows and suddenly gave us something that we didn’t have before: an expansive view over all of the housetops in the neighborhood! It’s a bright and peaceful space. Joëlle and I really enjoy it; it’s the place we go to when the kids aren’t at home or after they’ve gone to bed. They have their playroom; the office is our room.

This house is not big but ends up feeling bigger than it is. One reason is that we kept the stairs and circulation areas as transparent as possible, fostering more interaction and bringing in more light without sacrificing space. Instead of using the standard hardwood in the second-floor hallway, we laid square one-and-three-quarter-inch birch boards with gaps between them to allow sunlight from the windows to pass right through. Eventually, I’m going to remove a few more boards to let the light come through better, once the kids are older and I don’t have to worry about their feet getting caught. But it’s already a house where you can’t hide too much, which is perfect for our family. Joëlle and I always know what the kids are up to, even when we’re in different rooms, and they always know that we’re close by. We can talk through the floors, and I can look down at the kids having breakfast in the morning, which helps keep us all together, even when we’re busy.