Attic Conversions near you

The joists that form an attic floor were typically sized to carry the ceiling below, not a floor with people, furniture and stored items on it. A structural engineer checks their size, span and spacing, and the walls and beams they bear on, and designs any reinforcement, such as sistered or new, deeper joists. Changes to the roof framing are also engineering work: rafters, ties and the knee walls in a storey-and-a-half house often help hold the roof together. Natural Resources Canada's guide to finishing attics notes that collar ties between each pair of rafters give structural support to both the roof and the new ceiling, but their size and position belong on the engineer's drawings, never cut or moved on site.

A room people sleep or work in needs a permanent staircase, not a pull-down ladder or a steep ship's ladder. The building code sets the rise and run of the steps, the width, the headroom over the stair, landings and handrails, and a stair that meets them takes real floor space on the level below. Finding that space, often by borrowing from a bedroom, closet or hallway, is one of the first design questions, and our staircases page explains how a stair is designed and built.

In an unfinished attic, the insulation sits on the floor and the space above is ventilated and cold. Once the attic becomes a room, the insulation and air barrier have to follow the new heated space: the sloped ceiling, the knee walls, the ceiling of any flat section and the floor behind the knee walls. Natural Resources Canada describes insulating the rafter spaces snugly against the tops of the walls for a continuous thermal envelope, leaving a clear space above the insulation for roof ventilation, and sealing a continuous air and vapour barrier to the rafters and end walls.

NRCan also warns that houses with half storeys have a major air leakage path through the floor joists just beneath the knee walls, and that roofs with little space for insulation and ventilation, such as cathedral ceilings, need a qualified contractor. Before any of it starts, have old attic insulation checked for vermiculite, as our attic insulation page explains.

An attic bedroom sits high above the ground with one stair down, so its window is a critical way out. Under the Ontario Building Code, as the City of Ottawa's advisory explains, a floor level containing a bedroom needs an egress window that opens from the inside without tools and gives a clear opening of at least 0.35 m² with no dimension under 380 mm. Above the basement, the sill must be no more than 1,000 mm above the floor, which can be achieved with steps, built-in cabinets or counters under a higher window.

Upper-storey windows also have to protect children from falling. The advisory explains that an openable window with a sill less than 900 mm above the floor needs a guard or a window limiter, and on an egress window the limiter must be possible to release without tools. Other provinces' codes may differ, so confirm the rules with your municipality, and plan working smoke alarms for the new room and the stair.

An attic conversion almost always needs a building permit. Toronto's permit guidance, for example, requires one for structural or material alterations and for new windows or doors where there were none before, which covers new floor framing, a stair opening, dormers and new gable-end windows. Dormers and raised roofs also meet zoning: Ontario's citizen's guide to land use planning notes that zoning bylaws control building heights and densities, so a design that adds height or floor area may need a minor variance. Expect inspections of the framing, insulation and fire safety before the room is finished, and separate electrical inspections.