Is my existing foundation strong enough to support a second storey in Ottawa?

Adding a second storey can add a lot of space without a bigger footprint, but the first question is whether the existing foundation can carry the extra load. The answer depends on how the house was built, what the foundation is made of and what soil sits beneath it, and only an engineer's assessment can tell you for sure.

A bungalow's foundation was designed to carry one storey plus the roof. A second storey adds significant weight to the same footings and walls, so it's common for the original design not to have been intended for it. Age alone doesn't tell you the answer; the actual footing size, wall construction and soil do.

The way to find out is to have a structural engineer assess the house. That usually involves reviewing any original drawings, looking at the foundation walls and footings, and sometimes testing the concrete. Soil information matters too, and a geotechnical investigation may be recommended. Ask for written fee quotes for both before you commit; these costs are small compared with the risk of overloading a foundation.

Soil is a particular concern on clay. On filled ground, peat or sensitive clay, including Leda clay, the Building Code requires footing sizes to be engineered, so a house on those soils needs an engineer's numbers rather than assumptions about what the footings can carry.

If the foundation isn't adequate, there are reinforcement options. Underpinning pours new concrete beneath or beside existing footings to enlarge them. Piles installed alongside the footings can transfer load to deeper, stronger material. Interior posts, beams and new pads can take load off the walls. Older foundations of rubble stone or concrete block may need wall reinforcement as well as footing work. Which approach is right, and what it costs, depends on your house, so ask for an itemized structural line in every quote.

A second-storey addition needs a building permit, since structural alterations and one- and two-storey additions are on the City's permit list, and the design will need structural drawings. Both the owner and the contractor are responsible for making sure the permit is obtained. Renovators aren't licensed by the Home Construction Regulatory Authority the way new home builders are, so ask for written contract and warranty terms. Ask each contractor whether they have WSIB coverage or are exempt.

To compare contractors who have handled foundation assessments and second-storey work, browse the Ottawa Construction Network directory and get itemized quotes.

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Looking for experienced contractors? The Ottawa Construction Network connects homeowners with qualified professionals:

• 613Bins
• JC Carpentry
• Humble Homes - property maintenance
• ARTEXPRO Tile & Finishes
• Geerts Roofing Inc