They’re usually hidden, done quickly in those early and heady days of new construction, but the footings upon which your new home rests are among the most critical of building elements.
Footings need to be set on undisturbed soil, or – as needs be – on compacted, clean, well-draining fill. They also need to be below the depth of frost, which is 1.2 metres or 4’, in general. Those who have rocky building sites may be able to set frost walls directly onto rock – call our inspectors to make sure, however.
A basic one-storey wood-frame home demands a minimum footing width of 25 cm, or just about 10 inches. That’s pretty scant, and most builders will go well beyond that, which we don’t mind: remember, Code is the bare minimum acceptable, and nothing stops a builder from going above and beyond.
We didn’t see large footings required for residential builds, because the above width was good for spans of up to 16 feet (4.9 metres). However, with the growing popularity of engineered trusses, we’ve started seeing homes with open joist spans of 25, 30, even 35 feet: the greater the joist span, the wider the footing must be.
For example, a one-storey stick home with a 25-foot joist span will require a 15 1/2” footing. A 30-foot span would need 18 1/2” footings.
Add another storey on to a build, and the demands on footings increase: a 25-foot joist span on a two-storey home will demand a footing of just more than 21 inches.
ICF (insulated concrete form) houses also require heavier footings, as does brick fascia.
Confused? Don’t be. Our inspectors are trained to calculate these numbers for you as part of the plans review we do on each new home build or addition sent our way. It’s one of the many reasons why (apart from the fact it’s the law) that you need to obtain a permit.