Commercial additions and new storeys in Toronto, designed for permit.

Yes, if the whole building stays within three storeys and 600 m² of gross area once the storey is added, and no part of it is a restaurant, bar or other place of assembly. Two existing floors of 200 m² plus a new 200 m² storey come to exactly 600 m², which is still within the limit. Anything more, or a fourth storey, and the Architects Act calls for an architect and an engineer, who also carry out the general review (the designer's site reviews during construction) that the Building Code then requires. A professional engineer designs the structure either way. The zoning height and storey limits have to allow it too.

No. The Architects Act (and the Building Code's table for the designer's site reviews) counts every floor above grade, measured to the outside of the exterior walls. The Code's Part 9 test uses only the largest floor. The zoning by-law's gross floor area counts floors above and below ground (800.50(320)), and in a CR zone it then subtracts areas such as below-ground parking, basement storage and mechanical rooms, elevator shafts and exit stairs before the floor space index is worked out (40.5.40.40). The site plan exemption's 600 m² is different again: it is the addition alone, measured as zoning gross floor area, and must be under 600 m². A building can pass one test and fail another, so all of them are worked out at the size check.

Not if it is under 600 m² on its own, kept out of the front yard and free of the uses the by-law lists. Two cautions. The exemption does not cover a use the zoning permits only with conditions, and in the CR zone the by-law lists retail stores and eating establishments that way (40.10.20.20), so don't assume a shop addition is exempt until the City confirms it. (A building with apartments follows a separate test, in which a retail store is allowed.) And the City can still require site plan approval near a rail line or a valley, or for access, safety or a road or laneway widening.

A professional engineer. Our BCIN classes don't include structural design for commercial buildings, and even in small buildings the Building Code requires an engineer to design any underpinning, or a foundation dug below a neighbouring building's footings and close enough to disturb the soil under them (within the soil's angle of repose, drawn from the bottom of those footings; Division C, Article 1.2.1.2). The engineer's drawings and ours go to the City as one coordinated set.

It depends on each wall's limiting distance: its distance to the property line, or to the centre line of the street or lane it faces. Under Part 9 of the Building Code, a wall less than 1.2 m from that line can have no unprotected openings (glazing or openings that aren't fire-rated). Farther away, the share allowed rises with distance and falls as the wall gets bigger, and a shop is allowed about half what an office is (9.10.14.4). A sprinklered building, or glazing of wired glass in steel frames or glass block, may have up to twice as much, and a storey at street level facing a street, with a limiting distance of at least 9 m, isn't limited. The wall is measured from the ground to the ceiling of the top storey, so a new storey can change the numbers for the windows below it, unless the floors are fire separations rated at least 45 minutes, which lets each storey be counted on its own (9.10.14.2).

Toronto charges non-residential development charges (a City charge on new development, paid once) only on non-residential floor area on the ground floor, at $805.64 per m² (the rate in effect since June 26, 2025), payable when the building permit is issued. A ground-floor addition is charged on its area. Read as written, a storey above the ground floor adds no ground-floor area. The City also collects the Toronto Catholic District School Board's education development charge on non-residential gross floor area: $1.67 per sq ft until December 2, 2026 and $1.77 from December 3, 2026. The City's page doesn't limit that one to the ground floor, so ask the City whether either charge applies to your addition before you budget.

It can mean loading and bicycle parking. A shop or personal service shop needs no loading space under 500 m² of gross floor area and one Type B space (11.0 m by 3.5 m, 4.0 m clear, or 4.4 m in Policy Area 1 where the building has no apartments) from 500 m²; an office needs one Type B from 500 m² too. An addition must provide any loading space it adds or get a minor variance, though in a CR zone under Development Standard Set 2 or 4 (SS2 or SS4 in the zone label), a lot with a lot area under 1,000 m² is exempt (220.5.200.40). Under Zoning By-law 569-2013 an addition must also meet Chapter 230's bicycle parking requirement (and, where required, shower, change and bicycle maintenance facilities) unless a minor variance authorizes otherwise (230.5.10.11). Car parking for these uses has maximums, not minimums, under Zoning By-law 569-2013 (accessible spaces aside), but an existing building's lawful number of spaces may not be reduced (200.5.10.11), which matters if the addition goes over the parking lot.

Then the storey needs a minor variance from the Committee of Adjustment, which may authorize one only if it finds the variance minor, desirable for the appropriate development or use of the land, and in keeping with the general intent of the zoning by-law and the Official Plan (Planning Act, s. 45(1)). A height increase too large to count as minor needs a zoning by-law amendment (a rezoning) instead. The size check and zoning review tell you which before any design work.