In Dundas, Two Heritage Districts and the Spencer Creek Floodplain Decide What Your House Can Take

Heritage districts, century homes and what a heritage permit means

Dundas has 97 individually designated properties, most of them inside the Cross-Melville Heritage Conservation District, which the former Town of Dundas designated in 1990 under By-law 3899-90. On 13 May 2026 Hamilton Council passed By-law 26-090 designating a second district, Melville-Park West: 331 properties generally bounded by Sydenham Street to the east, Park Street West to the south, Brock Street South to the west and Victoria and Melville Streets to the north. The district plan describes a concentration of building stock from 1880 to 1930, one to two-and-a-half storeys, clad in brick, stone and stucco: Late Victorian, Edwardian Classicism and cottages.

Inside either district, any exterior alteration, construction or demolition needs a heritage permit under Part V of the Ontario Heritage Act. There is no application fee, but the City will not issue a building permit on a designated property until the heritage permit is approved. Interiors are not regulated, which is why a basement suite itself is usually unaffected; the plan's note is that structural interventions, and interior work with an exterior presence such as new windows and doors, do need a permit.

For a separate entrance that matters directly. The Melville-Park West plan says new entrances and exterior staircases should go on secondary elevations, set back from the front, and additions are not permitted on the front façade and may not raise the ridge above the original. Single-storey rear porches and decks out of view of the street are exempt from the heritage permit, as is replacing non-historic windows and doors in the same size. Everything else is confirmed with Heritage Planning staff before work starts.

Hamilton's ADU rules on a Dundas lot

Dundas is zoned under Hamilton's Zoning By-law 05-200, and the additional dwelling unit rules are in Section 4.33 (office consolidation dated August 2026, last amended by By-law 25-075 on 16 April 2025). A single detached dwelling may contain up to two additional dwelling units, each half of a semi and each street townhouse may contain up to two, and a lot may also carry one detached ADU, to a maximum of four dwelling units on the lot; none of this applies in rural or open-space zones. A detached ADU sits in the rear or interior side yard, 1.2 metres from the side and rear lot lines and 4.0 metres from the house, no taller than 6.0 metres, no larger than 75 square metres or the floor area of the house, whichever is less, with combined lot coverage capped at 45 per cent and an unobstructed path at least 1.0 metre wide and 2.1 metres clear from the street to its door.

The full breakdown, including how the City reviews a three- or four-unit house differently from a two-unit one, is on our Hamilton page. What is Dundas-specific is the overlay: the City's own ADU page warns that a property may also need Conservation Authority or Heritage approvals, and in Dundas both are common. The Melville-Park West plan states that additional units in existing dwellings and sympathetic detached ADUs are the preferred means of intensification in the district, so a legal basement apartment is welcome there; it is the exterior that gets reviewed.

Permits, fees and the applicable-law gate

Hamilton takes building permit applications online through my.hamilton.ca. Under Building Permit By-law 15-058 the fee for an additional dwelling unit in an existing house is a flat $515, a detached ADU in the rear yard is a flat $1,030, finishing a basement is $4.06 per square metre, and a deck, open porch or exterior stair is $5.36 per square metre, all against a $291 minimum. The City lists a walkout basement, underpinning to gain a full basement, waterproofing foundation walls, replacing weeping tile and creating or enlarging door and window openings as permit work, so an egress window or a new stairwell in a century foundation is never a side job.

Ontario collects no development charges on a second unit in an existing house. Hamilton's ADU process runs through the building permit, and the City's Municipal Addressing By-law requires you to apply for and post a unit address, for a fee. Hamilton's rental housing licence currently applies only in Wards 1, 8 and parts of Ward 14.

The step that catches Dundas owners is applicable law. Before a building permit can issue, other approvals must be in hand, and Hamilton names the heritage permit, the Hamilton Conservation Authority and the Niagara Escarpment Commission among them. For a single-family house with an ADU you do not file the applicable-law checklist; staff tell you what applies. Our approach is to answer those questions before we draw, not after the City asks.

Spencer Creek, the two-zone floodplain and the escarpment

Growth in Dundas in the 1950s led residents to petition for the Spencer Creek Conservation Authority, founded in 1958 and now the Hamilton Conservation Authority. Since 1 April 2024 HCA permits are issued under Ontario Regulation 41/24. The regulated area takes in floodplains, watercourses, wetlands and 30 metres around them, river and stream valleys measured from the stable top of bank plus 15 metres, steep slopes including sections of the Niagara Escarpment, and Dundas Valley lands. Construction, additions and any change to a building's use or size inside it need HCA approval before the City will issue a building permit. HCA's Regulated Areas Map Tool is where we check an address first.

Dundas is the exception to HCA's one-zone floodplain approach. Because homes were built along Spencer, Sydenham and Ann Creeks before provincial flood policy existed, an October 2000 assessment created four Special Policy Areas managed as two zones, floodway and flood fringe, under Urban Hamilton Official Plan policies UD-1 to UD-3. The floodway stays free of structures and fill. In the flood fringe, residential development is possible with fill to the flood limit; in the UD-3 area, everything must be floodproofed to the regulatory flood elevation, mechanical equipment goes above it, a minor renovation or addition may not put a floor below the existing ground floor, and no habitable room may be in a basement or cellar. HCA's own 2025 policies add that a minor addition in a floodplain may not establish an additional dwelling unit or include a basement. On those lots we talk about a main-floor or detached unit, not a basement suite.

Above the valley walls, the Niagara Escarpment Commission's interactive map shows whether a property sits in its Area of Development Control, where a development permit, which the NEC calls similar to a building permit, is needed for new dwellings and for additions that exceed the NEC's exemption limits, while renovations that do not increase size, height or use are exempt.

How HMH sequences a Dundas job

HMH Construction is a licensed, WSIB-covered residential general contractor with offices in Mississauga and Milton. In Dundas the order of operations is set by the overlays, so we run three checks before we quote: the City's heritage mapping to see whether the house is designated or inside Cross-Melville or Melville-Park West, HCA's map tool for the regulated area and the two-zone floodplain, and the NEC map for escarpment lands. Only then do we open the interactive zoning map and read Section 4.33 against the lot.

The separate basement entrance is our specialty: engineering, permit, excavation, forming and pouring the stairwell, door and sill, waterproofing, back-grading and the drain tie-in, with the site work done in three days. On a district property we design it on a secondary elevation, set back from the front, with a heritage permit filed ahead of the building permit, because the City will not issue the second until the first is approved. In a 1880 to 1930 house that usually also means underpinning or a new footing, a permit item in its own right, and a 1,950-millimetre finished ceiling checked at the lowest duct before anyone commits.

Behind the entrance we design, permit and build the legal basement apartment to the Building Code's 30-minute fire separation and egress rules, and we build detached garden suites to the 75-square-metre, 6.0-metre standard, along with garage conversions and multi-unit conversions. We also do kitchens, bathrooms, finished basements, whole-home renovations, home and second-storey additions, quartz countertops and commercial fit-outs. Call 905-749-4608 for a straight read on your lot.