In Erin the Second Unit Question Starts at the Septic Tank, Not the Basement

Yes, if the septic system can prove it can carry both units. Zoning By-law 07-67 permits additional residential units only where adequate water and sanitary servicing is available to the Town's satisfaction, and where municipal services are not available you must provide proof that the private water and sewage services can accommodate the primary unit and the additional unit. In practice the Town's permit guides require a qualified designer's letter stating the existing septic system's capacity and condition. If it falls short, a new or altered system is a separate septic permit.

The plant is commissioning, but existing homes are not connecting yet. The Town's 1 September 2026 update says the Water Resource Recovery Facility started its first phase of commissioning on 8 July 2026 and the Erin Village pumping station finished commissioning on 13 August 2026. The Town's FAQ states that new developments connect immediately as the system is built, while the timing for existing properties inside the urban boundary depends on funding from higher levels of government. A sewer connection by-law covering who must connect and what it costs is still being developed.

Two. Section 4.1 of the zoning by-law allows a maximum of two additional residential dwelling units on a lot, either one inside the house and one in a separate building, or two inside the house. Each unit is capped at two bedrooms and at 50 per cent of the primary unit's floor area up to 130 square metres, except that a unit located in the basement may occupy the entire basement. Both units need adequate servicing, one parking space each, and a lot that fronts on an open, municipally maintained street.

Yes. The Town requires a building permit before starting new construction or renovation projects, and its 2026 fee schedule prices finishing a basement within a single-family dwelling at a flat $550, with plumbing at $330 and a new or enlarged door or window opening at $330 as separate line items. Applications go through Cloudpermit, and construction must start within six months of issuance. If the finished basement is really a future apartment, permit it as a secondary dwelling unit from the start rather than converting later.

Under Fees and Charges By-law 26-01, passed 22 January 2026, a new secondary dwelling unit within an existing house or building is $1,790 or $7.70 per square metre, whichever is higher. A below-grade entrance is $330 or $3.55 per square metre. An addition, alteration or renovation is $2,672 or $11.50 per square metre. If a septic evaluation is needed the fee is $330, and a new septic system permit is $825. All fees are invoiced after the Town reviews the application and are payable before the permit is processed.

Yes. Section 4.1.2 of the zoning by-law says each dwelling unit shall have a separate, private entrance, which is stricter than the Building Code's option of a shared, fire-separated exit. Exterior alterations for the unit go to the rear or side of the house unless you are converting an existing garage. The Town prices a below-grade entrance as its own permit item and wants it, with any window wells, on the site plan. HMH builds the separate entrance with the site work done in three days.

Often, but the conservation authority decides first. Erin is split between Credit Valley Conservation and the Grand River Conservation Authority, the Town asks you to check both regulation maps before applying, and agency approval is required before a building permit is issued. The zoning by-law also prohibits any additional residential unit within hazardous lands identified by the conservation authority. Under the Conservation Authorities Act the authority reviews and decides on its own permit first, and that permit still does not let you start before the building permit is issued.

Yes, as a detached additional residential unit. It must sit on the same lot within 40 metres of the house but at least 3 metres from it, in the interior side, exterior or rear yard while meeting the zone's yard standards, screened to the Town's satisfaction, no taller than the house and within the 4.5-metre accessory-building height limit. All accessory buildings together are capped at 10 per cent of the lot, with 116 square metres of ground floor on lots of 0.8 hectares or less. On septic, it needs the same servicing proof as an inside unit.