What are the NB Building Code requirements for garage floor drains in Bathurst?

The NB Building Code does not require floor drains in residential garages, and in fact many municipalities in New Brunswick — including Bathurst — discourage or restrict garage floor drains because of concerns about contaminated water (oil, gasoline, road salt, antifreeze) entering the municipal sewer system or the environment. If you want a floor drain in your Bathurst garage, you need to check with the city's building and plumbing inspection departments to determine whether it is permitted and what conditions apply.

The standard approach for residential garage drainage in NB is to slope the garage floor toward the overhead door rather than toward an interior drain. A slope of approximately 1/8 inch per foot (about 1%) toward the door opening is sufficient to direct snowmelt, rainwater tracked in by vehicles, and wash water toward the driveway and away from the garage interior. This eliminates the need for a floor drain entirely and avoids the plumbing and regulatory complications that come with one.

If you do want a floor drain in your Bathurst garage, there are several requirements and considerations. First, any plumbing work — including floor drain installation — requires a separate plumbing permit in NB, independent of the building permit and electrical permit. The drain must be installed by a licensed plumber. Second, the drain must include a P-trap to prevent sewer gas from entering the garage. In NB's cold climate, P-traps in unheated or intermittently heated garages can freeze and crack during winter — this is a real concern in Bathurst, which experiences some of the coldest temperatures in southern NB and the full force of northern Maritime winters. A frozen P-trap also loses its water seal, allowing sewer gas to enter the garage. If your garage will not be consistently heated, a floor drain with a P-trap may not be practical.

Third, where the drain connects matters enormously. A garage floor drain cannot simply discharge onto the ground surface or into a ditch — this would release oil, antifreeze, and road salt directly into the environment, violating New Brunswick's environmental regulations. If your property is connected to a municipal sanitary sewer, the drain may be permitted to connect to it, but many municipalities require an oil-water separator (also called an oil interceptor) between the garage drain and the sewer connection. An oil-water separator traps petroleum products and prevents them from entering the sewer system. These devices cost $500 to $2,000 for a residential unit and require periodic maintenance (cleaning out accumulated oil and sediment). If your property uses a private septic system, connecting a garage floor drain to it is generally prohibited because petroleum products and road chemicals will damage the septic field and contaminate groundwater.

Fourth, consider whether you actually need a floor drain or whether there is a simpler solution to the problem you are trying to solve. If your concern is snowmelt and water from vehicles in winter, the sloped floor toward the overhead door handles this effectively. If your concern is washing the garage floor, a squeegee and the sloped floor direct wash water out the door. If you want to wash vehicles inside the garage, that is where a floor drain becomes genuinely useful — but in Bathurst's climate, most vehicle washing happens at commercial car washes during winter months anyway.

For a heated garage or workshop in Bathurst where a floor drain is practical, here is the typical installation. The drain is set into the concrete slab during the pour — it cannot easily be added after the slab is cured. The slab is sloped from all directions toward the drain location at approximately 1/8 to 1/4 inch per foot. The drain connects through a P-trap (installed below the slab, within or below the frost wall) to either the sanitary sewer with an oil-water separator, or to a dedicated holding tank. The total cost for a floor drain installation including the plumbing, slab modification, and any required separator typically adds $1,500 to $4,000 to the garage construction cost.

Before making a decision, discuss your drainage needs with your garage contractor and with Bathurst's building inspection department. They can advise you on what is permitted in your specific situation and whether a floor drain is worth the added cost and complexity. Browse garage builders in your area through the New Brunswick Construction Network directory at newbrunswickconstructionnetwork.com.