Converting a basement into a rental suite is one of the most common renovation projects in the Lower Mainland, and plumbing is where most of the cost and most of the mistakes live. A full re-pipe of the basement is often the right answer, and it is worth understanding what that actually involves before you start.
What Changes When A Basement Becomes A Suite
A suite adds a kitchen, a bathroom and usually a laundry, all below the main house drains. The existing plumbing was designed for none of that. Drains may need to be cut into the slab to reach the new fixtures, venting has to be added for each of them, and the water supply needs to be sized for two households drawing at once.
The Sequence
- Layout and permit. Fixture locations set against the suite plan, and a plumbing permit pulled. Municipalities across the Lower Mainland inspect suite plumbing at rough-in and at final.
- Slab work. Concrete cut and removed along the drain routes, new drains laid to fall, and a backwater valve installed where the suite sits below the street sewer level, so a main-line backup does not come up through the new shower.
- Supply. New hot and cold lines to every fixture, with isolation valves so the suite can be shut off without shutting off the house. This is also the point at which Poly-B or galvanized piping in the rest of the basement gets replaced rather than tied into.
- Hot water. Either a second water heater for the suite, or the existing one replaced with a unit sized for the combined demand. Sharing an old forty-gallon tank between two households is the most common complaint we hear afterwards.
- Venting and rough-in inspection. Every fixture vented, the system pressure-tested, and inspected before the slab is patched and the walls are closed.
- Finish. Fixtures set, the laundry and dishwasher connected, and the final inspection booked.
The Things People Forget
A separate shutoff for the suite. A backwater valve. Sound insulation around drains that run under the main-floor living room. Access panels at the tub valve. Somewhere for the suite’s water heater to drain if it ever leaks. None of them are expensive at rough-in and all of them are expensive afterwards.
Before You Start
Confirm with your municipality that a suite is permitted on your lot, and choose the fixtures before the rough-in so the drains land where the cabinets and tub actually go. Then get a written scope that covers the whole sequence above, not just the visible plumbing.
Related: mechanical renovations · a basement suite conversion
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