Blog · Kitchener
How Much Headroom Does a Basement Unit Need in Kitchener, and How Do You Get It?
Kitchener now permits up to four dwelling units on many residential lots, and for most owners the basement is the first place to look. The question that decides whether a basement unit is simple or structural is usually headroom.
Last updated September 25, 2026 · Reviewed by the Kitchener Foundation Repair team
The City of Kitchener's guide to additional dwelling units says that since March 2024 up to four units are permitted on many residential lots, in all RES-1 to RES-5 zones, subject to lot size, setbacks and parking rules. A building permit must be issued before construction starts, and for some unit types the drawings must be prepared by a qualified (BCIN) designer or an architect. None of that is about foundations. But when the planned unit is in the basement, the first practical hurdle is often the height between the floor and the ceiling.
What height the code asks for
Municipal homeowner guides summarizing the 2024 Ontario Building Code for secondary suites list a clear ceiling height of 1.95 m in the unit, with 1.85 m permitted under beams and ducts. The designer preparing your permit drawings confirms which requirement applies to your house and which rooms it applies to, but those two figures are the ones most Kitchener basement conversions are checked against.
Those numbers are finished heights. A basement that measures just over 1.95 m from bare concrete to the bottom of the floor joists will not have 1.95 m once there is flooring, a ceiling finish, insulation and the fire separation drywall the unit needs between floors. Ducts and drain pipes hanging below the joists take away more.
How to measure what you have
- Measure from the top of the basement slab to the underside of the floor joists in several places. Slabs in older houses are rarely flat.
- Measure to the underside of the main beam and any bulkheads for ducts and plumbing.
- Subtract allowances for the new floor build-up and the ceiling finish. Your designer can tell you what those are for your plan.
- Note where the low points are. A basement that is short only under one beam is a different job from one that is short everywhere.
In many of the 1960s to 80s houses in Forest Heights, Stanley Park and Country Hills, the numbers come out close enough that moving ducts or reframing a bulkhead solves it. In older houses downtown and in Cedar Hill, and in stone or block basements that were never meant to be lived in, the floor usually has to go down.
Two ways to lower a basement floor
Underpinning. The existing foundation walls are extended downward in short, alternating sections. Soil is excavated under the old footing one segment at a time, a new, deeper footing and wall section is poured, and the process moves along the wall so the house is never unsupported over a long run. The result is full-height walls and the full floor area. It is engineered work, done in a set sequence, and it is how most basement lowering in older Kitchener houses is done. See underpinning and basement lowering.
Bench footing. Instead of going under the existing footing, a concrete bench is poured inside the basement along the base of the wall, stepping in from it, and the floor in the middle is dug down. The existing footing is not disturbed. It is generally less involved than underpinning, but the bench takes floor space all the way around the room, which matters in a small basement where every metre of floor is part of the unit.
Which one fits depends on the size of the basement, the condition of the walls, how much depth is needed, the soil and the water table. An engineer designs either one, and the design goes with the permit application.
Things that change when the floor goes down
- Drainage. A new, lower slab sits closer to groundwater. New weeping tile and a sump are commonly part of the job, and they are planned with it rather than added later.
- The sewer connection. Floor drains and any basement plumbing end up lower relative to the sewer line, which the plumbing design has to account for.
- Old walls. Stone and block walls may need repair before they are underpinned. Lowering a failing wall only moves the problem down.
- Neighbours. On semi-detached houses and tight downtown lots, underpinning a shared or close wall needs extra planning, and the engineer looks at the adjoining structure.
Order of operations
- Measure the existing heights and decide what the unit needs.
- Have the foundation contractor measure the walls, slab and footing depth, and dig a test pit if the footing or soil is unknown.
- Engineer designs the lowering method; the designer prepares the unit drawings.
- Building permit issued, then the structural work, then the unit build-out.
Owners in neighbouring cities go through a similar process with their own city; the foundation contractor also works in Waterloo and Cambridge. For how underpinning and bench footings are priced, see the Kitchener foundation repair cost guide. To have the basement measured before you commit to a unit plan, book a visit.