Turning Your Basement Into Income: Cost & Permits for a Secondary Suite

LUMA Build Design
Jul 6
5 min read

Finished basement secondary suite with separate entrance in an Elora home by LUMA Build Design

For a lot of homeowners in Fergus and Elora, the basement is the biggest underused asset in the house — a cold, half-finished space holding storage bins and a furnace. Turned into a legal secondary suite, that same square footage can bring in rent that offsets a real chunk of the mortgage, or give a parent or adult child a private place to live. Here is what that actually costs in Centre Wellington in 2026, what the permit process looks like, and how to tell whether your basement is a good candidate.

What a basement secondary suite costs in Centre Wellington

There is a big difference between simply finishing a basement and building a legal secondary suite, and the cost reflects it. A basic finish — rec room, maybe a bedroom and a bathroom — sits at the lower end. A full legal basement apartment, with its own entrance, kitchen, bathroom, egress and fire separation, is a bigger build. 2026 Pricing Guide

Legal basement secondary suite: from around $100,000 - $150,000, depending on scope and finishes
Existing Updates: These can be from $35,000 - $80,000

These prices all depend on scale of the project. We need to physical come see your location to give you an accurate cost breakdown.

What drives the cost

A legal suite versus a simple finish

A rec-room finish is mostly framing, insulation, drywall, flooring and lighting. A legal suite adds a full kitchen, a second bathroom, a separate entrance, an egress window, fire separation between units and proper sound control. Each of those is its own line item, which is why a suite lands well above a basic finish.

The separate entrance and egress

A legal apartment needs its own way in and a code-compliant way out. If your basement does not already have a side or rear entrance, cutting one in — excavating, building a stairwell and weatherproofing it — is a significant part of the budget. Bedrooms also need an egress window sized to code, which often means enlarging an existing opening and adding a window well.

Kitchen, bathroom and plumbing

Adding a kitchen and a bathroom below grade means new supply and drain lines, and sometimes a grinder or sewage-ejector pump if the basement sits below the municipal sewer line. That plumbing work is one of the bigger unknowns until we see the space.

Fire separation and soundproofing

Separating a suite from the main home to code — fire-rated ceilings and walls, proper doors, and sound insulation so neither household hears the other — is required for a legal unit and adds real material and labour.

Ceiling height

Low ceilings limit how finished the space feels and, in some cases, whether it can be a legal living space at all. Lowering the floor through underpinning solves it, but as noted above that is a $50,000-and-up scope on its own. It is worth discussing only for the right project.

Separate side entrance to a basement apartment in a Fergus Ontario home

The income side: what you can realistically expect

A basement apartment is one of the highest-return projects available to an Ontario homeowner. Rental income from a legal suite can offset a significant portion of monthly mortgage costs, and a properly permitted unit adds resale value in a way an unpermitted one never will. For multi-generational families, the math is different but just as strong: a parent who sells their own home and moves into a suite frees up capital while keeping family close.

ROI for your basement renovation depends on the scale but even a small upgrade can add serious value. Let's talk about rentals, the average rental in Centre Wellington earns $1,379 a month up 6.7% (CMHC) That alone is a great opportunity to earn income on your home.

how about Resell? That's where things can get interesting. Let's say you build a secondary suite in your basement so kitchen, bathroom, bedrooms everything adds extra space for either a rental or a family to have space to grow. These can go for $50,000 - $100,000 more then a identical home.

So yes it's absolutely worth the upgrade!

A real Centre Wellington basement suite

Here's an example that we see time over time. A couple in Elora consider moving to a new home as they find themselves in need of space for there children.

The issue? No finished basement and it's simply being used for storage.

The Solution

Adding usable space and giving them nearly 800 extra sq ft plus a added bedroom. Saving them thousands to move and upgrade and continue to stay in the home they loved!

What we can add. The opportunities to upgrade your basement are limitless check out this Elmira upgraded basement with a secondary suite kitchen, bathroom and bedrooms.

Permits and the Ontario Building Code

A legal basement suite almost always requires a building permit. Permits confirm the work meets the Ontario Building Code for egress, fire separation, electrical and plumbing — the things that keep the unit safe and insurable. Skipping permits is a costly mistake: unpermitted suites get flagged by inspectors and lawyers at resale, and buyers may demand remediation or a price cut.

The good news is that many Wellington County municipalities now permit secondary suites as-of-right on residential properties, in line with Ontario's push to add housing. At LUMA we pull all required permits and handle inspections as part of the process — you do not deal with the township yourself. Permit processing in Wellington County currently runs about 4 to 10 weeks, which we build into the schedule from the start.

How long does it take?

A standard basement finish typically runs 8 to 14 weeks from permit to completion. A full legal suite — with a new entrance, kitchen, bathroom and fire separation — takes longer, and projects needing waterproofing, underpinning or structural work longer still. The two most common sources of delay are municipal permit processing and mid-project product-selection decisions, which is why we lock finishes in during planning.

Is your basement a good candidate?

Ceiling height: enough headroom to finish comfortably without underpinning is a big head start.
Moisture: a dry basement, or one that can be properly waterproofed, is essential before any finishing.
Entrance potential: a spot where a separate side or rear entrance can be added cleanly.
Mechanicals: room to separate or relocate the furnace, panel and water heater so the suite is self-contained.

How we price it before you commit

Every basement is different, so the first step is always a site visit. We look at ceiling height, moisture, the mechanicals and where an entrance could go, then put together a realistic scope and a ballpark you can actually plan around — before you commit to anything. If something unexpected turns up, you hear about it first. A detailed quote comes before work begins, and any change is a direct conversation, not a surprise on the invoice.

As a family-owned company based in Fergus and Elora, we have spent over 20 years building across Centre Wellington, and basement suites are one of the projects we are doing most right now. We handle design, permits, all trades and final inspection, so you have one team from first visit to finished, rentable space.

Thinking about a basement suite?

Whether you are picturing a rental that helps with the mortgage or a private space for family, the place to start is a free consultation. We will tell you honestly whether your basement is a strong candidate and what it would realistically cost. Reach out to LUMA Build Design to book a site visit across Fergus, Elora, Elmira and Centre Wellington.