Garden Suite Cost Calculator Ontario (2026)
Pick your region, size, build type, foundation and services, and the calculator gives you a low and high number for every line a real quote should have, plus soft costs and a 10% contingency. A typical one-bedroom garden suite in Ontario runs about $185,000 to $235,000 all-in in 2026. The building is only part of that. The rest is in the ground.
Default example
Before HST. A starting point for a budget conversation, not a quote. Your lot decides the rest.
A 500 sq ft one-storey, one-bedroom garden suite on city services in Simcoe County works out to about $185,000 to $236,000 all-in in 2026, before HST. That covers the building, foundation, water, sewer and hydro from the house, drawings, permit, survey, heat loss design and a 10% contingency. Toronto runs roughly 20% higher. Rural septic work can add $15,000 to $55,000 on top.
Garden Suite Cost Calculator
Everything updates as you change it. Nothing is saved or sent anywhere.
Total all-in range (before HST)
See the soft cost line items
Per-square-foot check
Ranges are our estimates in 2026 dollars, before HST, for a suite built by a contractor to the Ontario Building Code. They do not include a minor variance, tree removal, rock blasting, a deck, furniture or financing costs. Bands: about $340 to $490 per sq ft all-in for Simcoe County and most of Ontario outside Toronto, about $420 to $575+ in Toronto and the inner suburbs.
What Is In a Garden Suite Quote, and what usually is not
Two quotes can be $80,000 apart and both be honest. One prices the suite. The other prices the suite plus the hole, the pipe, the hydro, the paperwork and the cleanup. Here is how to tell which one you are holding.
| Item | Usually in the builder’s price? | Calculator line |
|---|---|---|
| Walls, roof, windows, doors, insulation, drywall | Yes | Construction shell and finishes |
| Kitchen, bathroom, flooring, paint, trim | Yes, often as allowances. Read the allowance numbers, they are where the extras come from | Construction shell and finishes |
| Heat pump, ventilation, electrical inside the suite | Yes on a custom build; sometimes “by others” on a kit | Construction shell and finishes |
| Foundation | Custom: yes. Prefab and kit: usually not | Foundation |
| Water, sewer and hydro trench from the house | Often excluded, or shown as a small “allowance” | Servicing |
| Panel or service upgrade at the house | Often missed entirely | Servicing |
| Sewage pump if the suite sits too low to drain | Only if someone checked the fall | Servicing (watch for the warning) |
| Septic capacity check, upgrade or new system | Almost never in a prefab or kit price | Septic, plus septic design in soft costs |
| Crane, delivery, escort | Prefab: often extra. Freight on kits is usually quoted separately | Crane |
| Drawings, building permit, survey, heat loss design | Sometimes. Ask in writing | Soft costs |
| Sod, fence, interlock and garden repair on the trench line | Rarely, beyond rough grading | Servicing (a modest allowance only) |
| HST at 13% | Often shown separately at the bottom | Not included |
| Development charges | Not a builder item. Usually exempt for a qualifying additional unit, but confirm with your town | Not included |
| Deck, walkway, window coverings, furniture | No | Not included |
Last checked October 2026 · Sources: servicing cost guide, kit pricing guide, development charges guide
The HST line deserves its own sentence. On a $280,000 contract, 13% is $36,400, which is more than most foundations. Ask every builder whether their number is “plus HST” or “HST in”, and if the suite will be rented to someone outside the family, read our page on HST on a rental garden suite before you sign anything.
Already holding a quote?
Upload it and get a 60-minute plan or quote review with a builder for $249.99 + HST. We mark up what is missing, what is padded and what will turn into an extra.
Where Garden Suite Budgets Go Sideways
We have been building in Ontario since 1979. The building itself rarely blows the budget. The surprises are almost always outside the walls.
The trench nobody priced
A short city run under 15 m is about $12,000 to $25,000. Go past 30 m and it is $25,000 to $45,000. Add a 100 amp to 200 amp panel upgrade at the house for $3,000 to $10,000 and the “cheap” suite is not cheap any more.
The septic that was “probably fine”
A second unit adds bedrooms and daily flow. If the existing system has room, tying in runs about $3,000 to $8,000. If it does not, an upgrade is $15,000 to $45,000+, and an advanced treatment unit $35,000 to $55,000+.
The kit price that is a box of parts
A modular price that says “from $96,244” became $137,244 in our kit guide using only the low end of each add-on, before delivery, HVAC design or a deck. The high ends put it near $174,000.
The crane and the hydro wires
No side-yard access means lifting the suite over the house, about $5,000 to $12,000 for a day. Overhead lines, a narrow street or a soft lawn can mean a bigger crane, a road permit or a second day.
The floor that sits too low
If the suite floor is lower than the house drain, sewage will not flow uphill no matter how nicely you ask. A sewage ejector or grinder pump is roughly $4,000 to $9,000 installed, plus power and an alarm.
Finish creep
Every upgrade is only $1,500. There are forty of them. Pick the finish level before drawings start, and move items between rooms instead of adding new ones.
Rules of thumb before you trust any number
- Price the ground before the building. Servicing, septic and foundation decide whether you are at the low end or the high end.
- Treat any “from” price as the floor of the shell, not the floor of the project.
- Small suites cost more per square foot, not less. A 400 sq ft suite still needs a full kitchen, a bathroom, a permit and the same trench as a 700 sq ft one.
- Keep the 10% contingency until the drywall is up. Below grade is where the surprises live, and you do not see below grade until it is dug.
- On a rural lot, get the septic answer before you design. The bed location can decide where the suite is allowed to go.
How We Built This Calculator
No black box. Here is what each line is based on, so you can argue with it properly.
| Line | Simcoe baseline | What moves it |
|---|---|---|
| Construction shell and finishes | $260 to $285 per sq ft at 600 sq ft, custom stick frame, mid finish | Size (smaller costs more per sq ft), build type (ICF x1.07, prefab x0.92, kit x0.88), finish (basic x0.88, high x1.22), 2 storeys x1.05 |
| Foundation | Slab $15,000–$25,000; frost wall $25,000–$45,000; ICF frost wall $28,000–$50,000; piles $8,000–$15,000; basement $55,000–$95,000 | Footprint. A 2-storey suite has half the footprint, so a smaller foundation |
| Servicing, city | About $15,000–$33,000 at 20 m | Distance, roughly $300 to $650 per extra metre, plus utility fees, panel work and modest restoration |
| Servicing, rural | About $13,000–$27,000 at 20 m | Distance. Water from the well, hydro, and pipe to the septic, but no city sewer tie-in |
| Septic | OK $3,000–$8,000; upgrade $15,000–$45,000; treatment unit $35,000–$55,000 | Tank and bed size, soil, lot size, how many bedrooms the property ends up with |
| Crane | $5,000–$12,000 | Reach, crane size, road permits |
| Soft costs | About $4,800–$12,000 | Drawings, permit fee by area, survey, heat loss design, zoning review and registration; septic design and permit on rural upgrades |
| Contingency | 10% of everything above | Nothing. Keep it |
Last checked October 2026 · Sources: foundation options guide, servicing cost guide, kit pricing guide, City of Toronto new garden suite permit guide
The regional multipliers are our own builder estimates, not a government index. Toronto at x1.22 reflects the gap between the $340 to $490 per sq ft we see in most of Ontario and the $420 to $575+ we see in Toronto and the inner suburbs. Cottage country and Northern Ontario carry travel time, freight and shorter trade lists. If your local builder laughs at the multiplier, ask them why, and you will learn a lot about their pricing.
If you are building in Simcoe County or around Georgian Bay, the baseline is our own backyard. ICFhome.ca builds garden suites here, and Georgian Bay Siteworks handles the trenching and servicing side.
How to Tighten Your Number
A calculator range is wide because it does not know your lot. Every step below takes a chunk out of the gap between low and high.
Check what your town allows
Size caps, height limits and setbacks decide whether the suite you just priced is even legal. The free Rules Checker takes a few minutes.
Get the $399 + HST Feasibility Report
We look at your actual lot: zoning, setbacks on your survey, servicing distance and fall, panel size, fire access and septic flags, with a ballpark budget, in 48 hours. The $399 + HST is credited toward permit plans or a build. Order the report.
Get drawings everyone can price
Builders cannot quote a sketch the same way twice. Our Permit Packages start at $1,499.99 + HST and give every builder the same set to price.
Get two quotes, then a second opinion
Put both quotes side by side against the table above. Then book a Talk to a Builder call, 30 minutes for $149.99 + HST or a 60-minute quote review for $249.99 + HST.
Run the return side
Cost is half the story. Put your number into the Rental ROI Calculator to see cash flow, yield and payback, and check the grants directory for local money.
Turn the range into a real number for your lot.
Send your address and survey. In 48 hours you get the rules, the servicing picture, the foundation we would use and a ballpark budget, with the $399 + HST credited toward plans or a build.
Garden Suite Cost Questions We Get Every Week
How much does a garden suite cost in Ontario in 2026?
A typical one-bedroom garden suite of about 500 to 650 sq ft costs roughly $185,000 to $235,000 all-in in 2026, including foundation, servicing, permits and finishes. That works out to about $340 to $490 per sq ft in Simcoe County and most of Ontario outside Toronto, and about $420 to $575 or more per sq ft in Toronto and the inner suburbs. Rural lots needing septic work cost more.
How accurate is a garden suite cost calculator?
Good enough to decide whether to keep going, not good enough to sign a contract. The building line is fairly tight. Servicing, septic and foundation swing the most because they depend on your lot: distance, soil, fall to the sewer and the size of your septic system. A $399 + HST Feasibility Report on your actual lot narrows that a lot.
What are soft costs on a garden suite?
Soft costs are the paperwork and design: permit drawings, the building permit fee, a survey or site plan, the HVAC heat loss and duct design, zoning review and unit registration, and septic design and permit on rural lots. In this calculator they usually run about $4,800 to $12,000 on a city lot. Heat loss design can be done through OntarioHeatLoss.ca.
How much does servicing add to a garden suite?
On a city lot, water, sewer and hydro from the house usually run about $15,000 to $45,000, depending on distance, depth, rock, and whether the panel at the house needs an upgrade. On a rural lot, septic work adds about $15,000 to $45,000 or more for an upgrade, and $35,000 to $55,000 or more for an advanced treatment unit. See our servicing cost guide.
Is a prefab garden suite cheaper than a custom one?
The box is often cheaper. The project is often closer than you think. Published Ontario kit and modular prices run from about $60,000 to $190,000, but most exclude the foundation, servicing, permits, crane and delivery. Our prefab vs custom comparison walks through where the savings hold up and where they disappear.
Does an ICF garden suite cost more?
A bit. This calculator adds about 7% to the shell for ICF walls, and an ICF frost wall runs about $28,000 to $50,000 against $25,000 to $45,000 for a conventional one. What you get back is a quieter, tighter, more fire-resistant building that is cheaper to heat. Our ICF garden suite page explains the trade-off.
Do these garden suite prices include HST?
No. The calculator ranges are before HST. At 13%, HST on a $280,000 contract is $36,400, so ask every builder whether their number includes it. If the suite will be rented to someone outside the family, special HST rules can apply. Read our page on HST on a rental garden suite before you sign.
Will a garden suite pay for itself?
Sometimes, slowly. On our default example, a $280,000 build renting for $1,950 a month nets about 6% a year before financing, which is roughly a 16-year payback if you pay cash. Borrowing changes that a lot. Put your own numbers into the Rental ROI Calculator.