Estimates, quotes and contracts
How to estimate a home renovation cost yourself: a step-by-step method
A seven-step method to estimate a Canadian renovation before you call contractors, from scope and measurements to unit ranges, one-time costs, contingency and GST/HST.
You can build a useful renovation estimate before any contractor visits by working in seven steps: write the scope, measure, choose a per-unit range, add one-time costs, add a contingency, add sales tax, then test the result against written quotes. The goal is not to predict the exact price; it is to know whether your plan fits your budget, to spot a quote that is unrealistically low or high, and to make every contractor price the same job.
This is the overview for the estimates section. The other guides apply the method or cover what comes next: the secondary suite worked example, the whole-home renovation budget, how much contingency to keep, comparing renovation quotes, the renovation contract checklist, deposits, holdbacks and payment schedules and contractor licensing, insurance and workers' compensation checks.
Step 1: write the scope
List every room and every change. For each one, note what stays, what goes and what is new. Be specific: "replace tub with tiled shower, toilet stays, new vanity 36 inches, new exhaust fan to exterior" is a scope; "redo bathroom" is not. Mark what you are still undecided about; those items become allowances.
| Scope question | Why it matters |
|---|---|
| Does any wall move? Is it load-bearing? | Structural work, engineering, permit |
| Do any fixtures move? | Plumbing and venting changes |
| New circuits or appliances? | Electrical capacity and permits |
| Heating or ventilation changes? | Ductwork, new equipment |
| Exterior changes (windows, doors, additions)? | Envelope work, zoning |
| What finish level? | Materials and labour hours |
Step 2: measure
Measure the floor area of each room in scope in square feet (or square metres, then multiply by 10.764). For kitchens also note linear feet of cabinets and the counter area; for bathrooms the shower wall area to be tiled; for basements the wall perimeter and ceiling height. Measurements let you check contractors' quantities later.
Step 3: apply a per-unit range
Multiply each area by an illustrative low-to-high range per square foot. The presets in the renovation cost estimator are a starting point, built from typical components and rounded; the cost guides explain each: kitchen, bathroom, basement and addition. Once you have a quote for a similar job in your area, replace the presets with real figures.
Step 4: add one-time costs
Some costs do not scale with area:
- design, drawings and engineering,
- building permit and any zoning application,
- waste bins and disposal,
- testing for asbestos or other hazardous materials in older houses,
- temporary kitchen, storage or accommodation,
- appliances and fixtures you buy yourself.
Step 5: add a contingency
Add a percentage for the unknown. A common planning rule is around 10% for cosmetic work in a newer house and 15–20% or more for older houses, structural work or plans that are not final. The contingency calculator adds it, and the contingency guide explains how to choose.
Step 6: add sales tax
Apply the rate for your province: for example 13% HST in Ontario, 14.975% GST plus QST in Quebec, 5% GST in Alberta. The sales tax calculator does this, and GST/HST on renovations explains PST in BC, Saskatchewan and Manitoba.
Step 7: test against quotes
Get at least two or three written quotes for the same scope. If they cluster near your estimate, good. If they are far above, look for scope you missed (structural work, code upgrades, access). If one is far below, look for exclusions. Use the quote checklist.
Worked example: a small main-floor project
Illustrative, Manitoba: a 50 sq ft bathroom and new flooring and paint in 600 sq ft of living space.
| Line | Calculation | Low | High |
|---|---|---|---|
| Bathroom | 50 × $450 / 50 × $850 | $22,500 | $42,500 |
| Living area refresh | 600 × $40 / 600 × $100 | $24,000 | $60,000 |
| One-time costs | permit, bin, protection | $2,000 | $2,000 |
| Subtotal | $48,500 | $104,500 | |
| Contingency 15% | $7,275 | $15,675 | |
| Before tax | $55,775 | $120,175 | |
| GST 5% (RST is in the contractor's price) | $2,788.75 | $6,008.75 | |
| Planning range with tax | $58,563.75 | $126,183.75 |
The range is wide because finish choices are open. Narrow it by deciding on the bathroom finish level and the flooring material, then re-run the numbers.
When your estimate and the quotes disagree
- All quotes much higher: your unit ranges may be low for your city, or the house needs work you did not see (panel upgrade, structural repairs).
- Quotes far apart: scopes or allowances probably differ; standardise them.
- One quote much lower: check for missing permits, low allowances, time-and-materials clauses or no warranty.
Mistakes to avoid
- Estimating from a total found online with no idea what it includes.
- Leaving out tax and owner costs.
- Treating the contingency as an upgrade budget.
- Not writing down the scope, so each contractor prices something different.
FAQ
Is a contractor's estimate the same as a quote?
Not necessarily. An estimate is a best guess; a quote or fixed-price contract commits to a price for a defined scope. In Ontario, the Consumer Protection Act limits a supplier from charging more than 10% above an estimate in a consumer agreement unless you agree to changes. Ask which one you are getting.
Should I pay for an estimate?
Some contractors charge for detailed estimates or design work, especially for large projects. Agree in writing what you get and whether the fee is credited if you hire them.
How accurate can a homeowner estimate be?
At the planning stage, a wide range is normal. It narrows as the scope, finishes and quotes become firm.
Sources
- Canada Revenue Agency — GST/HST rates
- Consumer Protection Ontario — estimates and written agreements
- Office de la protection du consommateur — renovation contracts in Quebec
- Canada Mortgage and Housing Corporation — renovating and financing information
