A contingency reserve gives your renovation budget room for conditions you cannot yet confirm. Keep it separate from allowances for unselected products and from optional upgrades. The amount should reflect what remains unknown about your house and the planned work.
How much contingency should you carry?
| Planning reserve | Project profile | Typical uncertainty |
|---|---|---|
| About 5% | Tightly documented finish work with little or no demolition | Minor substrate repair, quantity variation, or coordination |
| About 10% | A defined kitchen, bathroom, or interior renovation that opens walls and coordinates trades | Hidden water damage, legacy services, framing correction, or a route that changes after opening |
| 15% or more | Older or poorly documented house, structural alteration, addition, basement, excavation, or several systems moving | Unknown assemblies, hazardous material, soil, drainage, foundation, or design exposure |
These bands are planning heuristics, not Ontario law or a statistic about every GTA renovation. Choose from the actual house: what remains concealed, how expensive access becomes later, how many systems interact, and how much design is unresolved. A measured built-in and a second-storey addition should not receive the same percentage without considering their different risks.
What is contingency different from?
The base contract pays for defined work. An allowance prices a known category whose selection or quantity is unresolved. Contingency is the homeowner's reserve for genuine uncertainty and approved choices. Ontario's Construction Act generally requires a basic holdback equal to 10% where a lien may arise; its retention, annual release, lien, and notice rules are technical, including changes effective in 2026. Holdback is not spare project money. Ask a construction lawyer about its application and timing on a substantial job.
What should contingency cover?
Reasonable uses include concealed rot, damaged framing, unsafe legacy work, an unrecorded drain, site conditions, or a design consequence that could not be confirmed before opening. It may also fund an owner-requested change, but call that what it is. Contingency should not rescue work omitted from a thin quote, unrealistic allowances, duplicate charges, estimating mistakes on fixed scope, unapproved extras, known permit or design fees, or upgrades you already planned.
Ontario's consumer renovation guide says estimates should describe and itemize the work and contracts should address materials, cost, payments, schedule, cleanup, warranties, and subcontracting. A reserve does not excuse a vague contract. Known work belongs in the scope.
How do you choose the percentage?
List the unresolved conditions before signing. For each meaningful unknown, record the possible condition, evidence available now, investigation that could reduce it, likely response, and who decides. A survey, drain camera, exploratory opening, engineering review, electrical load check, or material test can turn an expensive mystery into a bid item. If older material may contain asbestos, Health Canada recommends professional testing before renovation when it may be disturbed. Suspected asbestos needs assessment before disturbance.
Calculate the percentage against the construction scope that actually carries the uncertainty. Keep appliances, moving, storage, temporary accommodation, financing, and other household effects in their own budget lines. For a kitchen, begin with the categories in the GTA kitchen cost guide. For an addition, the second-storey guide shows why structure, envelope, weather, and temporary protection create different exposure.
How should you spend contingency?
When a surprise appears, pause the affected work, make the area safe, document the condition, check the original scope, define options, and record price, credits, tax, schedule effect, and approval. Use the process in the Ontario change-order guide. Reduce the remaining reserve when a change is accepted. Update the remaining reserve whenever a cost is approved.
What happens to unused contingency?
Leave the reserve alone until inspections, deficiencies, final invoices, and applicable closeout obligations are resolved. Then return what remains to savings or another deliberate purpose. Keep the unused reserve until the project’s final costs are settled.
