Ontario · New builds · 2026
Building a new home? The septic permit comes first — here is why.
On a serviced lot the sewer is somebody else’s problem. On rural land, your house cannot legally exist until the ground proves it can handle what the house produces. Get the sequence right and septic is a line item; get it wrong and it stalls the whole build.
The sequence that works: feasibility → septic design → septic permit → building permit → construct both → inspections → occupancy. Most building departments will not issue the building permit until the sewage system approval exists. Septic is not a trade you schedule late — it is a gate at the front.
FREE 2026 PDF
Homeowner’s Guide44 pp.
Costs, permits, contractor vetting, and the owner-builder path — updated for the 2026 Building Code.
No spam. Straight talk from a builder.
1 Something’s wrong2 What it costs3 The permit4 Who designs it5 The paperwork6 Approval
The part nobody tells you
Designers charge $800–$2,000 just for the paperwork in these quotes.
Ontario law lets you do that part yourself, on your own property. OntarioSepticDesigner.ca turns your answers into the same 26-page package the township clerk sees every day — calculations, drawings, forms, all of it.
Why septic leads the build
The building department needs to know the lot can lawfully support the dwelling — and for an unserviced lot, that means an approved sewage system sized to THIS house. Bedrooms and fixtures set the design flow, so the septic design needs your floor plan, but the septic APPROVAL gates the building permit — the full gating logic is here. The practical consequence: your septic paperwork belongs in the same week you finalize drawings, not the month the foundation pours.
The new-build septic timeline
| Step | What happens | When |
|---|---|---|
| Feasibility | Test holes, water table, setback envelope — ideally before you even close on the land | Before design |
| House plan freeze | Bedroom count and fixtures locked — they size the system | Design week |
| Septic design + package | Calculations, site plan, cross-section, forms — the full list | Days, not weeks |
| Septic application filed | Review by the local authority, possible site visit | 1–4 weeks |
| Building permit | Filed with the sewage approval attached | After septic |
| Construction | Septic usually goes in during rough grading — before landscaping, after heavy machines stop crossing the bed area | With the build |
| Inspections | Septic pre-backfill inspection + building inspections run parallel | Per stage |
The three new-build mistakes
Designing the septic to a draft floor plan, then adding a bedroom — the system is now undersized on paper and the approval reopens. Letting the excavation contractor park machines and stockpile fill on the future bed area — compacted soil fails perc behaviour. And treating the septic as the site contractor’s paperwork problem — it is YOUR permit, on your critical path.
The $18,950 line that never appears on a quote
A real worked example: 3-bedroom bungalow, conventional bed. Tank supplied and set, pipe, stone, fabric, one day of machine and labour, permit allowance — $13,049 with HST. The same job quoted at $32,000. The gap is design fees, markup, and labour you may not need to buy.
Two minutes on the free checker shows the numbers your own lot generates — daily flow, tank size, risk level — before anyone quotes you.
Who does what on a new build
The builder frames houses; the septic is legally yours. You can hand the design to a professional ($800–$2,000, joins their queue) or — because this is your own residence — produce it yourself the same week your house drawings freeze. Owner-built or contractor-built, the numbers are identical Code arithmetic: a 3-bedroom design and a 4-bedroom design differ by one worksheet line and several thousand dollars of bed. What the whole system costs new is on the new-system cost page.
New-build questions, answered straight
Do I need the septic permit before the building permit?
In practice, yes — building departments want the sewage system approval (or at minimum a filed application, locally) before issuing the building permit on an unserviced lot.
Can the house and septic be built at the same time?
Yes — approvals are sequential, construction is parallel. Most builds install the system during rough grading.
What if I add a bedroom during construction?
The design flow changes and the approval must be amended before the change is legal. Add the bedroom on paper BEFORE the septic files — oversizing slightly at design time is cheap insurance.
Does the same authority handle house and septic?
Sometimes — many townships issue both; elsewhere the health unit handles septic while the township handles building. Look up who covers your township.
My builder says they handle everything. Do they?
Ask three questions: who signs the septic application, who owns delays if review stalls, and is the $800–$2,000 design fee in the contract or an extra? “Handled” has a price and a queue; know both.
Start the septic paperwork the week your plans freeze
The free check sizes the system for your floor plan in 2 minutes. The $99.99 builder turns it into the filing-ready package — days ahead of any queue.