Your building permit drawings, explained in plain English

By the Give Me The Cost estimating team · Methods reviewed by a senior GTA estimator (25+ years in the field) · Updated July 2026
The short answer: a permit set is a numbered book. Sheets starting with A are architectural (A101 = basement plan, A201 = elevations…), S sheets are structural. Diamond-shaped tags mark wall types; boxed or oval tags mark individual windows and doors, which are listed in schedules — tables that spell out every size.

The sheet numbering system

SheetWhat it showsWhy you care
AS101–AS102Site planSetbacks, lot coverage, where the house sits
A001–A002Notes & assembliesThe 'recipes' for every wall, floor and roof
A101–A104Floor plans (basement up)Room layout, dimensions, door/window tags
A201–A204Elevations (N/E/S/W)What each face looks like, cladding, heights
A301+SectionsThe house 'cut open' — ceiling heights live here
A601SchedulesEvery door and window with exact sizes
A701+ / S sheetsStructuralFootings, beams, joists — engineer-stamped

The tags: diamonds vs boxes

Diamond tags (like W01, FW02 in a rotated square) identify a wall assembly — the layered recipe of that wall, defined on the assemblies sheet. Boxed or oval tags (W01, D04 in a rectangle/oval) mark an individual window or door, matching a row in the schedule. Same letters, different shapes, completely different meanings — even pros mix them up.

Five things worth checking on your own set

1. The egress window. Every bedroom needs a window big enough to escape through (or a door to outside). Look for "egress" notes on the window schedule. 2. Dimensions are to structure, not finished drywall — rooms feel a few inches smaller than the numbers. 3. The dual units: 8" [205] means 8 inches (205 millimetres) — Ontario drawings show both. 4. Fire-rating notes near property lines (Type 'X' drywall) — that's why your side walls may have few or no windows. 5. The permit stamp: a reviewed set carries the city's compliance stamp — that's the document your builder must build from, and changes need city approval.

Want your project's real numbers, not ranges?
Upload your drawings and get an actual material takeoff with an Ontario Building Code check — or start with the free calculators.
Get my takeoff →   Free calculators

Frequently asked questions

What does A101 mean on my drawings?
It's the sheet number: 'A' for architectural, first digit for the series (1 = floor plans), so A101 is typically the basement or ground floor plan. A201 starts the elevations, A301 the sections, A601 the schedules.

What are the diamond symbols on the floor plan?
Wall assembly tags. Each diamond (e.g. W01, FW01) points to a defined layer-by-layer wall recipe on the assemblies sheet. Boxed tags, by contrast, mark individual windows and doors listed in the schedules.

What is a door or window schedule?
A table (usually sheet A601) listing every door and window mark with its exact width, height and notes — the shopping list for every opening in the house.

Can I change things after the permit is issued?
Yes, but changes to the reviewed drawings need written approval from the building department — your builder can't just improvise on a stamped set.