In Alberta, a house wall less than 1.2 m (3 ft 11 in) from the property line can't have any windows, and at 1.2 m its windows can add up to 7% of the wall's area (NBC(AE) 2023, Table 9.10.15.4). The allowance grows with the distance, called the limiting distance, until it reaches 100%. That's the second printing of the National Building Code, 2023 Alberta Edition, in force since 17 August 2026 (Government of Alberta, 2026), and on Calgary's narrow infill lots it decides how many side windows a house gets.
Key takeaways
- As of October 2026, a house wall with a limiting distance under 1.2 m (3 ft 11 in) may have 0% glazing, and at 1.2 m it may have 7% of the wall's area (NBC(AE) 2023, Table 9.10.15.4).
- At 1.2 m or more, you can instead use the limiting distance squared as the window area in m², so 1.44 m² (15.5 sq ft) at 1.2 m and 4 m² (43 sq ft) at 2 m (NBC(AE) 2023, 9.10.15.4).
- At 2 m (6 ft 7 in) or less, no single window may take more than 50% of the allowance, and two windows serving one room must be 2 m apart (NBC(AE) 2023, 9.10.15.4).
- A wall under 1.2 m from the line needs a 45 min fire-resistance rating and noncombustible or specially tested cladding (NBC(AE) 2023, 9.10.15.5).
- Roof soffits can't project over a wall 0.45 m (1 ft 6 in) or less from the line, and soffits within 1.2 m of it must be closed and protected (NBC(AE) 2023, 9.10.15.5).
- On Calgary's zero-lot-line houses, the City's standing variance caps the 1.5 m side at 7% glazing with no single opening over 3.5% (The City of Calgary, SPV-001, 2026).
How close can a window be to the property line in Alberta?
No closer than 1.2 m (3 ft 11 in), measured from the wall. Under that limiting distance, Table 9.10.15.4 allows 0% glazing for every size of wall (NBC(AE) 2023, Table 9.10.15.4).
Limiting distance is measured at right angles from the wall to the property line, to the centre line of a street, lane or public thoroughfare, or to an imaginary line between two buildings on the same property (NBC(AE) 2023, Division A, 1.4.1.2). A wall facing a lane measures to the lane's centre line, so it gets more glazing than a wall the same distance from a neighbour's lot.
The wall in question is the exposing building face: the exterior wall facing one direction, measured from finished ground to the uppermost ceiling (NBC(AE) 2023, 9.10.15.2). These rules apply to buildings holding only dwelling units with none stacked over another, and to houses with a secondary suite (NBC(AE) 2023, 9.10.15.1). The Note lists detached houses, semi-detached houses and row houses, and excludes stacked townhouses (NBC(AE) 2023, Note A-9.10.15.1.(1)).
In Calgary, the City's renovation page puts it plainly: windows "are generally not permitted" in a wall closer than 1.2 m to any property line (The City of Calgary, 2026).
How much window area is allowed at each distance?
A percentage of the wall, read from the table by the wall's total area and its limiting distance. These are the code's values for houses, as of October 2026:
| Wall area | Under 1.2 m | 1.2 m | 1.5 m | 2.0 m | 4.0 m | 6.0 m | 8.0 m |
|---|---|---|---|---|---|---|---|
| 30 m² (323 sq ft) | 0% | 7% | 9% | 12% | 39% | 88% | 100% |
| 40 m² (431 sq ft) | 0% | 7% | 8% | 11% | 32% | 69% | 100% |
| 50 m² (538 sq ft) | 0% | 7% | 8% | 10% | 28% | 57% | 100% |
| 100 m² (1,076 sq ft) | 0% | 7% | 8% | 9% | 18% | 34% | 56% |
| Over 100 m² | 0% | 7% | 7% | 8% | 12% | 19% | 28% |
Note: maximum aggregate glazing as a percentage of the wall's area, from NBC(AE) 2023, Table 9.10.15.4. The full table runs to 25 m; the 100 m² row reaches 100% at 12 m. The Note adds that the solid part of a door doesn't count as glazing.
The code gives a second route. Where the limiting distance is at least 1.2 m, the total glazed area may simply equal the limiting distance squared (NBC(AE) 2023, 9.10.15.4). You pick whichever route gives more. For a 30 m² (323 sq ft) wall, the two routes compare like this:
| Limiting distance | Table route, 30 m² wall | Distance squared |
|---|---|---|
| 1.2 m (3 ft 11 in) | 7% = 2.1 m² (23 sq ft) | 1.44 m² (15.5 sq ft) |
| 1.5 m (4 ft 11 in) | 9% = 2.7 m² (29 sq ft) | 2.25 m² (24 sq ft) |
| 2.0 m (6 ft 7 in) | 12% = 3.6 m² (39 sq ft) | 4.0 m² (43 sq ft) |
| 4.0 m (13 ft 1 in) | 39% = 11.7 m² (126 sq ft) | 16.0 m² (172 sq ft) |
Note: arithmetic from the code's two routes for one wall size. A bigger wall gets more from the table and the same from the square, so run both for your own wall.
A stepped or angled wall can be split into portions, each read at its own distance against the row for the whole wall's area. The Note walks through the method (NBC(AE) 2023, Note A-9.10.15.4.(2)), which is guidance. A section of wall that encloses one room at 2 m or less can't be split this way (NBC(AE) 2023, 9.10.15.2).
What changes when the wall is 2 m or closer?
Two spacing rules start. At a limiting distance of 2 m (6 ft 7 in) or less, no single glazed opening, or group of them, may exceed 50% of the wall's allowance. Openings that serve one room must then be at least 2 m apart horizontally on the same wall, or 2 m apart vertically (NBC(AE) 2023, 9.10.15.4).
"One room" is wider than it sounds. Spaces count as a single room if the wall between them stops less than 1.5 m (4 ft 11 in) from the inside face of the exterior wall, and stacked spaces on the same storey count as one. Bedroom egress windows with a 0.35 m² (3.8 sq ft) opening are exempt from the 50% cap, and so are sprinklered buildings (NBC(AE) 2023, 9.10.15.4).
Take a side wall 10 000 mm (32 ft 10 in) long and 3 000 mm (9 ft 10 in) from finished ground to ceiling has 30 m² of face. At 1.2 m it gets 7%, or 2.1 m² of glass, and no single window may pass half of that, 1.05 m² (11.3 sq ft). Two windows of 1.0 m² (10.8 sq ft) each fit, kept 2 000 mm apart if they light the same room.
Glass block, or sprinklers in every room behind the wall, closets and bathrooms included, can double the allowance (NBC(AE) 2023, 9.10.15.4).
What does a wall under 1.2 m from the line need?
A 45 min fire-resistance rating, and cladding that won't carry fire to the neighbour. The rating also covers any wall above the face that encloses an attic or roof space (NBC(AE) 2023, 9.10.15.5).
The construction rules by distance, as of October 2026:
| Limiting distance | Wall rating | Cladding | Clause |
|---|---|---|---|
| Under 0.6 m (2 ft) | 45 min | Metal or noncombustible, or a thin cladding with flame spread of 25 or less over 12.7 mm gypsum sheathing, or a wall tested to CAN/ULC-S134 | 9.10.15.5.(2) |
| 0.6 m to under 1.2 m | 45 min | The same options, plus some treated or tested claddings on furring up to 25 mm | 9.10.15.5.(3) |
| 0.45 m (1 ft 6 in) or less | As above | No projecting roof soffit over the wall | 9.10.15.5.(8) |
| Over 0.45 m | As the distance requires | Soffit face stays at least 0.45 m from the line | 9.10.15.5.(9) |
| Soffit reaching within 1.2 m | n/a | No vents or openings; covered with sheet steel, unvented aluminum, 12.7 mm gypsum soffit board, 11 mm plywood, 12.5 mm OSB or 11 mm lumber | 9.10.15.5.(11) |
Note: summary of the code's options; the cladding clauses name specific standards, so check the product's listing with your designer.
The general ban on combustible projections within 1.2 m of a property line doesn't apply to a house with one or two dwelling units. Enclosed solid projections, such as a chimney chase, are the exception: their faces follow the under-1.2 m wall rules (NBC(AE) 2023, 9.10.15.5).
Alberta added one relief here. Window limits and wall construction rules don't apply to a house wall facing its own detached garage or accessory building, where that building serves only the house, sits on the same property, and the house is the only major occupancy there (NBC(AE) 2023, 9.10.15.4 and 9.10.15.5).
How does Calgary handle zero-lot-line houses?
Through a standing variance. SPV-001, revised 5 March 2026, covers Calgary blocks where each house sits 1.5 m (4 ft 11 in) from one property line, the easement side, and at 0 m on the other, the zero side (The City of Calgary, SPV-001, 2026). Its conditions on glazing:
- No windows or unprotected mechanical openings on the zero side where the limiting distance is under 1.2 m.
- On the easement side at 1.5 m, glazing up to 7% of the face, with no single opening over 3.5%.
- On a three-storey house, no windows on either side wall of the third storey, and the 7% is figured on the wall up to the second-floor ceiling.
The variance also lists the accepted claddings (fibre cement, stucco or vinyl, with 15.9 mm (5/8 in) Type X gypsum sheathing in places) and asks for 12.7 mm (1/2 in) Type X gypsum inside both side walls. A Maintenance Access Right of Way agreement between the lots records the spacing. A house that doesn't fit SPV-001 has to follow the code as written or apply for its own variance.
Does a slow fire response change the rules?
It can, outside a city. Where the first fire truck able to fight the fire takes more than 10 min to arrive in 10% or more of calls, and the house isn't fully sprinklered, you use half the actual limiting distance in these rules (NBC(AE) 2023, 9.10.15.3). A wall 4 m from the line would be read as 2 m. If you're building on an acreage, ask your municipality's safety codes officer whether it applies; the Rocky View County permit guide covers permits there.
Seeing side windows at full size
At 1to1 Plans Calgary, your floor plan is shown at full size on a walkable LED floor, and elevations go up on a wall-size screen behind it. On a narrow infill, you can stand in the room that a side window serves, see how much light the allowed glazing gives, and decide whether it belongs there or on the front or back wall. Changes are shown on the spot.
Sessions are quoted for the plan, and the quote is free (see pricing). See for builders, the other building code guides, or book a session. Bedroom windows also have to meet the egress window rules.
Questions
Can you have a window 1 m from the property line in Alberta?
No. In Alberta, a house wall with a limiting distance under 1.2 m (3 ft 11 in) may have no glazed openings at all, as of October 2026. The City of Calgary's renovation page says the same: windows are generally not permitted in a wall closer than 1.2 m to a property line.
What is limiting distance in Alberta?
In Alberta, limiting distance is the distance from a building's exterior wall to the property line, measured at right angles to the wall. Facing a street or lane, it's measured to the centre line instead, and between two buildings on one property, to an imaginary line between them.
How much glass can a side wall have at 1.2 m in Alberta?
In Alberta, a house wall at a limiting distance of 1.2 m can have glazing up to 7% of its area, or 1.44 m² (15.5 sq ft) under the distance-squared route, whichever is more. No single window may exceed half the allowance, and windows lighting one room must be 2 m apart.
Do eaves have to stay back from the property line in Alberta?
Yes. In Alberta, a roof soffit can't project over a wall that sits 0.45 m (1 ft 6 in) or less from the property line, and elsewhere its face must stay at least 0.45 m from the line. A soffit within 1.2 m of the line must have no vents and be covered in a protective material.
Does the window limit apply to a wall facing my own garage?
No. In Alberta, the window limits don't apply to a house wall facing its own detached garage or accessory building, as long as it serves only that house and stands on the same property, as of October 2026.
Sources
- NBC(AE) 2023, Table 9.10.15.4 nrc-publications.canada.ca
- Government of Alberta, 2026 alberta.ca
- The City of Calgary, SPV-001, 2026 calgary.ca
- The City of Calgary, 2026 calgary.ca
