Our Perth two-storey design has the living room window 700 mm off the side boundary, and the only other glazing opens under the covered alfresco. The certifier says the room fails natural light. Does the side window count at all, and does light through the alfresco count?

The certifier is right about the side window, but the alfresco glazing may still carry the room. At 700 mm off the boundary, the side window cannot count toward natural light, because the code sets a 900 mm minimum and you are 200 mm short. [1] The alfresco glazing can count, but only if the alfresco passes the "open verandah, carport or the like" test. [1] [2]

The baseline. Natural light must be provided to all habitable rooms. [1] The usual way is windows with an aggregate light transmitting area, measured exclusive of framing members, glazing bars or other obstructions, of not less than 10% of the floor area of the room. [1] Roof lights open to the sky can do the job at not less than 3%, or you can use a proportional combination of windows and roof lights. [1]

Test 1: the side window and the 900 mm rule. A window required to provide natural light that faces a boundary of an adjoining allotment must be not less than 900 mm horizontally from that boundary. [1] At 700 mm the window can stay in the design, but it cannot be counted toward the 10%. The rule is about a boundary of an adjoining allotment, so if that side faces something other than a neighbouring lot, look again. On the facts given, it fails.

Test 2: glazing under the alfresco. A window counts if it is open to the sky or faces a court or other space open to the sky, or an open verandah, carport or the like. [1] The window does not need to see the sky directly, but the covered space it looks onto must be open. Do not assume every covered alfresco qualifies: the word doing the work is "open". Open sides under a roof fit the wording. An alfresco closed in with walls, glazing or screens starts to look like a room, and the answer turns on how the certifier classifies it.

Test 3: if the alfresco is enclosed, borrowed light applies. Light can come through glazed panels or openings from an adjoining room, including an enclosed verandah, under a harder test: [2]

• the glazing between the living room and the enclosed space must be not less than 10% of the living room's floor area; and
• the enclosed space itself needs windows of not less than 10% of the combined floor area of both rooms that are open to the sky or face a court, a space open to the sky or an open verandah, carport or the like, or roof lights of not less than 3% of the combined area open to the sky, or a proportional combination. [2]

Practical next step. Ask the certifier whether they treat the alfresco as an open verandah or the like, and if not, which borrowed light figures they are applying. Then total the clear glazing onto the alfresco against 10% of the living room floor area (a 30 m² room needs 3.0 m²). If it falls short, the options are larger openings onto an open alfresco, moving the side window out to 900 mm, or roof lights where the room sits under a roof.

WA edition note. WA is on NCC 2025, and a permit applicant may still elect NCC 2022 (Amendments 1 and 2) for applications made before 1 May 2027. [4] The 10%, 3% and 900 mm figures and the open verandah wording are unchanged in NCC 2022, so the election makes no difference here. [3] No WA variation to this clause was found; confirm with your certifier.