Building Planning and Foundations
Building Planning and Foundations
This domain tests the planning rules that make a dwelling safe and usable-room sizes, light and ventilation, egress, glazing, stairs, guards-and the foundation rules that transfer loads to soil.
Planning rules
- Habitable rooms need minimum area and width; one habitable room must be at least 120 sq ft, other habitable rooms at least 70 sq ft, and no horizontal dimension less than 7 ft except kitchens. Ceiling height is generally 7 ft.
- Natural light: glazing area not less than 8% of the floor area. Natural ventilation: openable area not less than 4% of the floor area. Bathrooms and kitchens need mechanical ventilation alternatives.
- Emergency escape and rescue openings in sleeping rooms and basements: net clear opening 5.7 sq ft, minimum width 20 in., minimum height 24 in., sill height not more than 44 in. Window wells must provide 9 sq ft and 36 in. horizontal projection.
- Guards are required at drops over 30 in., with a 36-in. minimum height and limits on openings. Stairways need minimum width, headroom, tread, riser, and handrail dimensions.
Foundation rules
- Footings bear on undisturbed soil or engineered fill, with minimum width and thickness from the code tables. A one-story dwelling typically uses a 12-in.-wide footing; a two-story dwelling uses 15 in. unless an engineered design applies.
- Foundation walls need minimum thickness, reinforcement, and anchorage. Anchor bolts are commonly 1/2 in. diameter at 6 ft on center, within 12 in. of ends, with 7 in. embedment.
- Provide foundation drainage and dampproofing/waterproofing where required; backfill after inspection.
Worked example
A basement bedroom window measures 22 in. wide by 26 in. high. The product is 22 x 26 = 572 sq in., or about 3.97 sq ft. It satisfies the 20-in. width and 24-in. height minimums, but it fails the 5.7-sq-ft net clear opening requirement. The examiner's point: dimension minimums and area minimums are separate tests.
Traps
Do not count the rough opening; use net clear opening. Do not apply the 8% light rule to the whole house instead of the room. Do not use a 12-in. footing for a two-story dwelling just because the soil looks firm.