Guide
Loft floor area and knee walls: Norway's 1.90 m rule explained
Which parts of a sloping loft count as floor area in Norway? A worked example of the 1.90 m height line, 60 cm allowance and knee-wall geometry.
Calculators
Loft floor area calculator
Type in your loft’s width, knee wall and roof pitch, and see how much floor counts under your country’s rule, and where the loft is high enough to live in.
How it is counted
House Madness doesn’t know yet how Ireland counts floor under a sloping roof, so the result is the whole floor between the knee walls.
An example
A loft 6 m wide with 1 m knee walls under a 40° roof, 10 m long, has 60.0 m² of floor between the knee walls; 60.0 m² of it counts as Floor area.
Questions and answers
What counts as floor area in a loft?
It depends on the country. Most count the floor only where the ceiling is high enough: in Norway NS 3940 counts it from 1.9 m free height, plus 0.6 m beyond that line under a sloping roof. Germany’s Wohnflächenverordnung counts it half from 1 m and in full from 2 m. Pick your country above to see its rule.
Is a room that counts as floor area a room I may live in?
Not by itself. A room to live in also needs its room height, an escape window and daylight. The calculator shows where the loft is high enough; the app checks the windows and the daylight room by room.
My loft isn’t symmetrical. Can I still use this?
The calculator assumes the same roof on both sides. For an asymmetric roof, dormers or a hipped end, draw the loft in House Madness: it counts each room under the real roof.
Read more
- Guide
Stair rules for homes in Norway, Sweden, Denmark and Germany compared
Riser, going, width, headroom, guards and the stairwell opening for a stair inside a house under TEK17, Boverket, BR18 and DIN 18065, side by side, with a worked example.
Draw the whole house, free
House Madness counts every room this way as you draw, in 3D, and prints the drawings for the application.