You always order by daylight size: the clear opening visible from inside. Your new skylight fits straight away.
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Daylight size= your order size
The clear opening visible from inside. Measured along the inside of the curb, from edge to edge.
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Roof openingstraight curb = daylight size
The opening in your roof. With a straight curb (/00), it equals the daylight size. With a sloped curb (/20 or /30), it is 20 or 30 cm larger.
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External skylight size= daylight size + 160 mm
What you measure on the outside of an existing skylight. The flange extends 80 mm on each side. Subtract 160 mm to find your daylight size.
















