Measuring a roof lantern: how to take the right dimensions

Measuring a roof lantern comes down to three dimensions: the clear opening of the roof, the outside size of the upstand and the height of the upstand. With those dimensions, a few photos and the type of roof covering, a manufacturer can prepare a quote. At DagLichtDesign you receive it in your inbox within 24 hours. A construction drawing is not needed; a photo or sketch is enough.

The dimensions you need

Different dimensions are used interchangeably for roof lanterns. Keeping them apart prevents a frame that does not fit.

The clear opening determines how much light comes in. The outside size of the upstand determines the size of the frame. The difference is the thickness of the upstand plus the insulation, on both sides. With 5 cm of timber and 5 cm of insulation, that is already 20 cm in each direction.

• Clear opening: the free opening you see from inside
• Outside size of the upstand: measured over the outside
• Pitch: a standard 8°, you do not need to supply it
• Height of the upstand above the roof covering

Measuring a roof lantern step by step

Measure in at least two places in each direction, because a roof opening is rarely perfectly square. Always note the smallest dimension.

If there is no opening yet, for example because the extension still has to be built, give the size you want and have the contractor build the upstand to that size. That is often the easiest route: the roof lantern determines the opening, not the other way round.

• Measure length and width at both ends
• Measure both diagonals: equal means square
• Measure the upstand height at every corner
• Note where the low side goes and where the water must drain

Roof lantern dimensions: stock or made to measure

Every DagLichtDesign roof lantern is made to measure. The lean-to in 1, 2 and 3 metres is always in stock, which keeps the lead time short. If your opening matches one of those sizes, look at the standard sizes, for example the 2 metre lean-to roof lantern.

For larger dimensions each type has its limits. A lean-to goes up to 5 metres wide in a single panel, a gable roof up to 6 metres long and 4 metres wide per roof plane, and a hipped roof up to 9 m² of glass in one piece. Beyond that it becomes modular or glazing bars are added. For a length of 4 metres, see a 4 metre roof lantern.

Taking photos that actually help

A good photo often says more than a list of dimensions. Take them in daylight, ideally with a tape measure in the picture.

If the roof lantern will meet a wall, the wall-abutting lean-to roof lantern is the right type. In that case also state the wall type, such as brickwork, render, sand-lime brick or timber cladding. Each one has its own junction profile.

• An overview of the roof showing where the roof lantern goes
• A close-up of the opening or upstand, with a tape measure
• The roof covering: EPDM, bitumen or something else
• An adjoining wall, if the roof lantern will meet it

What to send with your enquiry

The more complete your enquiry, the more precise the quote. If you do not know something, leave it open. The quote lists the glass options side by side, so you can compare HR++ double glazing and triple glazing straight away.

No dimensions and no drawing? Then they will come and have a look. You can send your enquiry via the quote page. A quote is valid for 30 days.

• Dimensions, photos or a sketch
• Preferred roof type, or your question about it
• Glass preference: clear, obscured or solar control
• Frame colour, and whether you collect or want delivery

Frequently asked questions