Hello.
Hoping this is the right forum, I have a question about installing a skylight on a flat roof after construction.
We bought a house built in 1934, which was extended 10 years ago. The extension partly has a flat roof, especially over the stairwell area. It is insulated, and the ceiling under the vapor barrier is covered with panels. The flat roof is about 11 m (36 feet) long with a 1% slope and approximately 1.70 m (5.5 feet) wide. The hallway with the stairs is a bit dark, and we don’t want to have to turn on the lights during the day. So we want to install a fairly large skylight, preferably 120 x 240 cm (47 x 95 inches).
We have already had three roofers come to provide quotes. Each sees a different issue that the others don’t mention:
1) The first roofer/carpenter thinks a 1% slope is too shallow, especially since water might pool in front of the skylight. He suggests tearing up the entire flat roof and installing a steeper slope. Elsewhere, I’ve read that 2% is standard according to DIN, but less is possible if high-quality bitumen membranes are applied and regular checks are done. To prevent water collecting behind the skylight, a kind of wedge might be installed.
2) The second roofer says spanning more than one rafter with cross beams is not allowed. He claims the others are experts who don’t know this. Since the rafters (8 x 16 cm (3 x 6 inches)) are spaced about 75 cm (30 inches) apart, the skylight can only be up to 150 cm (59 inches) long.
3) The third roofer says the entire ceiling paneling must be removed to open the roof in the right place. You have to work from the bottom up. He discussed this with a drywall installer and sees no other option. Whether the existing panels can be re-used is uncertain. Other roofers suggest working from the top down: first make a smaller opening and drill a hole through the ceiling paneling. That way, you know exactly where you are and can work accordingly. This approach sounds reasonable.
As laypeople, we are quite uncertain. Can you help?
Regards,
heiteck
Hoping this is the right forum, I have a question about installing a skylight on a flat roof after construction.
We bought a house built in 1934, which was extended 10 years ago. The extension partly has a flat roof, especially over the stairwell area. It is insulated, and the ceiling under the vapor barrier is covered with panels. The flat roof is about 11 m (36 feet) long with a 1% slope and approximately 1.70 m (5.5 feet) wide. The hallway with the stairs is a bit dark, and we don’t want to have to turn on the lights during the day. So we want to install a fairly large skylight, preferably 120 x 240 cm (47 x 95 inches).
We have already had three roofers come to provide quotes. Each sees a different issue that the others don’t mention:
1) The first roofer/carpenter thinks a 1% slope is too shallow, especially since water might pool in front of the skylight. He suggests tearing up the entire flat roof and installing a steeper slope. Elsewhere, I’ve read that 2% is standard according to DIN, but less is possible if high-quality bitumen membranes are applied and regular checks are done. To prevent water collecting behind the skylight, a kind of wedge might be installed.
2) The second roofer says spanning more than one rafter with cross beams is not allowed. He claims the others are experts who don’t know this. Since the rafters (8 x 16 cm (3 x 6 inches)) are spaced about 75 cm (30 inches) apart, the skylight can only be up to 150 cm (59 inches) long.
3) The third roofer says the entire ceiling paneling must be removed to open the roof in the right place. You have to work from the bottom up. He discussed this with a drywall installer and sees no other option. Whether the existing panels can be re-used is uncertain. Other roofers suggest working from the top down: first make a smaller opening and drill a hole through the ceiling paneling. That way, you know exactly where you are and can work accordingly. This approach sounds reasonable.
As laypeople, we are quite uncertain. Can you help?
Regards,
heiteck
Hello,
a 1% slope is really very slight. The first roofer was right about that. How to carry out the replacement should be discussed with a structural engineer. If I were you, I would definitely seek advice from a local professional anyway (architect, civil engineer).
Regards
a 1% slope is really very slight. The first roofer was right about that. How to carry out the replacement should be discussed with a structural engineer. If I were you, I would definitely seek advice from a local professional anyway (architect, civil engineer).
Regards
B
Bauexperte21 Sep 2012 12:46Hello,
The 1% is a bit too low, as E.Curb has already confirmed... if you don’t want to change the slope of the flat roof, there are more cost-effective options to bring daylight into the dark hallway. These light tubes (or solar tubes) are now distributed nationwide by major suppliers in the industry; in my opinion, it should not be a problem for you to get a quote for installation through one of the roofing contractors.
Best regards
heiteck schrieb:
The hallway with the staircase is a bit dark, and we don’t want to have to keep the lights on during the day. So now we want to have a skylight installed. It should be quite large, preferably 120x240cm (47x94 inches).
The 1% is a bit too low, as E.Curb has already confirmed... if you don’t want to change the slope of the flat roof, there are more cost-effective options to bring daylight into the dark hallway. These light tubes (or solar tubes) are now distributed nationwide by major suppliers in the industry; in my opinion, it should not be a problem for you to get a quote for installation through one of the roofing contractors.
Best regards
Hello E.,
thank you for your reply. So, what I left out: We initially asked the architect responsible for the extension about the project. He then drew us a nice pyramid (140cm x 200cm (55 inches x 79 inches)), which also formed the basis for the first quote. The slope was not an issue for him; the idea of the wedge came from him. The question about the lintels only came up later when, for cost reasons (the glass for the pyramid alone is supposed to cost 2000 EUR), we had already decided on a simple roof lantern instead. Yes, we can ask him about the lintels, even though he is not a structural engineer. Hopefully, he will still talk to us when he finds out that we are turning down the pyramid.
Regards,
heiteck
thank you for your reply. So, what I left out: We initially asked the architect responsible for the extension about the project. He then drew us a nice pyramid (140cm x 200cm (55 inches x 79 inches)), which also formed the basis for the first quote. The slope was not an issue for him; the idea of the wedge came from him. The question about the lintels only came up later when, for cost reasons (the glass for the pyramid alone is supposed to cost 2000 EUR), we had already decided on a simple roof lantern instead. Yes, we can ask him about the lintels, even though he is not a structural engineer. Hopefully, he will still talk to us when he finds out that we are turning down the pyramid.
Regards,
heiteck
Thank you, building expert, for the tip. I once showed my wife these recessed lights in a home magazine. She didn’t seem very enthusiastic. I think she wants to see the sky.
Did I understand correctly? The spots allow more light through a smaller opening, so the barrier for draining water is smaller… also because they are round.
Is it possible to say which size of spot corresponds to which skylight area?
Regards, heiteck.
Did I understand correctly? The spots allow more light through a smaller opening, so the barrier for draining water is smaller… also because they are round.
Is it possible to say which size of spot corresponds to which skylight area?
Regards, heiteck.
B
Bauexperte22 Sep 2012 01:04Hello,
There’s nothing wrong with personal taste or preferences ; I was mainly considering the costs. By the way, apart from the considerable financial expense, cleaning skylights can be quite troublesome… perhaps your wife hasn’t thought about this, or have you volunteered for regular cleaning?
There are different systems and variations of these spots; some are almost flush with the roof surface, some look to an untrained eye like a vent pipe for a toilet or bathroom. For flat roofs, however, all manufacturers offer special spots; the existing roof slope is always taken into account.
Try searching Google for Velux + daylight spot; Velux is one of the better-known manufacturers of such spots. They have a “light calculator” tool where you can enter the details of your extension, and after completing the inputs, you can see under which lighting conditions you would save how much energy — measured in lux or the equivalent of 60 W incandescent bulbs — by installing a daylight spot.
For various reasons, I am not a fan of double-hinged windows/skylights; that’s why I like to offer these spots to my clients where I find them sensible.
Best regards
heiteck schrieb:
I once showed my wife these recessed ceiling lights in a home magazine. She didn’t seem very enthusiastic. I think she wants to see the sky.
There’s nothing wrong with personal taste or preferences ; I was mainly considering the costs. By the way, apart from the considerable financial expense, cleaning skylights can be quite troublesome… perhaps your wife hasn’t thought about this, or have you volunteered for regular cleaning?
heiteck schrieb:
Did I understand correctly? The spots let more light in through a smaller opening, so the barrier for draining water is smaller… also because they are round.
There are different systems and variations of these spots; some are almost flush with the roof surface, some look to an untrained eye like a vent pipe for a toilet or bathroom. For flat roofs, however, all manufacturers offer special spots; the existing roof slope is always taken into account.
heiteck schrieb:
Can one say which spot size corresponds to which skylight area?
Try searching Google for Velux + daylight spot; Velux is one of the better-known manufacturers of such spots. They have a “light calculator” tool where you can enter the details of your extension, and after completing the inputs, you can see under which lighting conditions you would save how much energy — measured in lux or the equivalent of 60 W incandescent bulbs — by installing a daylight spot.
For various reasons, I am not a fan of double-hinged windows/skylights; that’s why I like to offer these spots to my clients where I find them sensible.
Best regards
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