Flat roof considerations: Safety, Rain and Shine

[puntloos]

So two semi-separate issues but. 

 

Current design:

<inside>

15mm Plaster Board 

i Joist

18 mm OSB

Vapour Barrier

Insulation 200mm

18mm OSB

GRP

<outside>

 

My 2 questions:

 

1/ Safety: without railings the roof is somewhat dangerous for anyone under 18yo. (and I have a 3yo). Of course, securing the access stair/rooflight should be fairly doable incl alarmed etc, but I was wondering: I have to stick to ridge height as per planning permissions. Are handrails/balusters acceptable anyway, or do they count towards the ridge height?

 

2/ Slightly slanted GRP. So as above I'd like people to be able to walk on the top floor but would that be a problem? And can we slant the roof somehow to prevent rain from staying?

 

Current design: (big skylight is all the way to ground floor, the small skylight doubles as access to the roof

 

[Mr Punter]

I would not bother with safety.  If you include handrail it will need to be fully safety compliant.  Planning would not want it used as a roof terrace / observation deck.

 

The roof needs a fall of min 1:60 preferable 1:40 which is normally achieved with timber firrings.  You can have it so it falls in 4 directions like the pitched roof.  This will be good for the skylight as it will let it drain.

[puntloos]

8 minutes ago, Mr Punter said:

I would not bother with safety.  If you include handrail it will need to be fully safety compliant.  Planning would not want it used as a roof terrace / observation deck.

Meaning, I couldn't get a roof terrace without further planning permission, right?

Or would it 'pretty much never' be allowed? (privacy of neighbours?)

 

I suppose "in general" I tend to try and prepare for such eventualities, so at least have the fixings ready to attach handrails at some point? Or would "safety compliant" mean a massive increase in cost? (I suppose the stairs TO the roof would have requirements?)

 

 

Quote

 

The roof needs a fall of min 1:60 preferable 1:40 which is normally achieved with timber firrings.  You can have it so it falls in 4 directions like the pitched roof.  This will be good for the skylight as it will let it drain.

 

[Adam2]

So you're thinking of a roof sloping down? I can't believe without full fall protection building control would pass that let alone planning which will depend on factors we can't tell from the info here. For the cost and hassle, would you really use it? We had a bedroom balcony , loved the idea but hardly ever used it and  won't include one in our new build.

[puntloos]

1 hour ago, Adam2 said:

So you're thinking of a roof sloping down? I can't believe without full fall protection building control would pass that let alone planning which will depend on factors we can't tell from the info here. For the cost and hassle, would you really use it? We had a bedroom balcony , loved the idea but hardly ever used it and  won't include one in our new build.

 

Well, to be clear the only idea 'for now' is to be able to access the roof to e.g. clean the roof light. Would that not be allowed?

Clearly it's dangerous to go on any roof by using a ladder from the outside since you could jump off if so inclined. Why would 'inside ladders' be any different?

Edited April 7, 2021 by puntloos

[pdf27]

5 hours ago, puntloos said:

Well, to be clear the only idea 'for now' is to be able to access the roof to e.g. clean the roof light. Would that not be allowed?

Clearly it's dangerous to go on any roof by using a ladder from the outside since you could jump off if so inclined. Why would 'inside ladders' be any different?

If you're only using it for cleaning access then just providing a secure fixing point near to the access is enough - you'd then use a "fall restraint" system (basically a rope too short to let you reach the edge) and no further safety provision is required.

If you want to use it as a roof terrace you need a properly engineered system of barriers - nobody is going to believe a claim about using fall restraint for that - and then you need full planning, building control, etc.

[Adam2]

9 hours ago, puntloos said:

Well, to be clear the only idea 'for now' is to be able to access the roof to e.g. clean the roof light. Would that not be allowed?

Ahh - sorry - from your description which seemed to imply (to me at least) that people would be using it inc children that you had other intentions ?

 

 

[puntloos]

1 hour ago, Adam2 said:

Ahh - sorry - from your description which seemed to imply (to me at least) that people would be using it inc children that you had other intentions ?

 

 

No, I definitely did!  

 

But to be clear if I were ever to open the roof to 'the public' it would have to be as secure as any other dangerous fall, so with full railings etc. My question elsewhere - Stuff on top of a house pertained to if I would be allowed to put railings that would exceed the allowed ridge height. GIven that that answer was 'no'(without add'l planning permission) I only want a roof access for cleaning purposes and a very secure lock. I doubt I'd even dare go on it myself.

 

[Bitpipe]

3 minutes ago, puntloos said:

No, I definitely did!  

 

But to be clear if I were ever to open the roof to 'the public' it would have to be as secure as any other dangerous fall, so with full railings etc. My question elsewhere - Stuff on top of a house pertained to if I would be allowed to put railings that would exceed the allowed ridge height. GIven that that answer was 'no'(without add'l planning permission) I only want a roof access for cleaning purposes and a very secure lock. I doubt I'd even dare go on it myself.

 

 

A balcony is an external area that is intended for domestic use and designed for that purpose. It needs to be approved by planning and conform to building regs.

 

A roof is not intended to be accessed in any way or walked upon apart from people who have the necessary experience of working at height , insurance etc and are there for some kind of essential purpose (e.g. a roofer). They should have external means to access the roof (ladders, platforms etc) , you could provide access from inside but ask yourself how often that will be needed and do you want a messy trade getting your interior, ceiling etc grubby?

 

If you open your roof 'to the public', including your family, then you'd be in contravention of your planning permission (overlooking neighbours etc) and you'd be legally liable for any falls or worse. 

 

Can't think why a properly constructed roof will need access for maintenance. If keeping the window clean is your concern, may be cheaper to spec a self cleaning glass for the roof light and let the rain do the job for you. 

 

[puntloos]

1 hour ago, Bitpipe said:

 

A balcony is an external area that is intended for domestic use and designed for that purpose. It needs to be approved by planning and conform to building regs.

 

A roof is not intended to be accessed in any way or walked upon apart from people who have the necessary experience of working at height , insurance etc and are there for some kind of essential purpose (e.g. a roofer). They should have external means to access the roof (ladders, platforms etc) , you could provide access from inside but ask yourself how often that will be needed and do you want a messy trade getting your interior, ceiling etc grubby?

 

If you open your roof 'to the public', including your family, then you'd be in contravention of your planning permission (overlooking neighbours etc) and you'd be legally liable for any falls or worse. 

Yeah, definitely not doing that. (it also seems moderately stupid to go on a slightly sloped roof with no barrier to stop, well, death. )

 

1 hour ago, Bitpipe said:

Can't think why a properly constructed roof will need access for maintenance. If keeping the window clean is your concern, may be cheaper to spec a self cleaning glass for the roof light and let the rain do the job for you. 

 

I've never had much faith in self cleaning glass but perhaps it would be sufficient.. 

 

Regardless, the flat section of the roof probably needs 1-2 skylights anyway so I figured allowing them to open enough to actually allow professionals to climb through might not be a bad idea. But as you said, for the few times that's needed it would be okay to pay the extra cost to get some 'device' to go up there. 

 

[Bitpipe]

Also what's your shading strategy for that large skylight and can it be opened to facilitate stack ventilation?

 

 

[puntloos]

1 minute ago, Bitpipe said:

Also what's your shading strategy for that large skylight and can it be opened to facilitate stack ventilation?

 

 

Good question and my answer is only half-baked (not checked against 'reality')..  I was planning to allow it to open, and I put in electrochromic ('smart glass') in this direction: https://www.iqglassuk.com/products/invisio-thermally-broken-rooflight/s53537/

 

Do you have any suggestions? ?

[Bitpipe]

1 hour ago, puntloos said:

 

 

Good question and my answer is only half-baked (not checked against 'reality')..  I was planning to allow it to open, and I put in electrochromic ('smart glass') in this direction: https://www.iqglassuk.com/products/invisio-thermally-broken-rooflight/s53537/

 

Do you have any suggestions? ?

 

I only have experience with Velux Integra windows, which I have been very happy with. Velux sell external motorised blinds that run off the same controller.

 

Only drawback for you is that Velux have a min 15^o roof pitch requirement, however that could work in your favour as it would address any drainage issues and other potential problems that come with completely flat roofs. @jack had leak issues but did not use GRP.

 

We have two flat roof sections, each about 3m x 2m. One has peeling top coat which has been replaced once (and peeled again) and the other does not have enough fall so has a permanent puddle on it. No leak issues though.

 

@Weebles may be able to help as they have a flat roof with large light, they also had a nasty window related leak (eventually resolved).

[jack]

11 minutes ago, Bitpipe said:

Only drawback for you is that Velux have a min 15^o roof pitch requirement, however that could work in your favour as it would address any drainage issues and other potential problems that come with completely flat roofs. @jack had leak issues but did not use GRP.

 

Our entire roof is flat (well, flat-ish - most of it actually has a 5° slope, which is better than 1:20). We were advised that fiberglass would be difficult over such a large area due to thermal expansion issues, although I've since learned that this likely wouldn't have been the problem it was made out to be.

 

The leaks happened where the Resitrix membrane joined scuppers passing through the parapet wall. We have five scuppers, and three of them failed (one failure only became apparent when the scupper was removed).

 

Our Fakro rooflight is built on an upstand and nothing in that area has ever leaked.    

[Weebles]

On 07/04/2021 at 15:34, Bitpipe said:

 

@Weebles may be able to help as they have a flat roof with large light, they also had a nasty window related leak (eventually resolved).

we do have 100% flat roof (slight pitch for water run off purposes) with roof lights. One is an access hatch so we can access the roof to clear off leaves. We have a high-ish parapet at the edge but I wouldn’t go up there if not for leaf clearing. Not cleaned the roof lights in 2 years. Seem ok (no self cleaning glass here).

 

solar heating is an issue and we had an external film applied last year so we’ll see if that helps this summer

 

as @Bitpipe notes we had a leak (I did a blog entry I think). Roof membrane was not the problem. Poor window design and installation was. Now resolved. Thankfully. 

[Nick Laslett]

Should I be worried about putting in a roof light on a flat roof, or is the issue only to do with installation and there should not really be any problems?

[puntloos]

On 13/05/2021 at 14:55, Nick Laslett said:

Should I be worried about putting in a roof light on a flat roof, or is the issue only to do with installation and there should not really be any problems?

 

'worried' is the wrong word, I don't think there's anything structurally harder than normal (pitched or normal walls) but I'd note that typically there are 2 issues with use of such:

1/ cleaning tends to be harder - and self-cleaning glass apparently is expensive but I haven't actually seen any quotes yet - does anyone know a rough ballpark for triple-glazed-but-standard vs triple-glazed-plus-selfcleaning per sqm?

2/ Hard to fight solar gain. So, perhaps you'd want triple-glazed-with-builtin-shutter-and-selfcleaning (which of course is GBP 20,000 per sqm or something.. happy to hear more accurate estimates )

Edited May 16, 2021 by puntloos

[Mr Punter]

I would reduce the size of the rooflight as you will end up with lots of unwanted solar gain at the top of the house.

 

I have had a Velux with a curb electrically operated in a stairwell and that worked well.  You do not need to go outside to clean them as they flip round to give you access internally.  They do electric blinds and external shutters as well.  I think most of their electric stuff can be solar powered if you want to retrofit the functionality but have no run the power.

 

Velux also do a flat roof rooflight without a curb but they don't seem quite as good.

[puntloos]

20 hours ago, Mr Punter said:

I would reduce the size of the rooflight as you will end up with lots of unwanted solar gain at the top of the house.

 

Yes it'll have to be calculated and perhaps mitigated. I'm not expecting a 100% open standard window, but have built-in blinds or smartglass.

20 hours ago, Mr Punter said:

I have had a Velux with a curb electrically operated in a stairwell and that worked well. 

curb? kerb?

An upstand? - https://www.aspirerooflights.co.uk/2018/12/21/630/

20 hours ago, Mr Punter said:

You do not need to go outside to clean them as they flip round to give you access internally. 

Only works if they can be safely reached

20 hours ago, Mr Punter said:

They do electric blinds and external shutters as well.  I think most of their electric stuff can be solar powered if you want to retrofit the functionality but have no run the power.

I've got the power

20 hours ago, Mr Punter said:

Velux also do a flat roof rooflight without a curb but they don't seem quite as good.

Why does the curb matter?

[Mr Punter]

Kerb - upstand.  Not curb - restriction.  I think I must have come over all American.

[puntloos]

On 07/04/2021 at 07:30, pdf27 said:

If you're only using it for cleaning access then just providing a secure fixing point near to the access is enough - you'd then use a "fall restraint" system (basically a rope too short to let you reach the edge) and no further safety provision is required.

If you want to use it as a roof terrace you need a properly engineered system of barriers - nobody is going to believe a claim about using fall restraint for that - and then you need full planning, building control, etc.

 

Hi pdf27, do you know what's required for such a "secure fixing point"? Do you have any example design or something for me to look at?

 

[pdf27]

1 hour ago, puntloos said:

Hi pdf27, do you know what's required for such a "secure fixing point"? Do you have any example design or something for me to look at?

Easiest option is to go for something compliant to EN 795 - that's suitable for both fall arrest and fall restraint, and is pretty cheap provided you've got something suitable to bolt it on to. Something like https://www.equip4work.co.uk/tractel-pa-fixed-anchor-point.html?keywords= should be fine.

[puntloos]

38 minutes ago, pdf27 said:

Easiest option is to go for something compliant to EN 795 - that's suitable for both fall arrest and fall restraint, and is pretty cheap provided you've got something suitable to bolt it on to. Something like https://www.equip4work.co.uk/tractel-pa-fixed-anchor-point.html?keywords= should be fine.

 

Ah, but the 'snag' then is that the roof itself needs to be able to catch a 100kg weight bouncing off the roof (if I read this site correctly).

Can normal roofs hold that from one anchor point? Or would the SE need to design that special?

[saveasteading]

2 hours ago, pdf27 said:

fall arrest and fall restraint, and is pretty cheap provided you've got something suitable to bolt it on to.

 

This worries me. I have always resisted demands for fall arrest systems to be installed on the roof by the contractor. Why, I hear you ask?

 

If we provide a hook point, then the window cleaner might tie himself onto it, but with what? A fancy fall arrest system with automatic brake and proper harness? Or a rope?

It is false security and might be worse than nothing.

 

If the line is short enough to stop you getting near the edge that is one thing, but not for catching the fall over the edge or though the skylight.

 

If you end up hanging by the waist on a rope, or even in a proper harness (stops the artery in the crutch I think) , you will not survive long, and need to be got down. Therefore needs access equipment on the ground too.

 

On the other hand, a professional maintenance company might bring their own safety equipment, including dead weights for the fixing.

 

Whenever I explained this to a consultant or client, they backed down and dropped the demand, because it had become their decision.

 

If you have to consider cleaning the skylights (and safe cleaning is in the regs) then the cleaner can provide their own equipment, and you can approve it in principle...Actually you should ask how they intend to do it safely.

 

And please don't consider the roof for a terrace or even an occasional lookout.

 

Which of these would you trust?

 

 

 

 

[puntloos]

7 minutes ago, saveasteading said:

 

This worries me. I have always resisted demands for fall arrest systems to be installed on the roof by the contractor. Why, I hear you ask?

 

If we provide a hook point, then the window cleaner might tie himself onto it, but with what? A fancy fall arrest system with automatic brake and proper harness? Or a rope?

It is false security and might be worse than nothing.

 

If the line is short enough to stop you getting near the edge that is one thing, but not for catching the fall over the edge or though the skylight.

 

If you end up hanging by the waist on a rope, or even in a proper harness (stops the artery in the crutch I think) , you will not survive long, and need to be got down. Therefore needs access equipment on the ground too.

 

I'd be inclined to agree this is not great.. but if I understand @pdf27correctly, the reqs require a house to have some type of fixing point?

 

For context, this is my roof:

 

The big skylight is over void, won't be really openable (perhaps to let some heat out but no more). 

The small one would - theoretically - be usable to get to the roof if one were so inclined. 

 

 

 

 

7 minutes ago, saveasteading said:

On the other hand, a professional maintenance company might bring their own safety equipment, including dead weights for the fixing.

 

Whenever I explained this to a consultant or client, they backed down and dropped the demand, because it had become their decision.

 

If you have to consider cleaning the skylights (and safe cleaning is in the regs) then the cleaner can provide their own equipment, and you can approve it in principle...Actually you should ask how they intend to do it safely.

 

So do you think that the skylights are 'safely cleanable' without providing any roof access?

 

7 minutes ago, saveasteading said:

And please don't consider the roof for a terrace or even an occasional lookout.

 

Nah, I gave up on that idea without making it a *proper* terrace which I don't think is worth it. (plus not allowed anyway, I don't think)

 

7 minutes ago, saveasteading said:

Which of these would you trust?

 

 

 

 

 

I assume your question is rhethorical but I'd trust the affixed-to-the-roof one more  - assuming it's well-built of course, I have no idea how to make a roof solid enough to be able to withstand such a pulling action....