Glass roof for extension, has anyone done this? Pitfalls, tips, recommendations please!

NatNat77

Hi All

We're due our planning decision on Thursday and are looking to build a 6m ground and 4m upstairs extension. Width approx 9m. We can't have a tiled roof on the 2m part of the ground floor extension roof due to the pitch it would need and I hate the idea of having a flat roof. So I'm thinking of having glass, something like the pic below. 

Has anyone got any experience of these, and have any recommendations, tips or pitfalls before I work on persuading the hubby? 😂

An approx idea of cost would be good too. 

Thanks in advance xx

grumbler

AFAIK, there are planning restrictions on the percentage of total glazed area (that includes all doors and windows). I think you'll struggle to get planning permission on such big glass roof.

Find the regulations and check yourself or with your architect.

theoretica

There may be other restrictions - but the ones I have read were thermal insulation - so it may be possible, but you may need expensive glass.  Which direction will it face?  You will also want to think about blinds and how hot it will get in summer.  Can anyone look in?

NatNat77

Thank you, I was planning to do that and aware we'd need planning permission. Wasn't aware there were restrictions on the total amount of glass though so I'll check that out, thanks

BUFF

also, if it is below a window that can operate as a fire escape then Fire Brigade may want proof that the glass can withstand weight of an escaping person (this could be a Scottish thing though).

grumbler

Also, glass roof needs a decent pitch too. Otherwise it'll be green and dirty. The one in your photo seems to have about the same pitch as the smallest one for good tiles, possibly even bigger.

stuart45

The 25% of floor area for glazing is a Building reg, but there are ways around it such as a SAP rating.

Doozergirl

stuart45 said:

The 25% of floor area for glazing is a Building reg, but there are ways around it such as a SAP rating.

You are correct, it's nothing to do with planning.  Planning would happily gove permission for a plate glass greenhouse on the back of the house, it'sBuilding Control that determine whether the glazing is thermally efficient.  

Over 25% glazing they will ask for a SAP calculation.    If it passes, great, if it doesn't then the person that does your SAP calculation can work out what you need to mitigate the heat loss and get it passed.  

Doozergirl

grumbler said:

Also, glass roof needs a decent pitch too. Otherwise it'll be green and dirty. The one in your photo seems to have about the same pitch as the smallest one for good tiles, possibly even bigger.

It needs a pitch for water run off.   The only green roof windows I've ever seen have been made of acrylic, not glass.   Cleaning is a consideration but self-cleaning glass has been a thing for a long time.  It's not going to guarantee being crystal
clear but the occasional clean is helpful.  Our own have been up for three years at virtually no pitch at all and I think they now need some attention but I'm waiting for them to stop building and kicking up dirt next door.
 

NatNat77

Thanks everyone, lots to think about! We're having quite a big set of bifold doors too so we'll definitely be over 25%. Will be mitigated slightly by the French doors and kitchen window/door that will be coming out but we live in a brick built house from the 1950s so there's not much we can do to insulate the walls without major upheaval. We are planning on retiling the roof though and will add extra insulation there. Will need to see what else can be done. The boiler is quite old I think but didn't want to replace it while it's still working.
I'll do some more research 😁

Rosa_Damascena

Glass roofs such as this are currently fashionable, but they scream out "lean to" to me. Would you not consider a slim lantern to fit instead?