GRP flat roof Balustrade

[gambler103]

Hi all,

 

After some advice/ideas. 

 

We have a large flat roof section at our house with 2 large full height dormers able to directly access it. Please see photo. We renovated the whole property a few years back which included the dormers and flat roof and it was always the intention (planning permission was approved) to fit a balustrade and decking to turn the space into a terrace.

 

Time and money got away from us and we are only now getting round to the project. We also have the issue of a poorly installed GRP flat roof which will be renovated and likely relaid with GRP again, this time with the appropriate fall on it and GRP which doesnt flake off (cheers original contractor).

Issue is - everyone im talking to (Roofers and Balustrade suppliers) seems to have very different ideas about what the best solution is and now im totally confused. We had originally planned for a frameless glass 'U' shape balustrade to feed back to the dormer sides with a floating composite deck. Seems to be 2 camps of flat roof Balustrade installer. The 'never penetrate your deck' ones and the 'its fine if done properly' ones. Have been told recently that frameless glass is probably not appropriate as the run along the edge of the roof is 16 meters and the wind could do its work over a shortish spell to 'loosen' the fixings underneath the glass channel by buffeting the long glass section (and eventually causing a leak through the loose fixings). The chap said he would advise only doing frameless if you could fix directly to steel (which we do have but they are about 20cm down under the deck. Have also been told that side of house fixings probably not an option due to that area being where the guttering is.

 

Another contractor has told me that he will do the frameless but it needs to be fitted 'flat' on the deck ie not following the fall of the deck and propped up blocks. The blocks would be approx 4 inches high to maintain the flatness across the deck! Have seen pictures of a previous install and it doesnt look good. Surely you can install a Balustrade flush to the deck angle?!

 

What do you think? At the moment the favourite is still to penetrate the deck with posts that are 'done properly'. Any advice or ideas would be well appreciated!

 

Cheers

G

[Conor]

Whatever you do, it's imperative that the system fixes in to the structure of the building, i.e. steel or concrete. The ideal way of doing would be to have a parapet wall made of reinforced concrete, tied in to the block work / steel below. Your flat roof then abuts this with an upstand and flashing up and over the wall. This is how I did mine. My SE specced a 200x400mm RC ring beam for the balustrade channels, the rest were fixed in to steel beams. The balustrade company supplied 100mm M14 stainless steel anchors. 

 

My system can definitely be laid on a fall, as the glass panels sit in adjustable carriers. 

Edited October 13, 2024 by Conor

[SteamyTea]

As above.

The GRP is just a water/weatherproof coating in your instance, it is not structural at all.

 

[gambler103]

Thanks for the responses.

 

A parapet wall has been briefly discussed but I think got dismissed because of the nature of the drainage from such a large roof. All of the water would have to go under or along the inside of the wall in a gully and out of the sides of the house. Seem to remember the guy I spoke about it with thought it would be to much of a re-design?

 

Has anybody successfully installed a balustrade (of any kind, we arent just looking at frameless glass) directly onto a flat roof?

 

THanks

[lookseehear]

 

On 14/10/2024 at 10:29, gambler103 said:

Thanks for the responses.

 

A parapet wall has been briefly discussed but I think got dismissed because of the nature of the drainage from such a large roof. All of the water would have to go under or along the inside of the wall in a gully and out of the sides of the house. Seem to remember the guy I spoke about it with thought it would be to much of a re-design?

 

Has anybody successfully installed a balustrade (of any kind, we arent just looking at frameless glass) directly onto a flat roof?

 

THanks

 

We're also trying to work out the solution here - did you get anywhere?

[gambler103]

On 27/01/2025 at 11:37, lookseehear said:

 

 

We're also trying to work out the solution here - did you get anywhere?

Hi, still looking into the finer points of it for install later this year. ATM we are looking at a balustrade with posts every 1.2m and the fixings being integrated into the deck renovation. The balustrade company we are working with does what they call 'waterproof fixings' which are an extra bracket fixed onto the deck that the posts then fix onto (rather than the bottom of the post fixing directly the deck). My roofer then thinks if he paints a rubber or GRP solution over the top of it all and laps it up the posts for a couple of inches it might be good for a few years but he said its unlikely they will be able to give me warrantee for that part of the roof install. In the event of a leak im trying to get the decking part of the terrace modular so if a leak is seen we can remove part of the deck hopefully reseal it with more rubber. This seems to be the most robust way of doing it but im still very much open to ideas?

[lookseehear]

That sounds interesting but I'm also not that keen on the idea of having to replace something after a few years to keep it watertight. I've come to the conclusion that the easiest option might be to cast a 200x100 ring beam on top of the outer skin as a mini parapet, which means I can fix posts or the balustrade channel (if we go frameless) into the concrete. I would cast drainage channels through the ringbeam at intervals and have single ply membrane run right through these into collector boxes, which avoids having the posts/channel in the drainage pathway. I did a sketch somewhere that I can dig out if you're interested.

[gambler103]

Yep, the other remaining option is to sit something weighty on top of the roof to connect the balustrade to rather than puncturing the roof.

 

I looked at the parapet option but wasnt happy with the drainage as my roof is pretty large.

 

A couple of suppliers I spoke to floated the idea of a metal frame but it added significant cost. One of the suppliers as per below.

 

https://www.brightonbalustrade.co.uk/2024/01/17/installation-of-glass-balustrade-systems-to-flat-roofs/

[crispy_wafer]

51 minutes ago, gambler103 said:

Yep, the other remaining option is to sit something weighty on top of the roof to connect the balustrade to rather than puncturing the roof.

 

I looked at the parapet option but wasnt happy with the drainage as my roof is pretty large.

 

A couple of suppliers I spoke to floated the idea of a metal frame but it added significant cost. One of the suppliers as per below.

 

https://www.brightonbalustrade.co.uk/2024/01/17/installation-of-glass-balustrade-systems-to-flat-roofs/

Just want to say a thx for posting this, I have a small section of flat roof to which doors open and needing a balustrade without puncturing the covering was my preferred solution.  I had thought about having a deck frame fabricated and balustrade fixing to this.  This will help immensely with my idea. 👍