Flat Roof sheet metal options

[rideforever]

Got a 4m x 3m space over an extension thinking about putting a terrace on it, cold roof.
Was thinking zinc is a good long term option as it will have a deck on it, but the min fall is 3degs apparently meaning it would be a lot higher than other options. I don't know if there are other options like having taller seams for a 2deg fall?
Lead is 1.8 I believe, and GRP even less.
Whats the best option?
I saw a large GRP roof being laid, looked easy but don't think it will do well with a deck on top.
Torch on roof is okay but will need 20yr replacement cycles I imagine.
Lead looks like it would be 2" strips with wooden rolls between them, quite a lot of work and a lot of seams.
Any advice ?
Cheers

 

[freddiemercurystwin]

What floor finish for the terrace are you wanting to use, decking/paving slabs etc? Is this a new build not built yet or a musing on an existing roof?

We're assuming you've got the whole deck is structurally sufficient, planning constraints, the whole fixing the handrails difficulties etc is in hand.

 

[rideforever]

What floor finish for the terrace are you wanting to use, decking/paving slabs etc? Is this a new build not built yet or a musing on an existing roof?

We're assuming you've got the whole deck is structurally sufficient, planning constraints, the whole fixing the handrails difficulties etc is in hand.

Victorian, it would be 2nd floor level over a 1st floor extension, access is easy as there is a turn in the staircase. Timber deck. Doubling up on the rafters subject to engineers rpt. About 4m on the line of fall. Needs to be as low as possible to prevent overlooking.
Modern balconies have been built that overlook the gardens, have been told "something is poss" by planning.
Would only cover half the space of the existing tiled roof due to overlooking.
Higher fall means smaller size due to overlooking.
Balustrade, L shaped attached on 3 sized, ventilation on 4 sides and through firings.

 

[freddiemercurystwin]

Why do you want metal? I would go for epdm.

 

[rideforever]

epdm

Thanks, will look it up don't know much about epdm.
Well as there is a wooden deck ontop and it might move around I would prefer a "permanent" solution.
Also zinc looks solid and easy to install, no chemicals, solvents or glues.
Not sure if 2 degs with zinc is possible if higher seems lifted with a 1 cm step would be possible.

 

[freddiemercurystwin]

An edpm roof will last longer than a timber deck, (it's lifespan should 40-50 years), or are you going for composite decking? Anyway the deck won't move around it's weight will hold it down just fine. You would place a protective membrane between the roof finish and the joists, or you can sit the joists on adjustable pedestals to ensure your deck is level. https://www.rubber4roofs.co.uk/manu..._Tgssyj_u6cJWY1v_X6bceCAOspdhvYOEEaipl2x9isBe

Zinc is not really a DIY install, you need to use the proper seam tools to join it etc and they have massive cutters in the van to cut down sheets to size. Besides you would (normally) only use zinc where it can be seen.

 

[rideforever]

An edpm roof will last longer than a timber deck, (it's lifespan should 40-50 years), or are you going for composite decking? Anyway the deck won't move around it's weight will hold it down just fine. You would place a protective membrane between the roof finish and the joists, or you can sit the joists on adjustable pedestals to ensure your deck is level. https://www.rubber4roofs.co.uk/manu..._Tgssyj_u6cJWY1v_X6bceCAOspdhvYOEEaipl2x9isBe

Zinc is not really a DIY install, you need to use the proper seam tools to join it etc and they have massive cutters in the van to cut down sheets to size. Besides you would (normally) only use zinc where it can be seen.

Thanks yeah EPDM looks simple. I would round off the edges of the deck joists, and staple a layer of epdm around them so they don't sit directly on the membrane, hopefully that will prevent tearing.
Thanks