Hi all, long time no see.
I'm planning to build a rear extension under PD.
3 bedroom semi.
Roughly 4mW x 4.5mL up against the boundary, with the adjoining wall becoming a new party wall.
Neighbours have agreed in principle, I told them they could use it to form part of their own extension in the future.
Flat roof, small parapet wall on boundary side.
Clear span of joists will be 4200 (ish)
For light and space I would like to retain the ceiling height as it is in the existing downstairs. 2.6m, also putting in a flat roof light in the centre of the roof. So joists will likely need double or tripling up.
I would also like the eaves to overhang the extension slightly, maybe by a foot on two sides
The height from existing ceiling to patio as measured outside is 2725mm
I've worked out the roof thickness as 456mm
15 PB and skim + 195 joist + 70 furring strip + 18 deck + 156 insulation (inc. 6mm ply) + 2mm membrane (EPDM)
This gives a total height of 3181mm. (what have I missed?)
This seems excessive to me, not only will the roof end up looking very chunky and high in relation to the rest of the house, it would go over the pd eaves limit of 3m, and until the neighbours build their extension, would make them feel like they're living in the West Bank.
I could probably get away with 170x72 C24s to shave off 25mm
I've considered a cold roof, but that idea seems about as popular as 1970's glam rock stars, warm deck seems to be the 'in' thing.
I'm not sure of what hybrid options are available, or how much I can get away with putting insulation between the joists.
Or am I worrying too much, and it'll look fine and no one will care about the extra height and I'll win the lottery and marry a model?
I'm planning to build a rear extension under PD.
3 bedroom semi.
Roughly 4mW x 4.5mL up against the boundary, with the adjoining wall becoming a new party wall.
Neighbours have agreed in principle, I told them they could use it to form part of their own extension in the future.
Flat roof, small parapet wall on boundary side.
Clear span of joists will be 4200 (ish)
For light and space I would like to retain the ceiling height as it is in the existing downstairs. 2.6m, also putting in a flat roof light in the centre of the roof. So joists will likely need double or tripling up.
I would also like the eaves to overhang the extension slightly, maybe by a foot on two sides
The height from existing ceiling to patio as measured outside is 2725mm
I've worked out the roof thickness as 456mm
15 PB and skim + 195 joist + 70 furring strip + 18 deck + 156 insulation (inc. 6mm ply) + 2mm membrane (EPDM)
This gives a total height of 3181mm. (what have I missed?)
This seems excessive to me, not only will the roof end up looking very chunky and high in relation to the rest of the house, it would go over the pd eaves limit of 3m, and until the neighbours build their extension, would make them feel like they're living in the West Bank.
I could probably get away with 170x72 C24s to shave off 25mm
I've considered a cold roof, but that idea seems about as popular as 1970's glam rock stars, warm deck seems to be the 'in' thing.
I'm not sure of what hybrid options are available, or how much I can get away with putting insulation between the joists.
Or am I worrying too much, and it'll look fine and no one will care about the extra height and I'll win the lottery and marry a model?