Minimal flat roof dormer build up

[colu]

Hi,

I'm looking for help regarding what options I’ve got to minimise the build up of my flat roof for my planned loft conversion. Currently head room is tight and I’ve been told cold roof is the only way I'm going to achieve 2m of headroom. Ideally I want to avoid a cold roof but the head room is the most important thing. I would like to get to 2.1m if at all possible. I’ve attached a drawing of the current cold roof option.

It's an L shaped dormer design with the longest span being 4.5m. Currently 170mm joists are specified then the ply and ventilation gap . I'm looking at SIP's, waiting for a quote to come back but its more the cost of getting in to place that worries me and I'm not sure a crane will be possible. I've also seen several composite metal roofs meant for commercial/industrial applications, these look quite interesting as they are coming out around 120-150mm self supporting and with insulation. Are these practical to use on a loft conversion? Has anyone had any experience of using them? Can you cover the underside with plasterboard?
I may be able to rotate the joists 90 degrees to cut the span down to 3.5M if the ridge steel can handle it, does this give any other options?
Any help/ other ideas would be much appreciated as this may stop the conversion going forward.
Colu

Untitled

• colu
• 18 Feb 2013
• 1

 

[jeds]

Looking at that I would have thought your best bet is to look at lowering the floor. Whichever roof configuration you end up with isn't going to make that much difference.

 

[luisdesign]

I agree with Jeds the only way to make significant head height changes is by setting the floor joists lower. You won't be able to get 100mm out of adapting the roof construction.

With the commercial roofs you need to be aware that they usually require you to include a further false ceiling below which would eradicate any space savings. That and your average domestic builder may not be experienced in their installation.

It might seem like a real pain in the bum to have to put in lower ceilings as it means disruption to the rooms below - but you are only going to do this once, and it would be a shame to be unsatisfied with the expense you went to in making a loft because you brush your hair along the ceiling or are constantly hitting your head on the lights.