How to construct a shallow sloping roof with minimal thickness.

[Andy H]

I am building a single storey building under permitted development rights and am subject to a maximum build height of 2.5m. In order to get a good ceiling height I am digging below ground. The less space I can take up in the roof construction the less I need to dig out.

 

I would like to get a U value of 0.15 or better and am happy to have any structural beams that may be required to remain exposed rather than loose space by covering them up with plaster board,  providing it meets fire regulations. The building is to be  an ICF construction, 12m by 6m and will not have any internal walls to provide structural support.

 

I currently have 2 ideas:

 

 1 an insulated floor panel called 'themafloor' by Thermohouse which is like an insulated form that can span the 6m onto which a 100mm concrete with rebars is poured - this would give a depth of 32cm but would need a small amount of additional insulation to get to a U of 0.15 along with a waterproof topping.

 

2 Cold pressed steel beams that span the 6m to which are attached an insulated roof panel from somebody like Kingspan. I am assuming that the cold pressed steel beams could be left exposed but I may be wrong.

 

Any thoughts on these options and any other ideas would be appreciated.

Edited January 26, 2021 by Andy H