Maximising space inside PD porch

[Coops]

Evening folks

 

I'd like to add a porch to the front of the house on account of the dog trying to leg it every chance he gets. Anyway - don't want or need to go any bigger than PD size but I do want to maximise space internally. Heres the thing...I'm planning to build in double skin block, 75mm insulated cavity and a decorative rainscreen  from local stone to match existing, problem is this leaves me with a nigh on 400mm thick wall possibly more by the time I've stuck some plasterboard on internally...is this overkill for what is essentially enclosed external space?

 

Got to be a simpler way? 

[tonyshouse]

Glass? Do you know what area is allowed under pd? 

[Olf]

Including the porch in thermal enevelope of the builiding will likely trigger need for building control

[Coops]

I'll separate the two spaces with an exterior door. No BC approvals required but ideally would like to insulate. 

[Temp]

Can you get local stone as slips?

 

Wet plastered 5-10mm

Single Block 100mm

Membrane?

EWI & Stone Slips 

 

Something like..

https://www.blackmountainquarries.co.uk/products/stone-cladding-slips/random-cladding-slips/

 

More..

https://www.blackmountainquarries.co.uk/products/stone-cladding-slips/

 

 

[Coops]

I have considered slips and EWI Temp, I just don't know how id get my local quarry to machine them. There is a system called Surecav https://www.surecav.co.uk/ designed for exactly this application, it basically maintains a consistent cavity which negates the requirement for a backing block.. where the hell I'd find anyone willing to sell me 6m2 though I'm not too sure..

 

[Temp]

Can you build the outer leaf from stone?

[Coops]

Yeah I could for sure, it's just I'll be using random stone to suit the period of the existing property, so really difficult to maintain a decent, consistent cavity. The common building solution (around here at least) seems to be block - cavity/insulation - block and then an outer decorative facing stone. Maybe I'm overthinking it and I should just try and keep the cavity as clean as I can. 

[Temp]

Or just apply for planning for a slightly bigger porch.

[Coops]

Yes, that's another option, but to be honest I'd struggle to fit anything bigger than 2500 x 1200 anyway. 

[Olf]

8 hours ago, Temp said:

Or just apply for planning for a slightly bigger porch.

May not help too much - I did that as included porch in planning application for all the changes,  had to scale it back to 1400mm protrusion from the front wall to comply with local planning guidelines. Check your council's website for something like that to see how big can you get either way.

[Coops]

I wouldn't want or have the space to go bigger than PD allowance in any case.