Garage to porch conversion: using what's there

[WWilts]

Garage demolition, side porch to replace it. Small, Building Regs exempt. Design fixed by planner. Existing external walls of main dwelling will form 2 (internal) sides of the porch. Currently garage has a double skin wall (outer stone, inner brick). Concrete floor. About 550mm below main dwelling floor level.

Can the existing foundations for the front elevation be retained and used? What would determine whether or not?
Any particular approach recommended to join the side wall securely to the existing external side wall?
If retaining the existing concrete slab, what layers would you use to build it up by about 275mm? Then it will be level with an existing step that leads from main dwelling down to existing garage floor.

[nod]

Normally you would get a Structural Engineer to determine the method of joining the two and foundations also 

Followed up with a drawing 

Who has told you you don’t need building regs 

Structural alterations normally require BC 

[WWilts]

14 minutes ago, nod said:

Who has told you you don’t need building regs 

LA building control. Exempt, and they will not issue completion certificate

[nod]

New one on me 

[Temp]

I think porches are exempt but only if you retain the external grade door between house and porch. If you are replacing the door with an internal style door  and heating the "porch" then I think you do need building control.

 

If you want to build in brick I think you need to dig a hole next to the slab to see if its got proper foundations. If not then perhaps look at a timber frame?

 

6 hours ago, WWilts said:

If retaining the existing concrete slab, what layers would you use to build it up by about 275mm?

 

I'm thinking you need a few courses of bricks then a DPC and DPM on sand blind. Then insulation and screed. 200mm PIR and 75mm screedwould be good.

[Temp]

PS Perimeter insulation before the screed.