Hi
We're in the process of trying to do an eco-refurbish on an existing out-house/ garden room adjacent to our house. We had to go through planning as this plus kitchen extension over sq footage. The garden room has 2 existing stone walls - 1 to lane and 1 adjoining wall to neighbours garden. There is an existing concrete floor in the room. We want to use a timber frame and green roof which is fine but building control have said we need to dig up floor to ensure damp proof membrane throughout, he recommends knocking down stone walls which we don't want to do. If we keep the walls then he wants a bitumen or other impermeable membrane to ensure no condensation or rising damp issues occur. We would rather use natural finishes. Is there anyway to overcome this? Are there any natural finishes that building control would be happy with - we need examples as this guy seemed reluctant to budge! Any advice would be much appreciated.
thanks
Hayley

Use lime and you will never have any problems with damp -- dont use cement.

Certainly don't knock down the walls without checking if that would mean you need planning permission to build a "new" outbuilding.

Hi Hayley.
I would try asking the Building Control officer if he is prepared to put the demands in writing, highlighting exactly which clauses of the building regulations they are attempting to enforce.

I do not believe they can make you demolish anything unless it is unsafe.

Further they cannot make you hack off rendering or dig up floors. What they can do is make you insulate, but only if you are 'adding a layer' such as rendering or renewing the floor anyway. This is quite complicated however and several exclusions can apply

Regarding underpinning, they can only make you do this if the walls are unsafe or if you intend to add loading to the existing walls in some way. As tony says though, this can often be avoided by cute design.

If the levels allow you could also put a DPM on top of the existing concrete floor eg top to bottom...

Screed
Insulation
DPM lapped up walls
sand blind
Existing concrete floor.

or perhaps

Engineered oak
18mm flooring grade chipboard T&G
Insulation
DPM lapped up walls
sand blind
Existing concrete floor.

What do you plan to build your timber frame on? The BCO may want to see you dig holes in the conc floor to put in some sort of foundations in anyway.

Well, if there's existing then it's existing, but it's not totally clarified as to why if there is planning passed it's to be altered now?

Unless a building or structure is listed or in a conservation area then there's nothing to prevent demolition. There's also no mechanism to force demolition either, unless unsafe.

However, if there is planning passed, then it's a little late to start trying to alter that to any great extent. The time for negotiations was before the app went in.

No, not unless, as I said, its listed or conservation area.

No, it's consent but not planning permission in a conservation area BUT you do need it to go hand in hand with planning permission.

It's not straightforward (nor indeed is demolition of a listed building or conservation area building or structure...) and there's quite a bit of case law to be taken into account also.