Why must I insulate wall that was part flat roof extension?

The work on my bungalow is ongoing and I cant believe that it was back in December 04 that I started asking questions. Everyone keeps telling me I must insulate the walls on the inside and by everybody I mean builder, architect, and engineer but after reading the posts on here I am against it. However we have now reached an impasse on one issueand I dont want to do sometging now and regret it later. So here goes.

I have demolished the existinng flat roof structure that was either a garage or another room next to the bungalow but attached to bungalow and left the wall adjacent to the door or etrance hall still standing as it formed part of an arch for front porch. This wall is cavity towards the rear as the boiler house was situated there,then it is single block when it gets more inside. I wanted the builder to take off all the oldplaster to this wall on the side that was part of the old room and put on new plaster. The presnt palster is badly marked as water came in through flat roof sometime ago. Builder agreed but when I had architect and engineer around they said I MUST have this wall dry lined. When I queried it they said I would have cold air meeting warm and that would form mould!! By my way of thinking this will be an internal wall and I am putting up a pitched roof, also putting in a porch door. So should I opt for that Kingspan Insulation board and not dry line or can I go with my method??

Hope I have made sense.

noah

Im having trouble picturing the wall you are talking about but anyway,
If you are hacking off the plaster then you will need some kind of work done to this wall and there is damn all difference in price between say an insulated board stuck onto wall and sand cement skim finish. It would make more sence to insulate from the inside in this case

I can't follow you either, but I think you may be referring to a potential cold bridge and this should be insulated to prevent heat loss and/or condensation.

ok, and thanks, i will let them use that kingspan stuff. To explain a bit further, imagine you are looking at a bungalow gable end and it has 2 large windows, one living room and other dining room. The entrance is on the right side of bungalow with an arch effect so u step into hallway and turn left to enter main house/corridor. Now look again from front and imagine a flat roof structure to right of bungalow but is linked to archway so go in through door and now on your right is a doorway to flat room or garage. The door is in the wall that I am talking about, it effectively links to bungalow and there was originally a boiler house directly behind the front door but outside. I have knocked wall thought, moved boiler house, then built up wall that was in effect the boiler house door and put in a port hole window for more light. then the flat room structure was demolsihed and a dining room and integral garge built onto bungalow with a pitched roof and wall is now an internal wall.

noah

A picture paints a thousand words...can I assume that what you're saying is that an external cavity wall has now become an internal cavity wall where the wall is still exposed at higher level, above the flat rof line? If this is the case the wall in question probably does not have a stepped dpc or tray incorporated at the flashing line and thus it is good practice to dryline this wall internally to counteract this absence.