New roof without distrurbing ceiling

[Moonhawk]

We are intending to have a new roof put on our bungalow to allow the first floor to be developed into a livable space.

We would like to do this whilst keeping the ground floor as undisturbed as possible (i.e. the ceilings).

I know companies like moduloft do it - whereby they prefabricate the loft conversion - then take the old roof off and drop the new roof/loft conversion in, leaving a gap between the existing ceiling timbers and the new floor timbers that form part of the roof trusses. The new loft conversion essentially floats above the existing structure - but I don't know exactly how they do it.

I guess the trusses could have heels on and sit in between the ceiling timbers - or the wall plate could be built up a bit like the image below. grey is the wall, brown is the existing wall plate, green are the ceiling timbers and blue is the new timber used to build up the wall plate for the new trusses to sit on top of and for sitting between the existing rafters as support.



I was wondering if anybody had come across this type of work and how the new trusses are tied into the existing wall plate.

edit: after Googling around a bit more - I think the top blue plate would be termed a "pole plate". Is this right?

Edited by Moonhawk on Tuesday 24th January 19:55