Raising Roof for Loft Conversion: Best cost?

[Michael Morgan]

We have a 1970s bungalow with 2x4 ceiling joists and max headroom of 6'6 to the ridge beam. Loft is currently floored with T&G chipboard panels. No issues at present as the floored area sits over the central corridor of the house so the span is 1-2m.

The idea would be to have a full flat roof dormer (14m long) along the rear of the house and raise the ridge height of the house to allow 7-8' ceilings. Houses further along the road have done this with 3-4 bedrooms upstairs. They have a structural ridge beam (steel I beam) sitting on the gable end walls with the roof purlin walls built up to form bedroom walls and to support along the span.

At what point is it more cost effective to have a completely new trussed roof put onto the house? Am I missing something?

 

[foxhole]

Best get quotes for both options , ready made trussed roof timbers are cheaper to produce as it uses smaller timbers. It can be quicker option but not an option if you don’t want to move out while works are in progress.

 

[Michael Morgan]

What does a re-roof look like? Is it a case of scaffold up, tiles off, roof timbers off then crane in the new trusses? Guessing that it's nearly impossible to keep the house watertight? Or is there a method for re-roofing which keeps water out of the house whilst there's no tiles on?

 

[foxhole]

Either do it quickly during dry spell or ad a tin roof ( expensive).Pretty watertight once felts on.
Can be done without crane with enough bodies, did my garage roof (7mx5m) with just two of us as each truss is quite light weight.