Loft extension - can you remove existing roof and start again if not high enough?

[mulranno]

For a detached house obviously....and how much would it cost?

Never done this, so I've no idea what the cost is and that'll depend on where you live and the size of the roof.

But yes, you can, providing you can get planning permission for it.

Link below is what you can do and how much you can increase without planning.

www.planningportal.gov.uk/permission/commonprojects/loftconversion/miniguide

complete roof removal will need planning, you can put a dormer on the back and side.
we are doing this as have a 3 way pitched roof so need to have a side dormer for the regulated head height for the top of the stairs/landing
(what is more than the stairs for the actual house)
we have been quoted 5k all in including the stairs, work and materials including the steals to the stop point where we need to plaster.
some people have mentioned on here up to 30k.

www.planningportal.gov.uk/permission/commonprojects/loftconversion/miniguide

Do you mean raising the roof

yes - it would be raising the roof

Sometimes it's easier to pinch a bit of space from the rooms below rather than a whole new roof. Is there enough ceiling height at 1st floor to do this instead?

My cousin did this I have no idea how much it cost.... but yes it is possible.

It depends as others have said. I know our local LA are obsessed with roof lines and our planning application wasn't granted in its original format (not for a loft extension) because the roof line would have been out of kilter with the rest of the road - they're very hot on not interfering with the street scene. We contemplated a loft extension - we don't have enough head height either but do have good ceiling height in the bedrooms and it would have been much cheaper to lower the bedroom ceilings slightly to get the head height.

Planning issues aside we looked at this and it was ridiculously expensive.

I should think lowering the upstairs ceilings would be a better option.