Adding dormer windows to an old property

[MisterBoy]

I've an 1860s Victorian property with a very spacious loft, which has already been converted (decades ago) into a big room, ensuite, etc. A couple of Velux skylights were added but I think it could be done much better.
It's the original roof and it is getting to the point that it could be reasonable to replace it, some lathes are apparently rotting and there's a lot of nail sickness.
But to me it seems like it would make sense to do any modifications at the same time, reconfigure windows and ideally add some dormers or similar - even a little terrace maybe to get the sun.

Is this an obvious decision, or could the roof as easily be replaced now and alterations made later?
Are alterations like dormer windows, etc, done by a roofer or a builder - do they require an architect as well?

It could be an amazing space but I can see the zeros lining up on the bills already!

 

[freddiemercurystwin]

New dormer work is normally carried out by a builder + roofer. You don't need an architect (or any suitable designer) provided the builder knows exactly what he's doing but will he? Many talk the talk. If on the back of the house - probably don't need planning permission, on the front definitely needs planning permission. It will be more efficient/cheaper overall to do it whilst your have the roof done.

 

[catlad]

One of the main obstacles will be that if you need to remove any purlins, you will also need to comply with current insulation regulations.

 

[MisterBoy]

One of the main obstacles will be that if you need to remove any purlins, you will also need to comply with current insulation regulations.

As in, for the whole roof/building?

 

[catlad]

It depends on whether your roof has only one purlin.