Garage roof question - dormer/extension

[Evecob]

Hi,

Is anyone able to help, we are trying to decide if it is worth doing a first floor extension for a house we are in the process of buying. We will need to get planning permission for a first floor extension over the garage, but wondered if instead we could convert this type of garage roof into a room with dormers for example as a 4th bedroom? Would we still need planning permission? Would it be cheaper? Or better to get a proper extension?

Picture of the garage roof from the back garden attached.

Any advice is welcome!

It depends on how the roof is constructed. Is it very open in there already as in purlin and rafter roof or lots of trusses at regular centres?

Have other neighbours done it? That’s a good indication that it’s worth doing/possible to get permission.

I don't honestly know what its like up there, the garage is partially converted into a living space, and the garage thats left has a boarded ceiling.

We are in the process of buying it and selling our current property.

No other neighbours have done it yet I don't think, the houses are only 3 years old.

the house is not overlooked at the front or back