Alex
It all mounts up:
– Professional Fees
– Council applications
– Structural alterations at ground, first and roof level
– Dormers formation/ roofing/ cladding/ roof drainage
– Insulation, thermal and acoustic
– Windows or rooflights
– Doors/ skirting/ facings
– Heating
– Plumbing
– Lighting
– Power
– TV/ Telecom
– New walls, coombs, formation and plastering
– Flooring, carpet
– Plasterboard
– Decoration
– Staircase and handrails
– Fittings and fixtures
– Roof vents
– Mechanical vents
– Fire safety requirements, i.e fire rated doors, self closers, mains smoke detectors etc
…not to mention labour.
And don’t forget also that the formation of a new stairway usually means that areas of the first floor (or floor below attic level) also require works completed, redecoration etc.
Sure you can do a lot of the above yourself, but I would advise you to employ an Architect and Structural Engineer to complete the design, drawing production, authority approvals and provide guidance at the least.
Of course the above can be simplified if you just want to line the attic and use the space as a non-habitable room and put a ladder up. But then it isn’t really a loft conversion.