You don’t need to be a genius to realise that some types of roof are not ideally suited for conversion into living space. In fact, a surprisingly large number of properties have ‘the wrong sort of loft’ for one reason or another. Of these, probably the most challenging are buildings with shallow pitched roofs, because standard space-making solutions such as adding huge box dormers won’t compensate for a chronic lack of headroom. Even where a loft appears reasonably spacious prior to conversion, the available headroom will normally have shrunk by at least 300mm by the time you’ve added a new floor structure and insulated the rafters too.
The good news is, there’s nearly always a solution. But inevitably, complexity equates to higher cost — compared to the sort of cavernous loft that only needs a couple of skylights, a couple of layers of insulation and a beefed-up floor structure. A straightforward project of this type could probably be carried out for as little as £15,000 (less if you’re getting stuck in with some DIY), although a typical large dormer roof extension with a new double bedroom and en suite is likely to set you back around £35,000–£45,000.