Kettering lofts are the clearest illustration of the town’s two grades of Victorian house, because the difference is written directly into the roof timbers.
On the artisan terraces the rafters and purlins were sized to do the job and no more. A conversion is often perfectly possible, but the structure almost always needs strengthening rather than simply adapting, and where a previous owner has cut a purlin to fit a hatch or a tank the roof has been quietly weakened. That gets found at the survey, not when the floor goes in.
On the larger houses the roofs are generous, the timbers are heavier, and the head height is frequently there without argument. Those make some of the better conversions in the area.
Head height needs measuring either way, because floor build up and insulation take more out of a roof than anybody expects, and being a hundred millimetres short along the walking line is the difference between a bedroom and an expensive loft.
The permitted development volume allowance is forty cubic metres on a terrace and fifty on a semi or detached house. A dormer facing the road is not permitted development anywhere, and in the intact Victorian conservation areas here anything altering the roofline the street can see will be looked at hard. Our loft conversion page goes through the structural options and the order the work happens in.