Loft conversion survey

Headroom is measured, not estimated

The number that decides most loft conversions is the finished head height along the route people will walk. Existing ridge-to-ceiling height is not that number: the new floor structure sits above the existing ceiling, and insulation and finishes reduce the height again below the rafters.

The survey records the existing dimensions and explains how much of that is lost to the build-up, so you know at the outset whether the space works, whether a dormer is needed, or whether the roof would have to be raised — which is a planning question as well as a construction one.

Cut roof or trussed roof

A traditional cut roof, framed on site with purlins and rafters, usually has open space that can be adapted, with the existing members reinforced or replaced as the engineer directs.

A trussed rafter roof, common from the late 1960s onwards, is a designed structural system. The webs that cross the space are doing a job, and they cannot simply be cut out. Conversion is still possible but the structural solution is more involved, and that has cost consequences you should know before you fall in love with the idea.

• Rafter, purlin and ceiling joist sizes and spans, where visible
• Whether truss webs obstruct the usable space
• Condition of the covering, felt, battens and any earlier repairs
• Existing water tanks, flues and services routed through the space

The staircase decides the layout below

A loft conversion needs a permanent staircase meeting the same requirements as any other stair, with adequate headroom over the flight. Fitting it usually costs a bedroom, a landing or part of one, on the floor below.

Owners frequently plan the loft and forget the floor beneath it. The survey identifies where a stair can realistically land and what that does to the existing rooms, so the trade-off is a decision rather than a surprise.

Fire safety and building control

Adding a storey changes how the house has to perform in a fire. Requirements typically cover protecting the escape route, the fire resistance of the new floor, doors, and detection throughout.

These are building control matters, and they are the reason a loft conversion cannot be treated as a decorating job. Where a conversion has already been carried out without approval, the absence of documentation is something your conveyancer will need to address.