How to Convert a Pitched Roof to Flat

Converting a pitched roof to a flat roof is a relatively uncommon project, but it's one we do carry out. The most common reasons are to create a more modern look, to access a roof terrace, or as part of a major renovation.

Is it Structurally Possible?

Most structures that currently support a pitched roof can be adapted to carry a flat roof, but this requires a structural assessment. A structural engineer must confirm the walls, beams, and foundations can handle the changed load distribution.

Planning Permission

Converting a pitched roof to flat will almost always require planning permission, as it constitutes a material change to the external appearance of the building. In conservation areas and for listed buildings, approval may be difficult to obtain. Always check with your local planning authority first.

The Construction Process

The conversion involves removing the pitched roof structure, adapting the wall plates and any structural beams, forming the new flat roof structure (typically with timber joists and OSB deck), installing insulation and waterproofing, and finishing the perimeter details.

Cost Considerations

Converting a pitched roof to flat is a significant project. Costs depend heavily on the size, structural requirements, and specification. You should budget for structural engineering fees, building control, scaffolding, the roofing work itself, and any internal making-good required.