Loft Conversion: Roof Preparation and What Your Roofer Needs to Do First

The Roof Survey Before Conversion

Any reputable loft conversion company will require evidence that the existing roof is in adequate condition before starting work. This is not just a formality — a conversion involves structural changes to the rafters and introducing new loads to the roof structure. If the existing tile, felt, or batten is in poor condition, the sensible sequence is: survey, address any structural roofing issues, then proceed with the conversion.

Specifically: nail sickness on the existing tile will cause tile displacement during the conversion work (tiles are disturbed repeatedly during the structural phase) and will require addressing immediately after anyway. Perished felt should be replaced when structural work exposes it — doing it afterwards requires a second access event. Ridge and flashing issues are best addressed while the scaffold is in place for the conversion.

What Changes to the Roof the Conversion Requires

A standard loft conversion alters the roof structure in several ways: ceiling joists are replaced by structural floor beams (typically engineered timber or steel); rafters may be strengthened or replaced; the roof void is insulated at rafter level (warm roof construction) or at ceiling level (cold roof); and new windows or dormers are introduced. Each of these changes has roofing implications that require a roofer rather than the conversion contractor.

The weatherproofing at each new roof aperture — dormer cheeks, roof window flashings, and any new abutments — is roofing work. The quality of this work determines whether the conversion stays dry. It should be specified and quoted by a roofer at the survey stage, not improvised by the conversion contractor's labour.

Sequencing the Work Correctly

The correct sequence for a loft conversion in Aylesbury: 1. Roof survey by roofer — identify any pre-existing issues. 2. Address structural roofing issues (nail sickness, felt, ridge). 3. Conversion contractor installs structural frame and floor. 4. Roofer installs dormer, roof windows, and all weatherproofing. 5. Conversion contractor completes internal fit-out. Getting steps 3 and 4 reversed — or having the conversion contractor attempt the weatherproofing — is the most common source of post-conversion roof leaks.