Identify the roof structure first
Timber joists, concrete slabs and prefabricated roofs have different construction and assessment needs. Gather drawings and relevant product information for the existing system. If the type is unknown, ask how it can be verified. The roof covering reveals little about it. Do not remove structural elements to create space while spanning direction or possible prestressing remains unknown.
Coordinate the opening and product
Mark the desired position on a complete roof plan with surrounding walls and existing openings. Obtain the required structural opening and interface details from the supplier. Supporting framing must coordinate with these records; waterproofing, insulation and falls require their own design. A changed product may affect several drawings. Check the interface conditions as well as the visible glazing size.
Use a final released document set
Before work, agree who coordinates temporary conditions and methods and what checks are needed when the roof is opened. Keep old and new drawings with clear status so a concept is not used for construction. Record and report deviations from the expected conditions. Enlarging an opening to simplify installation is a design change, not an automatic allowance within an earlier calculation.
Practical checklist
- Gather information on the roof system
- Mark the opening on the complete roof plan
- Share supplier interface details
- Coordinate temporary conditions
A small opening is not automatically structurally insignificant.
Preparing your own project
Would you like this assessed for your home? See our information about other structural calculations. It explains which information is relevant to that brief. The project check helps you prepare your enquiry.
Unsure about a term? The structural glossary provides plain-language explanations and technical context. To understand how the documents are organised, explore our fictional example project .
Background and sources
Sources checked on 3 October 2026. This guide is not a project-specific assessment.
Editorial guide • updated 3 October 2026. General information; not a project-specific assessment.