A flat roof is more than its visible membrane. Drainage, upstands, penetrations and existing layers determine which questions must be answered before repair or renewal.
Which assembly is already there?
Collect drawings and records of previous renewal. A material name does not establish which insulation or substrate is present.
Where information is missing, investigation belongs in the proposal. Surface colour is not a reliable basis for selecting an entire roof system.
How will junctions be included?
Ask how outlets, roof edges and penetrations connect to the proposed layers. Additional insulation may change the available space around existing details.
A proposal should describe those relationships. A surface-area figure for new covering does not describe the whole roofing task.
What is installed on the roof?
Paving, solar panels and equipment require coordination of access, protection and possible relocation. Record who manages those components.
An existing load does not establish suitability for a new use. Capacity and conditions of use need separate assessment when the function changes.
How can options be compared?
Compare methods using the same boundary, assumptions and details. Keep an investigation stage open where existing layers are unknown.
The planner does not prescribe materials. It records the information a contractor needs to prepare a reasoned proposal.
Worth asking
Frequently asked questions
Can a new layer always cover the old one?
No. Condition, composition and junctions require assessment when selecting the method.
Is insulation calculated automatically?
No. The actual construction and current conditions require separate investigation.
Is a roof terrace an ordinary flat roof?
Use and protective layers add questions. Existing use does not prove suitability for a new function.