BS 6229:2018 Flat roofs with continuously supported flexible waterproof coverings. Code of practice

Weather resistance
Condensation
Roof coverings
Sound insulation
Flat roofs
Moisture control
Repair
Thermal design of buildings
Maintenance
Drainage
Fire safety in buildings
Fully-supported roof coverings
Roofs
Structural design

Link: BS 6229:2018 Flat roofs with continuously supported flexible waterproof coverings. Code of practice
Source: BSI Standards