Flat and low-slope roofs are common on offices, plazas, apartment blocks and warehouses across Lagos, especially on Victoria Island and in commercial parts of Ikeja. They are practical, but they have one big weakness: water does not run off them as quickly as it does from a pitched roof. In a Lagos rainy season, the wrong system, or a good system badly installed, will leak.
Here is a plain guide to the main options and when each one makes sense.
PVC membrane
PVC is a tough, flexible sheet membrane with heat-welded seams. The welded seams are its main strength: done properly, they form one continuous waterproof layer. PVC handles strong sun and heavy rain well and resists many chemicals, which makes it a good fit for commercial roofs and roofs with equipment on them.
Best for: offices, hotels, plazas and commercial buildings that need a long-lasting, low-maintenance roof.
TPO membrane
TPO is similar to PVC: a single-ply sheet with heat-welded seams, usually white to reflect heat. It is often a little cheaper than PVC. Quality varies between manufacturers, so the product and the installer both matter.
Best for: large, simple roof areas where reflecting heat is a priority.
EPDM rubber
EPDM is a synthetic rubber membrane, usually black. It is flexible and durable, but its seams are glued or taped rather than welded, so seam work must be done carefully. Being dark, it absorbs more heat than white membranes.
Best for: smaller roofs and budgets where heat gain is less of a concern.
Torch-on bitumen
Torch-on (modified bitumen) sheets are heated and bonded to the roof deck in layers. This is a familiar and affordable option on concrete decks in Nigeria. It works well when installed with proper overlaps and a protective top layer, but it can crack and blister under years of strong sun if left unprotected.
Best for: concrete roof decks and budget-conscious projects, with regular inspection.
Liquid waterproofing
Liquid-applied coatings are painted or sprayed on and cure into a seamless layer. They are useful for roofs with lots of corners, pipes and parapets, and for refreshing an existing roof that is still structurally sound.
Best for: complex roof shapes, small areas and overlays on sound existing roofs.
What matters more than the product
- Drainage. Ponding water is the number one cause of flat-roof leaks. The roof needs a proper fall toward drains and outlets that are kept clear.
- Details. Most leaks start at parapets, joints, pipes and drains, not in the middle of the roof.
- Inspection. A quick check before and after each rainy season catches small problems early.
Not sure which system fits your building?
Great Prince Aluminium Roofing repairs and installs flat roofing systems, PVC roofing and waterproofing for commercial and residential buildings across Lagos. We inspect first and recommend the system that suits your roof and budget. See our Victoria Island and Ikeja pages, or request a free estimate.