Flat roofs fail at the details far more often than in the middle: upstands, drips, outlets and rooflight kerbs. Understanding that makes most flat roof problems much easier to diagnose.
These answers cover why flat roofs leak, what ponding water means, how EPDM, GRP and torch-on felt compare, expected lifespans, and when a patch repair is sensible rather than a full recover.
Do not assume every flat roof is suitable for walking. Some systems permit limited maintenance access, while others need protection or dedicated walkways. The underlying deck and structure must also be capable of carrying the load.
See also: Can I put decking on a flat roof?
Potentially, but the structure, waterproofing and drainage must be designed for it. Decking should not simply be laid over an ordinary flat roof without checking load capacity, protection of the waterproof layer and how water will drain.
See also: Can I walk on my flat roof?
Blistering can occur when air or moisture becomes trapped within certain roofing systems or when layers lose adhesion. Whether the affected area can be repaired locally depends on the material, extent and condition of the surrounding roof.
See also: Why does my flat roof keep leaking? · Can a flat roof be repaired instead of replaced?
