Commercial roofing
Commercial roof repair, overlay or replacement?
Compare targeted repair, overlay and full replacement for a commercial roof, and see what findings can change the recommendation.
Choose a targeted repair when the fault is local and the surrounding roof is sound. Consider an overlay when the parts you intend to retain are suitable for the new system. Consider replacement when widespread deterioration or hidden defects make retaining the existing roof a poor investment. A roof condition survey should explain which route fits your building and why.
What each option retains
| Option | When to consider it | What could rule it out |
|---|---|---|
| Targeted repair | Evidence points to an isolated flashing, fixing, rooflight or gutter defect and the surrounding roof is serviceable. | The same defect recurs across several bays, or investigation finds deterioration beyond the visible leak. |
| Overlay or over-sheeting | A survey shows that the elements to be retained can support the proposed roof system and that drainage, edges and openings can be detailed. | Unsuitable fixings or supports, trapped moisture, an unresolved hazardous material or a roof geometry that leaves critical details unworkable. |
| Strip and replace | Roof failure is widespread or the project needs access to repair or replace elements underneath the covering. | Ask how the team will protect the building and its users while parts of the roof are open. The work may need a different sequence or timing. |
Two leaks can point to different jobs
A drip below a rooflight might come from its perimeter detail. Water can also travel along the roof build-up before it reaches the room below. Give the surveyor a record of when and where water appears, previous repairs, and any changes to the roof or equipment. Ask them to separate the likely source from the area affected inside.
On older buildings, check the asbestos information before any intrusive inspection or work. The survey should state what was inspected, what remains concealed and which checks could change the scope. If Solar PV is planned, ask whether the preferred roof option makes sense for the period the array is expected to stay in place.
How to compare proposals
Ask each contractor to list what they will retain, remove and replace. Compare drainage, rooflights, insulation, access, temporary protection and exclusions separately. If the proposals assume different roof conditions, resolve that difference before comparing headline prices.
References. HSE guidance on roof work, HSE guidance on asbestos surveys and Industrial Roofing Services’ refurbishment options guide.
Weighing up your roof options?
Tell us where the problems are showing up, what has already been repaired and when you need to decide. We can discuss which parts of the roof need a closer look before you choose a scope.
Send a project enquiry