This is a walk checklist for a flat or low slope commercial roof. It is written to be carried rather than read, and it runs in the order the walk should go.
It does not replace an inspection by a roofer. It is what a facilities team can do between professional visits, so that the professional visit starts from something rather than from nothing.
Before you go up
Do not go up alone, on a wet or icy roof, or in high wind. Know where the edges, the rooflights and any fragile areas are before you step out, and use the building’s permit system if it has one.
Take a camera, a numbered roof plan, the last report and something to write on.
The drainage
| Look at | What a problem looks like |
|---|---|
| Outlets and sumps | Debris or silt in the sump, water still sitting in it |
| Strainers and domes | Missing, broken, loose or packed solid |
| Clamping rings | Bolts loose or missing, the membrane not gripped evenly |
| Scuppers | A blocked throat, damaged flashing, staining down the wall |
| Overflows | None present, blocked, or evidence that one has run |
| Gutters and downpipes | Debris, sagging, water marks, an open joint |
| Standing water | Water a day or two after rain, or a tide mark where it stood |
| Falls | Water running away from an outlet rather than toward it |
The perimeter
| Look at | What a problem looks like |
|---|---|
| Edge metal and coping | Open joints, lifted sections, staining on the wall below |
| Termination bars | Loose or missing fasteners, a bar that has pulled away |
| Parapet upstands | Membrane pulling away, a gap at the top, a slumped corner |
| Corners | The first place wind lifts and the first place a detail fails |
| Ballast at the edge | Scoured on the upwind side, piled on the downwind side |
The details
| Look at | What a problem looks like |
|---|---|
| Seams and laps | An edge you can lift, a dirt line, a step, hand applied mastic |
| Curbs around units | Gaps at the corners, flashing slipped, fixings through the membrane |
| Pipe boots and collars | Split at the top, clamps missing, standing away from the pipe |
| Penetrations and supports | Anything resting or fixed directly on the membrane |
| Rooflights and hatches | Cracked domes, failed seals, flashing lifted, a hatch left open |
| Expansion joints | Covers lifted, sealant failed, movement visible at the joint |
The field
| Look at | What a problem looks like |
|---|---|
| The open membrane | Splits, cuts, punctures, scuffs, anything dropped and left |
| Blisters | Raised, soft underfoot, larger than in the last photograph |
| Surfacing | Bare patches, granule or gravel loss, chalking on a coating |
| Color and texture | Areas darker, harder or more brittle than the rest |
| Walkways | Pads missing or worn, or ending short of where people walk |
| Anything green | Moss or organic matter, marking a spot that stays damp |
| Loose material | Offcuts, packaging, fixings, washers, tools |
Inside the building
| Look at | What a problem looks like |
|---|---|
| Ceilings and finishes | New stains, stains that have grown, sagging tiles |
| The deck, where visible | Damp, rust lines, drips running along a beam |
| Walls below upstands | Damp at high level, blown plaster, staining at a corner |
| Light fittings | Water near a fitting, which is a safety issue first |
| Insulation in the void | Damp, compressed or stained material |
| What the occupants say | Where it drips, and in which weather |
What to do with it
- Walk the same route every time. Comparability is the point of the record.
- Give every finding an area number and two photographs. Wide and close.
- Rate on three levels with a reason. Fix now, fix this year, watch.
- Never lift, cut or probe anything. Record it and send the photograph.
- Compare with the last visit before you leave. The change is the finding.
Want the reasoning behind these checks? Read how flat roofs work and what the membranes are.
Walked by Date Roof
Common questions
What order should a flat roof be walked in?
Drainage first, then the perimeter, then the details, then the open field, and finish inside the building. The order matters because the drainage and the perimeter usually explain most of what you find afterwards, and walking the field last means you are not crossing it repeatedly.
- Standing water sets the context for every other finding
- The perimeter carries the details that fail earliest
- Details are where handmade work concentrates, and so does failure
- The field is large, uneventful and best left until last
- The interior often confirms what the roof only suggested
Write the route into your own version of this checklist and number the areas on a roof plan. A consistent route is what makes two visits comparable, and comparability is the entire reason for keeping records at all. A roof walked differently each time produces a series of descriptions rather than a history of a building. Where two people walk the roof, give each the same route rather than splitting it, so that both see the whole building.
How often should a flat roof be walked?
Twice a year as a minimum, in spring and autumn, plus after any severe weather and after any work by another trade. Buildings with rooftop plant, grease extract or heavy service traffic need more, because the damage on those roofs comes from people rather than from weather.
- Spring, to find what the winter did
- Autumn, to clear drainage before the wet season
- After severe weather, whatever the schedule says
- After any work by a trade other than roofing
- More often where service traffic is heavy
Most warranties require documented inspection at a stated frequency, and most claims that fail do so on the records rather than on the defect. That alone usually justifies the schedule. The practical argument is simpler: an outlet cleared in October costs nothing, and the same outlet blocked in January costs a ceiling. Put the dates in the calendar a year ahead rather than deciding each time, because a walk that depends on somebody remembering is a walk that happens after the leak.
What is the single most useful thing to take up there?
A numbered roof plan. Every finding needs a location that survives the visit, and a photograph without a reference point on a plan is a photograph nobody can act on three months later when somebody finally approves the repair. Everything else on the roof is replaceable; the plan is what turns a walk into a record.
- Number the areas once and keep the numbering forever
- Mark outlets, equipment and fragile areas on the same plan
- Write each finding against an area number
- Photograph wide to place a finding, close to show it
- Repeat standing photographs from the same positions each visit
The plan also makes a pattern visible that a list never does. Mark every repair, every leak report and every finding on the same drawing over a few years, and a roof that keeps failing in one corner becomes obvious immediately. That is usually a detail or a design problem, and no amount of further patching will end it. Keep one master plan and photocopy it for each visit, so the numbering never drifts between one year and the next.
What counts as urgent on a flat roof?
Anything letting water in now, anything that will let water in during the next rain, and anything that is a safety problem for the people who go up there. Everything else can be scheduled, and labeling it urgent only devalues the word.
- An open split, lap or puncture, in any location
- A blocked outlet with rain forecast
- Water near a light fitting or electrical equipment inside
- A fragile rooflight with no protection around it
- Loose material or edge metal with wind forecast
Use three levels and no more: fix now, fix this year, watch. Write the reason next to the rating rather than the rating alone, because a finding marked urgent with no reasoning is the first thing a budget holder overrules, and a finding marked watch with no reasoning is the one that gets forgotten until it can no longer be watched. Report the urgent items the same day with the photographs attached, rather than holding them until the full report is written.
What should never be done on a walk?
Lifting, cutting, peeling or probing anything to find out what is underneath it. An investigation that opens the roof is a job with a plan and a way of closing it again, and doing it on a walk reliably turns a finding into a leak.
- Do not lift a lap to see how well it is bonded
- Do not cut or core without a plan and permission
- Do not peel back flashing to inspect behind it
- Do not step on a rooflight, ever, whatever it looks like
- Do not walk a wet, icy or very hot membrane unnecessarily
Record what you can see, photograph it properly and mark it on the plan. Most things nobody can identify turn out to be ordinary once a roofer looks at the photograph: an old repair, a survey core, a change of material. The few that are not are still better opened deliberately than discovered by accident.