Roof and Building Fabric Inspection
Unit 4, Northgate Distribution Park
| Report reference | AER-2026-114 |
|---|---|
| Client | Ms J. Halloran, Northgate Estates |
| Site | Unit 4, Northgate Distribution Park, Sofia 1528 |
| Asset inspected | Main warehouse roof, approx. 2,400 m², profiled metal deck |
| Date of survey | 14 July 2026 |
| Date of report | 16 July 2026 |
| Surveyed by | A. Petrov, operator BGR-OP-4471 |
| Status | Final |
1. Executive summary
The warehouse roof was inspected by unmanned aircraft on 14 July 2026. The roof is in fair overall condition for its estimated 18 years and construction type. The deck itself is sound; the issues found are concentrated in the rainwater goods and at the north ridge.
7 findings were recorded: 1 S1, 2 S2, 3 S3, 0 S4, and 1 not assessable.
Matters requiring immediate attention
- R-01 - Displaced ridge capping, north elevation. Two tiles are loose above the loading yard, one overhanging the eaves line. Ms Halloran was notified by telephone at 14:20 on the day of survey and the yard beneath was coned off the same afternoon.
Principal recommendation. Make the north ridge safe and re-bed the affected run before the autumn. In the same visit, clear the two blocked outlets - the ponding at the north-east corner is the most likely source of any future ingress.
Areas not assessed. The parapet gutter on the east elevation could not be seen from any safe flight position and is graded NA. It should be checked from a mobile platform when one is next on site.
2. Scope
This report covers a visual inspection by unmanned aircraft of all external roof surfaces, rainwater goods, parapets and roof-mounted plant.
Not within scope: internal inspection, subsurface or interstitial condition, structural adequacy, asbestos survey, electrical or mechanical testing, and drainage performance under load.
Commissioned by Northgate Estates for the purpose of informing the 2027 planned maintenance budget. Prepared for that client and that purpose.
3. Limitations
This survey is visual and non-intrusive. It records what was visible from the air, in the conditions on the day.
- No physical testing. No coverings were lifted, no fixings tested, no moisture readings taken. Condition beneath the visible surface is not reported.
- Structural condition is not assessed. The minor deflection noted at R-05 is an observation only and requires assessment by a structural engineer.
- Concealed areas. The parapet gutter on the east elevation, and the deck beneath the two roof-mounted AHUs, could not be viewed adequately. Both are graded NA.
- Conditions on the day. Overcast, 4 m/s south-westerly, dry, 24 °C. No rain in the preceding 48 hours, so standing water at the north-east corner indicates a drainage fault rather than recent weather.
- A point in time. Roof condition changes. This report describes 14 July 2026 only.
4. Method and conditions
| Aircraft | DJI Mavic 3 Enterprise, C2 class marking |
|---|---|
| Sensor | 20 MP visual |
| Operating category | Open, subcategory A2 |
| Ground sample distance | approx. 3 mm/px at survey height |
| Survey pattern | Perimeter orbit at 25 m, plus nadir grid at 30 m, 75% overlap |
| Weather | Overcast, 4 m/s SW, 24 °C, dry; no precipitation in previous 48 h |
| Time on site | 13:40 - 15:05 |
Airspace and permissions. The site lies outside any published UAS geographical zone. Zone status was checked against the Bulgarian CAA feed on 14 July 2026 before flight. Landowner permission for take-off and landing was held in writing.
Severity scale
Every finding carries one of the grades below. Grades describe observed condition and urgency - not cost, and not cause.
| Grade | Meaning | Suggested response |
|---|---|---|
| S1 | Immediate. Active failure, or a condition presenting a safety risk to people or a risk of rapid consequential damage. | Act now. Make safe pending repair. |
| S2 | Serious. Failure has occurred or is clearly imminent. Will worsen materially within one season if untreated. | Repair within [30] days. |
| S3 | Moderate. Deterioration beyond expected wear, not yet causing failure. | Next planned maintenance cycle. |
| S4 | Minor. Cosmetic, early-stage, or expected wear for the age and exposure of the asset. | Monitor at next inspection. |
| NA | Not assessable. The area could not be surveyed adequately, or the observation cannot be graded from imagery alone. | See Limitations. Further investigation required. |
5. Findings
5.1 North elevation
| Location | North ridge, approx. 4 m east of the west gable |
|---|---|
| Observation | Two ridge tiles displaced; mortar bedding failed over approx. 1.2 m. One tile overhangs the eaves line above the loading yard. |
| If untreated | Falling material into a trafficked area. Water ingress at ridge. |
| Recommendation | Make safe immediately. Re-bed the affected run and inspect the remainder of the ridge line. |
| Action taken | Client notified 14:20, 14 July. Yard coned off same day. |
| Evidence | AER-2026-114_R-01_north-ridge.jpg |
| Location | Parapet gutter, north-east corner |
|---|---|
| Observation | Outlet obstructed by leaf litter and a displaced sealant strip. Standing water approx. 8 m upstream, with tide-marking on the gutter sole consistent with repeated ponding. |
| If untreated | Ponding load; risk of ingress at the gutter lap. |
| Recommendation | Clear the outlet and review gutter maintenance frequency. No rain in 48 h, so this is a drainage fault, not weather. |
| Evidence | AER-2026-114_R-02_ne-gutter.jpg |
5.2 South elevation
| Location | South slope, bays 12-19 |
|---|---|
| Observation | Surface corrosion at approx. 30 fixing washers, concentrated along two purlin lines. No perforation visible; no staining on the underside visible from the eaves. |
| If untreated | Progressive loss of seal at the fixing, leading to point leaks. |
| Recommendation | Include in the next planned maintenance cycle. Replace washers on the affected lines rather than spot-treating. |
| Evidence | AER-2026-114_R-04_south-fixings.jpg |
5.3 Areas not assessed
| Ref | Area | Why | Suggested next step |
|---|---|---|---|
| NA-01 | Parapet gutter, east elevation | Not visible from any safe flight position - adjacent building at 3 m | Inspect from a mobile platform |
| NA-02 | Deck beneath AHU 1 and 2 | Obscured by plant | Inspect at next mechanical service |
6. Defect schedule
| Ref | Location | Finding | Grade | Recommended action |
|---|---|---|---|---|
| R-01 | North ridge | Displaced ridge capping | S1 | Make safe immediately |
| R-02 | NE parapet gutter | Blocked outlet | S2 | Clear; review frequency |
| R-03 | SW downpipe | Detached bracket | S2 | Re-fix within 30 days |
| R-04 | South slope, bays 12-19 | Corrosion at fixing washers | S3 | Next cycle |
| R-05 | Bay 7 | Minor deflection between purlins | S3 | Engineer to assess |
| R-06 | West gable | Lifted flashing, approx. 0.6 m | S3 | Next cycle |
| NA-01 | East parapet gutter | Not assessable | NA | Inspect from platform |
Totals. S1 1 · S2 2 · S3 3 · S4 0 · NA 1
7. Recommended actions
- Immediate: R-01 - make the north ridge safe. Completed 14 July; permanent repair still outstanding.
- Within 30 days: R-02 and R-03 - clear the outlet and re-fix the downpipe bracket.
- Next maintenance cycle: R-04 and R-06.
- Further investigation: R-05 requires a structural engineer; NA-01 and NA-02 require physical access.
Costs are not included. This report records condition; pricing the repair work would compromise its independence.
Appendix A - Image index
| Image | Finding | Description |
|---|---|---|
| AER-2026-114_R-01_north-ridge.jpg | R-01 | North ridge, oblique, 15 m |
| AER-2026-114_R-02_ne-gutter.jpg | R-02 | NE parapet gutter, nadir, 20 m |
| AER-2026-114_R-04_south-fixings.jpg | R-04 | South slope, oblique, 12 m |
Appendix B - Operator details
| Operator | Petrov Aerial Surveys EOOD |
|---|---|
| UAS operator registration | BGR-OP-4471 |
| Remote pilot | A. Petrov - A2 certificate of competency |
| Insurance | Lev Insurance, policy 88-2211-04, limit €2,000,000 |
| Contact | a.petrov@example.com · +359 2 000 0000 |
Prepared by Petrov Aerial Surveys EOOD. Visual aerial inspection only - see sections 2 and 3 for scope and limitations. EXAMPLE DOCUMENT.