BEMS research
What 2,000+ Commercial Roof Leaks Taught Us
Data from 2,163 commercial roof leaks in Chicago and Milwaukee portfolios: what causes them, when leak rates climb, and what repairs typically cost.
Building owners log roof leaks in BEMS, Inspec's building envelope management system, and Inspec records what caused each one and what the repair cost. This study looks at 2,163 leaks logged between September 2012 and September 2026 across portfolios managed by our Chicago and Milwaukee offices. Every figure is an aggregate across many buildings; no individual building or owner can be identified.
Finding 1
One leak in five is not the roof system
Of the 1,352 leaks whose cause was established, 79% came from the roof system itself. The rest came from where the roof meets a wall, from the walls, or from windows. Replacing a roof does not fix a wall or window leak, which is why we find the source before recommending a repair or a replacement.
A further 811 leaks were logged without a confirmed cause and are not included in these percentages.
Finding 2
The 20-year threshold
Roofs leak at a low, steady rate for roughly their first twenty years. After that the rate climbs: about 2.5 times the earlier rate at 20 to 24 years, and about 4.6 times at 25 years and beyond. Knowing where a portfolio sits on this curve is how an owner plans repairs and replacements before leaks become routine.
| Roof age | Roof sections | Leaks per 10,000 sq ft per year |
|---|---|---|
| 0-4 years | 242 | 0.048 |
| 5-9 years | 276 | 0.045 |
| 10-14 years | 215 | 0.042 |
| 15-19 years | 431 | 0.046 |
| 20-24 years | 381 | 0.112 |
| 25-29 years | 274 | 0.208 |
| 30+ years | 180 | 0.212 |
Finding 3
Why we do not rank roof types by leaks
A simple ranking of roof types by leak rate looks dramatic, but for most types one large portfolio produced most of the leaks. Set that portfolio aside and the differences between types shrink sharply. A ranking built on this data would mostly describe individual buildings and how they were installed and cared for, not the roofing materials — so we do not publish one. The age pattern above holds across many portfolios, which is why we report it.
Finding 4
What a roof leak repair typically costs
Across 1,307 roof repair jobs recorded since 2021, the median cost was $670 and the middle half cost between $460 and $1,090. Costs vary by portfolio: outside the largest one, the median leak repair invoice was about $1,050. Caught early, most roof leaks are a repair, not a replacement.
Finding 5
The problems our roof surveys find most
How this study was done
- Source: leak tickets, roof records and repair history in BEMS for clients of Inspec's Chicago and Milwaukee offices, 2012–2026.
- Leak rates use only owners who log leaks in BEMS, count only leaks attributed to the roof system, and are measured per 10,000 square feet per year from when each owner began logging (or the roof was installed, if later).
- Leaks from a roof that has since been replaced are not charged to the roof that replaced it (255 leaks).
- Any group smaller than 25 records or three owners is left out, so no building or owner can be identified. Repair costs are as invoiced, not adjusted for inflation.
See the roof systems we manage, how BEMS works, or talk to an Inspec roof consultant.