The 3 Most Common Leak Areas Commercial Roofing Companies in Los Angeles See

Roof leaks are one of the most frequent and costly issues for commercial property owners in L.A. Even with our mostly sunny climate, UV, thermal movement, and the occasional heavy storm can expose weak points. The tricky part? The water stain you see inside often isn’t directly under the leak on the roof.

Below are the three leak sources we find most often—what causes them, what to look for, and how to fix them fast.

1) Flashings & Penetrations (Skylights, Curbs, Vents, Parapet Walls)

Anywhere the roof membrane meets another element is a prime leak candidate. Typical culprits are deteriorated metal flashings, loose counter-flashings, cracked sealant at skylight curbs, and aged pipe boots. When flashing detail fails (or was never installed right), water finds a path into the assembly.

What to do next:

• Schedule a leak-focused repair to re-attach, re-seal, or replace failed details: Commercial Roof Repair.

• If you have old or yellowed skylights (common crack points), consider new, properly flashed units: Skylight Installation.

• Learn the basics of flashing design to spot issues early: 7 Must-Know Flat Roof Flashing Types.

Why it matters: Flashing is the primary waterproofing at all roof transitions and penetrations; when it’s wrong, the roof will leak. (NRCA guidance emphasizes flashing’s role at walls, skylights, curbs, and penetrations.) National Roofing Contractors Association

Safety side note for skylight work: OSHA treats skylights as “holes” and requires protection (covers/guardrails) during work—important for your vendors and liability. OSHA

2) Poor Drainage & Ponding Water (Drains, Scuppers, Gutters)

Flat roofs must move water off the field quickly. Clogged drains or undersized/poorly placed scuppers allow water to sit and “pond,” accelerating wear and loading the structure. Many codes require secondary (emergency) drainage when parapets are present so ponding doesn’t exceed design limits. ICC Digital Codes+1

What to do next:

• Clear drains/gutters and verify proper flow as part of routine maintenance: Maintenance Services and 6 Simple Commercial Flat Roof Maintenance Tips.

• If low areas repeat, consider localized repairs + a coating restoration to re-establish positive drainage: Coatings & Restoration.

• Brush up on seasonal readiness: 8 Tips to Prepare Your Roof for the Rainy Season.

Why it matters: The industry considers prolonged ponding undesirable (often defined as >48 hours). Beyond membrane wear, ponding increases live load and can threaten structural integrity in extreme cases. Mediaedge

3) Membrane & Seam Damage (TPO/PVC, Modified Bitumen)

UV, thermal cycling, and foot traffic degrade membranes and stress seams. On single-ply systems, heat-welded seams can peel or open; on modified bitumen, laps can split or fishmouth. Add blisters or punctures from trades and you’ve got a leak pathway.

What to do next:

• Have a tech trace and repair the defect now: Emergency Roof Leak Repair.

• If issues are widespread, evaluate repair vs. restore vs. replace:
  – Repair or Replace? 2025 Guide
  – Single-Ply vs. Modified Bitumen—What’s Best?

• Quick DIY tells (until a pro arrives): 9 Proven Flat Roof Leak Repair Tips.

Why it matters: Careful leak investigation and detail-oriented repairs reduce recurrence. (IIBEC has excellent resources on tracing leak paths and durable detailing.) iibec.org

Pro Tips for L.A. Property Managers

• Inspect at least twice a year + after big storms. Catching failures early is the cheapest fix. (How to Prevent Damage to Your Commercial Roof)

• Document everything. Photos and notes help with warranties and budgeting.

• Plan ahead. Rising material/labor costs mean waiting usually costs more: The Real Cost of Waiting to Repair a Flat Roof.

Need Help Now?

If you’re seeing stains, ponding, or active drips, we’ll diagnose the source and fix it right.

• Book a free commercial roof inspection (photos + recommendations): Get a Free Inspection

• Or jump straight to leak repair: Commercial Roof Repair | Emergency Roof Leak Repair

Sources & Further Reading

• OSHA 1910.28 — Fall protection requirements (skylights treated as holes). OSHA

• International Building Code §1503.4 & §1503.4.2 — Roof drainage & scuppers (emergency/secondary drainage). ICC Digital Codes+1

• IIBEC — Leak investigation & detailing articles. iibec.org+1

• NRCA — Role of flashing in keeping water out at penetrations/edges. National Roofing Contractors Association

• NRCA-referenced note on ponding water (>48 hours considered undesirable). Mediaedge