Flat roofs are a popular choice for commercial buildings and multifamily properties across Southern California. Their streamlined appearance, efficient use of space, and affordability make them attractive to property owners—but they also come with a unique set of challenges. One of the most common (and costly) problems? Leaks.

At Foothill Roofing, we’ve spent decades diagnosing and repairing flat roofing systems throughout the LA Valley. In this guide, we’ll break down the most common causes of flat roof leaks, why quick fixes often don’t work, and how we approach long-lasting, professional solutions that keep your building protected for years to come.

Common Causes of Flat Roof Leaks

1. Poor Drainage

Unlike pitched roofs, flat roofs don’t shed water easily. If drains are clogged or the slope isn’t engineered correctly, water can pond on the surface. This “ponding” leads to premature deterioration of roofing materials, increased weight load, and eventually, leaks.

2. Damaged or Aging Membranes

Most flat roofs rely on a waterproof membrane like TPO, EPDM, or modified bitumen. Over time, exposure to UV rays, heat, and weather can cause these materials to crack, blister, shrink, or pull away from seams—especially if the initial installation was rushed or subpar.

3. Seam and Flashing Failures

Seams—where two pieces of roofing material meet—are especially vulnerable. Improper welding, poor adhesive application, or lack of maintenance can allow water to seep underneath. Flashing around roof edges, HVAC units, or skylights can also fail due to expansion and contraction or incorrect installation.

4. Roof Penetrations

HVAC systems, pipes, vents, skylights, and drains all create openings in your roof. If these penetrations aren’t sealed properly (or seals degrade over time), they become direct channels for water intrusion.

5. Foot Traffic and Physical Damage

Flat roofs often serve as utility platforms, and frequent foot traffic can damage roofing materials—especially if walk pads aren’t in place. Dropped tools, heavy equipment, or careless service work can create punctures and tears.

6. Improper Repairs or Maintenance

We often find evidence of “band-aid” repairs: tar patches, duct tape, or incompatible materials used in a rush. These rarely last and usually make the problem worse. Skipping routine inspections also allows small issues to grow into major leaks.

How Foothill Roofing Fixes Flat Roof Leaks—Right the First Time

When property managers and business owners call us, they’re usually dealing with recurring issues or leaks that haven’t been solved by previous contractors. Here’s how our team tackles flat roof repairs the right way:

1. Comprehensive Roof Inspection

We don’t guess—we investigate. Our process starts with a detailed inspection of the entire roof surface, including:

• Drainage systems and slope evaluation
  
• Membrane condition and age
  
• Flashing and seam integrity
  
• Roof penetrations and equipment mounts
  
• Signs of ponding, mold, or structural stress
  

We use infrared moisture scanning when needed to detect hidden water beneath the surface.

2. Root Cause Identification

Instead of patching symptoms, we identify the cause. Whether it’s a blocked drain, a failed seam, or systemic issues from improper design, we make sure to address the source of the leak—so it doesn’t return.

3. Tailored Repair Plans

Flat roofs aren’t one-size-fits-all. Our repair approach varies depending on the roofing system, building use, and budget. Solutions may include:

• Rewelding or replacing damaged membrane sections
  
• Installing new flashing around penetrations
  
• Regrading or adding tapered insulation for better drainage
  
• Applying compatible roof coatings for added protection
  
• Full system replacement if the roof is beyond its lifespan
  

4. High-Quality Materials & Techniques

We use industry-best materials from trusted manufacturers like GAF, Carlisle, and Firestone. Our technicians are trained in advanced techniques for TPO, PVC, EPDM, and modified bitumen systems.

5. Preventative Maintenance Programs

After repairs, we often recommend a routine maintenance plan that includes scheduled inspections, drain cleaning, debris removal, and minor sealing. This proactive approach extends the life of your roof and helps avoid emergency calls.

Commercial & Multifamily Expertise

Flat roofing issues don’t just affect buildings—they impact businesses and tenants. Water intrusion can lead to:

• Interior damage and mold growth
  
• Disrupted operations or tenant complaints
  
• Insurance claims and increased premiums
  
• Property devaluation
  

We work closely with property managers, facility directors, and business owners across Los Angeles, Glendale, Burbank, and beyond to minimize downtime and ensure compliance with local codes.

Why Professional Repairs Matter

We understand the temptation to go with a low-cost repair or DIY fix, especially when budgets are tight. But when it comes to flat roofs, cutting corners usually means more leaks—and more costs down the line.

Working with an experienced, licensed contractor like Foothill Roofing means:

• Accurate diagnosis of issues
  
• Proper material matching and application
  
• Full documentation for warranties and insurance
  
• Long-term performance and peace of mind
  

Conclusion: Stop the Leaks—Start with a Pro

If your commercial or multifamily flat roof is leaking, don’t settle for temporary fixes or guesswork. The roofing pros at Foothill Roofing are here to provide expert analysis, precision repairs, and lasting protection tailored to your building’s needs.

We’ve been helping LA Valley property owners protect their investments for over 45 years—and we’re ready to help you too.

Call us today for a professional flat roof inspection and repair plan that works.