Why Flat Roofs Are Popular in Commercial Buildings

Flat roofs, more accurately called low-slope roofs, are common on commercial buildings because they cover large footprints efficiently, give space for HVAC and solar equipment, and are easier to access for maintenance. They also show up on many apartments, condos, and parts of Burbank homes. Their main weak points are drainage, seams, and flashing, so regular maintenance matters.

Last updated October 22, 2026.

What counts as a flat roof?

Almost no roof is truly flat. Low-slope roofs are built with a slight pitch, often from tapered insulation or framing, so water moves toward drains, scuppers, or gutters. Instead of shingles or tile, which rely on gravity and overlap to shed water, low-slope roofs use a continuous waterproof membrane.

Why commercial buildings use them

• Efficient coverage. Pitched roofs over a large retail or industrial building would be tall, heavy, and costly. A low-slope roof covers the footprint with less material and structure.
• Space for equipment. HVAC units, exhaust fans, and solar arrays sit on the roof instead of taking up ground space. That matters on tight urban lots like those along Burbank’s commercial corridors.
• Access. Technicians can walk the roof more safely to service equipment and inspect drains.
• Design. Parapet walls hide equipment and give buildings a clean, modern profile.

Flat roofs on Burbank homes and apartments

Low-slope roofs aren’t only commercial. Around Burbank you will see them on many apartment and condo buildings, on mid-century homes with low-pitched or flat sections, on porches and patio covers, on garages, and on additions built off the back of older houses. Many new ADUs have low-slope roofs too. These residential flat roofs face the same issues as commercial ones, often with less maintenance attention.

Where flat roofs tend to fail

• Ponding water. If drains clog or the slope is inadequate, water sits after rain, adding weight and stress to the membrane.
• Seams. The joints between membrane sheets must stay sealed. Heat cycling in hot Valley summers works on them over time.
• Flashing. Parapet walls, curbs around HVAC units, vents, skylights, and the transition to a pitched roof are common leak points.
• Punctures. Dropped tools, foot traffic, and other trades working on equipment can damage the membrane.
• Edges. Strong winds, including Santa Anas, can lift poorly attached perimeter edges.
• Aging surfaces. Coatings and cap sheets wear, exposing the layers beneath to sun.

How to keep a flat roof watertight

1. Keep drains clear. Check drains, scuppers, and gutters before the rainy season, after windstorms, and if trees are nearby.
2. Schedule periodic checks. A roofer can spot open seams, blisters, and flashing problems before they leak. A roof inspection is a good starting point.
3. Control rooftop traffic. Use walk pads near equipment and ask other trades to report any damage.
4. Fix small problems quickly. Water that gets under a membrane can soak insulation and spread far from the entry point.
5. Keep records. Log leaks, repairs, and warranty information.

Repair, coat, or replace?

Small failures are usually repaired. A roof that is sound but aging may be a candidate for a reflective coating. A roof with widespread leaks or wet insulation usually needs replacement. For the pros and cons of different systems, see our guide to choosing a commercial roofing material.

Energy and fire considerations

Low-slope roofs absorb a lot of heat in the summer. California’s Title 24 energy code often requires cool-roof products when low-slope roofs are replaced, and reflective surfaces can reduce heat on the roof. In fire hazard zones, the roof assembly may need a Class A fire rating. Your contractor and the City of Burbank or your local building department can confirm what applies.

Signs your flat roof needs attention

• Water still standing on the roof two days or more after rain.
• Stains on ceilings near exterior walls, skylights, or under rooftop equipment.
• Bubbles, blisters, wrinkles, or cracks in the membrane surface.
• Gravel or granules washed into piles, exposing the layers below.
• Loose or rusted edge metal, or a membrane pulling away from parapet walls.
• Plants, moss, or debris growing or collecting near drains.

Any of these is a reason to have a roofer take a closer look before the next storm.

Condos and HOAs

In most condo buildings the association is responsible for the roof, so leaks into a unit are usually reported to the HOA or property manager first. Owners of homes with flat sections should treat them as part of the whole roof, not an afterthought, when planning a re-roof.

Before you hire

Ask whether the contractor regularly works on low-slope systems, check the license at cslb.ca.gov, and ask for proof of liability insurance and workers’ compensation. See our commercial and flat roofing page for more.

Frequently asked questions

Are flat roofs more likely to leak than pitched roofs?

They are less forgiving. A pitched roof sheds water by gravity, while a low-slope roof relies on a continuous membrane and good drainage. Well-installed and well-maintained flat roofs can perform well.

How often should a flat roof be checked?

Many owners have low-slope roofs checked at least once a year, often before the rainy season, and after major windstorms or rooftop equipment work. Your roofer can suggest a schedule.

Can I put solar on a flat roof?

Yes, flat roofs often host solar using tilted racks. Make sure the roof is in good condition first and that the racking and attachments are compatible with the membrane and its warranty.

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