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Flat Roof Leaks in Heavy Rain

Where to Look and What to Do About It

If your flat roof leaks in heavy rain, it’s a problem that needs to be fixed ASAP.

To avoid unnecessary damage to other areas of your commercial building.

There’s also a good chance that the roof is leaking during smaller storms as well, slowly adding moisture to the interior of your building.

Finding the source of a flat roof leak is sometimes difficult.

In this post, we’re going to look at common problem areas that cause roof leaks on flat roofing systems and what to do next if you think you might have a leak.

Signs Your Flat Roof May be Leaking

Roof leaks show up in a variety of ways. And the leaks in your flat roof could be caused by several different problems. But for now, let’s look at some ways you might discover that you have a leak in the first place.

Here are a few things to look for:

  • Water spots on ceiling tiles
  • Pooled water on floor
  • Bubbling on painted walls
  • Discolored siding or stucco
  • Water stains around light fixtures
  • Water leaking from light fixtures
  • Water stains around outlets
  • Smell of mildew or mold inside
  • Moisture around windows
  • Visible damage to roof
  • Visible presence of mold
  • Higher energy bills

There are other ways that flat roof leaks present themselves on commercial buildings as well. Now, let’s explore some common causes.

Causes of Flat Roof Leaks During Heavy Rain

Pinpointing the cause of leaks for your specific situation may require a roof inspection by a professional roofer.

However, if you are comfortable walking on your roof and have a safe method for accessing the roof, here are a few things to look for.

A flat roof is designed with a very slight slope that directs water toward drainage.

Allowing your roof to shed water during heavy rains.

A healthy flat roof should not have any standing water.

Healthy Dry Flat Roof

The goal for any roofing system is to allow water to freely flow off the roof.

Standing or pooling water causes roof leaks.

#1 – Cracked or Broken Seams

Many flat roofing systems include a membrane.

The membrane can come in the form of TPO, EPDM, PVC, Modified Bitumen or some other type of roofing product.

Most membrane products come on a roll and are installed in long sections.

Each seam is welded together using heat and adhesives.

Weld seams are a common place for membrane leaks, because they can separate.

Here’s an example.

Broken Seam on Mod Bit Flat Roof

The cause of separation may be due to poor installation.

Wind causing the membrane to lift, bellow and flex.

The membrane could split from hail strikes or simply old age.

Whatever the cause of weld seam separation on a flat roof, it leaves a gap for water to leak through.

#2 – Poor or Clogged Drainage

If your roof sits next to trees, chances are you’ve seen some leaves or tree debris on your roof from time to time.

Leaves can clog flat roof drains.

Loose construction materials can also be a problem, when they get wrapped around drains.

Clogged Drains Cause Leaks on Flat Roofs

A clogged drain on a flat roof causes water to sit on top of roofing materials.

When this happens, water can pool and cause leaks.

#3 – Flat Roof Hail Damage

When hail strikes a flat membrane roof, it may cause a tear in the membrane.

Each hail strike could be cause for leaks on your flat roof during heavy rains.

Hail Strikes on Flat Roof

Hail leaks may not show up right away.

But they may take a few months or years to develop.

That’s why it’s important to get your roof inspected by a professional roofer after every hail storm of 1″ or larger.

#4 – Damage From Service Personnel

When maintenance personnel access your flat roof to repair or replace equipment.

Some cause damage to the membrane.

This could be from dropping tools.

Dragging equipment or supplies.

Maintenance on HVAC Flat Roof

Whenever you hire service personnel to access your roof, make sure they take care not to damage the roof.

In Conclusion

Flat roof leaks that occur during heavy rains may also occur during light rains.

If you need help identifying and fixing the source of roof leaks on your flat roof, contact a professional, local roofer.

If you need tips on selecting a great roofer, check out this post on how to hire a reliable roofer.

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If you are in or around Tulsa, Oklahoma and need roofing services, give us a call at (918) 250-7663 or contact us here.

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