When businesses compare commercial roofing proposals, the conversation often revolves around the obvious items:

• What roofing membrane will be installed?
• How much insulation is included?
• How long is the warranty?
• How much will the project cost?
• How quickly can the work be completed?

Those questions matter.

But they don’t tell the whole story.

A commercial roof is a system. Its performance depends on dozens of details involving drainage, insulation, flashing, penetrations, attachment methods and workmanship.

Two contractors can install the same roofing membrane on similar buildings and produce roofs that perform very differently over the next 10, 20 or 30 years.

The difference often comes down to details that are difficult to see once the project is finished.

Here are eight of the most important.

1. How Water Actually Moves Across the Roof

Commercial roofs are often called “flat roofs,” but they shouldn’t actually be flat.

Water needs a reliable path to drains, scuppers or gutters.

One of the first things a roofing contractor should evaluate is how water moves across the existing roof.

Look for areas where water collects after rain.

Those low spots can be caused by:

• Structural deflection
• Settled insulation
• Poor original roof design
• Incorrectly positioned drains
• Clogged drainage components
• Previous repairs that interrupt water flow
• Insufficient roof slope

Installing a new membrane over an existing drainage problem doesn’t necessarily fix it.

You may simply end up with a new roof that holds water in the same places as the old one.

That standing water can increase stress on the roof, collect dirt and debris and expose vulnerable areas to moisture for longer periods.

In some situations, tapered insulation can be used to improve drainage by creating slope beneath the roofing membrane.

The detail that matters: Before installing a new roof, the contractor should understand where water goes — and where it doesn’t.

A roof’s ability to shed water is one of the biggest factors affecting long-term performance.

2. What Is Happening Below the Existing Roof

Commercial roof problems are not always visible from the surface.

Moisture may be trapped beneath the membrane inside insulation or other roof components.

Covering wet material with a new roofing system can create several problems.

Wet insulation may lose some of its thermal performance. Moisture can contribute to deterioration of the roof deck or other materials. And trapped water can complicate future leak investigations because the location where water enters may be far from where it eventually appears inside the building.

That is why evaluating the existing roof assembly can be so important before deciding between repair, restoration, recover or replacement.

Depending on the building and roofing system, that investigation may include:

• Core cuts
• Moisture surveys
• Visual inspections
• Infrared scanning
• Examination of known leak areas

The goal is simple:

Know what you’re roofing over.

The detail that matters: A commercial roof shouldn’t be evaluated only from the surface. Understanding the condition of the materials underneath can prevent existing problems from being buried beneath a new system.

3. Insulation Thickness Isn’t the Whole Story

Commercial building owners often focus on the R-value of roof insulation.

That’s important, but insulation performance depends on more than the number printed on a specification.

The layout and installation matter too.

Gaps between insulation boards can reduce thermal performance.

Poorly fitted insulation around penetrations can create areas where heat moves more easily through the roof assembly.

Compressed, damaged or wet insulation can perform differently than properly installed dry insulation.

Many commercial roofing systems also use multiple layers of insulation with staggered joints.

Why?

Because staggering the seams can reduce continuous pathways where heat can move through gaps in the assembly.

The detail that matters: Don’t ask only, “How much insulation are you installing?”

Also ask:

How will the insulation be installed?

A carefully assembled insulation package can contribute to better energy performance and provide a more stable surface for the roofing system above it.

4. The Details Around Rooftop Equipment

Commercial roofs are rarely simple, uninterrupted surfaces.

They are usually filled with penetrations.

Think about everything that may pass through or sit on the roof:

• HVAC units
• Exhaust fans
• Pipes
• Conduits
• Vents
• Skylights
• Roof hatches
• Equipment curbs
• Supports
• Gas lines

Every one of those locations interrupts the roofing membrane.

And every interruption creates a detail that must be waterproofed correctly.

A large open section of properly installed membrane is usually not where the most complicated leak problems occur.

Leaks frequently develop around transitions, penetrations and equipment.

That is why curbs, flashing heights, corners, pipe boots and equipment supports deserve careful attention.

One especially important issue is equipment that has been added or modified over the years.

A building may have started with five rooftop penetrations and accumulated dozens more through HVAC replacements, electrical projects, communications work and equipment upgrades.

The detail that matters: The complexity of a commercial roof isn’t determined only by its square footage.

A 20,000-square-foot roof with numerous penetrations may require considerably more detailing than a much larger, simpler roof.

5. Membrane Seams and Flashing Transitions

Commercial roofing membranes are designed to create large, continuous waterproof surfaces.

But those surfaces still have seams, transitions and termination points.

With thermoplastic roofing systems, welded seams need proper preparation, temperature, pressure and technique.

With other membrane systems, seams and flashing connections depend on the manufacturer’s specified materials and installation procedures.

In either case, small workmanship errors can create vulnerable areas that are almost invisible once the installation is complete.

Corners can be particularly demanding.

Inside corners, outside corners, curb transitions and changes in elevation often require more detailed craftsmanship than wide-open areas of the roof.

The detail that matters: Quality control shouldn’t focus only on whether the membrane looks smooth from a distance.

The contractor should be paying close attention to seams, transitions, corners and terminations — the locations where small installation differences can have a large impact.

6. How the Roof Is Attached to the Building

A commercial roofing system has to do more than keep water out.

It also has to stay attached to the building.

Wind creates significant forces on a roof, and those forces aren’t equal everywhere.

Roof corners and perimeter areas can experience greater uplift pressures than interior sections of the roof.

Depending on the roofing system and building design, membranes and insulation may be:

• Mechanically attached
• Adhered
• Secured using other approved assemblies

Fastener patterns, adhesive application, substrate condition and perimeter detailing all affect system performance.

One attachment method isn’t automatically best for every building.

The right design can depend on factors such as building height, deck type, location, roof geometry and wind exposure.

The detail that matters: Roof attachment shouldn’t be treated as a generic one-size-fits-all specification.

The system should be appropriate for the building beneath it.

7. What Happens After Other Contractors Get on the Roof

A commercial roof doesn’t stop being vulnerable when the roofing crew leaves.

In many facilities, the roof functions almost like another mechanical floor.

HVAC technicians, electricians, plumbers, communications contractors and maintenance personnel may regularly access it.

Every service call introduces the possibility of roof damage.

Dropped tools, sharp equipment edges, dragged panels and repeated foot traffic can damage membranes.

Even seemingly harmless activities can create problems.

An HVAC technician may remove an access panel and place it directly on the roofing membrane. A contractor may set screws or sheet metal beside a unit. Someone may drag equipment instead of carrying it.

Months later, a small puncture becomes a leak.

The roofing material gets blamed even though the damage happened long after installation.

Walk pads and designated service paths can help protect heavily traveled areas.

Just as important is controlling rooftop access and making sure contractors understand that the roof is a waterproofing system — not a concrete work platform.

The detail that matters: Protecting a commercial roof requires managing what happens on it throughout its life, not simply installing it correctly on day one.

8. Whether Anyone Is Looking at the Roof Between Leaks

One of the easiest ways to shorten the useful life of a commercial roof is also one of the most common:

Ignore it until water starts dripping from the ceiling.

Many roof problems begin small.

A loose piece of flashing, clogged drain, small puncture or separated sealant joint may be relatively straightforward to correct when discovered early.

Leave it exposed to months or years of weather and the repair can become considerably more complicated.

Routine inspections can identify issues such as:

• Clogged drains
• Loose flashing
• Damaged membrane
• Open seams
• Deteriorated sealants
• Storm damage
• Debris accumulation
• Damage caused by other trades
• Problems around rooftop equipment

Inspections are particularly valuable after major storms or after substantial mechanical work has been performed on the roof.

A documented maintenance program may also help building owners understand how the roof is aging and plan future capital expenses instead of reacting to unexpected failures.

The detail that matters: Preventive maintenance isn’t simply about fixing leaks sooner.

It’s about finding conditions that could eventually cause leaks before water enters the building.

The Best Commercial Roof Is More Than a Membrane

When evaluating a commercial roof, it’s tempting to focus on the membrane itself.

TPO, PVC and EPDM systems all have different characteristics, but the membrane is only one part of the finished assembly.

A commercial roof also depends on:

• Drainage
• Insulation
• Attachment
• Flashing
• Penetration details
• Substrate condition
• Workmanship
• Ongoing maintenance

That is why two roofs constructed with similar materials can experience very different results.

The contractor who pays attention to the details beneath, around and above the membrane can often prevent problems that aren’t obvious when the roof is first installed.

Questions to Ask Before Your Next Commercial Roofing Project

Instead of asking only “What roofing system do you recommend?”, consider asking:

Where is water currently ponding, and how will the new system address it?

How will you determine whether moisture is trapped beneath the existing roof?

How will insulation joints and transitions be handled?

What is your process for flashing HVAC units, pipes and other penetrations?

How will the roof be secured at perimeter and corner areas?

How will high-traffic service areas be protected?

What should our maintenance program look like after installation?

A roofing contractor should be able to explain those details in language you understand.

Because the goal isn’t simply to install a new roof.

It’s to build a roofing system that protects the facility, helps control operating costs and performs as expected for as long as possible.

Have questions about your commercial roof?

Commonwealth Roofing Corporation can help evaluate the entire roofing system — from drainage and insulation to flashing, penetrations and long-term maintenance — so you can understand what your roof needs before deciding what to do next.

 

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