Why Your Commercial Roof Leaks at the AC Unit: Curbs, Penetrations & Parapets (Volusia County Guide)

The call almost always sounds the same. Water is coming through the ceiling tile in the back office, or down a wall near the stockroom, and it started after a hard afternoon rain. Somebody got on the roof, looked at the membrane, and it looked fine. Because it probably is fine.

On a low-slope commercial roof, the field of the membrane — the big flat expanse in the middle — is the part that fails last. It is one continuous sheet, it was installed by machine or by a crew working in a rhythm, and it has nothing interrupting it. The leaks come from the places where that sheet had to stop and turn: the curb under the air conditioner, the pipe going through the deck, the parapet wall at the edge, the drain, the sealant pocket around an oddly shaped support leg.

The U.S. Army Corps of Engineers, which manages one of the largest roof portfolios in the country, put it plainly in its roof management study: “Flashings are the most common sources of roof problems.” The same report lists, as a recurring design failure, “too much installed equipment placed on the rooftop, which requires extensive and complex flashing details and promotes increased roof traffic.”

This guide walks the details in the order we actually check them, tells you which requirements are genuine Florida Building Code and which are manufacturer or trade recommendations — a distinction that matters enormously when a warranty claim is on the table — and flags the specific things that go wrong on Volusia County roofs.

The Florida Rule Nobody Quotes: Your AC Unit Needs an 8-Inch Curb

Here is a requirement that sits in the Florida Building Code, applies statewide, and almost never comes up in conversation — including, frankly, in a lot of HVAC installations we find on existing buildings.

Two paths. Either the unit sits on a curb that stands at least 8 inches proud of the roof surface, or it sits on raised supports with the roof running underneath it — and in that second case the clearance underneath is set by unit size:

Width of rooftop unit	Minimum clearance below (FBC Table 1510.10)
Less than 24 in.	14 in.
24 in. to 36 in.	18 in.
Over 36 in. to 48 in.	24 in.
Over 48 in. to 60 in.	30 in.
Over 60 in.	48 in.

The logic is maintenance, not water. A roof is a consumable building component. Someone has to be able to get a hand, a tool and a sheet of membrane underneath that equipment to repair, recover or replace what is under it. When a 7-foot-wide package unit is set down on 4-inch sleepers, the roof under it effectively becomes unmaintainable, and the day it needs replacing, somebody is paying a crane bill to lift the HVAC.

The code does include an exception for existing equipment: where the building official judges that existing rooftop equipment already provides sufficient clearance to repair, recover, replace and maintain the roofing system, it need not comply with the table. That is a judgment call made by your jurisdiction, not by the roofer and not by the HVAC contractor.

The 8-Inch Confusion — Two Different Rules, One Number

This trips up owners, property managers and honestly a fair number of contractors, so it is worth being precise. There are two separate 8-inch rules in roofing, and only one of them is code in Volusia County.

The rule	What it governs	Is it code here?
8 in. curb height FBC‑B 1510.10	How high the curb under a rooftop mechanical unit must stand above the roof	Yes — adopted code, statewide.
8 in. base flashing height NRCA + manufacturers	How far the membrane flashing must run up a curb, wall or parapet	No — it is a trade recommendation and a warranty condition, not Florida code outside the High-Velocity Hurricane Zone.

We checked Chapter 15 of the Florida Building Code line by line. Section 1503.2 requires flashing “to seal roofing systems, where the system is interrupted or terminated” and to prevent moisture entering at parapet walls and penetrations — but it sets no minimum height. The 8-inch base flashing figure comes from the NRCA, which prints “8″ MIN. FLASHING HEIGHT” on more than twenty of its published construction details, and from the membrane manufacturers themselves. Johns Manville’s TPO specification, for example, states that base flashings “shall extend a minimum of 8″ (200 mm) above roofing level.”

That is not a reason to ignore it. Quite the opposite — because it is a warranty condition, a short flashing can cost you coverage even though no inspector will ever cite it. But you should know which hammer is being held over you. Inside the High-Velocity Hurricane Zone, which is Broward and Miami-Dade counties only, the 8-inch base flashing is mandatory code through RAS 111‑20. Volusia County is not in the HVHZ.

“I Can’t Flash That” — Why Spacing Decides Everything

When a roofer tells you a penetration cannot be flashed properly, they are usually not being difficult. Flashing a pipe or a curb is a physical act performed by a human with hands, a roller and a heat gun. If there is no room, there is no flashing — there is only sealant, and sealant is a maintenance item, not a roof.

The NRCA publishes the minimum room it believes a mechanic needs:

• 12 inches minimum between pipes
• 12 inches minimum between a pipe and a curb or wall
• 24 inches minimum between a wall and a curb

Its manual is blunt about shapes, too: structural supports that go through the membrane “preferably should be square or round,” because “H‑, L‑ and T‑shaped structural supports are not preferred because they are difficult to flash properly and may be a constant maintenance problem.”

And on the broader question, the NRCA does not hedge at all: “NRCA does not recommend using a roof as a location for HVAC equipment.” That ship has sailed on most Florida commercial buildings — the roof is where the equipment goes. But it tells you how the people who write the detail drawings think about the risk, and it explains their follow-up advice, which is genuinely useful: “Running conduits and pipes within the interior of rooftop curbs will minimize rooftop penetrations.” Every line that runs up inside the curb instead of through its own hole is one less future leak.

Pitch Pockets: The Detail Your Roof Is Probably Leaking Through

A pitch pocket — also called a penetration pocket or pourable sealer pocket — is a small metal collar set around an awkward penetration and filled with a pourable sealant. They exist because some things going through a roof cannot be flashed: an angle-iron support leg, a bundle of conduit, a threaded rod.

They are also, by the trade’s own account, a known weak point. The NRCA’s manual states that “Penetration pockets are not the preferred flashing method at the penetrations because they may be a constant maintenance problem.” Its preferred approach is explicit: “Prefabricated flashing, metal sleeves and curbs with premolded pipe flashings are preferred for sealing pipes or irregularly shaped support legs. Penetration pockets or pitch pans are acceptable as a last alternative.”

Three things an owner should take from that:

1. They need refilling. Writing in IIBEC’s journal, engineers at Wiss, Janney, Elstner describe the “annual maintenance of refilling or re-topping the filler material that is required by penetration pockets, regardless if they are filled with pitch, asphalt, or multi-part urethanes.” A pitch pocket is not a finished detail. It is an appointment.
2. Your warranty may not cover them. NRCA’s own magazine notes that “most roof system manufacturers take exception to penetration pockets in their warranties.” At least one manufacturer states flatly that it does not guarantee pitch pan performance because they are a maintenance item.
3. They are frequently avoidable. On a re-roof, an irregular penetration can often be enclosed in a new curb or sleeve and flashed properly instead. It costs more on day one and stops costing you anything after that.

If you have a roof with a dozen pitch pockets on it, you do not have a dozen details. You have a dozen scheduled failures, and the maintenance schedule is annual.

Condensate, Line Sets and the Things Bolted to Your Roof

Condensate running onto the membrane

You will read that code prohibits discharging HVAC condensate onto a roof. We went and read the code, and that is not what it says — no section of the Florida Building Code, Mechanical or the model mechanical code mentions a roof here. What section 307.2.1 actually requires is that condensate be “conveyed from the drain pan outlet to an approved place of disposal,” and that it not discharge in a way “as to cause a nuisance.”

The operative phrase is approved place of disposal, and whether a bare membrane counts is a call for your building official, not for a blog. What is not in dispute is the physical result. Condensate discharged onto a low-slope roof runs to the nearest low spot and sits there. The Asphalt Roofing Manufacturers Association defines ponding as water that remains on a roof for 48 hours or longer, lists runoff from rooftop equipment as one of its causes, and describes the consequence: standing water promotes biological growth, and “damage to the roof membrane may occur from chemical and physical attack by the bio-growth.” ARMA’s own guidance is that “rooftop HVAC condensate lines should be connected to proper drains to prevent condensate from draining onto the roof.”

Worth knowing for the residential side of a mixed-use property: FBC‑B 1503.7 does require that condensate lines and roof downspouts discharge at least one foot away from the structure sidewall.

Line sets, conduit and wood blocking

Walk almost any older commercial roof in Volusia County and you will find refrigerant lines and conduit resting on scraps of lumber. It is the default, and it is a bad default. Writing in IIBEC’s Interface, Karl Schaack notes that wood blocking deteriorates and warps, and “will typically not allow for adequate movement and/or load distribution, which can result in damage to the roof.”

Federal construction specifications are prescriptive about the right way. Unified Facilities Guide Specification 07 53 23 requires that where pipe supports and similar accessories are set on the membrane, reinforced membrane or walkpad material be adhered to the bottom of the accessory first; that they be installed “to permit normal movement due to expansion, contraction, vibration”; and — the part that matters most — “Do not mechanically secure set-on accessories through roofing membrane into roof deck substrate.”

Any fastener driven through a membrane to hold something down is a hole. It may not leak this year. It is still a hole.

Restaurant Roofs: Grease Is Not a Cleaning Problem, It Is a Chemical One

If your building has a commercial kitchen, this section is the most expensive one on the page. Grease from kitchen exhaust does not merely sit on a membrane looking unpleasant. Depending on what the roof is made of, it chemically attacks it. The Canadian Roofing Contractors Association put it in one sentence: “Simply put, grease destroys roof systems.”

Here is where we have to correct something that circulates constantly in this industry, including from people who should know better. The common claim is that PVC is the grease-resistant membrane. Manufacturers’ own published chemical resistance tables say the opposite. On the rating scale used by GAF and by Tremco — A for negligible effect, B for limited absorption or effect, C for extensive absorption and/or rapid degradation — the ratings for grease run:

Membrane	Grease	Animal fats	Vegetable fats
TPO	B — limited effect	B	B
PVC	C — extensive absorption / rapid degradation	C	C
KEE (PVC-KEE)	A — negligible effect	B	B

GAF’s guidance from that same document is that “the PVC‑KEE version is the better choice for roofs that may be exposed to grease and oils.” The NRCA’s magazine reaches the same conclusion about PVC generally: it “exhibits similar strengths and weaknesses in chemical compatibility as TPO,” and “grease, diesels, fuel… solvents and oils should be avoided.” KEE is the grease-resistant thermoplastic. PVC is not.

EPDM is treated differently again — not “clean it regularly” but “do not do this at all.” Carlisle’s owner’s manual splits the instruction by membrane type in a single passage: “Animal Fats/Vegetable Oils: EPDM Membranes — Do not exhaust animal fats/vegetable oils directly onto EPDM roof surfaces. TPO & PVC Membranes — Animal fats/vegetable oils must be regularly removed and the rooftop surface cleaned with a mixture of soap and water.” Mule-Hide publishes materially the same split. Asphaltic systems fare worst of all: grease dissolves the asphalt, in CRCA’s description, “to a slippery gelatin like consistency.”

Parapets, Coping and the Edge Everyone Forgets

Plenty of Volusia County commercial buildings — strip centers along Dunlawton, older storefronts in downtown DeLand and Daytona, flat-roofed offices and medical buildings — carry a parapet wall around the perimeter with a metal coping cap on top. That cap is a roof component, and it leaks in ways that look nothing like a roof leak. Water gets behind it, travels down inside the wall, and shows up as a stain several feet from where it entered.

Three pieces of NRCA guidance that most buildings get wrong:

• A membrane liner belongs under the metal. “Prior to installing metal caps, parapet walls need to be covered by a sheet membrane liner.” The metal is the first line of defense, not the only one.
• The coping must hang past the wall. The bottom of the exterior vertical face should sit at least one inch below the uppermost edge of the wall material, so water is thrown clear instead of wicking back.
• Do not caulk the bottom edge. NRCA specifically does not recommend sealing the joint between the bottom of the coping’s exterior face and the building exterior, because it “does not add to the waterproofing integrity of the assembly and may, in fact, hinder the ability of the wall construction to dissipate moisture.” A well-meant bead of caulk there traps water inside the wall.

Parapets have a second consequence that is pure Florida code, and it is one of the more serious items on this page.

If Your Roof Has a Parapet, It Probably Needs Overflow Drainage

A parapet turns your roof into a shallow tank. If the primary drains clog — and in Volusia County they clog with live oak leaves, pine needles, palm debris and wind-blown trash — the water has nowhere to go but up. Water weighs about 5.2 pounds per square foot per inch of depth. That adds up fast, and it is a structural problem before it is a leak problem.

The detail requirements are specific, and they are the things to actually look at when you are standing on the roof:

• Overflow scuppers go in the wall or parapet not less than 2 inches and not more than 4 inches above the finished roof covering (FBC‑B 1503.4.2.1). Too high and the water is already too deep before it does anything.
• The scupper opening must be at least 4 inches in height, and the secondary system is sized as though the primary system does not exist (FBC‑Plumbing 1108.3). It is not a supplement. It is a full backup.
• Secondary drainage must discharge separately from the primary system, above grade, somewhere people will notice it (FBC‑P 1108.2). If you ever see water pouring out of a pipe high on a wall, that is the system telling you the primary drains are blocked. It is a working alarm. Treat it as one.

While we are in the drainage section, one correction worth having: the quarter-inch per foot (2%) minimum slope in the code is a new construction design requirement. Reroofing is expressly excepted from it where the roof provides positive drainage. An existing dead-flat roof that drains can be re-roofed without rebuilding the slope — though adding tapered insulation is often still the right call if the roof ponds. We cover the related pitch question for sloped roofs in our guide to roof slope and why shingles cannot go on the flat part of your roof.

Walkway Pads: Not Code, But Very Possibly Your Warranty

We searched the Florida Building Code for walkway pads. They are not in it. There is no code requirement anywhere in the FBC that you install walkway protection on a roof.

Your membrane manufacturer is a different matter entirely, and the manufacturer is who pays a warranty claim:

• GAF states in its EverGuard walkway roll literature that the product “is required on a GAF-warranted roofing system,” naming HVAC, roof hatches and access doors as the areas it covers.
• Carlisle SynTec: “Walkways are required at all traffic concentration points (i.e., roof hatches, access doors, rooftop ladders, etc.), regardless of traffic frequency. Walkways are also required if regular maintenance (once a month or more) is necessary to service rooftop equipment.” Note the nuance in the same document — the pads are required, but are themselves classed as a maintenance item excluded from the warranty.
• Johns Manville uses “shall be provided” in its TPO specification for areas of routine rooftop maintenance and expected traffic.

This matters more than it sounds. The HVAC service technician who visits quarterly is walking the same line across your roof every time, in work boots, carrying tools, often dragging a gauge set. Over years that line compresses insulation and abrades the membrane. A roll of walkway pad costs very little next to a denied warranty claim.

The 25% Rule Applies to Commercial Roofs Too

Owners of commercial property are sometimes told that Florida’s 25% rule is a residential thing. It is not. The language appears in both code books — FBC‑Existing Building 706.1.1 and, identically, FBC‑Building 1511.1.1 — and it reads “any existing building or structure.” No occupancy limitation, no slope limitation, no exemption for single-ply.

The practical consequence on a commercial building: a run of patch repairs around failing curbs and pitch pockets, done piecemeal across a year, can cross the 25% threshold and trigger a requirement to bring an entire roof section up to current code. That is not always a bad outcome — sometimes it is the push a deferred roof needed — but it should be a decision you make deliberately with a budget behind it, not something you discover at the permit counter. Our full breakdown is in the Florida 25% roof rule explained.

One more re-roof provision worth knowing, because it directly concerns the details in this article. FBC‑EB 706.5 states that “existing vent flashing, metal edgings, drain outlets, collars and metal counterflashings shall not be reinstalled where rusted, damaged or deteriorated.” If an estimate for a re-roof quietly reuses corroded drain outlets and counterflashing, that is not a cost saving. It is a code problem and a future leak at the exact detail you just paid to have addressed.

Can Anyone Actually Get Up There?

Two mechanical code provisions decide whether your roof can be maintained at all, and they are worth checking on any building you own or are buying:

• FBC‑Mechanical 306.1 requires a level working space not less than 30 inches deep and 30 inches wide in front of the control side of an appliance. Equipment crowded against a parapet fails this.
• FBC‑Mechanical 306.5 requires a permanent means of access — interior or exterior — where personnel have to climb higher than 16 feet above grade to reach rooftop equipment. That access “shall not require the use of portable ladders,” and shall not require climbing over obstructions greater than 30 inches high.

A roof that can only be reached by a 24-foot extension ladder leaned against the back wall does not get inspected, which means small detail failures are found by the ceiling tile instead of by a person.

What Maintenance Actually Buys You (With Honest Numbers)

There is a widely repeated statistic that roofs under a maintenance program last 21 years versus 13 without, usually attributed to the NRCA. We traced that citation to its source. It does not come from the NRCA — the trail ends at a roofing manufacturer’s contractor-certification sales manual, with no study, methodology or sample size behind it. A second common figure, that maintenance extends roof life 25–50% per a government study, does not appear in any of the Army Corps or NIST documents it is attributed to. We are not going to use either one.

What we can cite is less dramatic and more useful. The Army Corps’ Unified Facilities Criteria for roofing states simply: “With good maintenance, the service life of a roof is extended many years and the life-cycle cost of roofing is reduced.”

And the Corps’ roof management study supplies the number that should actually worry a building owner. From a database of 413 roof sections, 291 — 70 percent — were replaced before reaching their 20-year design life, and almost half were replaced before 16 years. Drawing on a 1996 survey of NRCA contractors, the same report puts the actual average service life of membrane roofing at 16 years, about 80 percent of the 20-year design life everyone budgets around.

Roofs do not usually die of old age in the field of the membrane. They die early, at the details, from things that were findable. Johns Manville goes as far as making it a condition of coverage: “JM requires building owners establish regularly scheduled annual inspections… Records of all maintenance work performed must be retained for the entire warranty period.” If you have a manufacturer warranty on a commercial roof and no inspection records, you may own less protection than you think.

A Walk-the-Roof Checklist for a Commercial Property Owner

You do not need to be a roofer to spot most of this. If you can safely get on the roof, go look at these, in this order:

1. Every rooftop unit. Is it on a curb that stands clearly proud of the roof, or is it sitting low on sleepers? Can you see the roof surface underneath it?
2. The flashing at each curb. Does the membrane run up the side of the curb a solid hand’s width or more, and is it terminated under metal counterflashing — or does it stop short, held down with a bead of sealant?
3. Condensate lines. Follow each one. Does it reach a drain, or does it end in the air over the membrane? Is there a stained, discolored or algae-darkened area where it lands?
4. Pitch pockets. Count them. Look at the filler in each — it should be level and intact, not shrunken, cracked or dished below the rim.
5. Pipe and conduit supports. Wood blocks? Anything screwed through the membrane? Any support that has shifted and dragged across the surface?
6. The parapet and coping. Open joints in the metal, loose fasteners, caulk that has pulled away, staining on the inside face of the wall below.
7. Drains and scuppers. Clear of debris? Strainers present? Are there overflow scuppers at all, and are they low enough to work?
8. Standing water. Walk it more than 48 hours after rain. Anything still wet, or ringed with dirt and algae, is ponding.
9. Traffic paths. Is there a visible trail worn from the hatch or ladder to the equipment? Is there a walkway pad on it?

How We Handle Rooftop Details

Affordable Roofing & Construction has worked on commercial and residential roofs in Volusia County for more than twenty years. We hold both a Florida roofing license (CCC 1327602) and a general contractor license (CGC 1509441), which matters on commercial work where the scope crosses into carpentry, curb framing or structural repair at a rotted parapet.

On any commercial roof we are asked to evaluate, we document each penetration and curb individually rather than pricing a roof as a single square-foot number. Where a penetration can be re-detailed into a proper curb or a prefabricated boot instead of another pitch pocket, we will say so and price it both ways, because one of those two options stops costing you money and the other does not.

Estimates are free. If the honest answer is that your roof has five good years in it and needs four details rebuilt, that is the answer you will get.

Frequently Asked Questions

Why does my commercial roof leak near the AC unit when the membrane looks fine?

Because low-slope roofs very rarely fail in the open field of the membrane. They fail where the membrane was interrupted — at the curb under the unit, at pipe and conduit penetrations, at pitch pockets and at the parapet. The U.S. Army Corps of Engineers states in its roof management study that flashings are the most common source of roof problems. Rooftop equipment concentrates all of those details in one place and adds regular foot traffic on top of them.

Does Florida code require my rooftop AC unit to be on a raised curb?

Yes. Florida Building Code, Building section 1510.10 requires roof mounted mechanical units to be mounted on curbs raised a minimum of 8 inches above the roof surface, or on raised equipment supports with a minimum clearance set by Table 1510.10 — ranging from 14 inches for units under 24 inches wide to 48 inches for units over 60 inches wide. There is an exception where the building official determines existing equipment already allows the roof beneath it to be maintained.

Is the 8-inch flashing height a code requirement in Volusia County?

No, and this is commonly confused. The 8-inch minimum for membrane base flashing height is an NRCA recommendation and a manufacturer warranty condition, not an adopted code requirement outside the High-Velocity Hurricane Zone, which covers only Broward and Miami-Dade counties. The 8-inch figure that is code statewide is a different rule — the curb height under rooftop mechanical units in FBC 1510.10. Both numbers matter, but only one of them will be cited by an inspector.

Can I run a restaurant kitchen exhaust onto a TPO or PVC roof?

Only with an active cleaning program, and PVC is a poorer choice than most people assume. On the chemical resistance tables published by GAF and Tremco, grease rates TPO as B (limited effect), PVC as C (extensive absorption or rapid degradation) and KEE as A (negligible effect). KEE is the grease-resistant thermoplastic, not PVC. Carlisle instructs that animal fats and vegetable oils must not be exhausted directly onto EPDM at all, and that on TPO and PVC they must be regularly removed and the surface cleaned. Grease dissolves asphaltic systems outright.

What is a pitch pocket and should I be worried about mine?

A pitch pocket is a metal collar around an irregular penetration filled with pourable sealant, used when a penetration cannot be properly flashed. The NRCA’s manual calls them “acceptable as a last alternative” and states they are not the preferred method because they may be a constant maintenance problem. They require periodic refilling, and most manufacturers take exception to them in their warranties. If your roof has several, they should be on an annual inspection list — or re-detailed into proper curbs at your next re-roof.

Does my flat roof need overflow drains or scuppers?

If the perimeter construction — typically a parapet wall — would trap water when the primary drains back up, then yes. FBC-Building 1503.4.1 requires secondary emergency overflow drains or scuppers in that situation. Overflow scuppers must be placed not less than 2 inches and not more than 4 inches above the finished roof covering, with an opening at least 4 inches high, and the secondary system is sized without counting any flow through the primary drains.

Does the Florida 25% roof rule apply to commercial buildings?

Yes. The rule appears in FBC-Existing Building 706.1.1 and identically in FBC-Building 1511.1.1, and the text says “any existing building or structure” — there is no residential-only limitation and no exemption for low-slope or single-ply systems. Repairing, replacing or recovering more than 25 percent of a roof area or roof section in any 12-month period triggers a requirement to bring the whole roof system or section to current code, subject to the exception for systems already built to the 2007 Florida Building Code or later.

Are walkway pads required on a commercial roof?

Not by the Florida Building Code — there is no FBC walkway pad requirement. But major membrane manufacturers require them as a condition of their systems. GAF states its walkway roll is required on a GAF-warranted roofing system; Carlisle requires walkways at all traffic concentration points regardless of frequency and wherever equipment needs servicing monthly or more often; Johns Manville’s TPO specification says they shall be provided. For warranty purposes that is the requirement that will be enforced.

Who is responsible for a leak caused by the HVAC contractor?

That depends on your contracts and, in a leased building, on your lease. It is a common and genuinely frustrating situation: a service tech cuts a new penetration, sets a curb badly or leaves a line set resting on the membrane, and the roof leaks months later. The practical defense is documentation — photograph the roof before and after any mechanical work, and require that any new penetration be flashed by a roofing contractor rather than sealed by the mechanical crew. For the landlord and tenant side of this question, see our guide on who pays for the roof on a Florida commercial lease.

Related Reading

• Commercial Roofing Services in Volusia County
• TPO vs. EPDM Flat Roofing in Florida: Choosing a Membrane
• Silicone Roof Coatings & Flat Roof Restoration: When Coating Beats Replacement
• Who Pays for the Roof on a Florida Commercial Lease?
• The Florida 25% Roof Rule Explained
• Flat Roof Maintenance Tips for Florida Commercial Building Owners
• Project: Commercial Roof Replacement in Ormond Beach

This article is general information for Florida property owners and is not legal, engineering or code-compliance advice. Code citations are to the Florida Building Code, 8th Edition (2023). Code application is determined by your local building official, and requirements differ between jurisdictions. Manufacturer specifications, warranty terms and chemical resistance ratings vary by product and revision — confirm requirements for your specific system with the manufacturer. Product names are referenced for technical accuracy and do not imply affiliation or endorsement.