Every leak has a cause, and on a leased commercial building the cause is very often a tenant improvement nobody told the landlord about. A new tenant takes a suite, their contractor needs a rooftop unit, an exhaust fan and a conduit run, and by the time the landlord hears anything, the roof has three new penetrations detailed by an electrician with a tube of sealant.
Roof penetrations are not inherently a problem. Every commercial roof has them, and a properly built curb or pipe boot will outlast the tenant. The problem is uncoordinated penetrations — cut by trades who do not do roofing, sealed with materials that are not compatible, and never recorded anywhere.
Here is what typically gets added during a build-out, what it costs the building, and how landlords keep control of it.
What Tenants Actually Add to a Roof
Build-outs generate rooftop work more often than owners expect:
- HVAC units. A restaurant, salon or fitness tenant needs cooling and ventilation the base building never sized for.
- Exhaust fans. Kitchen hoods, bathroom fans, welding or paint booth exhaust, lab venting.
- Make-up air units. Larger and heavier than most landlords anticipate.
- Refrigeration lines. Running from a rooftop condenser down through the deck.
- Electrical and data conduit. Often the worst offender, because it is added last and by the trade least likely to think about waterproofing.
- Signage and antennas. Roof-mounted signs, satellite dishes and cellular equipment, all fastened through the membrane.
Each of these is a hole in an assembly that was watertight the day before.
Why Uncoordinated Penetrations Leak
A penetration done right is a small piece of roofing: a curb built to height, flashed into the system with compatible materials, with a proper counterflashing and a cover that sheds water away from the opening. Done wrong, it is a hole with sealant around it.
The failures we find repeatedly:
- Pitch pans filled once and never topped up, cracked open by thermal cycling
- Conduit laid flat on the membrane and strapped down through it
- Curbs set too low, so wind-driven rain gets under the flashing
- Wrong sealant on a single-ply membrane, which never bonds and peels within a season
- Old penetrations abandoned in place, not removed and patched
- New units set on blocks that abrade the membrane every time the fan cycles
North Texas makes all of it worse. Summer heat cycles the deck daily, spring storms drive rain sideways, and freeze-thaw swings open every marginal joint. Our guide to rooftop HVAC and roof leaks covers the mechanical side in more depth.
The Warranty Problem
The financial exposure is bigger than the leak. Most manufacturer system warranties require that any new penetration be installed by an approved contractor using specified details, and that the manufacturer be notified of alterations.
A tenant's electrician cutting a conduit sleeve does not know that clause exists. When the roof is inspected years later, the manufacturer sees unapproved work, and the coverage the landlord paid for at installation is suddenly in dispute — often for a section of roof far from where the tenant ever worked.
The same principle applies to the contractor's workmanship coverage. No roofer warrants a roof other trades have cut into unsupervised.
An Approval Process That Actually Works
Landlords who avoid this problem all do roughly the same things.
Write it into the lease and the build-out package. Not just a consent clause buried in the lease, but a line in the tenant improvement instructions that says roof work requires written landlord approval and must be performed by the building's roofing contractor.
Require a rooftop plan. Before work starts, the tenant submits what is going up, where, and how it will be flashed.
Use one roofing contractor for all penetrations. The tenant's mechanical contractor sets the unit; the building's roofer flashes it. That single rule prevents most of these failures.
Inspect at close-out. A short roof inspection at the end of the build-out, photographed and filed, establishes the roof's condition and catches anything cut without approval while responsibility is still clear.
Update the roof record. Add every new penetration to the building's file with photographs and dates.
Finding and Fixing What Is Already Up There
Most buildings that have turned over a few tenants already have unrecorded penetrations. A survey finds them: every curb, pipe, sleeve, strap and abandoned opening documented and compared against whatever record exists.
From there the work sorts into three piles — details that are sound and just need recording, details that need to be properly reflashed, and abandoned penetrations that should be removed and permanently patched. Handling them as planned commercial roof repair is far cheaper than handling them as emergencies, and it re-establishes a clean baseline for the next tenant. If leaks are already showing up, our guide to commercial roof leak detection explains how the source gets traced.
Frequently Asked Questions
Can a tenant put new equipment on my roof without approval? Most commercial leases require landlord consent for roof work, but the clause is often ignored because the tenant's contractor never sees the lease. Landlords who write the approval step into the build-out package get told before the holes are cut.
Do uncoordinated roof penetrations really void a warranty? They can. Most manufacturer system warranties require that penetrations be installed or approved by a certified contractor using specified details. A penetration cut by an unapproved trade is a common reason coverage is denied later.
How do I find penetrations a previous tenant added? A roof survey documents every curb, pipe, conduit run and abandoned opening, then compares them against the record. Anything undocumented gets photographed, assessed, and either properly detailed or removed and permanently patched.
Turning over a suite or planning a build-out? Call Cannon Roofing at (940) 627-1045 or request a free quote. We flash tenant penetrations properly and document them for your building file.