Most metal warehouse roofs leak from the same short list of places: fastener washers that have hardened and split, side laps and end laps that have opened up, worn closures at the ridge and eave, aging skylights, penetrations, gutters that overflow back into the building, and steel that has rusted through. When leaks keep turning up in new places after every round of patching, the roof as a whole has reached the end of its sealing life. The lasting fixes are a coating system that treats every fastener and seam, a retrofit roof-over, or replacement of the panels that have failed.
We do not offer leak call-outs or patch repairs. Our work starts with finding out why a roof leaks and then scoping the fix that ends it.
Why metal roofs start to leak
A metal roof moves every day. A long run of steel panels grows in the afternoon sun and shrinks overnight, and on an exposed-fastener roof each screw pins the panel to a purlin and fights that movement. Over thousands of cycles the screws loosen, the holes wear oval, sealant in the laps tears and the washers lose their grip. The climate in San Antonio and Austin adds to the strain: long hot summers, strong UV and sudden storms that drop cold rain on a sun-baked roof and make it contract all at once.
A leak, then, is usually a symptom of a roof that is wearing out evenly, not of one damaged spot.
The usual leak points
Fastener washers
The rubber washer under each screw head is the seal. UV and heat harden it until it cracks. A screw that was overdriven at installation crushed its washer from day one, and an underdriven screw never sealed at all. Screws that missed the purlin and were left in place let water in from the start.
Side laps
Where one panel overlaps the next along its length, stitch screws hold the lap closed. When they loosen, or the sealant in the lap ages, wind-driven rain and capillary action pull water across the joint.
End laps
On long roofs the panels are lapped end to end over a purlin. On a low slope, water slows at that step and can back up into the joint, and the mastic tape sealing it dries out and shrinks. End laps also rust from the inside, out of view.
Ridge and eave closures
Foam closures fill the gaps under the ribs at the ridge and eave. They shrink, crumble and get pulled out by birds, and wind then drives rain straight past them.
Skylights
Translucent panels turn brittle in the sun and crack under hail. Fasteners pull through them, and the laps where they meet the metal rarely match the steel profile exactly.
Penetrations and curbs
Pipe boots split with age, and HVAC curbs added years after the building went up were often flashed with a bead of sealant rather than a proper detail.
Gutters
Eave gutters that are undersized, clogged or sagging overflow in a heavy downpour, and water can run back over the eave into the wall or the building. Internal valley gutters on multi-span buildings are worse, because when they overflow the water goes straight inside.
Foot traffic and hail
Technicians servicing rooftop units walk the same routes for years, and every step that lands between ribs or on a lap bends the steel and strains the fasteners nearby. Spring hail adds dents that crack the paint and can split skylight panels. The worn path around an HVAC unit is often where a new leak first shows.
Rust-through
Once corrosion has eaten through at the laps, the eaves or under rooftop equipment, there is no seal left to fix. The steel itself is the leak.
Make sure it is the roof
Not every drip is a leak. Metal buildings sweat. When the vapor retarder facing on the insulation is torn, warm moist air reaches the underside of the roof panels, condenses and drips. If water appears on cool mornings when it has not rained, condensation is the likely cause, and the answer lies in insulation and vapor control, not sealant. Plumbing and HVAC condensate lines produce drips too.
Real leaks also travel. Water runs along purlins and across insulation facing before it drops, so the wet patch on the floor can sit a long way from the entry point. Keep a simple log of each leak: date, rainfall, wind direction and location. It is the most useful record you can hand to anyone surveying the roof.
Why patching rarely ends the problem
A tube of sealant over one fastener fixes one hole on a roof that has thousands of them, all the same age and under the same stress. Next summer opens the next ones. Meanwhile each leak in a warehouse costs more than the patch: wet product, ruined packaging, slick floors, and racking that has to be cleared so somebody can find the drip. Over more than 20 years of commercial roofing, the roofs we have seen stay dry belong to owners who stopped chasing drips and treated the roof as one system.
Long-term fix one: a coating system with full fastener and seam treatment
When the panels are still sound and the leaks come from fasteners, laps and details, a restoration coating system is the right answer. It is far more than a coat of paint. Failed and stripped fasteners are replaced or upsized, every fastener head is sealed, side laps and end laps are reinforced with seam sealer and fabric, closures and penetrations are rebuilt, and then the whole field is coated to the manufacturer’s specified thickness. Every likely leak point on the roof is dealt with in one project. The limit is the steel: a coating seals sound metal, so any panels that have rusted through are replaced before the system goes on. Our metal roof coating service explains what that system includes.
Long-term fix two: a retrofit roof-over
When leaks are widespread, the steel is rusting through, or the insulation has been soaked by years of water, a retrofit is the better investment. A new metal roof goes on above the old one on sub-purlins tied into the existing purlins, with new insulation in between. Choosing a standing seam roof for the new surface takes exposed fasteners off the weather side altogether, which removes the main cause of leaks on the old roof. The building stays covered throughout.
Read about our metal roof retrofit service for the full scope. For warehouses along I-35 and I-10, see metal roof retrofit in San Antonio, and for distribution and manufacturing buildings along I-35 and SH 130, see metal roof retrofit in Austin.
Long-term fix three: replacing failed panels
Some roofs leak because a defined set of panels has failed: a rusted run along the eave, the area under an old cooling unit, or panels punctured by hail. Replacing those panels with new ones matched to the existing profile, then treating the roof around them, can be the right scope. Where the failures are spread across the whole roof, or the insulation and purlins need attention from above, full re-sheeting with new R-panel roofing is the cleaner option.
Choosing the fix
The right answer comes from the condition of the steel, the pattern of the leaks, the state of the insulation and how long you plan to keep the building. A proper survey checks fasteners and laps across the roof, measures corrosion, looks at the underside from inside and sets all of that against your leak log. If you have been searching for commercial metal roofers near me from a warehouse in Seguin or a plant in Georgetown, ask every contractor you call which of these three fixes they recommend, and why.
Tell us where the building is, when it leaks and what is stored or made under the roof, and we will survey it and recommend the long-term fix that suits the building. Send those details through our contact form, or call us at (210) 775-0995.
To upload drawings, specs and plans please go to the form on our contact page.
Get in Touch