Cleaning, Re-Fastening and Sealing
A sound panel can be brought back with careful work. We clean the surface and wire-brush any rust to bright metal, replace loose screws with larger-diameter fasteners that bite into fresh metal, and seal laps with butyl tape instead of loose caulk. Ridge caps, endwall trim and penetrations get new formed metal and closures where the old pieces have shrunk or split. Each repair is marked on a roof plan so the owner can see which areas have been done.
A coating can then protect the whole roof. A silicone roof coating or a compatible acrylic seals small gaps, reflects heat and shields the steel from the weather, and a roof coating restoration is often cheaper than replacement when the panels are in decent shape. The coating is only as good as the repairs beneath it, so the fastening and laps are corrected first.
Framing New Metal Over the Old
When the panels are rusted through, or the owner wants a roof that will not need fasteners exposed to the weather, a new roof can go on top of the old. A retrofit framing system sits on the existing purlins, creates a flat plane above the old panels and carries a new standing seam metal roof with concealed clips. Insulation fits in the gap, which reduces heat gain and noise.
The work stays dry throughout because the old roof remains in place until the new one is closed in. We check the structure first, since the added framing, insulation and panels add weight, and we confirm that the existing panels are firmly fastened so they act as a safe working surface. The tear-off of an old roof, with the open deck and the risk to goods inside, is avoided, which matters on any building that keeps working.
Warehouses and Flex Buildings in the Valley
Exposed-fastener metal is a familiar roof on warehouse and flex buildings, and the valley has plenty of them. East Pasadena and Lamanda Park hold the city's most concentrated industrial space, with small flex and warehouse units along East Foothill Boulevard. Beyond the city, the City of Industry is almost entirely industrial, with more than 3,000 businesses employing about 67,000 people and about 92 percent of its land zoned industrial, while Vernon, with its food manufacturing and metalworking, and Irwindale, with Southern California Edison and Ready Pac Foods, add industrial buildings of their own.
These buildings hold inventory, forklifts and people, so how the work is staged matters. For a warehouse under a leaking panel, we protect racking and product first, and sequence the repair in sections so no part of the roof is open overnight. The same approach applies to warehouse roofing generally, and we plan around loading hours in the City of Industry and similar districts.
Heat, Condensation and Cool Roof Rules
Bare metal under a summer sun gets hot enough to cook the space beneath it. Highs here have reached 113 F, and an October 2023 advisory brought days near 100 F, so the load arrives outside the peak season too. A reflective coating or white-coated new panel lowers the roof surface temperature, and with it the cooling load on whatever is below. California's cool roof rule applies to low-slope nonresidential roofs, and an alteration over half the roof, or 2,000 square feet, can trigger an aged reflectance of 0.63 and emittance of 0.75.
Condensation is the other issue. Warm, humid air meeting a cool metal underside drips back into the space, and the drip is often mistaken for a leak. We look for it before blaming the fasteners, and add insulation or a vapor barrier where it is the cause. In a Very High fire hazard zone (Pasadena maps zones in the Arroyo Seco and upper Hastings Ranch, among other areas), the roof assembly must also be Class A when more than half of the roof is replaced in a year.
Commercial Roofing Questions
Can an exposed-fastener metal roof be fixed without replacing the panels?
When the steel is sound, yes. We replace failed fasteners, seal laps and flashings, and coat the surface. The limit is corrosion: panels with rust through the steel at the laps or cut edges cannot be fixed and have to be replaced or covered by a new system. A walk of the roof tells us how far the corrosion has gone.
Is it better to coat a metal roof or retrofit a new one over it?
Condition of the panels is what separates the two. A roof with sound steel and tired fasteners responds well to repair and coating, and it keeps its cost low. A roof with widespread rust, or an owner who wants concealed fasteners and insulation, is better served by a new framed metal roof over the top.
How do you protect a warehouse full of inventory while the roof is open?
We work in short sections and close each one before leaving, and we cover racking and stored goods ahead of any work above them. Panel replacement is staged along the roof so no area stays open overnight. We coordinate with the operations manager on forklift lanes, loading times and the days when the building is quiet.
Why does my metal roof rust at the laps and not in the open field?
Water lingers at the laps, where the panels overlap and trap moisture against bare edges. Dirt collects there too, which keeps the steel damp long after rain stops. Cut edges and screw holes also expose bare steel. Cleaning, sealing the lap with tape and coating the repaired steel stops the cycle before it eats through.
Does a metal roof retrofit trigger the cool roof requirement?
The rule covers low-slope nonresidential roofs, so a flat-pitched metal roof is likely to be included when the work is a new roof or touches more than half the surface or 2,000 square feet. We check the slope and the scope, and specify a coating or panel finish whose aged reflectance and emittance meet the 2025 energy code.
