The question on a worn corrugated metal roof is rarely whether to fix the screws. It is whether the panels under the screws deserve the work. A shop or storage shed leaking along lines of fasteners can be restored in place at modest cost if the steel is sound, or it can be wrapped in a new system if the owner wants the roof settled. A property manager should know which of those two roofs they own before approving a repair list, because the list for one is counted in screws and the other is counted in square feet.
We restore and retrofit exposed-fastener metal roofs in the Bronx, NY, and we show the owner the cost of each route against what the building will be used for.
Panels Worth Saving
An exposed-fastener roof is ribbed or corrugated steel screwed through its face into purlins, with a rubber washer under each head. It is cheap, quick to build and common on sheds, storage buildings, small warehouses and light industrial shops. The structure is often sound long after the roof has started to leak, because the parts that fail are the cheap ones: washers, sealant tape and trim closures.
That is the case for restoration. If the steel is solid and the purlins are straight, replacing the fasteners and renewing the seals gives the building years at a fraction of a new roof. If panels are rusted through or the framing is bent, restoration is wasted money, and we say that before pricing anything.
Soundview Sheds, Auto Shops and Storage Yards
The Bronx River waterfront on the western border of Soundview is mainly used for storage, warehousing, and automotive repair and modification. Those are the uses that tend to sit under simple metal roofs, and the owners of such buildings usually want the lowest cost per year of dry space. We make no assumption about any single building, and the first walk tells us what is up there.
Metal is not a new material in the borough. The Kingsbridge Armory, completed in 1917, covers a 180,000 square foot drill hall with a curved metal roof, and the lesson for any metal roof is that the panels outlast their fasteners and laps.
Why Screws and Laps Let Go
Each panel expands and contracts along its length every day, and a fixed screw works at its own hole through every cycle. The washer hardens in the sun, the hole elongates, and a path opens around the shank. Laps between panels depend on sealant tape that dries and cracks. Ridge and eave closures leave gaps wherever the profile does not match the trim. Rust begins at scratches, cut edges and fastener heads.
Wind does the rest. Throgs Neck is a narrow spit bounded by the East River and Long Island Sound, which gives roofs open wind exposure, and a panel with backed-out screws rattles and lifts there. Fasteners that have worked loose are the usual first step toward wind damage. The Central Park station runs from a July average of 95.7 F to a record low of -15 F, so the steel moves through a wide range every year.
We walk the roof with a cordless driver and test fasteners as we go. Backed-out and stripped screws show the extent of the problem. We look for loose, dented or rusted panels, check the purlins and deck where they are visible and note the age of the finish. From below we look for stains, condensation and pinpoints of daylight, and soaked batt insulation tells us the roof has been leaking for a while.
Closures at the ridge and eaves get a close look, because profile-matched foam or metal pieces shift, and a gap there lets wind-driven rain travel uphill under the panel. The gutters come next, since rust shows there first.
Restoring the Roof in Place
Restoration means pulling failed fasteners and setting larger, better-sealed ones at the right torque, since an over-tightened screw crushes its washer and leaks. Laps and penetrations are sealed, rust is cleaned and primed, and a continuous silicone or acrylic coating goes over the whole roof. The building stays open throughout and the price stays modest.
A roof coating restoration proposal sits next to the retrofit price, so the owner sees what each route buys. Restoration pays best on sound panels when the owner may sell, redevelop or repurpose the building in a few years. The coating restoration process, with its adhesion test and moisture check, applies on metal as well.
Retrofitting a New System Over the Old
Retrofit installs a new roof over the existing panels. One approach uses sub-purlins or a framing system to carry new standing seam panels with no tear-off. Another lays insulation and a membrane such as TPO over the metal. Both routes cost more than restoration, add insulating value and take the exposed screws out of the story, and both add weight, so an engineer looks at the framing first.
A building held for the long term, with real heating or cooling bills, gets more from a retrofit, since the added insulation lowers the load and stops cold panels from sweating.
Working on Live Shops
Shops and storage buildings keep running during roof work. Pallets and bundles stay clear of bay doors, stock gets covered, and vehicles and machinery under open bays are sheeted over before screws come out. Screw replacement is loud, so the hours are agreed with the tenants, and drop cloths and catch pans control falling debris and sealant drips. Metal slicked by dew or rain is a fall risk, so the crew works it dry and ties off at every edge. Old translucent panels and skylights are fall risks and get covered or replaced early.
The roof is cleared of loose screws at the end of each shift, because a dropped screw lands in a tire as easily as in a bin. A commercial roof inspection after the work confirms every fastener was addressed.
Timing and Records
Coatings want dry, moderate weather, so restoration runs from spring through early fall. The Department of Buildings issues the 2022 NYC Construction Codes. Permits come from there. The closeout record lists how many fasteners were replaced, shows the lap and penetration seals in photographs and notes the coating batch, so a later crew can match the system.
A spring and fall preventive maintenance visit keeps washers, sealant and drains in working order. Send the roof age, the building use and where it drips.
Commercial Roofing Questions
How many fasteners does a metal restoration actually involve?
Often thousands on a shed-sized roof. Each screw that has backed out, stripped its hole or lost its washer gets replaced, and we count them during the walk so the price is per fastener.
Can a rusted metal roof be coated?
Rust on the surface gets brushed, treated and primed, then coated. Panels with holes through the steel have to be replaced, and a screwdriver probe shows which kind we have.
Is a retrofit better than a tear-off?
In most cases it is. The old panels keep the building dry while the new system goes on, and disposal costs fall. The framing has to be sound, and an engineer checks it for the added weight.
Why does water drip inside when the roof is not leaking?
That is usually condensation, where moist indoor air meets a cold metal panel. Added insulation, a vapor barrier or better ventilation cures it, and a retrofit with insulation often removes the problem entirely.
What replaces the old screws?
Larger-diameter screws with new sealing washers, driven to the right torque. Tightening too far crushes the washer and recreates the leak.
Send the Building Use and the Roof Age
Tell us what the building is used for, how old the panels are and where the drips show. We will walk the roof, test the fasteners and give you a written choice between restoring and retrofitting.
Request a Roof Assessment