Metal Roof Coating Layers, Bottom to Top
Rust Prep and Primer
Coatings stick to clean, sound steel and nothing else. The prep starts with a pressure wash to strip chalk, dirt and pine sap, then wire-brushing or grinding wherever rust has lifted the paint. Bare and rusted spots get a rust-inhibiting primer matched to the topcoat. Skip it and the rust keeps working under the new film until the film blisters and lifts. On an old roof, much of the labor goes here.
Sealing Laps and Screw Heads Before the Topcoat
Leaks on an old metal roof tend to start at the end laps, the side laps and the screws, and a coating alone won't stop them there. Before any topcoat, a good roofer will back out or replace loose and stripped screws, then cover each screw head with sealant and bed a reinforcing fabric strip in a base coat along every end lap, ridge and curb. A topcoat rolled over unsealed laps just bridges a gap that keeps moving with the heat.
Silicone Coating
Silicone is the pick where water sits. One coating maker describes it as resistant to ponding water, meaning water that stays on the roof for more than 48 hours, which makes it the usual choice on low-slope porch and shop roofs. It has trade-offs: the same maker says silicone roofs tend to look dirty within 6 to 12 months, losing a little reflectivity, and silicone is slick underfoot when wet. Under pines and oaks that dirt pickup is worth thinking about before you choose a white.
Acrylic and Elastomeric Coating
Acrylics are water-based and stretch with the steel as it heats and cools. That coating maker recommends them only on steep-slope metal roofs where water doesn't pond, because they break down under standing water. They hold their color and reflectivity better than silicone, so they suit a pitched house roof that people see from the street. Since acrylic is water-based, ask the roofer how many dry hours the product needs before rain; Jackson averages about 110 days a year with measurable rain.
Repainting a Faded Factory Finish
If the original paint is chalky but the steel underneath is sound, a cleaning, primer where needed and a field-applied metal roof paint can bring back the color. The Metal Roofing Alliance makes the point that metal roofs can often be repainted rather than replaced. Field paint won't match the life of a factory PVDF finish; those factory paint systems are explained on Galvalume metal roof, along with the EPA's figures on reflective roofs and cooling.
Why Jackson homeowners call Jackson Metal Roofing Pros
- One independent metal roofer gets your request, not a call list
- A free measure, deck check and written estimate
- Ask for panel system, gauge and paint finish in writing
- The roofing permit is part of the scope: ask who pulls it
- No charge to the property owner for the referral
Metal Roof Coating Candidates and Lost Causes
A coating is a good bet when the panels are still solid, the rust is on the surface, and the leaks trace back to fasteners and laps. It's money thrown away when:
The steel is perforated
A coating can bridge a pinhole but not a panel that's rusted through across its width.The framing has moved
Sagging purlins or a soft deck will crack any film laid over them.The old coating is peeling
Loose paint or an earlier failed coating has to come off first, which can cost more than the coating.Water stands for days
A low roof that ponds needs the drainage fixed or a silicone system, not a cheap acrylic.
When most of those apply, the roof is a candidate for metal roof replacement instead.
Metal Roof Coating Prices and Bid Lines
HomeGuide's national cost guide puts coating a metal roof at $0.50 to $4.00 per square foot, depending on rust, access and repairs, and painting one at $1.20 to $2.70 per square foot on average. No source publishes Jackson prices, so the written bid is the number to compare. It should name:
Cleaning
Pressure wash, plus any cleaner or rust converter.Rust treatment
Which spots get wire-brushed or ground, and the primer product.Fasteners
How many screws get replaced, and the replacement size.Seams
The sealer and fabric used at laps, ridges and penetrations.Topcoat
Product name, color, number of coats and the dry film thickness the maker calls for.Warranty
Any warranty is the coating maker's own published term for that system, so ask for the document rather than a verbal promise.
A coating over metal panels needs no tear-off under Section R908.3.1 of the 2018 IRC, one reason it costs far less than new metal. For a roof that leaks at only a few spots, metal roof repair may be all it needs.