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Roof Coating Quality Control
Surface Knowledge Is Key
Every Coating Leaves a Number Behind
Most coating failures are not material failures. They are application failures, and every one of them is measurable while the work is still open.
Film thickness, adhesion, substrate temperature and dew point can all be read on site, with instruments, in minutes. Reading them costs almost nothing. Not reading them is what turns a twenty-year system into a five-year one.
Quality control at Sicon Group is a role held by a person, not a box ticked at handover. It runs under our ISO 9001 quality management system, and the readings are recorded and handed over with the guarantee pack.
Four Readings That Decide How Long a Coating Lasts
Each reading is taken to a stated method, logged against a location on the roof, and available to you afterwards. Select a reading to see what it measures and what a pass looks like.
Dry Film Thickness
Taken with a calibrated gauge across a set pattern, not wherever the coating happens to look thickest. A reading only means something against a specification: 166 microns is right if the system called for 150, and a problem if it called for 250. Under-thickness is the most common reason a coating never reaches its stated life.
Wet Film Thickness
Read with a comb gauge while the coating is still wet, because that is the only moment it can still be corrected. If the wet reading is short, material is added before it cures, instead of the shortfall being discovered weeks later.
Wet film between 150 and 175 μm. The last tooth to touch paint reads 150; the first clean tooth reads 175.
Example: 150 μm wet at 55% volume solids leaves about 83 μm dry per coat. Two coats give about 165 μm, which is the 166 on the dry film gauge.
Adhesion
A lattice is cut through the coating to the substrate and the cut edges assessed. It is the test that separates a coating that has bonded from one that only looks finished. The method applies to films up to 250 microns, which covers most roof systems.
Substrate Conditions
Nothing is applied until the substrate sits at least 3 °C above dew point. Below that margin, moisture condenses on the steel as the product goes down and the bond is compromised before it cures. Surface temperature, air temperature and relative humidity are recorded rather than estimated.
Three Hold Points, Not One Final Check
An inspection at handover can only tell you what went wrong. Inspections during the work can still change the outcome, which is the entire point of holding them.
Condition Survey
The existing roof is assessed and photographed, corrosion is graded, the site’s corrosivity category is considered under ISO 12944, and any existing coating is adhesion tested. A system specified without knowing what is underneath is a guess.
Wet Readings and Conditions
Wet film thickness is checked per coat as it goes on, dew point and surface temperature are logged before each session, and recoat intervals follow the product data sheet rather than the programme.
Dry Film and Sign-Off
Dry film thickness is measured across the area to a set pattern, adhesion is confirmed once cured, and the readings are signed off against the specification before the guarantee certificates are issued.
What Ends Up in Your File
A guarantee is only as good as the evidence behind it. If a coating is ever questioned, these are the documents that settle it.
Film thickness readings by area
Wet and dry, logged against a location rather than a single sample.
Adhesion test results
Cross-cut classification, with the photographs.
Application conditions
Surface temperature, air temperature, relative humidity and dew point per session.
Product and batch records
What was applied, from which batch, at what spread rate.
Photographic record
Before, during and after, from the same positions.
Signed guarantee certificates
Workmanship and material, back to back, from Sicon Group and the supplier.
Quality Control Questions
Questions worth asking any contractor before a coating system is approved. The answers are how we work.
What is dry film thickness, and why does it matter on a roof?
Dry film thickness is how thick the coating is once it has cured, measured in microns. Every coating system is specified at a thickness, and the life the manufacturer quotes assumes that thickness was achieved. Apply it thinner and it weathers through early; apply it much thicker and some products crack or fail to cure properly. It is measured with a calibrated gauge to ISO 2808, and 166 microns means nothing until you know the specification called for 150.
How do you test whether a coating has actually bonded?
With a cross-cut test to ISO 2409. A lattice of cuts is scored through the coating down to the substrate, and the edges are examined to see whether anything lifts. The result is graded from Class 0, where nothing detaches, to Class 5. On a roof coating this is the test that separates a system that will hold from one that looks perfect and is already letting go underneath.
Can a roof be coated in any weather?
No, and this is where programmes and quality most often collide. The substrate has to be at least 3 °C above dew point, or moisture condenses on the steel as the coating is applied and the bond is compromised before it cures. Relative humidity, surface temperature and the product’s own minimum and maximum application temperatures all apply. On a South African site that often means starting later and stopping earlier than the programme would like.
What quality control records do I receive?
Film thickness readings logged by area, adhesion test results, the application conditions recorded per session, product and batch details, a photographic record, and the signed guarantee certificates from both Sicon Group and the material supplier. It is handed over as one pack. See our industry certifications for the management system it runs under.
Ask for the Readings, Not Just the Quote
Any contractor can quote a coating system. Ask what film thickness it is specified at, how that will be measured, and what you will be given at handover. If you already have a quote, bring it and we will go through it with you.