Roof coating
| Roof coating | |
| What it is | A liquid coating applied to a roof covering after cleaning |
|---|---|
| Status | Contested within the trade |
| Position of this article | Neither side is independently sourced here |
| Sourcing | None found meeting this site's standard |
A roof coating is a liquid product applied over a cleaned roof covering, sold as restoring appearance, sealing the surface and extending the life of the roof. It is the most contested practice in roof cleaning and the one on which a homeowner is most likely to be given confident and contradictory advice.
**This article does not adjudicate the dispute.** No source meeting this site's standard was found for either position: the case for coatings is made almost entirely by parties selling them, and the case against is made largely by roofers and contractors who do not, with neither side supported by an independent body whose material could be verified. What follows sets out what is claimed, what is disputed and which questions a reader can answer for themselves.
What is claimed for coatings[edit]
The claims made are that a coating restores the colour of a faded covering, seals a porous surface against water absorption, prevents or delays the return of moss, lichen and algae, and extends the life of the roof, often by a stated number of years and with a guarantee attached.
The appearance claim is the one least in dispute: a coated roof does look different, and immediately.
What is disputed[edit]
Four objections recur, and this article records them as objections rather than as findings.
The first is moisture. A roof covering is designed to shed water and to allow what is absorbed to dry; a coating that seals the outer face is said to trap moisture within the tile, where freeze-thaw can then act on it. The second is adhesion and lifespan: a coating applied over a weathered, porous surface is said to fail progressively, and a partly failed coating is harder to deal with than an uncoated tile. The third is that coatings are typically applied after pressure washing, so the surface being coated is one the cleaning has just abraded, and the coating is then doing work the original finish was doing before it was removed. The fourth is the guarantee, which is only as good as the company standing behind it and is commonly measured in decades.
Questions a reader can answer[edit]
Several questions can be settled without resolving the dispute.
What does the covering manufacturer say about coating their product, and does coating affect any warranty on it? Is the roof faded because the finish has worn, in which case a coating is replacing something lost, or dirty, in which case cleaning alone addresses it? Is the roof sound — a covering that is failing is not improved by coating it, and a slate roof shedding slates through nail fatigue is not a coating problem at all? Who stands behind the guarantee, for how long, and what is their trading history? And what does the coating do to a future repair, since a tile matching a coated roof will not be available.
Why this article carries no verdict[edit]
A reference work that picked a side here would be presenting one trade's commercial position as a finding. The material available divides cleanly along commercial interest, and the absence of an independent source is itself the most useful thing this article can report: it tells a reader that confident claims in either direction, including any encountered in a quotation, are not backed by evidence they can check.