The siding on a three-building townhome complex was shedding paint in sheets — the coating never had a chance to stick
A property manager walked me around a three-building townhome complex in the west end this summer because the aluminum siding was peeling — not flaking, peeling, in sheets you could pull off by the corner. The repaint was four years old and already worse-looking than the forty-year-old finish underneath it. This post is for property managers and condo boards with aluminum or steel siding, soffits, or panel cladding in the portfolio: why paint lets go of metal siding in sheets, and what separates a repaint that lasts fifteen years from one that fails in three.
1. The white powder is the whole story
Factory-finished aluminum siding doesn’t rot and doesn’t rust in any way that matters. What it does, over twenty or thirty years of UV, is chalk: the original baked-on finish breaks down into a fine white powder. Wipe a dark cloth across an old panel and it comes away looking like it’s been dragged through flour.
Paint applied over that chalk isn’t bonded to the siding. It’s bonded to loose powder, and the powder isn’t bonded to anything. The new coating can look perfect for a year or two — then thermal movement and moisture get behind an edge, and it releases in sheets. That’s the failure I was looking at: the sheets pulled off clean, with chalk visible on the back of every piece. Most peeling-siding calls I get in Ottawa are this, and it’s entirely preventable at the washing stage.
What to look at: wipe a dark rag firmly across an unwashed panel on your building. Heavy white residue means any repaint quote that doesn’t include oxide removal is a repaint you’ll be redoing.
2. Metal needs a bonding coat, not just “exterior paint”
The second failure I see is primer — either there wasn’t one, or it was a general-purpose exterior primer that has no business on slick metal. Aluminum is a hard, non-porous surface. Standard exterior paints grip wood and masonry by keying into texture; on metal there’s nothing to key into, so adhesion has to come from chemistry.
A siding repaint that lasts uses a bonding primer rated for aluminum, or a direct-to-metal (DTM) acrylic system, applied to a properly de-chalked surface. That combination routinely gives 12 to 15 years on siding. Skip either half and 3 to 5 years is typical — which is how a “cheaper” repaint becomes the most expensive line in the maintenance budget.
What to look at: pull the spec or invoice from your last siding repaint. If it doesn’t name a bonding primer or a DTM product, the failure clock is probably already running.
3. The sun side fails first, and tells you why
Peeling siding almost never fails evenly. South- and west-facing elevations take the most UV and the widest temperature swings — aluminum panels expand and contract every day, and in an Ottawa summer a dark panel in afternoon sun is doing a lot of moving. A marginal bond that survives on the shaded north wall gets worked loose on the sun side within a couple of seasons.
That pattern is diagnostic. Failing on the sun sides while the north elevation holds usually means adhesion was marginal everywhere and the sun found it first. Failing around fastener lines and panel laps points at movement and moisture instead. Either way, spot-touching the peeled areas without fixing the surface prep just restarts the same failure.
What to look at: walk the south and west elevations specifically. If that’s where the peeling concentrates, budget for a full prep-and-repaint of those elevations, not a touch-up.
4. What a repaint that holds actually involves
The sequence matters more than the paint brand. First, a proper wash — not a quick rinse, but a cleaner that cuts the oxide, followed by pressure rinsing until a rag test comes up clean. Second, an adhesion test patch: prime and paint a small area, let it cure 48 hours, and try to peel it. Third, bonding primer or DTM acrylic over the full surface, applied within the product’s recoat window. On a multi-building complex I’d also stage the work one elevation at a time so the board can see the rag test and the test patch results before committing the whole envelope.
What to look at: ask any bidder how they’ll verify the chalk is gone before priming. “We always wash first” is not an answer; a rag test and a test patch are.
What to do if you’re seeing any of this
If your siding is showing chalk, curling edges, or sheet peeling, here’s what I’d check first: the rag test, the sun-side elevations, and the spec from the last repaint. I assess aluminum and steel siding, soffits, and panel cladding for condo and multifamily buildings across Ottawa — Kanata, Nepean, Barrhaven, Orleans, Stittsville, Westboro — and I’ll tell you plainly whether you’re looking at a wash-and-repaint or living with it another few years. Call 613.325.3011 or email yasir@heims.ca.
— Yasir, HEIMS Construction
HEIMS Construction is an Ottawa-based commercial painting and drywall contractor serving condominium corporations, property managers, and institutional clients across the National Capital Region. We are licensed, WSIB-covered, and carry $5M in commercial general liability insurance.