Marrickville sits under the approach to Sydney Airport, and that shows on the roofs as a fine dark film rain never quite shifts. Add the slate, terracotta and corrugated iron on the suburb's Victorian terraces and workers' cottages, and roof cleaning here has less to do with moss than with lifting an industrial deposit off century-old material without damaging it.
What settles on a Marrickville roof is different from anywhere else we work, and it is not organic.
The suburb lies beneath the flight path, and the fine particulate that comes with that, combined with soot from the Illawarra Road and Marrickville Road corridors, builds an even grey-black film across the whole roof plane. Because it lands uniformly there is no obvious dirty patch to prompt a clean, and it is slightly greasy, so rain streaks it rather than clearing it.
The building stock complicates the job. Much of Marrickville is Victorian and Federation terraces and semis, which means shared party walls, box gutters running between neighbouring roofs, and slate or Marseille terracotta laid over a century ago. Workers' cottages behind them often carry original corrugated iron, now well past its first coat. None of that tolerates high pressure: slate delaminates, aged terracotta has lost its glaze, and iron sheds whatever paint is left.
Down toward the Cooks River the ground is damper and the plane and fig canopy heavier, so the southern pitches there add moss to the soot.
Access is the practical constraint. Terrace roofs are reached over a neighbour's property or from a narrow rear lane, and we plan that before the day rather than on it.
On a terrace, roof problems are rarely confined to one house, and that changes the maintenance calculation.
Box gutters running between neighbouring roofs drain to a single outlet, and when that blocks the water does not spill over an edge. It backs up under the tiles and into the roof cavity, frequently on the other side of a party wall. A blockage you did not create can become water in your ceiling, and sorting out who pays is a conversation nobody enjoys.
The soot film has its own cost. Left sitting on aged terracotta and slate it holds moisture against a surface that has already lost its glaze, and on original corrugated iron it accelerates the breakdown of what paint remains. Replacing a slate or iron roof on a heritage terrace is specialist work priced accordingly, and in a conservation area the council will have a view on the replacement.
There is a straightforward presentation return too. Marrickville roofs are highly visible from the street and from the rear lanes, and on a row of terraces the difference between a cleaned roof and its neighbours is obvious.
Because access is planned rather than improvised, we also get a proper look at the box gutters and valley irons while we are there.
It is mostly fine particulate from the flight path combined with soot from the Illawarra Road and Marrickville Road corridors. It lands evenly across the whole roof, so there is no obvious dirty patch to prompt a clean, and it is slightly greasy, so rain streaks it instead of clearing it. We lift it with a low-pressure soft wash and cleaning solution rather than relying on water alone.
That is why high pressure stays off these roofs. Workers' cottages often carry original corrugated iron well past its first coat, and a forceful jet would remove whatever paint is left. The same goes for slate, which delaminates, and for aged terracotta that has lost its glaze. We use a low-pressure soft wash matched to each material.
Terrace roofs are usually reached over a neighbour's property or from a narrow rear lane, so we plan access before the day rather than improvising on it. That planning also gives us a proper look at the shared box gutters and valley irons while we are up there, and you receive before-and-after photos of the finished roof.
Often, yes. On many terraces the soot film is the real issue, and left in place it holds moisture against slate and de-glazed terracotta and speeds the breakdown of the paint on old iron. Down toward the Cooks River, where the ground is damper and the plane and fig canopy heavier, southern pitches carry moss as well as soot.
How we clean tile, terracotta and metal roofs across Sydney, what the process involves and what it costs.
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