Concrete Tile Moss Removal

A concrete tile roof carries more growth than it looks like it does. The tiles are large, the profile hides a lot, and from the ground a roof that is genuinely packed can read as merely dark.

The cleaning itself is the easy part. The care goes somewhere else entirely.

Where the growth actually is

On the face of a tile, growth is cosmetic. Concrete does not mind it.

In the laps — the overlap where one tile sits over the next, and where one column of tiles meets the one alongside — it is a different matter. That overlap is a drainage path. Water running down the roof is meant to pass through the laps and off the tiles below, and growth packed into a lap turns a path into a pocket.

Underneath the tiles is the underlay, and the underlay is the layer with an actual life span. Tiles will outlast it comfortably. Water standing where it should have been moving is how the underlay gets asked to do more than it was meant to.

So the work goes into the laps and the pans rather than the faces, and the faces come clean as a consequence.

The part that takes the care

Concrete tile cracks under a foot placed in the wrong part of the tile. It does not crack loudly, and it does not leak immediately — the water goes onto the underlay, spreads, and shows up on a ceiling a year later somewhere that makes no sense.

That is the whole reason a tile roof takes longer to plan than to clean. Weight goes over the batten line, in the lower third of the tile, on the route worked out before anyone steps up. On a complex roof with hips, valleys and a couple of changes in pitch, that route is most of the thinking.

Anything cracked or slipped gets flagged, including the ones that were already like that when we arrived — and we will tell you which we think are which, because an old break is weathered and dirty along its edge and a fresh one is not.

What is under the tiles matters more than the tiles

A tile roof is really two roofs. There is the tile, which is doing the shedding, and there is the underlay beneath it, which is the actual waterproof layer for anything that gets past.

Concrete tile lasts a very long time. Underlay does not — on a roof from the eighties or nineties it may already be well past its intended life, and it is the thing that fails while the roof still looks perfect from the street.

That changes what is worth looking at on a visit. Growth packed into the laps matters because it puts water onto the underlay rather than off it. Cracked tiles matter for the same reason. Neither is a tile problem; both are underlay problems arriving through the tiles.

Where we can see the underlay — at the eaves, around vents and skylights, anywhere a tile has slipped — we will tell you what state it looked to be in.

Clean without soaking it

Tile tolerates more water than cedar or shingle, and that is not a reason to use more. Water driven into a lap under pressure ends up on the underlay, which on a roof of any age is exactly the layer you would rather keep dry.

The growth comes out of the laps by hand, the pans are cleared down their length, and what comes loose goes off the roof rather than washing down into the next lap or into the gutter.

What we tell you afterwards

Which slopes were worst, whether anything is cracked or slipped, and what could be seen of the underlay at the eaves and around any penetrations. Tile roofs are usually the ones where the covering is in better shape than the layer under it, and knowing that is worth more than a clean roof.

Different covering? See cedar shake or asphalt shingle.