It’s All About Climate

In his short story “–And He Built a Crooked House” the great Robert Heinlein had a character cautiously opine that a house is, by and large, a device to keep off the rain. This is quite accurate. If you are wet, or your stuff, then life is not good.

And so all house design is tied closely to climate, and the materials available. Steeply sloped roofs speak of shedding snow. Flat roofs are for desert climes. Stone houses with stone roofs are built in stony regions, while earthen walls and sod roofs are for stone-free and timber-light conditions.

At this moment I am in Washington state. They’re having record rainfall. This is a good thing, since without plenteous rain there are wildfires in summer. People spend their home maintenance dollar coping with the rain. A good tight roof is a prerequisite, and if it’s fireproof metal then so much the better.

But then you get this kind of thing. This is a service building in a park, not a structure that gets a lot of love. It has a wooden roof, probably cedar shake. Because of the copious rain this roof may not actually be that old. But it’s got a couple seasons of growth on it, to get that deep cushiony moss and the rampant ferns.

Moss is a major problem for structures in this area, and there’s a considerable industry devoted to washing it off of manmade structures. The older residents of the region have mostly adapted to it, however. These trees for instance have formed a symbiosis with the moss!






It’s All About Climate — 4 Comments

  1. I understand that you don’t want moss on a wooden roof, as it will rot and weaken the wood. It will eat a thatched roof too, though that won’t go as fast just because the layer of thatch is so much thicker, and I see mossy older thatched roofs around that just wait until it’s time to renew the thatch (after at least 40 years, though the really mossy ones are probably a few decades over date); I don’t think the moss gets removed separately.
    Also not on a metal roof, as it will keep it wet and rust it.

    But why does it need to be removed from stone and tile roofs? I don’t understand how those could be harmed (in a human lifetime) by moss growing on it, but people still remove it even though it looks lovely and green, and helps with slowing down storm runoff.

    Does anyone know the reason why?

    • It might have something to do with the timbers that support the stone or tile. Being wood, they are not resistant to moisture.

  2. Ah, you have met our moss and ferns here in the Pacific Northwest! We actually have a natural cycle of rainy winters adding to vital mountain snowpack that gets us through the usual drought summers. Unfortunately, that balance has shifted with climate change, and the wildfires are getting much worse despite even more rain deluges in the winter. The fear is that with rising temps, the snowpacks will decrease, and then we really will be in trouble in the West.

  3. I don’t know why they clean the moss and lichen off of stone or tile roofs, but they do. The moss does fall off, especially in heavy storms, and it clogs the gutters and stuff. Perhaps that’s why?
    If you go to Iceland, there’s tons of moss. Fields of it, ten inches thick. If you reach down and pick up a piece, it comes up just like a mattress — not connected to the ground in any way. That’s because underneath the moss is black lava, from the volcanoes. Eventually the moss does break down the rock, but it takes centuries. All the soil now on Iceland was made that way.