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crabapplesteam OP t1_jaa95ly wrote

Reply to comment by HemHaw in How do you know when to replace or fix a shed? by crabapplesteam

Oh interesting - why not?

I was thinking of putting some kind of coating over the roof tiles, based off of what some other folks had said - and part of that process is pressure washing. I'd love to hear your opinion on what other options I have.

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Deadpressed t1_jaacltp wrote

It'll rip the granules off the shingle. Certainly possible to clean, just don't pressure wash.

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scarabic t1_jabhi3q wrote

People think pressure washers are literally magic and will quickly and easily strip away only what they consider to be dirt while having zero impact on the wood or other material underneath.

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GarrettR33 t1_jabkir4 wrote

See: me pressure-washing my cement patio with a rented high PSI gas machine and thinking “I should do the sides of the planter box while I have this” and pretty much annihilating the thing.

Been looking at buying a low budget Ryobi 1800 PSI electric unit just for getting lichen off the fence and other light duty stuff when the winter’s over, do you figure that’s probably safe?

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vee_lan_cleef t1_jadiu0r wrote

It will be fine, the key with pressure washing is to keep the nozzle as far away from the surface as you can, although with an 1800 PSI pressure washer you will have a hard time damaging wood unless you put the nozzle right on the surface, or use the narrow angle jet-type nozzle which don't have much for anything except extremely durable materials like steel. If you have never used a pressure washer I would recommend testing out the various nozzles and distances on a piece of scrap wood so you can get a good idea of how easily it might damage something.

Honestly, I live in the northeast where it gets extremely humid and I've been pressure washing yearly for two decades, I can't say I've ever permanently damaged anything, but you obviously want to be careful with anything that's painted (although a proper exterior paint, applied correctly, should be able to be pressure washed without stripping it) or finer decorative materials.

Also, my personal suggestion for an electric pressure washer having been through many crappy ones is anything by AR Blue, inexpensive but the parts that matter are good. The one I have now ended up running for multiple hours overnight while dry (a lesson to never leave them plugged in...) and it was so hot I thought for sure the pump would have failed, and was surprised the thing didn't short circuit or catch fire, but it's been years and I am still using it with no problems.

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vee_lan_cleef t1_jadh32e wrote

I have a pool shed in the northeast that gets heavy moss growth under trees, I pressure wash it yearly and it does not damage the shingles. The trick is to use a lower pressure electric one with a wide angle nozzle at a reasonable 8-12" distance from the surface. Also, you obviously need to direct the spray downwards towards the edge of the roof.

If you go using the high-pressure nozzle on a gas 3200 PSI pressure washer, then yeah you're going to fuck your shingles up.

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exiestjw t1_jaakxww wrote

If you're planning on keeping the shingles you have to be very gentle with them. Even just cleaning off the shingles, its going to mess them up. Its just that they'll be messed up more, faster, by leaving the organic material up there.

Anything you try to do besides gently cleaning them off in an attempt to make them last longer will just make them last that much less because it will disturb them too much.

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