The good thing about having a nice, powerful pressure washer is that it's fantastic at getting things clean. The bad thing about it is that it's too good at getting things clean. For instance, doesn't this look like a pretty normal bit of patio decking, maybe a little in need of a deck brushing in spots, but otherwise, perfectly normal?
Most of my deck looks this way. I've been cleaning it with a deck brush and cleaning fluid, then coating it with Thompsons deck sealant, every two years, and it's only six years old. Looks like it's in pretty good shape, right?
Well, this is what happens when I use the pressure washer on it to clean up those little spots that seem like they need a deck brush:
Holy cow. Turns out that it's got a thick layer of grime that's gray in places, and brown in others. Looks like the "natural weathering" of the deck, people say, but it turns out to be something which washes right off, leaving the wood looking much more vibrant and attractive. The difference is so striking it feels like I'm painting woodgrain onto it rather than peeling off gunk; each swipe leaves a clear border between grime and wood.
Then again, maybe what I'm really doing is the equivalent of sanding it, stripping off a layer of "weathered" wood to reveal the wood underneath. I think that's unlikely, though. If I hold the washer in one spot, I never get a groove, I just get it to a particular level of golden yellow wood color and then it stops. And the clean spots don't feel even slightly lower than the dirty spots. I find it very unlikely that the wood is that weathered on the surface but completely different so close below that you can't feel the difference. Besides, a scratch in the wood doesn't show the "clean" surface that the pressure washer is exposing, even if it's a gouge. And finally, the washer's doing the same thing to mildew stains in places. In any case, if it's really sanding the wood, that's fine too. That's actually recommended before treating with sealant, though it's far too much work for people to actually do it.
The downside as I mentioned earlier is that it does such a great job that I feel like the work is never done. I look at the huge deck and see some areas that seem clean and others that need a washing, but once I wash those, the other areas now look dirty. The job has ended up far larger than I originally anticipated, and even though it's not really arduous work, like scrubbing would be, it is time-consuming. Especially when I keep going back to redo areas that seemed good enough before.
Unfortunately, even the pressure-washer won't take off some of the grease globs and stains that the grill has left behind. Maybe next time I do this in two years I'll experiment with adding some detergent to the pressure washer (it has a system for that).