I was wondering if anyone on here has had any experience with pressure washing decks.

The deck at my parent's mountain house (in the southern NC mountains) is in a very humid environment, where it rains almost every afternoon in the summer. As a result, some mildew has started to grow on parts of their front and back deck (especially the parts where there are trees hanging over it). The deck was built about a year ago (along with the house), and was built with Brazilian Ironwood because it's supposed to be more weather resistant.

Scrubbing the deck with a cleaner and a brush wasn't getting the job done, so we thought about using a pressure washer that we had purchased a few years ago. I talked to the guy at the local hardware store who sold us the Ironwood to see if there were any tips that he could give us. He agreed that pressure washing was the way to go (as he does it with his deck), and to use the lowest setting (widest nozzle) and start from about 12" away and work your way in until you start seeing results. He told us to be careful about scarring the wood with a strong nozzle setting (a solid stream), and not to go over about 2200psi on the wood. He said regular decks are resistant up to about 1700psi, but because the Ironwood is so dense, you need a bit stronger stream to penetrate deep into the wood. The pressure washer we have is electric, and is rated at 1650psi.

I did as he described, but also noticed that the areas I cleaned had a different color than the rest of the deck (obvious). The wood when first installed had a nice, dark red tint to it, and had weathered over the past year to the typical "grey deck" color. Some of the washed area resembled this dark red color, but is not uniform throughout the entire area. Additionally, you can see some of the spraymarks from the nozzle on the wood.

From anyone who has done anything like this before, are these results typical for the first few days while the wood dries? I figured that the high pressure makes the wood get wetter and deeper than it would in a typical rainstorm, and might take a while longer for it to dry. I'm going to go back to the hardware store tomorrow and talk to the guy, but just to ease my conscience about the possibility of ruining a section of my parent's new deck, I thought I would ask here, too

Thanks for any tips, advice, etc!

- William

8/14/2006 12:08:18 AM

did you seal the deck?

8/14/2006 12:23:10 AM

To be honest, I'm not certain about that. According to my parents, there wasn't anything done to the deck after it was installed. They said that one of the advantages of using the strong Ironwood was that it was tolerant to rot, and insects, and did not require any major maintenance like normal wood decks.

The spray nozzle setting that I used wasn't very strong at all; I put my finger over the end accidentally, and while it didn't feel great, it didn't hurt, and I wouldn't think that it would be strong enough to blast off any chemical sealant (if there was one applied).

I may also call the contractor tomorrow and see what they did. Fortunately, where we are located there is only one hardware store (about 50 miles away from a Home Depot or Lowes), so any parts/chemicals they might have used came from this store.

8/14/2006 1:32:37 AM

while not certain about this... i have heard that if you were to put your finger over a high pressured air nozel it would form air bubbles under the skin and force it to be cut out. i wonder if doing that with your finger in a pressure washer could do the same thing? maybe force the air through the skin without breaking it by the water being pushed behind it?

about the deck i know nothing...

8/14/2006 9:21:52 AM

Quote :

"Scrubbing the deck with a cleaner and a brush wasn't getting the job done"

Were you using a mild Clorox solution?

8/14/2006 9:53:41 AM

Quote :

"Some of the washed area resembled this dark red color, but is not uniform throughout the entire area. Additionally, you can see some of the spraymarks from the nozzle on the wood. "

while not a pressure waching expert or anything, it seems like you're almost answering your own questions. the wood is probably a different color (a) b/c you just cleaned a year's worth of dirt n grime off of it and (b) yes, the wood probably hasn't dried out entirely.

the reason you can see some of the spraymarks from the nozzle is most likely from an uneven spray - either one place is slightly dirtier than the adjacent area (so you can see where the spray cut into the dirt) or you scarred the wood a little.

[Edited on August 14, 2006 at 7:11 PM. Reason : i've only washed concrete, brick and stone, never wood. good luck.]

[Edited on August 14, 2006 at 7:11 PM. Reason : fuck]

8/14/2006 7:11:04 PM

Thanks for your advice. whtmike2k, you are absolutely right.

I went back down to the hardware store and spoke with another wood dealer, and he said that the Brazilian Ironwood is extremely difficult to clean, especially with a pressure washer, because of how the wood looks when it is wet. When dry (and not properly treated), it looks weathered and grey, but when wet turns into a beautiful dark red. When using the pressure washer, the wood is obviously wet and red, so you couldn't really see how evenly you were cleaning the wood, which caused the nozzle marks when it dried. In a couple of months, the part of the deck I cleaned will weather and look like the rest of the deck again.

Apparently this Ironwood is very bizarre and doesn't behave like normal wood. It's so dense, it won't accept any normal kind of sealant (it's so hard the carpenters couldn't drive a nail through it). While pressure washing can be done to clean the wood, it would never look all that great because of the problems I was having. It's recommended that every couple of years to help maintain the natural reddish color at all times is to take a floor sander and clean the top layer of the wood, and put down a special Penofin hardwood finish.

I don't think I'm going to take on that project myself. The front and back decks are about 2,400 sq feet combined, and with the Ironwood being insanely expensive, I would hate to be the one to screw something up

8/15/2006 12:37:40 AM

2400 sq feet? isn't that pretty big for a deck?

8/15/2006 2:00:02 PM

i just did this like 2 weeks ago

the guy at the store was exactly right, whatever you do DO NOT turn the pressure up high to start, start out realllllll light and wide and gradually go up. if the wood starts to splinter you are using WAY too much pressure.
I would advise that you go purchase some deck cleaner (about 5 bucks) and spray the area first and let set for about 30 minutes. Oxygen bleach will do the same thing but may cost a little more. after it has set you can begin spraying. Once it begins to dry take notice, the wood may look yellow at first but it will eventually fade to the correct color. I do advise sealing it afterwards though.

ONCE AGAIN. NO HIGH PRESSURE NO SPLINTERING AND NO CHLORINE BLEACH!

8/15/2006 3:56:36 PM