My deck is about 10-15 years old and I don't think it has ever been cleaned in it's lifetime by the 2 previous owners. I want to clean it up and stain it this year so I started today by soaking the deck with water and scrubbing it with a deck brush and a bleach, soap and water solution. It worked well and LOTS of dirt was coming off but I could tell there was more that was deeper into the wood however I could see the true colour of the wood coming through.

Most of the decking is dry now and it has turned into a pale grey colour. The layers of dirt is gone but the sun bleached tone is there still. I assumed it was gone because it wasn't there while the boards were wet.. How do I get rid of the grey now? The photos are before and after. The after is a lot more pale than the picture shows and I only did the small patch where it shows btw.

 

I would continue with the deck cleaner and brush. Just know that there is only so much you can do with wood that's been exposed to the elements for 10-15 years. It will never be clean like new.

Don't be tempted to try pressure washing. A low pressure machine or tip might get a bit more dirt out but if you use too powerful a machine, choose the wrong tip or hold the tip too close to the wood you'll end up tearing into the wood and really raise the grain.

 

Should have been using a deck brightner and a pressure washer, once dry sand it, rinse again, let dry then stain.
Decking that old is at the end of it's life.

 

Maybe water, bleach and oxalic acid one more time....and than stain dark brown.

 

What is your bleach/soap mixture?

I rarely use a deck brightener as bleach usually does the same thing for less money. This is how I clean decks; wet the deck with water and then spray on a bleach solution with a pump up garden sprayer, let it set but not dry and then rinse. I use a pressure washer because it's quicker but a garden hose will work just as well. Care must be used with a PWer as too much pressure will damage the wood!

The bleach solution works best at about 40-50% bleach. Never stronger as too much bleach will destroy wood fibers! Bleach works best on mildew and for lightening the wood. For other grime I might add TSP to the mix. When needed I'll use an old broom to scrub with as it's easier on an old back

It looks like your deck might clean up good enough to use a semi-transparent stain, if not - use a solid deck stain.

 

The wood may be too far gone. Mine sat for about a year and a half before I figured out the builder was not coming back to seal it. I had to scrub twice with a bleach/water solution to get the grey out of mine and you are going to have way more grey than I did.

I would certainly start looking at solid stains in case this doesn't clean up well enough before you get tired of working on it.

 

I ended up pressure washing it all and it cleaned up quite good, still looks to be some mold or dirt in the boards. It did make the wood have a slight fuzz to it but nothing bad at all, due to this I'm thinking about a light sanding to get rid of it. I wont be staining until about April/May as thats when the wood finally gets a chance to start drying out. With that in mind, should I sand it now or wait until right before I go to stain?

Also, I am going with a dark semi-transparent, I like the look and hopefully to hide the oldness of the boards. Solid stain is out as I hate the look of it even if it will be the best option for my deck.
The picture is this after it dried, the dirt or mold is still somewhat visible in the centre of the boards. fyi, I never finished where my dog is standing as I ran out of gas.

 

The fuzz is from using too much pressure or being too close to the wood with the wand

Usually it takes 1-3 days for the wood to dry but a lot depends on weather conditions and how much sun/wind the deck sees. A light sanding should be sufficient, you don't want/need to sand it as smooth as you would the hardwood inside your house.

Did you apply any more bleach or just pressure wash?

 

I just pressure washed it, probably wont be doing that again or at least ill be a lot more careful. What grit should I use?

 

80-100 grit is good enough. Basically you just want to knock down the fuzz. The stain will soak in better if it's slightly rough versus slick. Sanding wood smooth closes up it's pores.