Help With Process of Cleaning Large Decks

I have a customer has a large deck roughly 3500 sq ft that they want to get pressure washed and sealed with a clear sealer.There is no sealer on this deck as of now. This deck is 2 stories and goes from 2nd to 3rd story and also has a pool deck with privacy fence and about 220 ft of handrail. Top and bottom decks are almost identical at 1000 sq ft and pool deck is roughly 1400 sq ft.I will post some pics when I figure it out. Guy also has nic nac furniture and stuff wants to get pressure washed.
I have a few questions.

1 Most say their process is normally to use a stronger house wash mix and then pressure wash it off or should I use either hydroxide or percarb cleaner and follow with an oxalic or neutralizer and rinse since I will be sealing it? The top floor and pool deck have heavy graying.

2 I am coming up with roughly 30+hrs of pressure washing here, does that sound reasonable. I seem to get about 200sqft hr it seems on heavy graying wood , the shaded areas aren’t so bad. Also picketts are slow!

3 Is there a clear sealer that I can spray on like a thompson water sealer but is actually worth spraying down , even if I have to back roll it? Or is everything going to have to be painted on with a brush or back brushed?

1 - No existing stain to remove, no need or any reason to use sodium hydroxide. It is a bit harsh on wood and encourages “fuzzies”. Not a house washer or otherwise, we only work on wood. But AFAIK, most house wash mixes are stronger than what is needed and acceptable for exterior wood. Our normal wood mix is 1.5% sodium hypochlorite with a bit of soap as a surfactant and cleaning agent. With heavy mold/mildew no stronger than around 2%. A percarb cleaner followed by an acid may be preferable, depends on the species and condition of the wood. A few pictures with additional details would help.

2 - Your math does not add up. 3500 sq. ft. at 200 sq. ft./hr comes to 17.5 hours, not 30. Too many variables, ie: vertical wood, pergolas, upper stories, access etc. to make a blanket production rate but 200 sq. ft. per hour to clean wood is very low. Do you have help? Shurflo or like pumps to apply chems? A decent PW with a pump putting out at minimum 4 gals./minute? Specialized wands? Your chemicals should do the work, not higher pressure to “clean” wood. It doesn’t, only slows you down and can damage wood.

3 - Never have and never will apply a clear stain/sealer. IMO they are a waste of time and money. Without pigment, the wood grays quickly and requires a lot more maintenance. Application again depends on the circumstances. We use specialized HVLP stain sprayers as much as possible, but usually “cut in” with natural bristle brushes (~95% of our work is using oil based wood stain). Found it more productive than doing a lot of masking. Whatever stain you use, check with the manufacturer’s instructions or give them a call with any questions.

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1 This is a salt treated pine deck so nothing special really. I have a 12v pump and can spray the solution easily or a percarb cleaner following each with oxalic or neutralizer. Also this guy wants the undersides done, I assume a the 12.5% would be safer and better for algae spots on underside?

2 I figured 200 sq ft an hr off a past deck I had to do with severe graying and some algae. This deck in question has no algae (except some underneath) only graying. Also I added substantial time for the hand rails (230ft of handrails here) and post and also he wants the undersides of the two 1000 sq ft decks washed. And a privacy fence around the pool deck. Along with another 200 sq ft on ground level with a small outdoor shower.

3 Thanks for the tips on stains, I have sprayed paints before but only inside a home or other hobbies etc. I have been trying to push him towards a different stain for the longevity and better protection etc., but I don’t think he wants to go that route. I have a stain guy coming to look at it today to get his opinions on which stains to use. Its likely that I may have him apply the stain. I have researched and hear most people on the forums suggest either Bakers Gray away, Armstrong clark stains or Ready Seal. Ready seal being having some fading issues but is easier to apply.

4 Equipment is 4 gpm washer also have another 4gpm that I may use as well. I’ve kicked the idea around of getting an 8gpm machine to help me out and may if I pick this job up to do the flat surfaces and house washes. But I wouldn’t think I’d need that many gpm for wood.

Hey Thanks alot Rick, I’ve read enough that you are one of the gurus around here and I really appreciate it.

1 & 2. I assume “salt treated” means “pressure treated southern yellow pine” to us Yankees! Good on the 12v pumps, we keep a backpack pump up on the truck in case both Shurflo’s blow out on a job (happened a few times). Yeah, with the undersides, the bleach mix I suggested will do the trick. Sodium hypochlorite is much more effective in killing than percarbs. Hope they don’t want you to stain the undersides!

In general, if the wood is in good shape, I find a percarb cleaning followed by an acid really brightens the wood. The finish looks a bit better if using an oil stain. 6 - 8 oz./gal. of percarb, followed by 4 oz./gal. if using oxalic, or 6 oz./gal. of citric acid (my preference) should be fine. Depends on the stain you are going to use as far as rinsing. We use Ready Seal which is paraffin oil based and compatible with a acidic surface, but with most oil and waterbased wood stains, a good water rinse after the acid has brightened is a good practice.

  1. We’ve been using Ready Seal for 13 yrs. now. Have found that color retention is a bit better than most oils on the market. Did a one year test on my own ipe’ ( a very hard, dense wood) deck yrs. ago. RS outperformed by a slight degree the 3 other “premier” oil stains tested (Baker’s was not one of them) and only Defy, a waterbased stain kept color better. The downside of a true paraffin oil like RS is that when first used on particularly softwoods, to do the job right, you use a lot of stain. Thereafter, if kept on a treatment schedule (2 yrs. horizontals, 4 yrs. verticals), stain quantity is ~60% of the initial staining. The upside is that maintenance is much easier and the customer saves on labor costs.

  2. A 4 GPM PW is fine for wood. High pressure is not used for wood, pump water fIow is your friend. Unless you are carrying water or the residence has a high GPM feed, needing 8 GPM can be a problem. We have a lot of customers on private wells in our area and we continue to use an AR 4.5 GPM pump. Still have the original after 13 years!

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Yes southern pine pressure treated is what we are working with. I have been washing houses and do small patios and driveways here and there. I have washed many of decks in the past at a previous job but never one for my business this size and I know I always spend more time than I believe it will take to get it looking great.

We have a couple 12v pumps and pump up sprayers. Thanks for the tips

I have heard mixed reviews about the ready seal, but I will take your word for it as you never know who just selling something.I have been explaining to customers that they will need to maintain it afterwards on a schedule like ready seal requires.

Also have you ever used the bakers or the armstrong clarke stains?

Yes we have areas here also with wells or the tap is off well.

I have attached pics of the deck, there are two levels of deck and etc, only doing inside of pool deck fence.


Nice job. That PT SYP will clean up nicely. From the pics, I’d use a sodium percarbonate wood cleaner followed by an acid neutralizer. That wood will glow! Rinse afterwards if not using Ready Seal.

I’ve used Armstrong-Clark stains a few times in the distant past, but am not a fan of linseed oil for a few reasons. It is a high quality stain. The owner, Jake Clark and I are very good friends, I pick him up at Phila. airport and Jake stays at my home at times when here in the area for seminars. Jake has it half right, with his oils being half paraffin and half linseed! Most colors offered use trans oxide pigments which are the best on the market.

Never used Baker’s, a more heavily pigmented stain than my preference. For years was non compliant and technically VOC illegal here in the northeast. Don’t know of the formulation/legality now.

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Thanks alot Rick, I appreciate your insight, I will try to put my hands on some sodium percarbonate and oxalic for this job. Probably order some from bob at pressuretek. By the way my wife has some family in Pennsylvania their in Pottesville I believe that’s spelled right, its near the old Yuengling factory.

Bob and Pressure Tek are terrific, couldn’t do business with a more deserving company. Yuengling, especially for its cost, is a very good beer. Oldest, continuous operating brewery in the U.S. Back in the 1920’s, to financially survive Prohibition, they started making ice cream. Still do!

BTW, the shadowbox fence in your pics is most likely low grade western red cedar. Same chems and process. Just be careful with the water pressure coming out of your wand/tip. Cedar is a lot softer than PT SYP.

Ok thanks for the heads up on the cedar, I will post pics if we get the job. Thanks again for all your help.

That’s going to clean up real nice and look great. Hope you got the job