Decks, Patios, Porches and Docks - Do I need to prime my deck before staining it?

My wife and I bought a townhouse about 18 months ago and the deck has been in disrepair since day one. The previous owners left us with chipping, cracking, and peeling paint and/or stain.

Here are some of the "before" pictures:

http://www.math.utexas.edu/~narula/deck/

So I bought a 2400 PSI Pressure Washer from Lowes and the local pressure washing store sold me "Brite Side" -- an industrial strength cleaner/degreaser used to clean tar off of 18 wheelers. The guy said he uses it all the time as a deck cleaner. He said to spray it on, let it sit for about 5 minutes, and then pressure wash it off.

The results were decent, but not what I was hoping for (no pictures yet -- I need to go take some). I wanted a clear wood deck that I could stain with a pretty light semi-transparent stain. But I just couldn't get all of the purplish stain off. I got about 35% of it off of the vertical stakes, about 65% off the stairs, and about 85% off the floor boards where one would walk. I tried a belt sander but it didn't work either so I just lightly sanded the whole deck (to get rid of the "fuzziness" that pressure washing causes) and considered my options:

Obviously I either needed to get a more powerful pressure washer, hire somebody to finish the job, or just settle for an opaque stain about the same color as what I started with.

To be cost effective, I chose option number three (there's a reason I didn't just hire somebody in the first place!). I used the available color pallete from Lowes and picked a color that is just slightly darker than my existing color and I bought a gallon of it (the color is called "Gooseberry"). I'll need more than a gallon, but since they have to mix it, I can't return it. I want to be sure there are no problems before I go back and buy the other two gallons that I'm going to need. This is what I bought:

http://www.lowes.com/lkn?action=productDetail&productId=194762-86-79901A/01

I decided against purchasing a deck primer when I was at Lowes because it was on the order of $20 a gallon and the lady that was assisting me said it really woudln't make much of a difference.

Well, I was out at our local "discount" store tonight and they had gallons of Olympic brand deck primer for $6 each. For $6 a gallon I coudln't resist so I bought three gallons. I can always return them later if I don't need/want them. The cans say:

-- Alkyd/Oil Wood Primer
-- Provides a sound base for topcoat application
-- provides excellent adhesion
-- ideal for all wood surfaces
-- mildew resistant on the primer film

So here are my questions:

1. Do I need this primer? Should I just take it back? Does primer go bad sitting in a shelf for a long time? Should I buy the $20 per gallon primer at Lowes? The primer that I bought mentions that it works well against wood prone to "tannin bleeding". What is this and do I need to worry about it?

2. Can I apply either the primer or the deck stain with my pump-up deck sprayer? What is the recommended way to apply deck primer and/or stain? Is there a certain order (ie, do the vertical slats first, then the railing, then the floorboards) or does it make little difference? I've got tons of plastic sheeting so I'll be using that to catch the drippings that fall through. Any other suggestions?

Thanks for the help.

Paul Narula

Paul, I do not know about using a primer on a deck. Some people use a solid stain then seal it with a good waterproof sealer. But priming the deck. I would stick with a good oil stain product. I have some articles on staining and sealing wood decks. Just cut and past this link http://decks.hemmingsjones.com/links.html you should find some good information there.

Just view your photos. I would suggest using a deck brighter and cleaner. Do not use chlorine bleach. There is a product called Oxygen Bleach that comes in a powder that dissolves in water. It opens wood pores so that your deck sealer will penetrate more deeply. There is an artical you can read just cut and past http://decks.hemmingsjones.com and scroll down and read.

I also see from your photos that your deck stairs was painted. If so you will have to either strip it or sand it. Remember to use a breather or mask to protect your lungs from the arsenic in the PT wood.

Good Luck Paul,

Paul,

I received your e-mail and came here to answer. Wow, a lot of questions and scenarios. This could get long so here goes.

First, to properly clean that deck, based off of the pictures, would be to use a sodium hydroxide based stripper. You can get these from paint supply stores as well and will probably be better than the Lowe's and Home Depot products. I want to warn you though that when using these chemicals you should take all safety precautions when working with them. Wear googles, long pants, preferably a waterproof boot(be careful of the deck becoming slippery), and follow all instructions. The next part is the MOST important part. It isn't the pressure washer or the PSI that makes the difference in cleaning. Pressure causes damage and that is all you will do if you have too much of it. About a 1000 psi is all you should need. The pressure washer should be viewed as a tool ONLY that aids in rinsing. The key is in "dwell time", dwell time is how long you keep the chemical working on the surface. On this deck I would recommend about 30 minutes. The only way this will work is if the surface is wet, you will need to keep misting the deck during this 30 minutes. Do not let it dry. The deck will turn darker and that will be okay as the stripper does this. After completing the washing while the deck is still wet you will want to apply a brightener, I use oxalic acid based wood brighteners. I personally have my own line of products and not as familiar with the over the counter products. I do know that Wolman has these type strippers and brighteners. After you apply the brightener you will see the wood lighten up. Allow to dry for at least 48 hours and apply your finish. You may be able to apply a natural oil based sealer, with a tone also, at this point. A penetrating oil base product is best and most recommended for decking.

If you choose to go with a semi or solid finish you will want to consider the following. First, in my opinion, you do not get much better than the Cabot products, and their decking stain is very durable. It is an oil base that penetrates the wood and leaves the pigmentation closer to the surface for UV protection. The extra dollars will be well worth it in both longevity and performance. You can still find oil base semi-transparent or semi-solid products from other manufacturers.

If you choose the solid or opaque route, which I would not recommend, you will need to use a primer. These will certainly peel when deteriorating and if you do not get the surface right could lead to more work or you spending more dollars down the road for someone else to fix. The primer will give it a new surface to work from. Again, I like the Cabot product. The solid decking has teflon in it for more longevity on the walking surfaces.

Now with all that said, you have many obstacles based off of your pictures. The biggest is the close proximity of your neighbors decks. They will probably get upset with any of the chemicals or stain getting on their property. A pump sprayer may be dangerous. You may need to apply both chems and coatings with a brush or other method. Applying stains and sealers with a chinese bristle brush or a lambs wool applicator works well. I would certainly make sure I cover and mask off everything that could get damaged. This includes the siding on your house. You have probably found out by now that this is a bigger job than most people think.

I hope I have helped you with your questions. Good luck with your project. Be careful.

thanks for the replies. i took some "after" pictures this morning to give readers a better idea of how well the pressure washing went:

http://www.math.utexas.edu/~narula/deck/after/

I'm realizing now that I probably should used a deck stripper instead of a cleaner/degreaser when I was doing the pressure washing. I never stopped to consider that I didn't have the right liquid -- I just assumed I needed more PSI. I found this article about deck strippers:

http://masterhandyman.com/columndetails.cfm?pubdate=20040703

The guy basically confirms everything Everett says in his reply -- including the part about letting the stripper sit for a while and not being so worried about high PSI. I should have posted here before I got started with this...

With that said, I'm going ahead with my plans to use the opaque stain I bought at lowes. I'll may regret this decision at some point in the not-too-distant future, but I've got to get this project finished. I'll post more picture when I'm done. Thanks for the advice. I may come back to this thread in six months when my deck is peeling and cracking again...

Paul