Deck refinishing question? Help!

Deck refinishing question? Help! · 12-11-2008, 03:45 AM

Hey guys, to let you know what I've got. I built a wooden patio deck about 2 years ago now out of pressure treated pine woods. I didn't want my deck to become the ol drabby dark, dull brown boards that they become left untreated with further treatment. So I turned to the internet for discovery of what to do to prevent this.

Now I discovered this product called New Wood Defender by Flood and bought some and used it according to the manufacturers directions. It is designed to regulate the moisture that leaves the pressure treated board to prevent warping and cracking.

Now about a year later, understanding that this New Wood Defender was gonna protect me against cracks and warping but not against discoloration of my wood.

So i went out on a venture to locate the appropriate oil or finish. I ended up settling for a type of finish that is designed for fencing, not specifically for decking. Anyways now i have a finish that has black mold underneath it on almost every board.

I think my error was placing this discoloration type finish on top of the New Wood defender too quickly, thus locking that regulated moisture within those boards. NOw my deck hasn't discolored in the sense of what one would typically see however I have got to refinish it.

I was wondering if I should go invest in a belt sander and 'get to sanding' or is there some type of finish remover that I could place on this finish to remove both the top finish and possibly the mold.

Hey, i am open to discussions and suggestions.

Thanks in advance for all your help and time regarding this issue.

Chris

ptt49er · 12-11-2008, 09:45 AM

Rent the best pressure washer you can and be careful with it. Water at high PSI's can do some damage rather quickly. I'd can't help but think that would do all you needed done on a deck.

JackLeg · 12-11-2008, 09:48 AM

Chris: I don't have a solution for the mold and discoloration, BUT, I definitely would NOT sand PT wood. We used to make outdoor furniture out of it and that is some nasty stuff.

I think that DaveO and several others who work with PT will agree with me on this. You migh try pressure washing with some kind of cleaner. Just m2cw.

Good luck!

DaveO · 12-11-2008, 07:27 PM

Here's my .02 cents worth. To start PT pine without anything finish-wise applied to it will turn a light gray as the UV light slowly bleaches it out. Second the New Wood Defender product won't prevent cracking, checking or warping, it might slow it down a little. There is no finish product available that will mediate the moisture exchange on something like a deck board. Deck boards face the harshest conditions that any wood can. Full sun exposure and rain exposure on one side, little sun exposure and minimal rain (moisture) on the other, often coupled with poor air flow on the underside in the case of a low deck. PT lumber starts out very wet, even for outdoor use. It will dry, and then get wet again and dry some more. This type of cycle will wear it out.
After a year I would suspect that the New Wood Defender has been degraded by the weather and UV exposure to the point that it really shouldn't be included in the equation.
The next issue you are facing is the use of a oil based stain product. Oil based finishes primarily use linseed oil as their base. Linseed oil is great food for mold and algae. I am going to guess that your deck gets a lot of shade. This is where you will see this problem the worst.

What I recommend doing is cleaning the deck with an oxygen-based bleach (Oxy-clean) scrubbing well, that will remove the mold stains and might reduce the stain color a little. If you are impatient like me and don't have a bunch of plantings around the deck that you care about a regular bleach (sodium hypochlorite) deck cleaner/brightener will make fast work of this job and bring your boards back to their natural color or lighter.
Once everything is clean and dry and the weather conditions are right...not too hot or cold and preferably overcast to avoid a lot of direct sun on the surface. Apply a synthetic resin/epoxy based finish. Either clear, which will give the shortest longevity or semi-transparent to opaque which will greatly increase the longevity. One product line that I have found that really works well is Defy products from SaverSystems - http://saversystems.com/woodproducts.php

Or just let the wood do what it's is going to do naturally, and leave it unfinished. Clean it once a year. I doubt anything that you can apply to a deck will increase it's longevity, but it will increase your work load. Finishes do make it look more attractive, and that is the primary reason to use them.

MTCW,
Dave

Truefire · 12-12-2008, 03:27 AM

Originally Posted by DaveO

Here's my .02 cents worth. To start PT pine without anything finish-wise applied to it will turn a light gray as the UV light slowly bleaches it out. Second the New Wood Defender product won't prevent cracking, checking or warping, it might slow it down a little. There is no finish product available that will mediate the moisture exchange on something like a deck board. Deck boards face the harshest conditions that any wood can. Full sun exposure and rain exposure on one side, little sun exposure and minimal rain (moisture) on the other, often coupled with poor air flow on the underside in the case of a low deck. PT lumber starts out very wet, even for outdoor use. It will dry, and then get wet again and dry some more. This type of cycle will wear it out.
After a year I would suspect that the New Wood Defender has been degraded by the weather and UV exposure to the point that it really shouldn't be included in the equation.
The next issue you are facing is the use of a oil based stain product. Oil based finishes primarily use linseed oil as their base. Linseed oil is great food for mold and algae. I am going to guess that your deck gets a lot of shade. This is where you will see this problem the worst.

What I recommend doing is cleaning the deck with an oxygen-based bleach (Oxy-clean) scrubbing well, that will remove the mold stains and might reduce the stain color a little. If you are impatient like me and don't have a bunch of plantings around the deck that you care about a regular bleach (sodium hypochlorite) deck cleaner/brightener will make fast work of this job and bring your boards back to their natural color or lighter.
Once everything is clean and dry and the weather conditions are right...not too hot or cold and preferably overcast to avoid a lot of direct sun on the surface. Apply a synthetic resin/epoxy based finish. Either clear, which will give the shortest longevity or semi-transparent to opaque which will greatly increase the longevity. One product line that I have found that really works well is Defy products from SaverSystems - http://saversystems.com/woodproducts.php

Or just let the wood do what it's is going to do naturally, and leave it unfinished. Clean it once a year. I doubt anything that you can apply to a deck will increase it's longevity, but it will increase your work load. Finishes do make it look more attractive, and that is the primary reason to use them.

MTCW,
Dave

Hey Dave, let me clarify in case I created any misunderstanding by the manner in which i wrote the post. Maybe i didn't do a very good job of conveying the message i was attempting to. The finish i applied i don't believe was an oil based finish of any kind. Furthermore, I am not 100% sure but i don't think it had any type of linseed in it either. I know that it wasn't a linseed oil for certain.

I know I should remember these things, heck i read the labels and used the finish. Hey what can i say...

This was a surface finish (went on opaque, dries clear) and not a pourous type finish thus creating a clear layer that this mold has been growing up under exponentially.

I am trying to discover if there is a certain type of finish remover out there that would dissolve this finish into an easily removable sludge, that would allow access to this mold. That is the reasoning behind me mentioning utilizing a belt sander to reach this 'layer', if you will.

Now, i was simply using this finish to attempt to maintain that original wood look and it wasn't applied so much for the control of cracking and what not.

to answer your question the deck gets full sun from 930-sunset all times of the year thus raising another question for me. That finish must really be a great quality sealer and was wondering if i should have let the wood weather a little longer than a year before applying this finish, maybe the wood would have been drier, I don't know. Merely brainstorming.

I appreciate your work and effort that you have used in the response to this post. Thanks for the attachment hyperlink and know that i will certainly look into that.

Thanks again Dave, Chris

Truefire · 12-12-2008, 03:36 AM

OH by the way DAVE, I really appreciate that turning stock that I got from you several months back. I have made some really beautiful duck calls out of it.

Just wanted to thank you for it again.

take care, Chris

Matt Schnurbusch · 12-12-2008, 09:24 AM

Chris,

Unfortunately, there is no short answer for this one. Nor is there an easy fix.

The deck will need to have the finish completely stripped off, so that you can get to and clean the mold. Dave is 100% right about the bleach. It is the only thing I know of that kills mold dead.

The stripper and it's application and use will depend on the finish being removed. If it's an oil based product one of the two product below will more than likely get it. If it's latex... I wish you luck! I run away screaming from latex strip jobs. I have used two different products for oil stripping. HD-80 (really strong), and EFC-38 (a little more mild). Both are available from: http://www.woodrich-brand.com/category_s/1.htm

Based on what I have read you will probably need the HD-80 because the finish is relatively fresh. No matter what you use to strip, make sure you neutrelize the wood with Oxalic, or Citralic acid afterwards rinsing heavily after each.

For stain I use a product from the same company I listed above. It's called Woodtux. The beauty of it is that when I do a deck for a customer I can go in and strip, neutralize, and stain in one day. With most other products, you have to wait for the deck to dry thoroughly before finishing. There may be other products that allow this as well, but I am most familiar with Woodtux.

I used to frequent a forum called The Grime Scene. Go here:
http://www.thegrimescene.com/forums/...ks-fences-etc/

The folks over there are really nice. There is a DIY section to the forum where you can ask questions, but I suggest searching in the above area. You could literaly spend days/weeks looking through all of the info.

Sorry to be the bearer of bad news. I certainly don't claim to be an expert in the field, but if I can help further, let me know.

Howard Acheson · 12-12-2008, 11:21 AM

What I would suggest you do is to go to your local library and get the June and July copies of Consumer Reports. CU has been testing deck treatment products for the past 10 years or so. They report on the results in the June or July issue each year updating results as products change. They also discuss best methods of cleaning and preparing the surface for coating.

CU is one place to get info on lots of deck products.

DaveO · 12-12-2008, 06:48 PM

Originally Posted by Truefire

Hey Dave, let me clarify in case I created any misunderstanding by the manner in which i wrote the post. Maybe i didn't do a very good job of conveying the message i was attempting to. The finish i applied i don't believe was an oil based finish of any kind. Furthermore, I am not 100% sure but i don't think it had any type of linseed in it either. I know that it wasn't a linseed oil for certain.

I know I should remember these things, heck i read the labels and used the finish. Hey what can i say...

This was a surface finish (went on opaque, dries clear) and not a pourous type finish thus creating a clear layer that this mold has been growing up under exponentially.

I am trying to discover if there is a certain type of finish remover out there that would dissolve this finish into an easily removable sludge, that would allow access to this mold. That is the reasoning behind me mentioning utilizing a belt sander to reach this 'layer', if you will.

Now, i was simply using this finish to attempt to maintain that original wood look and it wasn't applied so much for the control of cracking and what not.

to answer your question the deck gets full sun from 930-sunset all times of the year thus raising another question for me. That finish must really be a great quality sealer and was wondering if i should have let the wood weather a little longer than a year before applying this finish, maybe the wood would have been drier, I don't know. Merely brainstorming.

I appreciate your work and effort that you have used in the response to this post. Thanks for the attachment hyperlink and know that i will certainly look into that.

Thanks again Dave, Chris

OK, I am now a little confused. You said that first you applied the New Wood Defender (NWD). Which you are correct, is a water based finish with Alkyd Resin. The reason you can use it on un-weathered PT is that it's water-based formula won't conflict with the moisture in the wet PT lumber. According to Flood it will mediate the moisture loss as the very wet PT lumber dries to its EMC with the environment it's located in. Also according to Flood it can be coated after 1 year with another finish. This leads me to believe that after a year it has degraded to the point that it is not doing anything.
Here is where I am confused. What I read from your original post is that you then applied "the appropriate oil or finish. I ended up settling for a type of finish that is designed for fencing, not specifically for decking"
This is where I am getting my comments about the linseed oil from. What kind of product did you use a year after the NWD??? I think that your problems are more in that than the NWD.

You're very welcome for the wood, When I get another over-stock of scrap in the thicknesses you need I will send it your way.

Is there any way that you can take a picture of what you're talking about on your deck? That might help explain it better.

Dave

gordonmt · 12-12-2008, 08:29 PM

Chris,
I will be the first to admitt that I do not know everything there is about deck finishing but I can give you the advice that I followed and was successful with. I might also let you know that I got my advice from my some folks at my company that suppliy many of the ingredients that go into the making of many of the finishes that are used by the finish industry (we don't make it, we make it better)
First off, strip the existing finish off down to the bare wood. Pressure washing seems to work the best in conjuction with good quality deck cleaner and a scrub brush. Remember the first three rules of finishing (refinishing) Preparation, preparation, preparation. Let the wood completely dry out (days) and wait for a good cloudy warm day to start refinishing.
I have used the Cabot semitransparent deck surface stains with great success. I can tell you that they are highly rated in Consumer reports and they contain one of the highes levels of UV absorbers in the industry. My deck has lasted over three years between reaplication. I also chose a color that closely resembles the grey untreated wood to make the color last even longer.
My two cents.

Howard Acheson · 12-13-2008, 11:20 AM

Yes, some Cabot products have tested well in the past. However, Cabot changed formulations a year or so ago and Consumer Union has only a years experience with the new formulations. Therefore, CU has not issued a full report on them yet.

The top rated at this point, is a Flood SWF - Solid. It's a waterbased opaque stain. It exceeds the second place product by quite a bit. Opaques continue to be the longest lasting deck treatments.

You are so right about preparation. Time spent there and doing it correctly pays off in longevity. The CU article spends some time discussing preparation.