# Painting Plywood



## zr2paul (Apr 15, 2009)

This is my situation ... customer has a cabin/cottage that is finished with Plywood on the interior. The only source of heat is a wood burning stove which obviously is only on when he is there. He tells me the cottage has a very good vapour barrier so the plywood is protected from outside elements.

I was going to go with an oil based primer and use oil based paint for walls and ceiling but my supplier is telling me I might have issues if the cabin gets too cold/damp on the inside during winter.

I don't want to use exterior paint in the interior for obvious reasons. I'm second guessing myself and would like some opinions. Anyone done a job like this? Results? Any Opinions?

Thanks!

Paul


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## TooledUp (May 17, 2008)

Why oil on the inside? I don't think it would fail but it would almost certainly cause a lot of condensation in the winter. If I had to use oil then I'd go for a permeable paint so that the wood can breathe.


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## clammer (Feb 13, 2009)

Paul 
I do a lot of work on foreclosed properties.Something I been finding is interior paint just peels right off when exposed to cold and moisture.This has happened in just a few months between the time an inspector looks at the property and I do. Happens on doors ceilings trim and walls.If I had the choice I would look into using exterior piant if I could


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## zr2paul (Apr 15, 2009)

I've thought about using exterior paint but the problem is exterior grade paint has toxins that release and are not healthy for interior living spaces. Even my supplier mentioned it isn't a good idea especially since my client has young kids who spend a lot of time there.

I was thinking of using solid deck stain for the interior but it still has the same problem as exterior grade paint.

There has to be something out there for this type of application???

Paul


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## WisePainter (Dec 27, 2008)

oil primer, latex top coat.


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## zr2paul (Apr 15, 2009)

Will the oil primer expand and contract with the wood or is it going to crack and peal? 

Paul


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## TooledUp (May 17, 2008)

zr2paul said:


> Will the oil primer expand and contract with the wood or is it going to crack and peal?
> 
> Paul


You're not a painter are you zr2paul?


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## Painter Girl (Mar 25, 2009)

Most oil primers will flex a bit when the wood expands and contracts due to not having a typical "hard" cure like an oil based glossy topcoat.

I would look into SW prep rite or Zinsser Coverstain and then you can top coat with any latex maybe even a low VOC exterior to reduce the amount of harmful emissions. 

We also have had many unheated garages peel like sunburn with a regular interior paint.


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## WisePainter (Dec 27, 2008)

TooledUp said:


> You're not a painter are you zr2paul?


That's what I meant to post.


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## sage (Apr 29, 2007)

TooledUp said:


> You're not a painter are you zr2paul?


 
Took the words right out of my mouth.
Sage


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## Ardee (Jun 9, 2008)

Thin your primer 10-15%


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## clammer (Feb 13, 2009)

One thing I have to say is on some of the properties I have worked on.You can see the water running right down the wall due to the temepture changes. If you are a painter I would listen to my paint rep If it peels in it's on there back


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## zr2paul (Apr 15, 2009)

Reason I ask about the Oil Primer working in these conditions is because I know that whatever product I use it HAS to be flexible enough to work with the plywood and different climat conditions (SE Ontario, Canada). Oil is not as flexible or at least that's what I have understood from my short career in painting. I'm still new to the painting industry and have basically only done interior residential (some commercial) work so forgive me for trying to learn more.

Whether my supplier is correct or not I can't have a product that is going to fail because at the end it's on my back. It won't effect my supplier but makes me look bad as a contractor, I'm sure you can understand that.

Thanks Painter Girl...I was thinking of using Zinnser since it will hide all the knots in the plywood, especially since they want to use a light color glossy grey on the walls. I'm going to contact Zinnser directly and ask them about my situation just to varify. 

Paul


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## zr2paul (Apr 15, 2009)

Zinnser left me a message and he only recommends their 123 for this application. So Zinnser 123 is what I'll be using and a Semi Gloss latex for the rest. Thanks everyone for their input, much appreciated!


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## nEighter (Nov 14, 2008)

Here is what I think. You need to coat the walls with a water vapor primer. Then topcoat with a latex paint. There should be no condensation because the house should have the appropriate ventilation to evacuate the water vapor from the house. I understand that is logs, and plywood for the walls, I don't know what the exact R value would be for that, but the main reason for the condensation is the water vapor in the air condensing on the colder substrate. In northern climates vapor barriers need to be put closest to the hot side, in this case, since the walls are really the only means of any type of vapor barrier, then to prime it with a vapor barrier primer would be your only means to add one. With the right ventilation you should not encounter much condensation. If I were in your shoes, I would do this. :thumbsup: good luck.


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## zr2paul (Apr 15, 2009)

This is a 16x32 cabin/cottage that is one big room. Walls are 2x6 studs with a R22 insulation on walls with a vapour barrier. The attic has R40 insulation with a vapour barrier and the floors have R22 insulation. All walls and ceiling are finished with 1/2" Plywood, floor has 5/8 T&G Plywood and 1/2 Plywood. The only source of heat is when they are there using the cottage...other than that, water will freeze in the winter. As for ventilation, I didn't see anything via the photos but I know the attic was properly vented.

Anyway...so putting some sort of vapour barrier paint would not be a good choice as the plywood would be in the middle of two vapour barriers (big NO NO).


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## WisePainter (Dec 27, 2008)

So when is this gonna get done?


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## zr2paul (Apr 15, 2009)

So I spoke with the Zinnser Sales rep directly as I thought when he mentioned to use 123 that there was a Latex verision and an Oil version but there is only a latex. He's telling me to go with the 123 because it's good for plywood applications and because it's latex which will be better than oil in regards to expansion of wood and allowing the wood to breath and not trap moisture. He then tells me that oil primers will trap any moisture coming from under the plywood and cause the primer to bubble. I explained to him that the cabin has a vapour barrier with insulation so I'm not worried about moisture so then he says to go with either the Zinnser ORDORLESS Oil Primer or the Zinnser COVERSTAIN Oil Primer.

I call 2 of my suppliers and one says Zinnser Oil Base Primer is good for the application and the other supplier says why use OIL? He says to use a 100% Acrylic Latex Primer as it's more flexible and won't seal the wood, allowing it to breath. Talk about fence sitting on applications!

Thankfully client doesn't need this done for another month or 2.


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## [email protected] (Feb 24, 2008)

It seems that the logical primer would be the latex not the oil. It seems there could be more risk with the oil than the latex??? Just some thoughts..


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## Ardee (Jun 9, 2008)

I don't think expansion, contaraction and breathing of the plywood is the concern. Knots are. Heavy knots should have shellac(Zinzer's Bin) on them to help prevent bleeding. I always give heavy knots two coats. Interior latex is my choice of top coats only because of the environment.


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## NACE (May 16, 2008)

Plywood is made of a matirx of wood fibers blended together with a bonding agent and compressed under great pressure. Alkyds and the solvents used to manufacture and reduce alkyds, will soften the glues used to bond the fibers and eventually delaminate and compromise the adhesion of the primer. Latex is less noble to the glue, and will not disolve it. In additon, latex will form a more uniform foundation that will minimize flashing, be more flexible, and be more breathable. Oils will penetrate into the different porosity's of the wood, and may become "resin starved" or have less film integrity due to the resin being sucked into more porous areas. Fast drying primers become brittle and are not as dimensionally stable on a plywood surface that has a miriad of flexiblity rates. The bottom line is that a latex primer should always be used on plywood, in additon to MDO/MDF type surfaces. 123 or equivalent latex type primer is the correct choice.


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## PeteL (Apr 27, 2009)

NACE said:


> Plywood is made of a matirx of wood fibers blended together with a bonding agent and compressed under great pressure.


MDF, OSB etc yes, plywood=no. Plywood is thin sheets cut rotationally from the log and the veneers assembled in layers and pressed.


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## NACE (May 16, 2008)

PeteL said:


> MDF, OSB etc yes, plywood=no. Plywood is thin sheets cut rotationally from the log and the veneers assembled in layers and pressed.


And a glue is used to bond them, and the sheets may come from different trees. Alkyds soften and or compromise glues uses in the assembly of these products.


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## PeteL (Apr 27, 2009)

And I don't see penetration of any coating effecting the glue 1/8" in from the surface.


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## cande (Apr 24, 2008)

ICI Gripper or 123 is what I would use.


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## zr2paul (Apr 15, 2009)

Went with B-I-N . I want to thank everyone who was willing to help me out...it's much appreciated! It's great to have a forum like this and get different opinions from professionals. Cheers!

Paul


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## paintguy48 (May 1, 2009)

I agree with Ardee, spot prime the knots with a oil primer and then follow with a complete latex prime coat that is 100% acrylic. I use PPG Seal Grip or Porters Water-base Sta-Kill, both awesome. Not sure where your from, but these items may not be in your area. Yeah, stay away from exterior coatings for interior as mentioned do to the toxins as witnessed on projects. You might consider a finish coat that is mildew resistant as well.

Good Luck


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## paintguy48 (May 1, 2009)

Wow, didn't even see the second page. Sorry, hope everything worked out.


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## zr2paul (Apr 15, 2009)

That's the reason why I chose B-I-N over 123 ... BIN is rated good for Plywood and Excellent for Knots/Saps whereas 123 is only rated good for Plywood but not recommended for Knots. 

Spoke with my client this evening and looks like he wants to paint the floor as well. So I'm going with a 100% acrylic primer and a Latex Floor Paint. For some reason when I spoke to the sales rep at Zinnser he does not recommend their primer for floor applications (even though on their website under FAQ's they say its ok)...He toldm e to go with a 100% acrylic primer and it would be fine. He never gave me a clear reason why it can't be used on the floor...and I really don't see why not. Anyway, I'll stick to what the manufacturer says. Again thanks everyone! :thumbsup:


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