Painting pressure treated lumber

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I've read you have to delay painting PT lumber from everywhere from two weeks to a year. Latex paint... What's the deal?
And, how does one tell if PT wood is ready to be painted? It feels quite wet from the lumberyard/HD, but seems much drier in a cupla days. Does rain further extend the wait? Does a sprayer allow you paint sooner than brushing/rolling??
Also, just curious: Will non-PT wood last as long as PT wood (outside, of course), if it thoroughly painted? In the northeast. Any special painting methods required?
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EA




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On 9/29/12 12:41 PM, Existential Angst wrote:

I don't know how long you need to wait.
As for paint... might I suggest an opaque stain. Depending on the concentration and size of pigment, it will get deeper into the grain of the wood than paint, but from a distance looks like paint. It lasts a lot longer than paint and fades instead of flaking/peeling.
Last porch I built, I used PT lumber with a white opaque stain. Up close you could still see the grain of the wood, which was an attractive feature. From the road, it looked like a newly painted white porch. It stayed bright white for several years.
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Good idear, I'll look into it. I wouldn't use white stain tho, something red-ish -- which fades quickly in ultraviolet. Is there an exterior polyurethane that can protect pigments form UV? Or are there UV-impervious pigments?
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On 9/29/12 12:56 PM, Existential Angst wrote:

I just brought up white because it's the color we used on our porch. I'm no expert but in my experience nothing will stand up to UV... for very long. I'm sure a good paint shop could tell you what's out there that works best. Maintaining outdoor woodwork has always been arduous. Engineered composite lumber has held up to UV so far, as advertised, from what I can tell.
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The reason they recommend leaving pressure treated wood to dry for a while before painting it is because the pressure treatment process involves injecting water soluble chemicals into the wood under pressure. And, it takes time for the water forced into the wood to evaporate out again. Also, weather conditions vary and some paints (like top-of-the-line) exterior latex paints will allow moisture to pass through the paint film without lifting, whereas any kind of oil based paint will be lifted off the substrate as the water inside it evporates. So, there's no such thing as a "one drying period" fits all solution. Better to get a wood moisture meter and wait until the wood dries to a 19 percent moisture content, which is the same as kiln dried lumber.
It should be paintable then.
'Existential Angst[_2_ Wrote: > ;2935537']Is there an exterior polyurethane that can protect pigments > form UV? Or are there UV-impervious pigments?

Exterior wood stains and clear coats will use transparent metal oxides for UV protection. These metal oxides are transparent and either colourless (clear), yellow, orange or brown in colour under visible light, but are opaque to UV light. So, they help add a warm "amber" look to exterior coatings to be used over wood, but they block UV light from penetrating through the coating to damage the substrate.
But to answer your question, there are pigments used in architectural paints that are unaffected by UV light, and that would never fade. But, that doesn't mean that the apparant colour your eye sees won't change. In southern climates, the intense UV light will cause the paint binder to deteriorate, causing the paint to "chaulk" and the result will be that the paint will appear to fade in colour as the surface gets rougher and rougher.
Similarily, interior latex paints will gradually darken as airborne dirt particles accumulate on the paint's surface.
Here's a post I wrote up a long time ago when I was posting on a different forum:
ROCKS ARE GOOD AT BEING OPAQUE, BUT THEY'RE EVEN BETTER AT BEING OLD.
By the time you finish reading this post, that statement will make much more sense than it does right now, and it'll help you decide on which colours you want to see in your exterior paint's tinting formula, and which ones you don't.
There are different kinds of pigments used in architectural paints; coloured pigments determine the colour the paint film dries to, and extender pigments determine the gloss level the paint film dries to:
There are two kinds of coloured pigments:
A. Organic Pigments (produced from chemicals in a lab) The pigments used to tint architectural paints to the correct colour can be broken down into two categories; organic and inorganic, and each of those categories can be broken down into natural and synthetic. While artists often prefer natural pigments, the standard for architectural paints is synthetic organic and synthetic inorganic pigments which can be manufactured to precise colours repeatedly.
In general, it can be said that organic pigments are the "colourwheel" colours like red, blue and yellow, and all the secondary colours that can be made by mixing these three primary colours, like green, orange, purple, magenta, etc.
On the one hand, these organic pigments don't have good hide, but they disperse well in the paint so a small amount of colourant goes a long way to both change the colour of the paint as well as hide the underlying colour.
Also, these organic pigments aren't as stable, and tend to fade more rapidly due to exposure to the Sun than inorganic pigments.
B. Inorganic pigments (synthetic equivalent of coloured rocks) The inorganic pigments you'll find in a typical paint tinting machine a 1. White - which is titanium dioxide 2. Yellow Oxide - which is a mustard yellow in colour and is the synthetic equivalent of "Raw Sienna", which is named after the Italian village of Sienna where the rocks and soil are a mustard yellow colour.
3. Red Oxide - is reddish brown in colour, and it's the most common form of iron oxide. The Planet "Mars" is reddish brown in colour because of the iron oxide in the rocks, sand and dust on it's surface.
4. Brown Oxide is another iron oxide that's very close to chocolate brown in colour.
5. Raw Umber is a very dark brown that can almost be mistaken for black, and
6. Black - which is actually soot made by burning natural gas is special furnaces with insufficient oxygen so that copious amounts of soot are formed.
All of these "inorganic pigments" are the synthetic equivalent of the pulverized rock dust that artists have been using to paint with for millenia. Basically, they are synthetic rock dust that has all the same properties as pulverizing a real rock into dust, and using that dust as coloured pigments in a paint to give that paint colour and opacity.
Because rocks are pretty good at being opaque, paints that get their colour from rock dust tend to hide better than paints made from organic pigments like red, yellow and blue. Unfortunately, one of the problems with inorganic pigments is that they tend to want to clump together, and it's this clumping together of inorganic pigments that lowers their effectiveness at changing the colour of paint when tinting, and hiding an underlying colour. But, all things considered, inorganic pigments (best though of as pulverized rocks) make for better hiding paint than organic pigments.
Since synthetic red oxide pigment contains the same rust molecules that you find on cars, the synthetic and natural versions of inorganic pigments have identical properties. They hide equally well and are damaged by the same kinds of things; like acids. So, when we talk about synthetic paint pigments, it's not a stretch to talk about them as pulverized natural rocks.
Now, ANYTHING that is 300 million years old HAS TO BE extremely chemically stable or it would have decomposed by now. That chemical stability manifests itself in the fact that rocks are also extremely colour fast. If you turn over a rock that's been sitting in the Sun for 100 years, after cleaning and drying, you'll find the bottom is the same colour as the top! Rocks don't fade due to exposure to UV light, and neither does paint that gets it's colour from synthetic rock dust. So, since the planet Mars is just about exactly the same colour as the rust on my car, it's fair to say that Mars hasn't faded at all in the coupla billion years it's been exposed to the Sun.
So, pulverized rocks make for a better hiding paint, but it's the extreme chemical stability of rocks that make them immune to fading due to exposure to the Sun. That is, the shear age of rocks is an indication of their extreme chemical stability, and that chemical stability manifests itself as resistance to fading from exposure to the Sun when you pulverize a rock and use the powder to provide colour and opacity in your paint.
WHITE paints deserve special mention. There are different kinds of white pigments used in paints. Titanium dioxide is the most commonly used white pigment, and it has the highest hide of all white pigments except lead carbonate, (which they haven't used since 1974). However, the hide you get from titanium dioxide will depend on not only how much titanium dioxide is in the paint, but how well dispersed it is and how large those titanium dioxide pigments are. If they're too large, or too small, they won't "diffract" light well, which means that light won't bend much when it passes near a titanium dioxide pigment particle. So, different white paints can have different hiding ability just because of the amount of titanium dioxide in the paint (and generally the more TiO2 in the paint, the whiter the paint will be in colour). But, even paints with equal amounts of TiO2 in them may have considerably different hiding ability just because of the dispersion and size of the TiO2 particles in the paint. The problem with using TiO2 in exterior latex paints is that it acts as a catalyst in the process by which exposure to intense sunlight causes paint binder resins to "chaulk". So, a paint that's white because it has white titanium dioxide pigments in it will chaulk more outdoors than a paint that's white because it has white lead carbonate pigments or white zinc oxide pigments in it.
Consequently, in exterior paints intended for sale in southerly latitudes (like Texas, Florida and Southern California) it's most common to use zinc oxide as the white pigment in white, off-white or pastel colours than titanium dioxide.
Zinc oxide doesn't have as good hide as TiO2, but like copper, arsenic and boron, zinc is a natural fungicides, so using ZnO as the white pigments helps suppress the growth of mildew and mold on light coloured exterior paints. And, of course, the degree of dispersion and particle size are also important in paints that use ZnO as their white pigment.
Titanium dioxide is the second highest hiding pigment used in house paints. The highest hiding is black, which is actually carbon soot.
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nestork


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Very inneresting, informative. I feel like a quiz is coming.... :)
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EA


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I put rec.woodworking back in the header, figgered a few would find this useful.
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EA


"nestork" < snipped-for-privacy@diybanter.com> wrote in message
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On 9/29/2012 12:41 PM, Existential Angst wrote:

PT lumber is typically very very high in moisture content. Read that as often soaking wet. Paint needs to stay dry on the side that it adheres to a surface. If moisture saturates the surface under the paint the paint will fail.

Use a moisture meter or wait at least year. Method of application has nothing to do with how long the paint will last on a poor surface.
That said some better lumber yards, not home centers, carry kiln dried PT lumber, this is what you want if you want to paint right away.

That will depend on the wood. Fur, SYP, mahogany, ipe, cedar are a few commonly used woods for out door use with no protection or paint.
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On Sat, 29 Sep 2012 13:41:28 -0400, "Existential Angst"

Contains a lot of moisture and the paint will peel. I'd wait a year or so.

Not really, the rain does not get absorbed because the PT is saturated with other chemicals.

Look at the oldest house in your town. Chances are it is from the 1700's and if painted and cared for, still in good condition.

Wait for the snow to melt. Read the can, most paints should be 50 degrees or more, a few can tolerate 40 degrees.
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never paint PT wood, as it will just peel the PT chemicals prevent paint adhesion.........
and you far better off using composite decking because over time PT wood still fails.......
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Hmmmm..... how bout if I torched the wood, to sort of surface-singe it? Would that help adhesion?
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On Sat, 29 Sep 2012 17:43:10 -0400, Existential Angst wrote:

If you are going through that trouble, why not use KDAT instead? Kiln Dried After Treatment
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Too late. Plus this is stockade fencing, not too many local choices. Basically it looked sturdy and was there. Plus a kind of experimental installation, so I went cheap/convenient, not really planning too much ahead. Turned out pretty well, so now the painting issue.
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On Sun, 30 Sep 2012 13:04:42 -0400, "Existential Angst"

I'd use a solid stain. Durable and less likely to peel. I used in on my deck with good results on the railings and balusters. On the flat portion of the decking, it does not hold up so well with foot traffic.
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I put up stockade type fencing made of PT 3 years ago:
http://mysite.verizon.net/despen/fence /
One part is 2 years older than that.
There is nothing on the wood and it still looks as good as when I built it. I wouldn't dream of painting it, that would be a huge mistake.
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Dan Espen

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wrote:

Composite had its share of failures in the past too. Don't go for the cheapest stuff if you go that way.
There are also many woods that made good decks, but are pricey too. Mahogany, ipe, etc. I used tiger wood a couple of months back.
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On Sat, 29 Sep 2012 18:49:15 -0400, "Mike Marlow"

I bought mine at www.advantagelumber.com 25 boards and hardware to do a 12 x 16 deck was about $1000 delivered. This is what I bought http://www.advantagelumber.com/tigerwood_decking.htm
If you like wood, this is lovely to look at. I gave it a Penofin oil treatment.
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On 9/29/2012 4:34 PM, bob haller wrote:

Actually have never had a problem with paint peeling on PT provided the lumber was "dry".

Agreed.
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wrote:

buy from a major long term manufacturer...........
honestly i DONT LIKE WOOD for long term outdoor use.....
concrete doesnt cost that much more and lasts far longer.......
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As I was just starting my deck project, guy doing my garage cement floor said he could build a cement porch. Sorry, it just isn't the same feel. And I got to paint the iron railings and floor on my cement side porch. That takes more work now for me. My Eon decking is holding up well after 6 years. So is neighbors. I don't know if the company reformed after closing.
On part of the wood sticking out, I used a mild stain, which seems to waterproof and prevent mold. That wood looks good. Much of the raw wood is turning black in sections. I'd like to clean and paint other parts.
Greg
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