I have a large outdoor carving made of big box store untreated redwood. It has been outdoors unpainted for over 20 years in a very hot and dry environment.

 

You can paint PT lumber. Just sticker it and let it dry a little for a few weeks. Use a real good primer.

I've got painted PT lumber on all the corner boards in my barn. 32 years and counting...........

That said, if that's all you want out of it, you can use untreated lumber. I'd use something that will really seal the ends of the boards well.


Most wood in a vertical orientation will last a long time. I've seen many barns with untreated/unpainted plywood sides that are decades old.

If you laid it down flat I doubt it would last 20 years.

 

I made a mailbox once, the post was treated, but there were two 2x4's up top, just little supports. I assumed they would be fine if well painted. They rotted out in 2 years.

 

Pressure treated wood is really only effective when the wood is in contact with or just above the ground. Something like a bench sitting on a deck should last several years and more if you keep it stained or oiled regularly. Using something rot resistant like redwood, cedar, cypress or even white oak will give you longer service. Crappy wood on the other hand may not last long.

Note that paint or varnishes, especially on a horizontal surface that sits out in the weather, may actually lead to it rotting more quickly. Film finishes crack fairly quickly from exposure and when it rains, water gets underneath the finish but can take a long time to dry out causing rot to set in. Even when not horizontal, cracks form at joints allowing water to seep into endgrain and gets trapped there.

So for longer life, I recommend a semi transparent stain to get the color you want instead of paint because it will give some water and UV resistance but allow any water that does get in to dry out more quickly. Just be prepared to re-coat every few years, especially on horizontal surfaces.

 

Pressure treated wood is really only effective when the wood is in contact with or just above the ground. Something like a bench sitting on a deck should last several years and more if you keep it stained or oiled regularly. Using something rot resistant like redwood, cedar, cypress or even white oak will give you longer service. Crappy wood on the other hand may not last long.

Note that paint or varnishes, especially on a horizontal surface that sits out in the weather, may actually lead to it rotting more quickly. Film finishes crack fairly quickly from exposure and when it rains, water gets underneath the finish but can take a long time to dry out causing rot to set in. Even when not horizontal, cracks form at joints allowing water to seep into endgrain and gets trapped there.

So for longer life, I recommend a semi transparent stain to get the color you want instead of paint because it will give some water and UV resistance but allow any water that does get in to dry out more quickly. Just be prepared to re-coat every few years, especially on horizontal surfaces.

I have finished building a deck in front of my home with a ramp to get the grocery cart to the top. I was reading someone else post about building a deck from white oak but he had a problem that the screws sealed so tight when the wood dried that he couldn't remove them to re-adjust the planks.
So when I built mine I put one stainless nail in the middle of each plank and when the deck dried I was able to lift up the plank and remove the nail from the bottom I replaced them with a stainless screw for decks which I bought them from from Kreg for their deck attachment. But I again used just one stainless screw in the middle of the plank. A couple have bowed but a wedge driven between the slats before screwing down solved that problem. The planks were 1 1/8 inch thick and are laying as flat as designed. No finish has or is planed to put on the aging deck. They are a nice silver color now and because the screws were installed after the deck dried out I can remove the screws with no problems. The deck and the benches were all assembled with stainless fasteners.

 

The idea that you have to wait (I had heard 6 months) that long to paint pressure treated is not true. The manufacturers basically tell you to put some water on the wood to test. If the water gets absorbed into the wood then you can proceed to paint it.

I painted some pressure treated wood fencing like the next weekend it was installed after doing that test. That was maybe 6 years ago and it's just starting to fail in some small areas. I used solid acrylic stain, which seems more or less like a paint to me.

 

The idea that you have to wait (I had heard 6 months) that long to paint pressure treated is not true. The manufacturers basically tell you to put some water on the wood to test. If the water gets absorbed into the wood then you can proceed to paint it.

I painted some pressure treated wood fencing like the next weekend it was installed after doing that test. That was maybe 6 years ago and it's just starting to fail in some small areas. I used solid acrylic stain, which seems more or less like a paint to me.

Thats a good point, I was so focused on answering your question I didnt realize you kind of asked the wrong question. You should be purchasing KDAT, kiln dried after treatment.

 

Back to the "couple of years", if it's painted well (primed first) I think you will get at least that much life out of it.

 

I just put my fence in. It was atleast a month before It wa# dry enough to stake finish, but it’s in the sun all day..

 

I built a timber frame patio cover about five years ago. I built it out of Douglas Fir. I sprayed it down with a water based preservative named Tall Earth. It looks really ugly for the first year or so. Its that green color the old pressure treated lumber used to be. But slowly it turned from green to brown then to gray. Now it looks great, like its been there for a hundred years and I see no signs of rot. So then I used it for several other timber projects. The company advertise it as a preservative and I buy it from Amazon. I started using it because i decided i would no longer use a top coat of any kind any more on outside wood structures because of the maintenance required. Hers are two pictures. The left is a section of a car port I built last year using Tall Earth. Its just starting to turn gray. The one on the right is a section of the patio cover built about five years ago very gray. So far no signs of rot anywhere.

 

Here in a few weeks I have to go to S&W and get the finish for my fence. I’ve already pressure washed it once, but will have to do it again..

 

You’ll probably be fine for a few years with untreated. With a good stain I’d say it would last twice as long as paint. Issue with paint is it’ll crack and allow moisture in as the temperatures change and the wood expands and contracts. Still again you should be fine for a few years regardless.

 

Huh? You really think stains lasts longer that paint? I mean, look at house paints. Depending on climate, sun exposure and colors, modern acrylic exterior paints can easily go 10-15 years between painting, maybe even 20 years.

 

My recent solution for a completely untreated outdoor bench was to tilt the seat planks (very comfortable) to shed water and cap the ends of the legs with PVC "wood."

I used Douglas Fir for the seat and American Beech for the legs. All our Beeches are dying of Beech Leaf Disease so I'm starting to mill them for projects using my band saw. Beech does not have much decay resistance but the water will run right off of the legs.

Unpainted, unfinished, pine-sheathed barns can last many many years as long as water does not sit in one place and the boards can dry after a storm.

PS: Some might note the lack of stretchers on the bench. I made them unnecessary by mortising and epoxying the legs 1 inch into the bottom of the seat planks.

 

My recent solution for a completely untreated outdoor bench was to tilt the seat planks (very comfortable) to shed water and cap the ends of the legs with PVC "wood."

I used Douglas Fir for the seat and American Beech for the legs. All our Beeches are dying of Beech Leaf Disease so I'm starting to mill them for projects using my band saw. Beech does not have much decay resistance but the water will run right off of the legs.

Unpainted, unfinished, pine-sheathed barns can last many many years as long as water does not sit in one place and the boards can dry after a storm.

PS: Some might note the lack of stretchers on the bench. I made them unnecessary by mortising and epoxying the legs 1 inch into the bottom of the seat planks.

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That is a great looking bench.

 

i wanted to put a little bench like this together for the pier (composite pieces are from a company called 2x4 basics). if it worked out well, i was going to build another one. easy peasy, just a few screws and there you have it - instant seating.
the local lumber yard had beautiful treated 2-bys, straight and flat, no knots, so i picked up 5...
prob should have just bought them at big blue...each 2x4x8 was 20 bucks...had i known that, i would have milled up some rough white oak and made a nice one...oh well...

 

Marine paint. Works for boats.

 

Surprised no one has mentioned KDAT (Kiln dried after treatment) Pine. Can be painted immediately with the added bonus of being more stable than the Big Box soaking wet treated lumber. Won’t check as much either when subjected to a lot of direct sunlight/heat. Used it for Adirondack chairs and has held up admirably…without warping or twisting.

 

actually, when i called the local lumber yard, they told me they had kdat, and told me yes - certainly, paint or stain right away. it'll never be drier than it is right now.

 

For what it’s worth, I built a pair of Adirondacks out of untreated 2x4’s as my first project. I used an outdoor grade paint and expected them to last a season and I would use the skills I’d learned to build a nicer set.

It’s been 2 years in direct Sun and contact with the ground and they look as good as they did when I started and are rock solid. I’m a little disappointed they’ve held up so well as I don’t have a reason to make new ones. The only thing I did was slather epoxy on the exposed end grain that was contacting the ground.

 

That sounds like a good plan. Unless you have a bad case of ground termites you should be good for a number of years.

 

use an exterior primer sealer first. i suggest visiting a sherwin williams store and talk to them about this.
if this pier is in salt water, products might be different than for fresh water.

 

here's the bench so far. the lumberyard's 2-by treated were just beautiful (for that kind of money, they better be!).
two coats of primer, three coats of exterior paint. the stretcher is on the floor. right now, you're seeing the underside of the bench seat slats; i'll flip the wood and paint the top in a couple days. it's been in the 90s and very, very humid :/

 

I hope you are right about your flex sealed trailer bunks. The risk is that if any water at all gets under the Flex Seal, it will never dry out and actually cause it to rot more quickly than if you had not put any sort of finish on it.

 

Glad you went with the KDAT. I forgot to mention that the quality tends to be top notch. Like you said, for the cost, it better be! Over the long term it’ll be money saved.
Redid my front stoop a few years back using KDAT. Painted immediately, and it’s holding up great.

ceabrm. Ya need more clamps buddy!

 

She who has the most clamps at the end, wins

 

For over 40 years I have never treated cedar or redwood decks while at the same time I have seen decks fall apart which were sealed on the surface and rotted due to retaining moisture on the underside.

In 1984 I put some redwood siding on a building. The customer wanted the bare wood look and so I painted the back of the siding and left the front bare. The wood looks the same as when I installed it. Before I installed the siding someone else installed the same siding and did not paint the back and in about four years some of it was falling apart. By painting the back the moisture could only come and go through the front.

For those who think that stain repels water better might want to see the paraffin content. It will repel water until it gets hot and the paraffin is gone in a few years.

 

For what it is worth - - - and I admit it may be not relevant... I read a study a few years ago where wood was tested and left outdoors on the ground for several years. Various types of wood; pressure treated, wood treated with marine borate powder, and wood treated with car antifreeze (ethylene glycol). The wood treated with ethylene glycol showed no signs of rot; it far out performed even the pressure treated wood. It was an interesting study but I have no idea if it has any applications or if paint would stick to wood that had been treated with ethylene glycol.