I'm going to have a ned shed to prime. It will be sided in groved, rough T11. My big question is whether to prime it with oil or latex primer? I know oil has been the gold standard in the past. But my understanding is latex is getting pretty good, expands and contracts well, and is easier for me to work with. Which would be the best?

I have some "Bullseye 123" and Kilz original at the house that I could use. If there is something better I would get that. I want the finish to last as long as possible. I will be topping it with Duration.



Also, how long does it need to dry after washing the sawdust off before priming? If it rains? We're having 90 degree days, 70 degree nights.

Thanks,
Jon

I prefer latex over oil. Much easier to apply, less mess and for the past 15 years or so latex has outperformed oil. Get a good grade of exterior primer, or use some of the top of the line no prime exterior paints offered by most major paint labels.

Hard call on the dry time as it would depend on wind, temperature, humidity and how wet you got it. You could also blow or sweep it off - T1-11 is a fairly rough surface anyway.

If you're just cleaning the sawdust off with water, then you're only getting the surface of the siding wet, and it should dry in a day or two, depending on humidity. But, if you're gonna prime and paint with oil based products, I'd give it a 3rd or even 4th day to dry just to be super safe.

My experience has been that oil based paints simply stand up better outdoors than latex paints.

However, the most important thing to the lifespan of any paint job is to do everything you can to keep the sun and the rain off the paint. If you do that, both latex and oil will darn near last forever; just like paint indoors does. So, having a real long overhang on your roof to shade and keep rain off that paint will extend the lifespan of ANY paint you put on that siding.

But, my own personal experience is that oil based primers and paints last longer outdoors, and I can't argue with what my own experience has been. In my humble opinion, the notion that latex paints are somehow as good or better than oil based paints is government propoganda designed to get people to use the less polluting water based coatings instead.

Oil based paints dry to a harder and more protective film and they have a much more robust and reliable film formation mechanism. It's hard to stop an oil based coating from forming a proper film, whereas extremes or rapid changes in temperature and/or humidity can both interfere with proper film formation of latex primers and paints.

So, if it were me, I would use an exterior alkyd primer and top coat with a FLAT exterior oil based paint. By choosing a FLAT oil based paint, you save on preparation time in the future when it comes time to repaint. That's because the existing paint will already be rough enough to accept another coat of flat exterior alkyd paint without any sanding to improve adhesion.

But, a good latex primer and a top coat of any company's top-of-the-line exterior latex will last a long time too, just not AS long in my humble opinion.

PS:
The following is a public service announcement to educate people on the foolishness of using KILZ sealer:

People seem to think that just because KILZ dries quickly, it's got some kind of different chemistry than a regular alkyd primer, and that just isn't so.

Here's the MSDS info on KILZ oil based primer/sealer/stain killer:

http://apps.risd.edu/envirohea...s/Furniture/kilz.pdf

Take a look at that MSDS, and the first thing you notice is that it doesn't just use mineral spirits as a thinner the way a normal alkyd primer would. It uses a 60 percent VM&P (Varnish Makers and Painter's) Naptha, 40 percent mineral spirits mixture for it's thinner. Naptha is camping fuel, and in order to keep a good flame going strong enough to cook on a windy day, naptha has to evaporate extremely rapidly, and it does. So, KILZ is nothing more than an ordinary interior alkyd primer that's been thinned with naptha, which evaporates very much faster than mineral spirits. THAT is why KILZ goes from "wet" to "tacky" so fast. What evaporates from KILZ as it dries is different than with ordinary alkyd primers, but what remains behind on the wall, however, is the same as if you'd used an ordinary interior alkyd primer.

But, let's think about that for a minute. It's true that naptha evaporates much faster than mineral spirits, so most of the thinner in KILZ will evaporate sooner than with a normal alkyd primer, but evaporation of the thinner does not mean that KILZ will cure to a solid film any faster. You see, oil based coatings (including drying oils like linseed oil, alkyds and "urethane modified alkyds" like polyurethane hardwood floor finish) cure by reacting with the oxygen in the air. And simply having a thinner that evaporates sooner only means that you get a head start on that chemical cure that follows where the coating reacts with the oxygen in the air. It doesn mean the reaction with oxygen to transform the liquid into a solid will occur any faster. So, the naptha makes the KILZ go from "wet" to "tacky" much faster, but the transformation from "tacky" to "dry" takes just as long with KILZ as any other interior alkyd primer.

The 15 to 30 percent magnesium silicate and 5 to 15 percent titanium dioxide also warrant comment.

Magnesium silicate is talc or talcum powder. On the Moh hardness scale that goes from 1 to 10, where diamond is "10", talc is "1". It's 5 million times softer than diamond.

http://www.realgems.org/pic/mohs%20en.jpg

Talc is the softest "rock" (if you can call it that) there is. Primers and inexpensive paints uses talc as an "extender pigment" which is what gives primers and paints their level of gloss. Were it not for extender pigments, all primers and paints would dry to a high gloss. Coarsely ground talcum powder is added to KILZ so that it dries to a rough or "matte" surface. Talc and calcium carbonate (aka: chaulk) are both popular extender pigments because they're both very soft "rocks" that are inexpensive to grind down into a powder. Using a soft rock to make the extender pigment lowers production costs.

The purpose in having the primer dry to a rough surface is that a rough surface provides much more surface area for the subsequent coat of paint to stick to. The more surface area the primer provides for the paint to stick to, the better the "apparant" adhesion of the paint to the primer.

Titanium dioxide is the high hiding pigment in primers and paints. It's what makes the KILZ white in colour. Titanium dioxide replaced lead carbonate as the high hiding white pigment in primers and paints in the mid-1970's when lead based pigments were banned in architectural paints.

You should know that ANY inexpensive interior alkyd primer will have talc or chalk as the extender pigment and titanium dioxide as the high hiding white pigment. So, when you buy KILZ, the only thing you're getting that you wouldn't get with an ordinary interior alkyd primer is the faster thinner evaporation rate because of the naptha. That is, your KILZ will go from "wet" to "tacky" faster than an ordinary alkyd primer, but the transformation from "tacky" to "dry" will take just as long.

KILZ is sold as a stain blocker, and the idea is that it thickens up so fast that the stain doesn't have time to dissolve into and diffuse through the wet KILZ film to the surface where it would discolour, or "bleed through" the KILZ.

That's what stain bleed-through is. When a stain bleeds through a primer or paint, what's actually happening is that something in the stain is dissolving in the wet primer or paint, diffusing through the wet primer or paint film, and discolouring the surface of the primer or paint. That discolouration remains as the primer or paint dries.

So, the whole point in using the naptha is to have the KILZ thicken up so fast that there isn't sufficient time for the stain to dissolve and diffuse through the KILZ film before it becomes too thick for diffusion to occur.

But, in a case where the stain is dissolving in the KILZ, you can stop the stain bleeding through by using a primer that the stain won't dissolve in, like a latex primer. The only things I can think of that are soluble in BOTH mineral spirits and water are alcohols, and alcohols for the most part are colourless liquids that don't cause stains on anything. So, if the stain dissolves in KILZ, it's soluble in either naptha or mineral spirits, in which case unless it's an alcohol, it's NOT soluble in water. So, you should be able to use any latex primer to block and hide that stain.

If people understood that KILZ was an ordinary interior alkyd primer that thickened up fast only because it used naptha as it's thinner, they'd realize that there simply aren't any circumstances where those characteristics are needed in a primer. In fact, in most cases they'd realize they'd be better off with an ordinary interior alkyd primer that would dry slower and self level better to show fewer brush strokes.

So, save that gallon of KILZ and use it whenever you find that you need an alkyd primer to thicken up real fast so that it's already "tacky" within a few minutes, but then takes the typical 2 to 3 hours to become "dry". My guess is that you'll come to the realization that there are are no such situations where that kind of drying profile is needed, and if you bought a gallon of ordinary interior alkyd primer and a quart of Coleman camping fuel, you'd have the best of both worlds; you would have the slower drying time of an ordinary alkyd primer, AND you could make your own KILZ should you ever find that you needed such a product.

PS2:
Zinsser's Bullseye 123 is a latex primer where the acrylic binder resin has been chosen because of it's ability to stick to smooth surfaces. Use it when you need a primer to stick to smooth surfaces. It's no better than any other latex primer at sticking to easy to stick to surfaces, like wood and T1-11 siding.

You said that latex primers and paints "expand and contract well". That's true. ALL latex primers and paints, both interior and exterior have more than enough elasticity to stretch and shrink with wood outdoors. Really the only difference between interior and exterior latex paints is the amount of mildewcide and UV blockers in them. It's oil based paints that dry to much harder films that have difficulty expanding and contracting with wood outdoors. That's why the primary difference between interior and exterior oil based paints is the hardness of the film they dry to. That's cuz hardness goes hand in hand with rigidity, and the harder the film the less elasticity the film will have to stretch and shrink with the wood. So, by using an exterior alkyd primer and FLAT exterior alkyd paint, you get a harder and more protective film that's still soft enough to stretch and shrink as the wood it's adhered to swells and shrinks.

Hope this helps.

This message has been edited. Last edited by: Nestor,

With t-111 I also recommend priming and painting the bottom edge and two inches up before hanging it. The bottom edge is most susceptible to damage.

quote:

Originally posted by Jaybee:
[...]
Hard call on the dry time as it would depend on wind, temperature, humidity and how wet you got it. You could also blow or sweep it off - T1-11 is a fairly rough surface anyway.

I found the local Benjamin Moore store has a moisture meter they loan out. The actual siding is very dry. The framing on the edges, door, etc. is still very wet. I guess I will prime at least the siding. We are getting frequent storms here right now. It could be weeks before the framing drys out.

quote:

Originally posted by Nestor:
[...]
Hope this helps.

Thanks, my background is science and that was interesting and helpful.

I stopped using paint on T-111 long ago.
Instead I've been using solid stain instead. And use two coats.
What you will find it it still looks painted but it does not peel like paint will over time.

It's very important to make sure that shed is built so it's a minimum of 6" up off the grade to help prevent splash back which will rot out the bottom of that siding.
Other places that rot out the fastest are the outside corner trim and the bottom cross piece on the doors trim.
Use 1X vinyl lumber for these and no more rotting trouble.
On the bottom cross piece on the door I fill the grove with caulking and add a piece of vinyl cove mouding. It serves to direct the water away instead letting it sit there and rot out the wood.

quote:

Originally posted by joecaption:
I stopped using paint on T-111 long ago.
Instead I've been using solid stain instead. And use two coats.
What you will find it it still looks painted but it does not peel like paint will over time.

.

Not only good advice, but I've known builders that stain the backside before it gets installed.

I seal the bottom and also 2' up the backside. Really no need to go up any further then that.

Hi, I replaced some T-111 siding on my house with newer better T-111 siding about 1.5 years ago. I sprayed "Mold Control" on both the inside and outside surfaces and around all the edges and into the grooves and let it dry. Then, I used Sherwin Williams general use latex primer and primed each piece of siding on BOTH SIDES, all edges and in the grooves with 2 coats. After that was thoroughly dry, I put the siding on the house, and painted it with 2 coats of Sherwin Williams "Duration" exterior Latex paint. This is on a South facing wall in the Corvallis, Oregon in the Willamette Valley where the winters are very wet and cool to cold.

I did EXACTLY the same treatment on siding that went on an upper level on the south wall of my attic (where there is no "interior wall"). We recently had a cold foggy spell that produce black spotty mildew for a lot of people in places they've never seen mold before. I also highly suspect I over-ventillated my attic by doubling the number of eaves vents on both sides of the house and doubled the number of roof vents. I have noticed steel tools left overnight up in the attic during wet foggy weather had condensation on them. The attic has been well sealed for gaps with tape, foam, calking, etc. I've also doubled the insulation so that I have probably 12" of fiberglass insulation throughout the attic.

On my Interior side of the attic, the primer'ed interior side suddenly had a large amount black spotty mildew form on it, I have since knocked it down with the "Mold Control" spray which works well. HOWEVER, the other older siding next to it(which has also been sprayed with "Mold Control" but has no primer on it's inside surface) does NOT show any black spotty mildew.

****My MAIN concern is wondering about the likelyhood of black spotty mildew growing the inside surface of the new siding(with primer on the inside) on the lower level surrounding the "living space" part of the house (and thus is a closed space with fiberglass insulation next to it and sheet rock drywall for the interior wall)??? The gap at the bottom of the siding and concrete foundation has been sealed off with calking to prevent rain from splashing up into that space (the old siding was not painted on the bottom and had black rot creeping up the inside of the siding. I think those wall spaces are pretty well sealed and tight and should be dry, but we have generally kept our house at 60deg F through the winter and we use a de-humidifier. We're probably going to start warming the house a bit more and running our ceiling fans(blowing down) to make the dehumidifier more effective.

***Should I drill a small hole(s) through the inside of the house through the sheetrock and try to put some kind of fiber-optic scope in to check for black spotty mildew(and other fungi)???

Thanks - Paul

This message has been edited. Last edited by: Pauliwog,

Paul,
You're resurrecting an old post from 6 months ago.

FWIW - For T1-11 today I'd use Hardi-Panel instead of wood. Much easier to paint than wood T1-11 and no rot. It has the look of wood but isn't nearly as rough and the grooves aren't as deep so you can paint it quite easily with a roller.