Pressure Treated

The most common deck wood used in America. Pressure treated wood is typically a low quality pine selected for it’s high content of sapwood and low content of heartwood. Sapwood is more easily saturated with chemicals but has less inherent insect and microbial resistance than heartwood. Pressure treating slows wood rot and can deter insect attack. It does not stop black mold or algae or the greying caused by sun and water. It has been found to have negative health and environmental issues, most notably in playgrounds, and water supplies in countries like New Zealand, which is a good reason to paint it with Clear Skies Satin. Chromated Copper Arsenate or CCA is not used on new residential pressure treated since 2004 but older pressure treated wood may still contain harmful ingredients and should be sealed.

Commonly used pressure treating chemicals today are: Nano particle size copper AKA micronized copper, ACQ-C (Alkaline Copper Quat Type C), ACQ-D Carbonate (Alkaline Copper Quat Type D, Carbonate formulation), CBA-A and CA-B (Copper Azole Types A and B), as well as SBX/DOT (Sodium Borate) and Zinc Borate preservatives. Of these the only one we would use is the Zinc Borate, which is what you find in healthy quantities on the bottom of each can of Rainforest Sealer and Mountain XT.

Pressure Treated wood typically has very high shrinkage rates the first year, particularly on horizontal surfaces. Because of the lower quality of the wood and the excessive amount of moisture and chemicals forced into the wood, most stains and wood finishes don’t last much more than a year on Pressure Treated wood. This is the hard truth no homeowner wants to learn about their pressure treated deck and is part of the reason Earthpaint wood finish became so popular. Because it lasts.


Recommended Deck Stain Colors on Pressure Treated Wood – Clear 00, Honey, Light Cedar, Acorn, Fawn, Brown Cedar, Cinnamon Stick, Toffee, Raisin, Warm Cinnamon and Bark.

Longest Lasting Stain Colors: Brown Cedar, Cinnamon Stick, Toffee, Raisin.


Three Options for Coating Pressure Treated Wood


1.) Paint  

2.) Stain  

3.) Stain and Top Coat


1.) Painting Weathered Pressure Treated Wood:

Paint seems to work the best. It will last the longest but maintenance can be more difficult than stained wood. Paint seals in a lot of the chemicals but it shouldn’t be painted until it has weathered one year. When you do paint pressure treated wood use Clear Skies Matte or Clear Skies Satin, one or two coats directly on the wood after washing with Lime Clean-Wood and Deck Cleaner. A clear top coat with Mountain XT Clear 00 is optional on the rails and creates a stronger weather barrier. This is a fast, easy and safe method to sealing pressure treated wood. Choose darker brown tones that hide dirt better unless you plan on washing your deck often. Apply one coat of Rainforest Sealer or Mountain XT the first year so the wood can acclimate safely. Then after the wood is weathered for one year you can apply Clear Skies Satin or Clear Skies Matte, 2-3 coats. Clear Skies will dry in an hour on a deck outside. If you spray be sure to back brush or roll the finish into the wood. Apply another coat in 2-4 years to bolster the finish and then every 3-5 years after that.


2.) Penetrating Deck Stain:

Most people like their decks stained natural. They want to see the natural wood grain come through. One coat of semi transparent stain is a good looking solution. Rainforest Sealer and Mountain XT have held up incredibly well, even in extreme conditions and allow the wood to show through. If you are only doing one penetrating stain coat then Mountain XT is the best deck stain. This cashew based resin has many inherent resistances to harsh exterior wood conditions and cashew resin doesn’t feed black mold and algae growth.

The simplest way to stain a PT deck outside is to wash it with Lime Clean – Wood and Deck Cleaner and apply one coat of Mountain XT Brown Cedar, Cinnamon Stick or Toffee. These colors last the longest. If you want the light color of new wood then Mountain XT Honey is a better choice than clear because it will provide more UV radiation resistance.  This is a penetrating deck stain that will never peel and be easy to maintain. It is high density resin that doesn’t evaporate but stays in the wood year after year allowing your maintenance coats to build upon previous applications strengths. After maintaining the deck you begin to get a petrification effect in the wood.


3.) Top Coat the Deck Stain With Mountain XT Clear 00 (for Weathered Wood):

In general it is best to apply only one coat of stain to pressure treated wood. This is because in the long run prep can be easier. For those who want to get longer durability out of a finish you may want to explore the option of a Stain and Topcoat. Specifically, stain with Rainforest Sealer and then topcoat with Mountain XT Clear 00 until the wood fiber is completely covered (1 or 2 coats). Mountain XT Clear 00 is engineered using tree based resins that are highly compatible with wood. It provides an impermeable weather barrier that significantly improves the appearance and lifespan of wood. This system is for weathered wood only. Apply one coat of stain only to new pressure treated.


Going Clear & Natural on Pressure Treated Decking

One of the great things about the Mountain XT Clear 00 system is that it allows people to get a Clear & Natural deck stain outside, without having to stain the wood. Many people really want the natural wood look but realize that ordinary deck stains fail in about 6 months, especially when no color is added to protect from the sun. With a strong top coat of Mountain XT Clear 00 the user now has the option to apply Rainforest Sealer Clear 00 first and then Mountain XT Clear 00, thus getting a gorgeous, clear and natural deck that can be maintained indefinitely. No other system we are aware of can do this. It is because of our exclusive cashew resin that this system works so well. Rainforest Clear 00 shouldn’t be used without Mountain XT Clear 00 since it is the outstanding UV filters of the inherent to the cashew resin that make this system work so well.


Two Considerations Before Top Coating Pressure Treated Decks

There are two things to consider when using Mountain XT Clear 00 on pressure treated. 1.) Weathering. 2.) Maintenance.  Weathering just means the wood needs to be exposed to rain, sun, sleet and snow for one year. This gives it a chance to expand and contract. The extractives and pressure treating chemicals will either migrate to the surface and wear away or bolster the wood cell walls. If applying one coat of penetrating stain none of this matters; you just wash, sand and apply the stain but if applying a Mountain XT Clear 00 the wood should weather first and then be maintained or it will end up needing to be sanded before recoating.


Maintaining Mountain XT Clear 00 on Pressure Treated Wood

If you use XT Clear 00 as a topcoat you are applying a film that will need to be maintained (washed and recoated). The benefit is that it looks better, longer. It is easier to maintain because all you have to do is roll the horizontals which generally only takes a couple hours to do, even on a large deck floor.  This means the floors and top rail should be rolled after the first year to bolster the film and then as needed after that. Usually, after the first couple years it gets so strong that it doesn’t need to be done every year but each situation is different and should be assessed every spring. Wood can be kept in excellent condition indefinitely with this method. Black mold and algae wash off the surface easily with a bi annual cleaning of Earth Clean. The deck stays in top shape, looking its best. If you don’t plan on doing this type of maintenance a single penetrating coat of stain is best.


Bi Annual Washing with Earth Clean – Heavy Duty Cleaner

Wash your new wood finish a minimum of twice a year with Earth Clean Heavy Duty Cleaner. Do this every spring after the pollen drops and every autumn after the leaves fall. This will remove the pollen and organic debris most likely to cause degradation. When pollen and organic matter are left to decay on the deck surface it absorbs moisture and dirt and accelerates wear and tear on the deck, reducing the lifespan of the deck stain. Washing twice a year will improve the lifespan of your deck and make it look better.


Pressure Treated Decks in Full, Harsh Sun Exposure

Intense Infra Red Radiation and Ultraviolet Radiation exposure is very demanding on a finish. It’s best not to apply a top coat of Mountain XT Clear 00 to decks that are exposed to this type of sunlight because pressure treated wood will shrink expand too much. The best deck stain color for intense sun regions is Cinnamon Stick. This is because it is an excellent balance of UV Blockers and Infra Red reflectors. Meaning it doesn’t get as hot as a dark brown (Toffee) would yet it is able to block most of the damaging sun radiation from reaching the wood. Colors with a cooling effect in harsh sun are Honey, Sage and Cool Leaf. Medium toned colors that hold up well in harsh sun are Brown Cedar, Fawn and Acorn. Toffee and Raisin will hold up a long time but will also have a tendency to get hotter than the other colors.


Pressure Treated Decks in High Mold and Mildew Areas

The best deck stain for high mold areas is Mountain XT. It is very important to do a good job washing with Lime Clean when preparing a deck in high mold areas. Mold spores are persistent and you don’t want to coat over them because it makes a difficult to fix mess. Wet the wood, apply Lime Clean let it sit 20-30 minutes, misting with water every five minutes or so to keep it wet. Then scrub or pressure wash it off. This will leave the wood properly prepared for coating. The colors that work well in high mold areas are Brown Cedar, Cinnamon Stick, Fawn, Acorn, Toffee, Sage, Cool Leaf, Raisin, Warm Cinnamon, Bark. It is important to wash the deck at least twice a year with Earth Clean so that mold spores that fall from trees cannot colonize. Typically decks that are in high mold areas are also decks that are good candidates for a top coat of Mountain XT Clear 00. This makes it easier to wash mold and dirt off the deck.


What We Do On Our Pressure Treated Decks

Wash first with Lime Clean- Wood and Deck Cleaner. Sand “against the wood grain” with 50 grit (looks cool, non slip, better penetration). Then we stain the deck with Toffee, Brown Cedar or Cinnamon Stick. These have proven to be the great deck stain colors for pressure treated decks.

Apply Rainforest deck stain and then Mountain XT Clear 00 to all the rails. This usually takes care of the rails for many years. Rails weather well and with a good stain and topcoat they last a long time, 3-6 years typically. The horizontal top rail needs to be checked every year but this is very easy to do.

Deck Floor
For new pressure treated wood just a single penetrating coat of stain like Rainforest or Mountain XT is the best. This way if we get busy or don’t feel like checking the deck in the spring we don’t have to. Once it has acclimated for a year we may roll a couple coats of Mountain XT Clear 00 over Rainforest Sealer Brown Cedar or Cinnamon Stick. When all things are considered this is really the best deck stain system for pressure treated wood.

Black, Old, Horribly Weathered Pressure Treated Wood Beyond Hope:

Don’t worry, simply Wash with Lime Clean – Wood and Deck Cleaner and watch as your wood is cleaned and brought back to life! Then simply follow the steps outlined above and your wood finish will look much better, much longer. For maximum brightening wash the wood in full sun, letting the Lime Clean sit for 30-60 minutes in full sun BUT make sure to keep it wet; don’t let it dry out, mist with water every 5-10 minutes so it has maximum strength. Repeat if needed for extreme situation.