Wood Preservation Guide

Overview

In this guide I will tell you everything you are going to need to know about wood preservation. This system will work weather you are staining a deck, a fence, a trellis or any other exterior wood structure. I recommend that you check out my video on deck staining prior to commencing your project and then using this guide for reference and additional information thereafter.

Materials

  • Pressure Washer – Make sure it is gas powered, with a minimum pressure and flow rating of at least 2500 PSI and 3GPM respectively. A higher PSI/GPM rate is okay, less than this is not! Also make sure you have all the attachments that connect to the pressure washer Including: enough pressure line for your particular job, a trigger, a chemical injector, and both a 25 degree high pressure tip and a low pressure tip for injecting the chlorine into the pressure washer.
  • Rain suit and Rain boots - to keep you dry when you pressure wash.
  • Chlorine - should you need to kill growth on your structure.
  • 50 grit sandpaper -  to smooth any rough areas after pressure washing.
  • 3 1/2” – 4” block brush - I use Purdy brushes exclusively.
  • A two gallon bucket
  • Rags - mistakes happen
  • Stir sticks
  • Drop Cloths
  • Stain - The Brands I like to use are Penofin, Cabot, and TWP
  • Paint Thinner - for cleaning brushes or cleaning up mistakes

I was going to put eye and ear protection here, but lets be honest, I don’t wear them and most likely, neither will you.

Preparing the surface

First move everything away from your project that you aren’t going to want to get water, dirt, or bleach on. Second set up your pressure washer. Every pressure washer is a little different, but if you rent one, have the guys who you are renting it from show you how to set it up. If you end up buying one the owners manual should give you a diagram on how to put everything together.

Next asses the condition of your deck. If you have any growth on your deck be sure to connect the chemical injector to your pressure washer and dilute chlorine into a bucket about 1 part chlorine for every 5 parts of water.

Now you may begin pressure washing. Review my video for tips on correct technique for pressure washing. Never start in the middle of a piece of wood without easing the tip onto the structure while the pressure is engaged. This will minimize stop and start marks, and always if possible pressure wash all the way though a board in one pass for the same reason. If the use of chlorine is required first, pressure wash the deck with the high pressure 25 degree angle tip and then WHILE THE DECK IS STILL WET apply chlorine using the low pressure tip and work from the bottom up. Applying the chlorine solution while the deck is still wet as well as applying the solution from the bottom up will make it so that you do not get spotting or blotchiness as a result of uneven application. Prior to applying the bleach liberally water all plants, shrubs, etc near the structure you are working on to avoid “burning” or killing anything. After applying the chlorine solution let stand about 5 minutes and then rinse. You can use the high pressure tip for this, but keep the tip well away from the wood surface, as we are done removing the top layer of weathered wood at this point and only trying to rinse the chlorine from the surface.

After you have completed all of this, you are now finished with the hardest part of the preparation. Now you must let the wood dry out. The time this will take will greatly depend on the weather. If you are in the middle of a hot spell and it is say 100 degrees, 24 hours should be sufficient time to wait. If it is cooler though drying out of the wood can take considerably longer (48 hours or longer). Use your best judgement but do not apply the stain if it looks like the wood still appears to be holding moisture. Also if you are refinishing a deck, try and keep it clean between now and when you stain by avoiding foot traffic if possible.

What kind of Material Should I Use?

Most exterior decks, trellises, fences etc, are probably going to be made of Cedar or Redwood. Occasionally you may see things built with a more exotic woods, such as ipe. Since ipe is a hard wood I would apply a hardwood oil to that kind of structure as opposed to a standard semi-transparent stain. Most peoples wooden structures aren’t going to be built out of exotic hardwoods though, and should be preserved instead with a high quality semi-transparent stain. You want to choose one that does three things: gives good UV protection, preserves the wood (contains mildewcide to prevent growth), and repels water. Now with all of that said there are three types of stains that stores will try to sell you when doing a project like this.

  • Clear Stain – this has no pigment in it and will more or less leave your wood looking natural. These preservatives will hold up well to foot traffic on decks however they do have their weaknesses. The draw back to these materials is that I haven’t seen one yet that offers decent UV protection (even though they say they do on the label) for your wood once applied.
  • Semi-transparent stain – My personal favorite choice for preserving exterior wood, especially decks; semi-transparent stains when applied still show the grain of the wood through the final product once dry. Additionally unlike clear preservatives semi-transparent stains also provide a pigmented coloring to the wood and can be bought in many different colors to accommodate your particular tastes. Where clear stains typically offer sub par UV protection for your wood, semi-transparent stains often offer a superior alternative. Additionally they offer the same water repellent and wood preserving qualities as their clear cousins. Another advantage to semi-transparent (sometimes called “tone”) stains is that if you are staining a deck, semi-transparent stains wear much, much nicer than solid coat stains when put up against foot traffic.
  • Solid Coat stains - These stains are solid in color and show none of the wood grain or wood character in the final product and can often be mistake for paint. If you plan on applying a solid coat stain to your wood structure let me urge you to think long and hard about the decision you are about to make. Once you apply a solid coat stain you are pretty much committed to applying such a stain to the structure for the rest of its life. I highly recommend against using it on walking surfaces as heavy foot traffic will become apparent in a very short duration of time. If you absolutely need to have the look of painted hand rails on your deck, or to have a solid color on your trellis, solid coat stains are probably the way to go.

In my opinion when preserving most exterior wood structures semi-transparent stains are the best all around choice as they offer the best of both worlds. Clear preservatives tend to breakdown sooner making them a higher maintenance finishes and solid coat stains can be equally horrendous nightmares if applied to the tread on a deck or if you ever want to have that natural wood look again. all I can say is weigh each materials advantages and disadvantages carefully before making your decision.

One last note on materials; use only an oil based preservative. They do make water based stains and hybrid oil/water based stains called emulsified oils, neither of which I am particularly fond of. Water based and hybrid based materials don’t tend to hold up nearly as well, so stick with oil based preservatives unless you like staining your wood structures frequently.

Sanding the Rough Spots

At this point there may be a few areas that some of you want to smooth out to make your deck look even better. You will notice that after we took the pressure washer to the wood, some of it may have gotten a little frayed, or some of the grain may have gotten “raised.” This usually happens after refinishing the deck a few times or if the deck is just simply old and weathered. Typically as a contractor no one wants to have their deck or trellis manicured like a piece of furniture as it just simply costs too much. If you are working on your own structure, however, and don’t mind taking the extra time, you could actually break out a DA and sand all of the really badly worn areas. I am not going to cover how to get out a drum sander to sand the planking of a deck in this article as, that is kind of an extreme measure for extreme cases.

For most decks you can just get a few sheets of 50 grit sandpaper, cut it in half (hamburger style for those of you that went to school in the same era I did) and then tri-fold that piece so you have a workable sheet. In the following link I fast forwarded to the part where I did this so you can see an example if that was confusing: deck staining video part 2. At this point I go around and smooth out the really bad areas by hand, sanding with the grain of the wood. As I said before if you would like to manicure all of your hand rails on a deck for instance, now would be the time to buy/rent an electric DA sander. A DA sander stands for dual action sander which spins and vibrates at the same time. Get a sander like this. Don’t get one of those square looking sanders that just vibrates because you will be spending your entire summer sanding your project if you do.

Sanding is very easy. If you are using a DA though, there are a few key points you need to keep in mind so that you don’t ruin your project or your sander. First always keep the sander moving.  If you keep the sander in one spot you will get an uneven appearance. Second always keep your sander flat to your work and never dig in with the corner of your sander. A lot of people do this trying to sand out an imperfection, and unless you really know what you are doing this will just cause a divot in your work and make it look worse than if you had just left the original imperfection alone. Third, (this is mainly for the health of the sander) change out your sandpaper when it shows signs of wear. If you have used a particular piece of sandpaper until you can see the sanding pad through the edges of it, you have waited too long and can ultimately damage to the sanding pad. Keep your sandpaper fresh and your DA will thank you. If nails protrude on your structure they can tear up your DA fairly quickly as well, so either be mindful of them or set them with a hammer and a punch if necessary. Always wear a particle mask and happy sanding.

Applying the Stain

Now at this point your wood structure should be clean, and all of the rough spots you wanted smoothed out should be sanded. If you are doing a deck and it has been a couple of days since you have pressure washed, or you have done a lot of sanding, You may need to take a broom or duster (I use old worn out paint brushes for dusters) to your project to remove all of the accumulated debris.

Next lets go ahead and and gather your stain, a stir stick, rags, paint thinner, your brush, and bucket. Open your stain and make sure it is stirred thoroughly each time you get some, or if your stain in your working bucket has been allowed to sit un-agitated for an extended period of time. The pigments and oils in a semi-transparent stain settle fairly quickly so just keep that in mind. pour some into your bucket and you are ready to go.

When staining a structure. Always work from the top down and if you are staining a deck make sure you don’t work yourself into a corner.  When staining exterior wood structures I almost always apply them with a brush. Spraying a stain is asking for trouble in most circumstances, and rolling them on will typically cause an uneven or too heavy of an application. To get the nicest finish I strongly suggest you apply your stain with a brush. You may be thinking this sounds crazy, but you would be surprised how big of decks I have done with a 4” block brush.

Apply ONE COAT of your stain evenly and out of direct sunlight if possible. More stain is not better and if multiple coats are applied you will be left with a sticky structure that you will never want to use or enjoy. With any exterior wood structure stain only a couple boards or sections at a time and carry them all the way through before starting the next set. Make sure you cover all areas around your structure with drop cloths as getting stain on cement, or anything else you don’t want it on can be a pain to remove. If you do make a mistake or stain get’s past your drop cloth, don’t panic. Use your paint thinner and rags to clean up your mistake. Don’t use water! Stains are designed to repel that stuff and using it will only make things worse.

Another tip to remember when staining is to never “fling” the bristles of your brush. This is caused when you apply pressure to the bristles and they spring straight when you release the pressure. If you are staining a deck against a house for instance and you “fling” the bristles toward the house, you will get a lot of little specks of stain all over your house. Masking your house in this instance shouldn’t be necessary as long as you are conscious of good technique and keep things clean.

Final Thoughts

After you have finished all of that you are finished! If you were staining a deck, check the label of the product you are using to see how long they recommend before you walk on the deck. Typically it would be a good idea to not walk on a freshly stained deck for 24-48 hours depending on the weather. Obviously never begin a project like this if rain is in the forecast, and always try to recruit family members or friends to help you stain your structure should they offer! For more information or for people who are visual learners, I again encourage you to check out my deck staining video on this topic. Good luck with your next painting project!

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