My 5 Secrets to Prevent Wood Rot

Rotted-Wood-SoffitLearning how to repair wood rot is a part of life when it comes to life in an old house. But what if you could prevent it? Working in a wet climate, like Florida, I have assembled a very specific routine to prevent wood rot on anything I build that will be outdoors. The expense of PVC, fiber cement and other “rot-proof” products aren’t necessary if you build things the time tested right way. If you want to continue to build with real wood and have it last decades, follow these simple techniques.


And don’t miss the last secret because it is the most important!

1. Prime All 6 Sides (with oil-based primer)

It’s not enough just to prime exterior wood after it’s all been installed. You have to prime all 6 sides of the wood. That means front, back, both sides, and especially both ends. The end grain of wood is like a sponge. If you don’t prime it you are asking for trouble. You have to prime everything before it is installed and after all the cuts have been made. If you have to trim a piece again then you have to prime that piece again at the cut.

On top of priming everything (I use 2 coats for extra protection) we use an oil-based primer. Oil-based primers penetrate the wood better than latex or water-based primers and therefore provide better resistance to water. They are also less prone to being scraped off during installation.

2. Build Sloped Surfaces

If you are building anything outside it has to be able to shed water. Porches, window sills, hand rails, everything has to be sloped or designed to shed water. You have to think like water when planning your project. If water lands on your project does it have a place to go or will it get stuck somewhere?

I see too many porch railings that are flat 2×4’s. Any horizontal surface will hold water and eventually rot. Whether you decide to round the tops on your railings like I do or install them at a slight slope along their length is up to you, but intelligent design means less trouble in the future.

Plugged Fasteners Cedar Porch Railing

This railing is sloped and the fasteners plugged. The white material is glazing putty to prevent water in the joint and maintain flexibility.

3. Plug Fasteners

Unplugged screws and nails are like highways for water. If you’re working outside you should be using stainless steel or galvanized fasteners anyway. But when you nail or fasten wood (especially on horizontal surfaces) it is worth the extra effort to countersink and plug the fasteners. Doing this not only prevents fasteners from rusting, but also avoids any divots in the wood that will catch water.

How To Plug Fasteners

      1. Pre-drill a hole, the depth and width of your plug, slightly larger than the fastener head.
      2. Drive your fastener in the hole.
      3. Put a bit of wood glue in the hole.
      4. Place the wood plug in the hole. (You can find the wood plugs I use at my affiliate link here)
      5. Pound the plug into place gently with a hammer.
      6. Sand the surface level.
      7. Fill any remaining gaps with window glazing putty.
4. Use Rot Resistant Wood

There are lots of choices when it comes to rot resistant wood. Most of the tropical hardwoods like Ipe, Cumaru and Teak are all great choices for decking since they are so hard and resistant to rot and insect damage, but they can be more expensive. Western Red Cedar and Cypress are my go to choices for exterior items like siding, trim and screens. They are readily available and provide decent rot resistance at a fair price.

5. Allow for Airflow
Benjamin Obdyke Rain Slicker

This rain screen is the best product to install under new siding to keep it from rotting. Easy to install and much faster than furring strips.

Wood will get wet outside. But the best way to prevent wood rot is to provide a way for the wood to dry out. All the other tips I’ve given you merely serve to prolong wood’s life if it is getting wet, but the key to making wood last for centuries outdoors is letting it dry out.

Tips to Provide Good Airflow

      1. Make sure the wood isn’t in direct contact with the ground.
      2. Use a Rain Screen or furring strips behind siding to allow airflow behind the siding.
      3. If possible, design your project with gaps between horizontal and vertical surfaces.
      4. Use a nail or a carpenter’s pencil between deck boards to space them evenly.
      5. Avoid having wood in direct contact with cement or masonry.

Follow these secrets and you’ll have a a project that will last longer than you and I will be around. Skip them and you may save some time and money for now, but in the long run it’s always cheaper to do it right the first time.
Do you feel it’s better to do it right the first time, or to just build quickly and replace when it wears out?


Photo Credits: Steve Quillian, Scott Sidler

Scott’s Disclosure: Some of the links above are affiliate links, which means I will get a small commission, at no additional cost to you, if you decide to make a purchase. I only recommend products or services that I have experience with and use myself, not because of any commissions I may make, but because I truly find these products useful. Please do not spend any money on any of these products unless you honestly feel that they may be of benefit to you.

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by Scott Sidler

I'm a historic preservationist and licensed contractor. I help old house lovers understand & restore their homes so they can enjoy the history and character that surrounds them more everyday! When not working, writing or teaching about old houses I spend most of my time fixing up my own 1929 bungalow with my wife Delores and sons Charley and Jude.


  1. Wondering about rain screens on said:


    Today, I had an interview with a carpenter with more than 30 years of experience. He has had no experience with rain screens. He said to me that rain screens are the same thing as Tyvek.

    Are they the same thing?


    • They are not the same thing. Tyvek, is a vapor retarder and does help to stop bulk water from entering the building. If you place siding directly on top of Tyvek then there is no airspace for water that gets trapped behind the siding to flow out of the building envelope. A rain screen helps prevent this and extends the life of the siding.

      • Thank you for the reply. So I’m guessing this means a rain screen is NOT some type of moisture barrier either. Is that correct?

  2. Kathy Manuel on said:

    Hello! Reading your articles gave me some hope. I recently bought a 1920’s colonial French home in October. After 3 weeks of my move, came hurricane Patricia. I’m still fighting with leaks from the roof and dormers. Can you recommend a good source that
    Sells cypress wood? My roofer destroyed the wooden dormers and a few boards on the side of the house. I so much want to restore my home.
    Do you also offer classes on restoring old windows?

    • Kathy, It depends what part of the country your in to find cypress. Many lumber yards in the Southeast have it but outside of that region you may be better off with things like red cedar or redwood. As for classes on restoring windows I have a book that may help you called Old Windows Made Easy. I also teach at a variety of workshops occasionally. The next one is in Tampa, FL Feb 19-21 2016. Let me know if you’re interested!

  3. stephen on said:

    Hey, ty for info. Wish I read this earlier. Already bought the wood (Pine planed kiln dried) for my balcony louvres. So even more keen now to give it a fighting chance to survive with the best finish possible.

    If I use a good decking screw, put sealent on the head, then apply 2 coats of shellac based primer over all the wood/fixings would that work? Not sure i have the skill for your plug recommendation.

    Also not sure how to seal where the M6 150mm bolts go through. The 30mm thick steel angle support and 100mm piece of wood. The side that has the steel angle support creates a gap that I cant really get too. Some kind of valve rubber type washer would be cool. Not even sure that exists though.

    Any ideas? Ty any help is appreciated

    • Stephen, if it’s exterior application don’t use Shellac primer. It’s not intended for exterior use. I’d stick with a oil based primer. You can also treat the wood with a borate treatment like BoraCare to help prevent termites and rot.

      • stephen on said:

        Ty for advice.
        I think you may have just helped me avert a disaster a year down the line. It was Zinsser B-I-N primer which on a closer look says interior and ‘spot’ exterior. I think by ‘spot’ exterior it is leaning more towards stopping a nasty stain coming through rather than a full exterior prime. I will drop by and exchange it for an oil based one like you suggested. Rot treatment is definitely a good idea as well.

        Oh and the bolt gap on the top where I was worried about water getting in. I think I’m going to use a rubber washer, under a steel washer & bolted tight on top. Then hang it from my steel bracket. The bracket is hollow which I didn’t realise before which can hide away the extra bolt.

        Can’t wait to get started ^^


  4. Thanks for tips and insight!! We are a Home Repair / Remodel company and like providing our customers and prospects with helpful tips definitely be posting your advice!!

  5. Granny on said:

    You use Glazing Compound, what about Painter’s Putty?

    • Painter’s Putty can work just as we’ll in that application.

  6. Rob Gier on said:

    My church is building playground equipment for Haiti. We don’t think we can transport oil based paint. Is there a water based paint that works well for pressure treated wood?

    • If you’re using pressure treated wood the first thing is to make sure you give it a few weeks to dry out before painting. If they won’t let you transport oil-based paint (which would surprise me) then any exterior latex wood primer should be fine. Kilz makes a good one and so does Binz. Then top with 2 coats of 100% acrylic paint.

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