Learning 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.
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
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- Pre-drill a hole, the depth and width of your plug, slightly larger than the fastener head.
- Drive your fastener in the hole.
- Put a bit of wood glue in the hole.
- Place the wood plug in the hole. (You can find the wood plugs I use at my affiliate link here)
- Pound the plug into place gently with a hammer.
- Sand the surface level.
- Fill any remaining gaps with window glazing putty.
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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
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
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- Make sure the wood isn’t in direct contact with the ground.
- Use a Rain Screen or furring strips behind siding to allow airflow behind the siding.
- If possible, design your project with gaps between horizontal and vertical surfaces.
- Use a nail or a carpenter’s pencil between deck boards to space them evenly.
- Avoid having wood in direct contact with cement or masonry.
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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?
Founder & Editor-in-Chief
I love old houses, working with my hands, and teaching others the excitment of doing it yourself! Everything is teachable if you only give it the chance.
Do it right the first time. Build things to last. Why waste money, time, and materials? Seems obvious to me.
I’m building an outside shower. I’m using cedar lumber. The site is on Nantucket Island I have an existing concrete pad ~3′ sq with a drian the pad is ~3″ above brick sidewalk grade Can install the 5×5 posts in SS chambers ~6″ high with small drain holes in the bottom to retard checking of the posts? Should I apply a preservative to the bottom of the posts.? What should I use ?