Ask the Builder: Stain new decking immediately to prevent splintering

DEAR TIM: Over the summer I ripped up the old boards on my deck and replaced them with new pressure-treated boards. Now that they’ve had time to dry out, I’m about stain the deck, but I’ve discovered that a handful of boards are already splintering and cracking. This is really disappointing, especially since I spent a little extra on the premium boards. What should I do to remedy this? Would power washing help or just produce the same result? Or should I replace the problem boards altogether? Should the warranty on pressure-treated boards cover this? – Adam W., Dallastown, Pa.

DEAR ADAM: I hate to break this to you, but the entire issue was caused by you. I assume the lumber suppliers and the store you bought it from didn’t tell you the best way to protect your investment as you left the store. That’s very unfortunate.

It’s also unfortunate you didn’t consult my website, AsktheBuilder.com, where you could have found several past columns about wood deck maintenance and care. If you’d spent just 30 minutes researching how to care for new lumber, you’d not have this problem.

Here’s what’s going on. Treated lumber is injected with chemicals that are mixed with water. Years ago, I worked with treated lumber that was so saturated with the chemical brew that when I’d drive a nail into it, this liquid concoction would squirt out alongside the nail shaft.

When the sun bakes this moisture out of the lumber, it creates significant tension stress within the wood fibers. Tension is the force that happens when you try to stretch or bend something. As the sun cooks out the water, the lumber shrinks.

This shrinkage usually causes tiny checking cracks to form. These are often about the width of a piece of paper and perhaps only 1/8 inch long. In extreme cases you can experience delamination along the boundaries of the summerwood and springwood. Summerwood is the dark ring you see in a log, and the springwood is the lighter-colored band.

When this delamination happens on flat-grained pieces of lumber, you end up with giant protruding splinters like I see in the photo you sent. There’s no way to repair these. Once you have cracks in the wood, you’ve got problems. Each time it rains, the water soaks deeper into the wood, and then the sun cooks it out again and again. Each time this happens, the tension forces usually cause the cracks to get bigger and bigger.

Power washing lumber is the worst thing you can do. The high-pressure, concentrated stream of water blasts away the less dense springwood. What’s more, it drives water deep into the cracks you already have. This is the last thing you want to happen.

To make matters worse, if your decking is close to the ground, say about 2 feet or less, water vapor coming up from the soil under the deck can damage the decking. This water vapor causes the face of the decking on the underside of the deck to expand because water is entering the wood fibers.

On the other side, the sun and any wind is doing the opposite, causing moisture to leave the wood. As we discussed, this causes the wood to shrink or get smaller. When this happens, the decking will almost always cup. This means the decking gets higher on the edges and lower in the center, much like a valley between two mountains.

You could have avoided this costly nightmare by just staining and sealing the wood as soon as it was installed. High-quality sealers stop water from entering treated lumber. You can often see water beading on decking that’s been treated with a great sealer.

While it requires much more work and stain/sealer, it’s not a bad idea to seal and stain all sides and edges of the decking before it’s installed. This means you need to have a place to set out each piece to dry after you’ve applied the sealer. It’s best to create a drying rack in a carport or inside a garage. The last place you want to place the freshly sealed boards is out in the direct sun where they can twist and warp as they dry.

You may be able to salvage some of the boards that are not too bad. I’d use a belt sander with medium sandpaper to see if you can make them look presentable. The great sealers and stains will stop water from entering tiny checking cracks, so if that’s all you see after sanding, I’d keep those boards.

Any others that have large splinters or delamination will have to be replaced. Don’t expect the lumber company to give you free replacements, as they know you caused the issue.

You may be able to get a significant discount on your replacement boards if you talk to the lumberyard manager. Mention that you feel the store should have given you a small pamphlet about how to care for the wood. I wish you the best of luck. Be sure to follow any and all directions on the labels of the sealer/stain you purchase.

Carter’s columns are archived at www.AsktheBuilder.com. You can also watch hundreds of videos, download Quick Start Guides and more, all for free.