Part of the education at Benjamin Moore’s Certified Stain Applicator course the crew at Warline Painting took at the Poco Inn and Suites in Port Coquitlam last month was about understanding wood and wood construction. For all of us, it was the most eye opening part of the course. We get calls to look at all sorts of problems with failures regarding deck stains and products. Understanding wood and learning about proper construction techniques has given us a new lens to see a deck through. One of the things we learned was that there is a right side up on deck boards.
And it isn’t the prettier side of the board.
Have you ever seen a deck where one board is rotting while the board right next to it is perfectly fine?
Chances are the rotting board has been installed wrong side up.
Let’s start with a quick lesson on lumber. When a log is cut it is done in a way that maximizes the value of the lumber produced. The most expensive cut being the centre cut or the cut that goes through the heart of the log. It is very unlikely you would be using this for a deck.
Most deck lumber is cut farther away from the centre of the log, which is called a flat grain cut. Depending on the wood type and cost it might also be an edge grain.
Freshly milled rough lumber contains about 25-30% moisture and is flat and square. As the wood dries out the lumber will deform depending on how it was cut. This will start to happen at below 25% moisture. The board will shrink and warp in the opposite direction of the rings in the wood. The result is either a cupping of the wood or a crowning, depending on which way you face the board.
A board that is correctly installed right side up (or bark side down) will form a crown and allow water to run off the edges. If the board is installed wrong side up (or bark side up) it will curve up on the edges when dry and water can gather and sit in the cup. That is a recipe for wood rot and problems.
If you look at a dry deck board from the end grain you can see the rings in the wood. They should be curving upwards, like they are forming a smile. You can easily remember which is the right side up by thinking smiley side up.
The type of wood, size and thickness of the board will also impact the degree of shrinkage and warping of a board. The harder the wood and the thicker the cut, the less warping there will be. Moisture, sun and repeated cycles of wet and dry will also impact a board. But I will bet that as we are called out to check out decks and their problems this summer, upside down boards are going to play a big part of figuring out why a product failed to perform the way it was supposed to.
So go outside and take a look at the end grain edges of your deck. Are they all smiling up at the sky? They should be. If not, you could be looking at cupping issues on your deck which could eventually cause problems.
Cupping boards are just one part of making sure your deck is properly constructed and protected. Be sure to check out our article on debunking myths about staining and protecting your deck here.
If you live in Vancouver and have a deck that needs restaining, be sure to give us a call. We can help you get to the source of your deck headaches and back enjoying those long Vancouver summer days on your deck again.