It’s a common occurrence. You’ve bought beautiful new timber outdoor patio furniture, and within weeks of placing it outside cracks start to appear. Is the timber poor quality? Is the furniture defective? Should you have treated the timber before exposing it to the elements?
Well, the good news is that the timber is probably just “checking,” a normal and natural process that, in most cases, is nothing to worry about.
A check is a visible but minor split or crack that appears parallel to the timber grain. It happens to almost all timber once exposed to the elements. Checking should not affect the structural integrity of your timber furniture and, as a naturally occurring process, can add a rustic charm.
Why Does Timber Check?
Checking takes place as timber dries and the sapwood (the soft outer layers of recently formed wood) shrinks around the heartwood (the much harder centre of the tree). Shrinkage occurs about twice as quickly radially as it does tangentially (i.e. along the growth rings compared to across the rings), and it’s this uneven shrinkage that causes the timber to crack.
Wood is hygroscopic. This means that it absorbs and holds water. In fact, about half of a living tree’s weight is water. For people who are not used to working with wood, it can be quite surprising to see water spurting out when you cut into green wood.
The huge amount of water that a tree loses very quickly after being cut down causes significant shrinkage. However, the process doesn’t end there. Even after green wood has been milled, cut and dried, timber will continue to absorb and expel moisture. Timber will naturally reach the point of equilibrium moisture content (EMC) with its environment. This is the point where the moisture content of the timber is the same as the surrounding atmosphere and the timber is neither absorbing or losing moisture.
However, that means that as the ambient humidity around the timber changes, the moisture content of the timber will also change to maintain the EMC. The shift from dry hot weather to humid or rainy weather can put a strain on the timber as the fibres absorb and expel moisture.
This process is especially noticeable when newly manufactured timber furniture is settling into a new environment.
Should you be worried?
Timber checking in the form of minor splits or cracks is nothing to be worried about. In the vast majority of cases, checking does not affect the structural integrity of the furniture and is simply the timber settling into its new state of being.
The checking process should settle down after a few weeks of being exposed to the environment. Although minor checking can continue throughout the life of the furniture.
Checking can be more severe in the case of poorly made furniture where joints, screws or nails have been incorrectly placed, weakening the timber. In cases like this, the poor construction may exacerbate the checking leading to major cracks.
To avoid this, you should always look for premium quality timber furniture made from hardwoods like teak that have a high oil content, which helps to minimise the change in water content.
How to prevent timber checking
While there is no way to completely prevent checking, there are a few things you can do to minimise it.
- Acclimate your furniture: Instead of immediately exposing your new furniture to the elements, consider keeping it inside or undercover for the first week. This could be especially useful if you purchase your furniture at the height of summer or the wet season. Gradually acclimating the timber to its new environment will help to minimise any dramatic changes in the moisture content of the timber and should help to minimise the checking.
- Avoid direct sunlight: Where possible, avoid leaving your timber furniture exposed to direct sunlight, especially in summer.
- Cover your outdoor furniture: When not in use, try to keep your outdoor furniture covered to protect it from direct sunlight and excess moisture.
- Buy the best: Purchasing premium quality outdoor furniture made from quality hardwoods like teak will help to minimise the appearance of splits and cracks.
- Treat the timber: Oiling or sealing the timber is a good way to minimise the changes in the moisture content of the timber and minimise the checking process.
At the end of the day, some minor splitting and cracking is inevitable. However, this is part of the charm of timber outdoor furniture. Minor splits and cracks, together with the rustic weathered patina that timber will naturally develop, can add character and charm to your furniture without affecting the structural integrity or shortening the lifespan.