Wooden gates are a natural product responding to the conditions that they are in, especially heat and humidity. In hot weather wooden gates can twist especially if one side of the gate receives more sunlight than the other. Wood is a hygroscopic material, which means it naturally absorbs and gives off water to balance out with its surrounding environment. Twisting is likely to be caused by one side drying out more quickly than the other. It is also quite common for small splits (shakes & checks) to occur during drying. This is nature at work and should NOT be considered a fault. This is not normally detrimental to the gates stability & structure and should rectify as temperatures cool.
So why do wooden gates to move opposite directions!
There are several causes of why wooden gates move but the most common reason is the wood drying out.
When a tree is first felled the timber is called green, and refers to the fact that the tree has not dried out and is very heavy and very wet as it is full of water. This timber needs to be dried out before it can be used effectively. Most timber these days is kiln dried. Quality wooden gates are made from timber where the moisture content has equalised with the surrounding humidity. The wood for our Courtyard & Driveway gates is dried to 16%. This timber is therefore stable and suitable for external use.
However, the gates once outside will adjust to their surroundings. So for example, for a gate in the winter the moisture content of the air will be on average 30% +. The gate will therefore absorb moisture. Then onto the summer where the moisture content is lower and the water will evaporate from the gate.
If your gate is south facing then one side is going to dry out more than the other side is, as one will be in sun and the other shade.
This means, unless the gates are treated correctly, as the wooden gates dry out one side it will shrink and therefore bend towards the sun. If one gate had more moisture in than the other then this is when you get one gate bending more than the other.
If a gate is under a tree then it can be in shade which is good as it does not dry out too quickly. On the flip side in the winter the gate can also get very wet as it is constantly dripped on in the rain. As it is in the shade it never dries off. Often you will find this is when green moss develops on the gate it as moisture in the timber soars over 20% allowing the decay process to commence.
This all sounds like bad news!!
However, there are solutions to these problems which can help prevent gates from warping!
Firstly, making sure the gates are correctly installed. Click here for our recommendations. By using the correct fittings it will give you a good starting place. Gate fittings play a crucial role in the movement of gates as they facilitates the easy opening or closing of the gate. The size of the hinge is important as well. A rule of thumb for gate hinges is that the hinge length should be one third of the width of the gate. An important consideration when hanging a gate is the weight, the width and what it is going to attach to (post, wall, pillar, etc.). As the gate gets heavier and/or wider, the hinges need to be more substantial.
It is important to make sure if the gates are installed near a hedge to keep the hedge well trimmed. If a gate is left open for extended periods against an over grown hedge it can put pressure on the gate that could cause movement in the wood.
Secondly, treat your gates with a modern UV wood oil such as Osmo or Restol – this greatly reduces the absorption and drying out of wood and significantly decreases natural checks and shakes in the wood – click here for more information
Using a drop bolt on each gate is also recommended as it reduces any potential movement in the gates.
Treat your posts with an oil suitable for sawn timber as well to reduce any movement.
For gates that are not hung make sure they are stored correctly. Either flat on bearers or short term against a wall with both styles evenly supported. Click here for more information.