Standard studwork timber is a fairly versatile product that can be used in many situations. It generally comes in a sawn size of 50mm x 75mm (3x2inch). The finish will be slightly smaller if you buy a planed products such as PSE or CLS.
As with most timber products, you can buy studwork timber untreated (this is standard). Or you can buy the same size timber that has been pressure treated.
Untreated studwork timber is not designed for outside use. Without any protection to wood will start to develop issues, such as, warping, twisting and signs of rot within 3-5 years. It will also be at a far greater risk of woodworm infestation.
Treated timber on the other hand, will last much longer outside (15-20 years). The treatment is designed to protect against rot and timber decay. Also the chemicals used, act as a repellent to wood burrowing insects, such as woodworm.
In general, pressure treated timber is not much more expensive than standard timber these days. So if you know the wood will be used outside, it makes sense to pay slightly more for a superior product, that will last.
Can you preserve untreated timber yourself?
If you are planning to use untreated timber outside, you may wonder if a wood preservative will help to protect the timber.
The answer is obviously yes. After all, this is what a wood preservative is intended to do. A good example of this is fencing timber. Often, they are not pressure treated. Instead they are dip treated.
Dip treatment is when the timber is placed in a tank of preservative. Following this, it is removed and left to dry. The result is essentially a faster version of applying the preservative manually with a brush.
Whilst this will offer protection, it is not permanent, and you will need to retreat the wood regularly. Otherwise it will be at risk of wood rot and other issues.
The problem with adding a preservative to untreated timber, is it only provides surface protection. Once this fades, the wood becomes exposed to the outside conditions again. If it isn’t retreated, it can begin to deteriorate.
When timber is pressure treated, the preservatives are applied throughout the wood, not just on the surface. To do this, the timber is loaded into a pressure sealed tank. This fills with the chemicals and then the air is sucked out of the chamber. The pressure creates a vacuum, which forces the treatment deep into the wood.
Essentially, pressure treated timbers have a preservative running throughout the entire piece of wood.
In comparison, if you apply a preservative manually, you are just adding a thin layer to the outside. This will need regular upkeep to maintain any level of protection.
Also, because timber below the surface is untreated, it will still be attractive to woodworm and other wood burrowing insects.
Jobs where you definitely need a treated timber
If you are using timber outside, really you should always use a treated product. However, there are some cases where you may decide to use an untreated product and preserve it yourself.
This is fine, as long as you are happy to do the work and reapply a preservative on a regular basis (annually for example).
You should also be aware; the life of this timber, will be less than a pressure treated product. Even if you preserve it yourself on a regular basis, it won’t last anywhere near as long as pressure treated wood.
When it comes to studwork timber. The two questions you need to ask are:
- What is it being used for?
- Will you be able to access it?
For example, lets assume you intend to build a small deck frame with your untreated studwork timber. This would be a problem, accessing the timbers will be far more difficult, as they will be under your deck boards. This is because your deck boards will be screwed down at regular intervals.
Also, for this type of job, the timber is likely close to the ground which means it is at a higher risk of moisture.
Ask yourself. Do you really want to spend time, taking up boards, to manually treat timber below? This is a nightmare job, and if most people are honest, it won’t get done.
A better option would be to spend around 10-20% more, to buy a pressure treated product and save yourself the hassle.
Basically, unless you have good access to the timber, you shouldn’t even consider using untreated wood. In the vast majority of cases, it will be more trouble than its worth.
You will almost always be better paying a fraction more and buying the correct timbers for the job (pressure treated).
Conclusion
Studwork timber can be used outside, providing it is a treated product. The best type of treatment would be pressure treated. This is a superior method that penetrates deep into the timber, providing long term protection against rot, mould, and woodworm. As well as the development of common timber defects, such as cupping, warping, and twisting.
Using untreated studwork timber is not recommended. It will deteriorate quickly. Even if you maintain it and add preservatives, it still won’t last as long as pressure treatment. Plus, you are setting yourself up for lots of future work to maintain, and eventually replace it.
