How long does a timber playground last?
This is a question many of you will have in your mind when considering your timber playground project. There are of course, other types of material you can choose from for your playground structure, including metal, composite plastic and even recycled plastic, but for now we will be considering timber.
In this article, we will look at the various points that affect the longevity of a timber playground and how many years of service it might offer.
What type of timber should we use to make our playground last?
In our opinion, the best type of timber to use for long-lasting playgrounds is a hardwood timber that is smooth to the touch (either naturally, or by factory machining), strong enough to withstand the rigours of playground life, and resistant to rot. An example would be Robinia (pseudo-acacia or Black Locust) – this is among the most robust types of timber available anywhere. This timber is very resistant to rot and does not require chemical treatment to preserve its integrity for up to 50 years.
If your playground budget can’t quite stretch to use hardwood such as Robinia, then you can use softwood timber, but it should undergo suitable Wood Preservative Pressure-Treatment to inhibit rot. The deeper the penetration of the preservative chemical into the wood, the longer it will be protected. The timber should also be ‘Play-Grade’ quality.
You should avoid using untreated softwood timber in any playground. This is because it will be very susceptible to rot if it gets wet, and therefore it could fail and break if left outside for only a couple of years. This is not good, because not only will you have to spend more money replacing the playground, but worse still, it may cause severe injury to children using the playground.
What construction method should we use for a long-lasting play-piece?
Here are 3 commonly used methods to create timber playground foundations. In all cases, adhering to the manufacturer’s recommendations is essential for long playground life:
Method 1 – In-ground Concrete Foundations
Traditionally the most common method of installation was to set the timber posts directly into the ground surrounded by concrete but there are some issues with this, and you will see why in the following paragraphs.
Method 2 – Concrete Foundations with Steel Feet
This method includes the use of ‘steel feet’ around the timber at the base of each ground-entry point will still provide a solid anchor point with the concrete foundations, while securing the timber part of the structure above the ground.
Method 3 – On-ground or Surface Mounting
If your play surface is already a solid material such as tarmac or concrete, you can bolt the main structural posts straight to the ground. This method will likely use surface-mounting plates and a suitable ground-anchor fixing. It is critical that sound anchor points are used to hold the plates in place, as loose mounting points can undermine the integrity of the whole structure.
You will notice that Methods 2 & 3 construct the foundations in such a way that the timber does not come in contact with the ground. You will see why this is important in the following paragraphs of this article.
What are the main causes of timber playground failure?
Rot setting in to the timber legs in contact with the ground.
If damp is so bad for timber, then what happens when it rains? Let’s face it – in the UK, not many weeks will go by before your playground is subjected to a rain shower, or even days of soaking drizzle. There are two main points that explain why rain won’t necessarily destroy your timber playground. Firstly – if the wood preservative treatment has been carried out correctly and has penetrated to a suitable depth, then this will repel rain and resist rot. Secondly, in most parts of the UK, there’s likely to be dry and sunny spells in approximately equal quantities to the rain and damp! This means that any timber above ground that gets wet in the rain, will also dry out in the sun. Therefore the rot has no continuous period of dampness (more than 20% moisture content) in which to grow and develop.
In the UK, we enjoy many and varied types of weather, but one condition that we’re never far away from is moisture and damp. In the concrete foundation we referred to earlier (Method 1), there is a small section of timber that is below the ground, and not embedded in the concrete. See Fig. 1 above – did you notice the black dots? This area is actually damp (more than 20% moisture content) for most of the year round and is the perfect breeding ground for rot and is not easy to spot until it’s too late! We can overcome this issue by using construction method 2 – setting Steel Feet into our concrete foundations.
Inferior Play-piece fixings
At every point where timber meets timber in a playground structure, there is likely to be at least one fixing point to hold it all together. In addition, swings and slides need to be attached to the timber with fixings or hangers, and rope climb nets, ladders and hand-rails are no exception. Fixings that are subject to rust, or premature wear are highly likely to fail sooner than high quality fixings, such as those made of stainless steel. Rust, or wear in the moving parts of a fixing over time, will cause the fixing to become slightly smaller than the hole in which it is mounted. This allows ‘play’ in the mounting (this kind of play should not be permitted in the playground!) Then begins a vicious circle of wear leading to play, and the timber will become further worn by the movement, thus causing additional play. The worn fixing can be replaced, but only if the hole in which its intended to be mounted has not been inadvertently bored out and damaged by the old fixing rattling around. If this enlargement damage has occurred, you may need to replace the whole timber piece into which the fixing is mounted.
This can be overcome by specifying high-quality fixings and components, and conducting regular playground inspections to monitor wear and tear. Swift action on inspection recommendations will prevent damage to structural parts, leading to lower maintenance costs and a longer-lasting playground.
Use of playground beyond intended design
This might well sound obvious – but a timber playground in a back garden used by a few children for several days of the year will not require the same construction quality standard and installation methods as that of a playground in a public park, likely to be used by hundreds of children each week. Public area or commercial playgrounds will require larger, stronger materials and components, additional fixings and professional-grade installation. Older children and teenagers who are heavier than young children might use the equipment, causing added strain, or in extreme cases the equipment may be subject to abuse or vandalism. Therefore, a playground designed for use in a public place will need to be designed and built with these points in mind.
Insufficient Timber Preservation Treatment
Ensure that the timber you use has been pressure treated to the required standard, and that the right methodology has been followed. If timber pieces are treated in the factory then sent to site where they are drilled, sawn and prepared for installation, each penetration of the timber after treatment is effectively breaking the intended preservation barrier. This can easily lead to premature rot, as the damp can penetrate straight into the timber where the hole or cut has been made, bypassing the intended protection. This issue can be overcome by forming the playground timber frame as a whole kit in the factory, then pressure-treating it after all cuts and holes have been made. Not only does this ensure correct and effective treatment, it also speeds up the installation time on site, meaning your playground can open sooner! Alternatively, any cuts or holes made in the timber after factory preservation should be treated again in accordance with manufacturer’s instructions before being used in the construction.
Hardwood rot-resistant timber does not require wood preservation treatment, and therefore can be ‘kitted’ in the factory, or cut/drilled on site as necessary.
How can we make timber playgrounds last longer?
In brief: for the longest-serving timber playgrounds in the UK, do the following:
Select a professional playground designer, manufacturer and installer, and check their credentials by obtaining recommendations, references or other background checks, e.g. what warranty is offered?
Consider the intended use for the playground and design and build accordingly
Specify rot-resistant hardwood timber and high-quality components and fixings
Construct your playground foundations in such a way to avoid timber being in contact with the ground
Conduct regular safety inspections (at least once per year) and act on maintenance recommendations promptly
There’s quite a lot in this article to consider, and some points which are not covered in great depth, such as Wood Preservative Timber Treatment, and Play-Grade Timber. Watch out for more articles covering these subjects and more!