As an established decking supplier, we outline some of the common mistakes to avoid when installing composite decking…
If composite decking is new to you, it’s natural to assume that installing composite decking will be done in the same way as wood. This is not the case. Composite decking has different properties and it expands and contracts at a different rate to timber. This difference must be considered when installing to avoid a costly repair and unsightly decking.
Installing composite decking needs a little preparation and planning to avoid issues later down the line. Failure to do so will result in warping, standing water or a collapsed deck to name but a few of the issues that you could face. Making these mistakes affects the look and strength of your deck. So how do you ensure safe decking? After all, failure to install according to the manufacturer installation guidelines will void your warranty, and you don’t want that, now do you?! Here’s our ‘dirty dozen’, a list of twelve mistakes we encounter on a regular basis here at NeoTimber®:
1
Insufficient Expansion Gaps Between Butt-Ends Of Decking
Composite timber contains wood and plastic. Because of the plastic element within the material, your composite deck boards will expand and contract to a far greater degree than ordinary timber decking. For this reason, we instruct you to install deck boards the appropriate distance apart (*1mm if the temperature is over 26 C, 3mm if 4 C – 25 C, 6mm if below 4 C) when butting them end on. This will create a sufficient expansion gap without pressing against each other, which causes warping and twisting of the boards.
2
Not Allowing Sufficient Ventilation Underneath The Deck
Because composite decking contains cellulose fibres (ours are from recycled wood), it absorbs a small amount of moisture. Rotting occurs when wood is exposed to extended periods of moisture without having time to dry properly. A minimum gap of 35mm should be left between your base, concrete, slab or turf, and the underside of deck boards to ensure sufficient airflow so that composite timber joists and composite deck boards are able to drain and dry completely.
3Using A Poor Quality, Substandard Subframe Material
As the title suggests, there are subframes and there are subframes. Unless the previous subframe was installed carefully, joists can become damaged through standing water and general erosion. Composite decking is different to timber, in that it requires significantly more support. Five joists will not cut it. You will need to either upgrade the existing subframe with additional joists, replace with new timber joists or install an entirely composite based subframe. If your deck is situated in an area with a high water table or which floods, a subframe comprised of plastic lumber would be the best option as it will not rot.
3Installing Onto A Substandard, Pre-Existing Timber Subframe
A wise man once said, “only a fool builds his house upon sand”. Your decking is only as strong as its foundations. It’s important to get your base right before you start laying your boards. Carefully choose the material for your subframe. If building a roof terrace or balcony, a steel subframe would be a preferable option as it is self-anchoring. If building close to water or a high water table, choose plastic lumber over timber as it will not rot. Timber for a standard subframe should be seasoned wood, able to withstand significant use.
4Installing On Wider Joist Centres
It may seem practical and sensible to reuse your existing timber subframe, but in this case that would be unwise. Timber decks usually have a joist centre of about 500mm whereas a composite deck joist centre should be placed 250 – 350mm apart. This is due to the difference in the inherent properties of the materials. Timber has a lower degree of flex compared to the recycled plastic that makes up composite. This flexibility only requires additional support while the recycled plastic and wood composite greatly increases strength and durability.
5Using An Alternative Supplier’s Composite Decking Clips
It’s tempting to think you know best, especially when it comes to doing something you’ve done before. But trust us, composite behaves differently to wood and so what works for wood just won’t work with composite. NeoTimber® are designers, manufacturers and suppliers of our own patented products. Our decking clips work best with our decking because they’re designed to do just that. Flexing and expanding as the decking changes shape.
7Not Treating Cut Ends Of Timber Joists
It should stand to reason that any timber you are using to build a decking subframe should be treated properly. Top, bottom, sides and ends. Not fully treating your timber is a simple, common mistake we encounter a lot here at NeoTimber® HQ. The main reason ends are missed is because it’s easier to paint joists when they’re suspended on the posts as you can paint top and bottom without having to allow them to dry first. Invariably, this means that the exposed ends which are butted against a wall or fence are not so easy to access and may get overlooked.
8Not Installing Double Joists Where Two Joining Boards Meet
A strong base is important when laying your decking. In the case of a long deck, one which exceeds 3.6m, a double joist should be installed when deck boards butt together. It is imperative that all joins are given extra support to make sure planks do not split or slip. Install deck boards with an appropriate expansion gap (as seen in number 1), according to the temperature at the time of fitting.
9Using Methods From Alternative Suppliers
If you have worked with composite timber before, it may be tempting to use the fixing method recommended by the supplier you last worked with. However, not all composites are made equal. Each composite has a slightly different composition and design and as such will require a different approach. We have worked tirelessly with our design team, professional installers and customers to understand the tolerances of NeoTimber® composite wood and to create an installation guide which best befits our product.
10Not Allowing For Adequate Drainage Slope
Any handyman with a spirit level might expect that a deck should be perfectly level, but doing so means that standing water will remain in-situ for long periods and your deck will be unable to drain properly. To ensure proper drainage, you should allow a fall of 1% (1:100). In practice this mean that your deck should slope slightly (away from your house) by 10 mm for every one metre of length. This will be a sufficiently small difference that it will not be noticeable to you, but will enable water to drain away easily, preventing slippery surfaces and rot.
11Specifying A Product Not Suited For The Setting
Within the NeoTimber® composite decking family, there are four distinct products. Each performs differently and is designed for specific functions. The Essential and Advanced products are partially hollow to make installation easier. Due to their hollow nature, these should not be used in areas of high footfall, commercial applications or in load-bearing duties. However, the Classic and Deluxe boards are solid and so are perfect for such applications.
12Installing Onto A Substandard, Pre-Existing Timber Subframe
As the title suggests, there are subframes and there are subframes. Unless the previous subframe was installed carefully, joists can become damaged through standing water and general erosion. Composite deckingis different to timber, in that it requires significantly more support. With composite, you will need to either upgrade the existing subframe with additional joists, replace with new timber joists or install an entirely composite based subframe. If your deck is situated in an area with a high water table or which floods, a subframe comprised of plastic lumber would be the best option as it will not rot.
Need Further Support or Advice?
If you’ve still got questions that have not been answered here, or you would like additional advice,
support or assistance then please give one of our friendly experts a call and we’ll be happy to help.
Just give us a call on 01530 382 180.