12 Common Mistakes To Avoid When Installing Composite 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.