Common installation mistakes in timber decking and how to avoid them

Your first timber decking installation can feel daunting. You have invested in your timber decking boards, have a vision in mind, and you do not want a silly mistake to ruin your plans – we have all been there! The good news is that you are not alone, and our timber decking experts are here to lend a hand.

We have put together the most common decking installation errors we see and hear about to help you ensure that you do not make the same mistakes.

Mistake No.1: Choosing the Wrong Timber Species

First up: choosing the wrong timber species for your decking. Grabbing a load of untreated Pine for your garden is going to end in disaster, and it is vital you choose the correct species for your application.

Different timber species bring vastly different properties to your decking project. The species you choose will affect durability, longevity and maintenance (as well as aesthetics), and we highly recommend working out what you need from your timber before you start looking.

For exterior timber decking, we recommend prioritising resistance to rot and external threats (durability class 3 or higher – ideally a durability class 1 or 2 for enhanced longevity), and choosing a strong species suitable to take the weight of people and outdoor furniture. Our top picks for long-lasting timber decking include:

• Yellow Balau
• Cedar
• Larch
• Jatoba
• ThermoWood

If your decking is going to be near water, such as if you intend installing it around a swimming pool, choose a timber extremely resistant to moisture-related rot. Ekki, Greenheart and Ipe, for instance, are excellent choices.

It is also vital that the species you choose for your decking joists is able to withstand direct ground contact and brings plenty of strength to your project.

Mistake No.2: Using the Wrong Fixings

Using the wrong type of metal for your fixings leads to quick corrosion, which can stain your timber and weaken your entire structure. On the other hand, the right metals will last for decades, withstanding a lot of wear and tear without budging. We recommend choosing corrosion-resistant metals such as:

• Stainless steel
• Hot-dipped galvanised steel
• Coated steels

Avoid aluminium and brass fixings for structural decking applications, particularly when working with tannin-rich hardwoods or in wet environments.

Mistake No.3: Not Considering Water Drainage

Decking boards and standing water are not friends. Even with a durable species, allowing water to pool on the surface of your timber can create issues, from rot to algae growth. In fact, poor drainage is one of the fastest ways to shorten the lifespan of your deck.

If boards are laid flat with no fall, rainwater has nowhere to go. To avoid this, always design your decking with drainage in mind:

• Build in a very slight slope to encourage water runoff
• Leave adequate spacing between boards to allow rainwater to escape
• Raise the deck off the ground to improve airflow beneath the structure
• Install proper drainage channels if you are building near walls or solid surfaces

If you are installing hardwood decking around a swimming pool or in a particularly exposed area, drainage becomes even more important. In these cases, combining a highly durable timber species with smart drainage design will dramatically improve longevity.

Mistake No.4: Not Considering Ventilation

Ventilation underneath the deck is just as important as surface drainage. Good airflow helps timber dry out quickly after rainfall, reducing the risk of rot and mould growth for a longer-lasting construction.

Your best bet for adding ventilation is to leave enough space between your decking boards and the ground to allow air to circulate. We recommend around 150mm of space as a minimum.

Mistake No.5: Cutting Corners on the Subframe

The subframe or substructure of your timber decking forms the foundation of your entire construction, so do not cut corners. Even though this is not a visible part of your decking, it pays to specify and install it correctly.

One of the biggest mistakes we see? Using cheap, untreated timber for joists, especially in areas with high moisture or direct ground contact. Even if your deck boards are durable hardwood, a weak subframe will compromise the entire build.

To get it right:

• Use structurally graded timber suitable for load-bearing applications
• Choose a species rated for ground contact
• Follow the correct joist spacing guidelines to prevent warping
• Install proper supports and footings to avoid shifting or sinking

Investing properly here means better stability, longer lifespan and far fewer headaches down the line.

Mistake no.6: Failing to Space Decking Boards Correctly

It might seem to be a small detail, but getting your board spacing wrong can cause big problems down the line. Timber is a material known to move, with changes in moisture and temperature causing your boards to shrink and swell.

If you do not leave enough space between each board, they will push against each other, leading to warping, cupping and splitting. On the other hand, if the gaps are too large, you create potential trip hazards, and the decking does not look quite right.

For adjacent decking boards, you will typically need to leave a gap of between 5-8mm, depending on species and moisture content. You can use decking spacers to make this easier and prevent movement during installation.

Board ends can be butted together if the moisture content is stable, though many installers prefer to leave a small 2–3mm expansion gap. Where a board abuts a post, add a 5mm gap. Where a board lies against a building, add a 10mm gap.

Mistake No.7: Screwing Directly into the Timber

Screwing straight into your hardwood timber is a risky business. Doing so can lead to splits, cracks and a less-than-polished finish lacking structural integrity.

We highly recommend pre-drilling pilot holes before fixing your decking boards. This reduces stress on the timber when screwing it into place and ensures your fixings sit flush and secure. Countersinking (where appropriate) also prevents raised screw heads which can catch on shoes or collect water.

This is such a simple task, but it is also one of the most skipped. Our advice? Spend the extra few minutes pre-drilling, and you will thank yourself in the long run.

Mistake No.8: Not Knowing When (and When Not) to Treat Timber

If you have used a durable timber species well-suited to outdoor use, it will not need any added protection from rain, fungus and insects. After installation, you can leave it untreated and enjoy a sturdy decking area for years to come with very little maintenance.

However, if you want to preserve the original colour of your timber boards, you will need to add a UV-protective finish. Sunlight causes timber to weather naturally to a rustic silvery-grey – a look so popular that some of our clients specifically request pre-weathered timber. Not everybody wants silver decking, though, especially if you have chosen a timber species specifically for its aesthetic appeal. In this case, a UV-resistant coating blocks the sun’s UV rays, prolonging  the natural colour.

After installation, your decking might need a little TLC. Oiling and staining your timber every year or so provides a little extra protection while ensuring your decking boards stay looking fresh and bright.

If you are not sure how to look after your timber after installation, get in touch with us and we will be happy to help.

Mistake No.9: Not Choosing Sustainably Sourced Timber

It is easy to focus purely on price, appearance and durability, but from where your timber comes matters just as much as how it performs.

Choosing uncertified or poorly sourced timber can have serious environmental consequences, from illegal logging to habitat destruction. This side of the industry has wide-reaching negative impacts on people and the planet, and it is something responsible specifiers and homeowners can actively avoid.

Look for timber certified by recognised schemes, such as the Forest Stewardship Council (FSC) and the Programme for the Endorsement of Forest Certification (PEFC). These certifications ensure the timber has been responsibly sourced from well-managed forests, with full traceability through the supply chain.

At EcoChoice, all our timber decking is sustainably sourced and independently certified. We can supply FSC and PEFC-certified timber to projects across the UK, from private gardens to large-scale commercial and public developments.

Find Timber Decking at EcoChoice

Ready to kickstart your timber decking installation? Make sure you choose the right species and ensure sustainable sourcing by working with EcoChoice.

Get in touch with our team to start your order.