Can you lay decking straight on concrete? When you shouldn't and when you can

Can you lay decking straight onto concrete? This is a question you should ask yourself if you have a patch of concrete where you want a new deck. It might seem like the perfect base to lay a new deck, but if you jump straight in and start laying decking directly on top you could be heading for trouble.

But it’s not as straightforward as you might think. Certain types of decking aren’t a good fit, while other types are the ideal answer for your garden decking ideas. Here the pros reveal what you shouldn’t do and what you can do to ensure you get a long-lasting deck.

Kevin Keen

Kevin has been in the industry for 25 years and handles everything, from the distribution and installation of portable structures to financing and manufacturing. He can speak with authority on every aspect of construction.

Can you lay decking straight onto concrete?

If you have an area of concrete where you want to lay decking, you need to consider whether it's possible. The simple answer is that you can, but it's not advisable in most cases as Kevin Keen, contractor and owner of Keen's Buildings shares, “Concrete retains moisture, putting wood decking directly on top of it can hasten rot, deterioration, or the formation of mould, drastically reducing its lifespan – sometimes by as much as half.”

Even if you follow a strict decking maintenance routine, the decking will still deteriorate much quicker on concrete.

Luke Dejahang, CEO of Crown Pavilions says, “Trapped moisture will lead to rot and decay in timber decking and mould and mildew in composite decking.” He adds, “Concrete and decking materials expand and contract at different rates, which can cause warping and instability.”

Over time this will lead to bigger problems such as structural issues as Dejahang shares. “Without proper airflow and drainage, the decking can become unstable and deteriorate over time.” If a deck becomes unstable, unwanted accidents can happen.

Luke Dejahang

Luke has vast experience in creating beautiful gardens across the UK, transforming them into tranquil paradises with luxury wooden gazebos that add elegance and charm to any outdoor space.

Try these to help lay decking over concrete

Laying decking over paving slabs

Paving slabs are typically made from concrete and present the same or similar issues as concrete as Keen shares, “The issues with paving slabs mirror those of concrete, they don't allow proper airflow and drainage, creating ideal conditions for mould and rot in timber decking.” He adds, “If the paving isn't perfectly flat, your deck boards could warp or sag, creating uneven surfaces.” Uneven decking is a trip hazard.

While laying decking directly onto paving slabs is not recommended, they can be used as a base as Keen explains, “Paving slabs can work effectively if used as stable bases for decking posts – assuming they're correctly leveled and set.” He adds, “I recommend spacing paving slabs at consistent intervals, usually every 1.2 to 1.5 metres, to anchor posts for decking frames.” Keen finishes with a note of caution, “Just avoid using them directly underneath deck boards.”

Cheapest way to cover concrete or slabs

The common options for covering an area of concrete are the typical options for a standard deck. As already mentioned, straightforward wood decking is not a recommended option for laying directly onto concrete. But timber is typically the least expensive, especially if you install yourself.

Keen says, "Although natural wood may appear less expensive at first, the constant upkeep – staining, sealing, and replacing damaged boards – raises expenses over time."

He adds, “Composite decking tiles or interlocking plastic deck tiles offer the ideal combination of cost, longevity, and simplicity of installation. Composite tiles require little maintenance and can last up to 25 years.”

Decking types for laying on concrete

Laying traditional timber or composite decking directly onto concrete isn’t recommended but specific types of decking can be used as Keen reveals, “Interlocking composite or plastic deck tiles, (like these Nicoman Composite Interlocking Decking Deck Tiles from B&Q), are specifically designed for direct installation over flat concrete surfaces.”

They are specially designed to overcome the issues that concrete causes as Keen explains, “Decking tiles have built-in drainage grids to mitigate water pooling issues, extending their lifespan considerably.”

Wooden decking tiles, (like these Wickes Acacia Garden Deck Tile from Wickes), are available, but Keen says, “I would choose composite or plastic due to their natural resistance to mould and moisture.”

Floating decks are a feasible alternative as Keen continues, “A floating deck is one that isn't attached to anything and typically rests on pads or pedestals that offer superior drainage.” He adds, “Because these floating systems are easy to install, require little setup, and provide a noticeable cosmetic enhancement, I have personally suggested them to clients with uneven concrete patios.”

Installing decking posts in concrete

Concrete posts can be directly put into concrete, but this can lead to issues as Keen explains, “Generally I recommend against embedding wooden decking posts directly into concrete because concrete traps moisture around timber, causing premature rotting.” He adds, “Within three to five years, you'll likely see structural weakness.”

One option is to use a sealant, or a bitumen paint like this IKOpro Black Bitumen Paint from Wickes, to protect the part of the post that is to go into the ground.

Alternatively, Keen suggests utilising metal post brackets or anchors instead. He says, “Attach the wooden posts after anchoring the metal bracket into the concrete. This easy method can increase a deck post's lifespan by decades.”

If you are looking to lay wooden decking you want to decide on what is the best wood for decking. Even the best wood can become slippery so make sure to read our how to make decking non-slip to avoid accidents. If you have composite decking that's looking faded, you should think of painting the composite decking.