Installing composite decking boards on an old terrace – is it possible?

What are composite decking boards and why choose them?

Let’s start with the basics. Composite decking boards are made from a mixture of wood flour and plastics. They combine the look of wood with the resilience of plastic – and that’s what makes them an ideal choice for a terrace, especially in our unpredictable Polish weather.

• they do not need painting or impregnation,
• they do not decay, crack or rot,
• they are non-slip, even when wet,
• easy to clean – all you need is water and a broom,
• available in a range of colours and patterns.

But can you simply… screw them onto the old structure?

Installation on an existing structure – when is it possible?

The short answer: yes, but not always. The longer answer: it all depends on the technical condition of your existing terrace.

Check before you start installation: 

1. Is the supporting structure stable?
   If the joists, posts or concrete base are undamaged, not rotten and not subsiding, they can be reused.
2. Does the surface have the right slope and drainage?
   Composite decking boards do not absorb water, but adequate drainage is still necessary. Without drainage, water will pool and damp will build up.
3. Are the existing boards nailed or screwed down?
   If so, they should be removed. Installing composite decking on old wooden boards is not recommended. 

Step by step – what does terrace renovation using composite decking boards involve?

Step 1: Remove the old boards. 

Start by removing the old wood. Even if it looks fine, it may be damp inside. Composite decking needs a stable, dry surface.

Step 2: Assess the structure.

Check the joists and posts. If they are in good condition, you can reuse them. If not, it’s better to replace them with new ones, preferably aluminium or composite.

Step 3: Install the joists for the composite decking boards. 

The joists must be spaced approx. 30–40 cm apart. This is key to the terrace’s durability.

Step 4: Lay and install the composite decking boards.

The boards are installed using special fixing clips, providing a neat finish and concealed joins. Note – leave a gap of around 5 mm to allow the material to expand and contract.

Replacing the boards – when is it worthwhile, and when is it not? 

When it is worthwhile: 

• The terrace structure is in good condition.
• You want to refresh its appearance quickly without major expense.
• You already have experience with renovation work or a contractor you trust.

When it is not worthwhile:

• The terrace base is unstable or rotten.
• The terrace does not have an adequate slope and drainage system.
• The existing boards are set low and there is no room for new joists.

Installation costs and savings.

Compared with building a new terrace from scratch, installing composite decking boards on an existing structure can cost up to 30–50% less. Why?

• You do not pay for foundations.
• You do not buy new joists (or only replace some of them).
• Less time spent on the work = lower labour costs.

This is a great option for anyone who wants to refresh their outdoor space without breaking the bank.

What should you watch out for when installing composite decking?

• Do not install without expansion gaps. Composite decking moves – it needs room to expand.
• Do not lay it directly on the ground. There must always be a structure or sub-base.
• Do not use wood screws. Composite decking requires special clips and screws.
• Do not forget ventilation. The terrace needs to “breathe” to prevent moisture from building up.

FAQ – frequently asked questions. 

1. Can composite decking be installed directly on old wooden boards?
   No. Even if they look fine, they may be damp. It is recommended that they are removed.
2. Do I have to replace the whole structure if only some of the joists are damaged?
   Not always. You can replace only the damaged components, but the whole structure must be stable and level.
3. Can I install it myself?
   Yes, if you have basic technical skills and tools. Otherwise, it is better to hire a professional.

In conclusion – time to decide!

Renovating a terrace using composite decking boards on an old structure is a great way to breathe new life into a tired space – quickly, at a lower cost and without a lot of mess. But, as with any investment, the key is to properly assess the current condition of the terrace.

If the foundations are solid, there is no need to start from scratch. All you need to do is replace the decking boards, spend a few hours working… and you can enjoy your new terrace for many years.