Ultimate Questions Answered About Installation

We’ve trolled the internet and found the most common FAQs that people ask about installing composite decking. Find below the answers to questions people regularly ask about:

1What timber do I use for decking frame?

If you’re building your deck yourself, our advice would be to ensure the support structure is safe, secure and strong.

To ensure a strong and safe structure, we advise using c16 graded timber. This type of timber has been structurally treated and will be safe and strong for many years to come.

Make sure you put a piece of landscape fabric and gravel down to thoroughly protect against any possible rotting.

If you are raising the deck, we would also advise 6 by 2, and for ground level 4 by 2 or 6 by 2 would be fine


2What is the joist spacing for composite decking?

The recommended joist spacing is 300mm apart. To ensure a strong, long-lasting substructure underneath your decking, it is extremely important that you follow the installation guide of the supplier. You could go 400mm apart with the joist space, however please bare in mind that this could create issues in the later years. Beyond this, the structure may experience bouncing, leading to further strength and structural issues later. It’s best to do it right the first time and stick to the industry standard of 300mm to ensure your warranty stays in tack.

3How do you lay composite deck boards?

Laying composite decking boards is similar to laying wood decking, where you will be able to use the same tools and materials, however there are some key points to remember and some changes in our experience if not known will create future issues. These are expansion gaps of 6mm end to end, 3mm side to side and 25mm away from any fix object. Your joist centre will need to be 300mm and its not advisable to drill composite decking boards, if you do choose to do this you must ensure you pre drill 2-4mm bigger than the screw head. In relation to tools always remember more teeth for you circular saw 40 to 44 will ensure a neat cut. Please do read the supplier’s installation guide to be safe and accurate

4Does composite decking expand?

Due to the weather changes, composite decking boards go through thermal expansion and contraction. They will expand in the heat and contract in the cold and during installation the correct spacing and gaps must be left. Please bare this in mind upon purchasing that you will have small gaps in the summer and large gaps in the winter. You must follow the supplier’s installation guide, especially on the spacing and gaps between the decking boards. If not, this could cause future issues

5How to cut composite decking boards?


Composite decking boards can be cut just like wood. If you are using a saw blade, we recommend using a 40-44 tooth saw blade. The key reason for this is that the more the teeth, the slower the cut. This implies you can do a better job with the material you are cutting.

When cutting with a 40 tooth saw blade on composite decking or any decking, always remember that the slower the cut, the better the finish. If you rush the cut, you will not get a smooth finish and may even have blade marks on the edge of your deck. So go slow and get a nice, appealing and neat finish.

One thing you may notice after you have cut the boards on a capped composite decking board is the hairs left over. You can remove these in two ways: Sanding the cut area, or even better, running a Stanley blade down the cut to get a smooth finish.


6Can composite decking be stained?

Yes. First-generation composite decking can be stained. There is no need to stain the second Generation due to its capping or shield feature.

If you are staining your first-generation composite decking, please allow the fade of the 3-month weathering process to be completed before applying any staining product. Due to the wood fibre surface, you can stain with most normal wood decking staining products.

Before applying any staining products, thoroughly clean your composite decking area and check with the supplier that this does not void your warranty.


7How much does it cost to install composite decking?

There is no difference between installing composite decking and typical wooden decking apart from the spacing, gaps and joist centre. As for the materials and cost of installation, it all depends on the design of your decking area.

A key consideration is the quality of the composite decking you are purchasing. This truly makes a huge difference. Ensure that all materials used during installation are grade A and tested. If they are, you will have no issues with colour for decades. Follow this link for homemade tests.


8Can you nail composite decking?

You can nail or screw composite decking boards just like wood. However, we don’t recommend this as the head of the nails don’t sink into the composite decking material well. The safest and most efficient method to fix the boards to the joists or substructures is using hidden fasteners.

9How do you install composite decking with hidden fasteners

Installing hidden fasteners is very easy. Most suppliers will supply a “T” clip hidden fastener. This can be compared to the metal hook fastening system. You could argue that a metal fastener is stronger; the downside is that they hook over the screw heads, making them difficult to access should you ever need to go under the boards or even use the reverse design. Some composite decking boards come in different designs on opposite surfaces.

Another great thing with “T” fasteners is that they offer a natural 6mm gap needed for expansion and contraction.


10Should composite decking be spaced?

Composite decking should always be spaced with the recommended gap of boards meeting end to end of 6mm, side to side 3mm and 25mm away from any fix objects. Increase gaps maybe required if you are installing below 5 degree. Always follow the supplier’s installation guide.

11Do you have to pre-drill composite decking?

Yes, if you are drilling composite decking you will need to pre drill 2-4mm bigger than the screw head. If you are drilling through a hollow design board this can be done but not advisable and pre drilling is a must to prevent splitting of the board. You will still need to pre drill with a solid composite decking board remembering to pre drill 2 to 4mm bigger than the screw head to help support the natural expansion and contraction of the composite decking boards. Remember if you do drill composite decking boards you do increase the risk of splitting and cracking in the later years of its service life.

12How far apart should deck posts be placed?

The general rule of thumb with deck posts is that they should be spaced no more than 1.5 metres apart. Most installers and fitters will position the deck posts every 1.2 metres to provide a completely rigid subframe.

13Is composite decking slippery in the winter?

Once ice, snow and algae build up on a wooden deck during winter, it becomes a serious slip hazard.

Composite decking will stand up to the harshest winter conditions. It will become less of a hazard than its wooden cousin, mainly due to its slip-resistant design and surface properties.

A deck becomes slippery mainly because of the build-up of algae, mould and mildew. These issues are almost completely resolved, especially in second generation composite decking, due to its shielding.

To ensure your deck stays safe in the winter, Ultra Decking advises you to brush off any leaves and dirt from your board regularly. Also, give your composite deck a soft brush with warm soapy water every autumn.

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