What Can and Can’t I Lay My Decking onto?

March 2022
Armani Eagle


We have been asked a lot recently about how you should prepare the surface for the pedestals supporting your decking area. In this article I will cover some of the most common questions asked regarding surface preparation so that you know the recommended way to install your decking area.

We will cover four main questions, and how you can lay you decking in these situations.

  1. Can I install my decking straight onto grass?
  2. Can I install my decking onto steep slopes?
  3. Can I install my decking onto a terrace roof with roofing membrane?
  4. Can I install my decking over existing paving?


Can I Install My Composite Decking Straight Onto Grass?

The short answer is yes! However, there are a few preparations that we recommend to ensure you get the most longevity out of your decking area.

Firstly, make sure that the ground is firm. If it doesn’t sink when you stand on it, you will be fine to install you decking on it. However, if you know that the ground is likely to get wet at some point in the year, we recommend installing some ground drains throughout the area to minimise the likelihood of water saturating the soil and making it soft. The best time to check if your ground is suitable without any preparation is to think about it during the winter, as this is usually the wettest time of the year, especially here in the UK!

Once you have sorted any water issues, we suggest laying a weed control membrane. This is readily available from your local DIY store local or builders merchant. Lay this throughout the whole area that you plan to cover with decking or paving, covering any area you think a weed could grow (basically everywhere!). If the grass is very long, we suggest cutting it before laying the membrane – it will make it much easier for you.

Now you are pretty much ready to start installing your first joists onto your pedestals, but first ensure that the pedestals have a steady footing. The easiest way to do this is to use old paving slabs. Place these on top of the membrane where you are looking to place a pedestal. This will help to spread the weight on the pedestal and will make it much easier to adjust, as the membrane and grass/ soil will not compress as easily.


Can I Install My Decking Onto Steep Slopes?

Yes – it’s a versatile system! However, there are a couple of things that you must know before just going ahead.

Firstly, ensure that the maximum build-up is no more that 1.1m, as this is the maximum build-up of the system. If it is, build-up the ground level using hard core, or even create a small concrete footing.

Once you have made sure all is within 1.1m, you will need to work out where your joists and pedestals are going. Let us know if you need help here – our team is always happy to help out. Mark each pedestal spot and dig a hole in the soil. We suggest digging a 30cm square at around 30-40cm deep. Once you have done this, either mix up some concrete (strongest option), or get yourself some hardcore. Fill each hole, ensuring that the finished surface is level (+ or – 10 degrees, 3 cm variation over a 30cm area). 

Now repeat the steps covered in the first question to ensure no weed growth later down the line and you will be all set to install your decking on pretty much any slope – no matter how steep.


Can I install my decking onto a terrace roof with roofing membrane?

Yes, A big benefit of our system is that is does not have to penetrate your roofing membrane. This means that you will never have any issues with leaking that were caused by our system being on your roof, balcony, or terrace.

There is barely any preparation required when installing onto a flat roof. One recommendation from us to be extra safe, is to use a rubber shock pad for the pedestal to create even more insulation between the pedestal and your roof.

One rule we will always suggest when working on a waterproof membrane – is to never penetrate it! Sounds obvious but try to never put a screw through it, as this will eventually let water through and into your house.


Can I Install My Decking Over Existing Paving?

Old paving is the perfect base to install our decking system on to. It is steady, won’t sink, and will protect your deck from weeds.

Before starting to install your decking onto an existing paved area, there is barely any preparation. We recommend laying a weed membrane to remove any possibility of weeds growing through your deck in the future, however this is optional.

You can now go straight ahead with the install – any solid man-made surface is great for installing our decking systems on to.


What Next? 

We hope this helps you to understand how our system will work for your decking area – but if you have any other questions, just give us a shout! One of our technical experts will surely be able to help you out.

Does this system sound like it will work for you? If so please get in touch with us as we’d love to work with you. Email us at sales@ovaeda.com or call our friendly team on 0208 159 2999