The answer to this is very simply yes you do need drainage behind your WoodBlocX retaining wall. Here we will take you through the process from selecting the right liner to ensuring that you have the right materials to hand ready for the build. 


Including a drainage medium behind your WoodBlocX retaining wall or any retaining wall for that matter is really important. We recommend using a lightweight pea gravel and filling two thirds of the height of the structure, you can then fill the rest with your choice of top soil, or if you are laying a patio on top, fill half with pea gravel or your choice of drainage medium and then fill with compacted Type 1.

If your garden is particularly susceptible to collecting surface water and feel you need an additional drainage source you could add a French drain to the base of the wall, this requires you digging a small trench, adding a perforated drainage pipe, which will needs to be directed away from the wall to either a main drain or to somewhere where it can easily soak away. Then simply fill with Type 1 or subbase and cover. The illustration below takes a cross section of a WoodBlocX wall, showing how to effectively add drainage behind the main structure.


Damp-proof membrane (DPM) is the best choice for our retaining walls. All of our products are built in the same way, from a series of small BlocX that slot together, this leaves lots of very small gaps that allow water to escape and air to flow through our structures, so we recommend installing a liner that covers the inside of the wall completely.

We recommend fitting them just before you add the capping to finish your retaining wall build. Your liner needs to be attached to the structure and the best way to do this is by lining an edge up with the final layer of BlocX and, using a stanley knife or tough garden scissors, cut small incisions into the liner so it can be slotted overs the dowels and held in place, then you can place it over the entire interior of the wall and over the buttresses. You may need several sheets to complete this process depending on the length of your wall.

Can I buy liners from WoodBlocX?

Yes! We stock high quality liners (DPM) to protect your retaining wall or other WoodBlocX structures.

  • Damp proof membrane (DPM)
  • Made from 100% recycled plastic
  • 4 x 5 metres (20m2)
  • Thickness: 0.25mm
  • Provides a damp proof barrier between WoodBlocX timber and soil
  • Must be installed to ensure the lifespan of your retaining wall

This raised bed liner is available in one size only: 4 x 5 metres (20m2)

Benefits of using WoodBlocX for your retaining walls:

Durable and strong
All of our wooden components are made from high-quality Scot's pine. We never use the heart of the tree, which is weaker. The wood is pressure-treated and because our BlocX are pre-drilled, the treatment penetrates almost 100% of the wood.

The structures are held together with a series of dowels to form a single solid unit, each dowel can withstand up to 0.9 tonnes of sheer force and they have more strength than masonry in some situations withstanding tension forces as well as compression. Our retaining walls will not crack with ground movement or frost.

All of our structures are guaranteed for 15 years when installed using our guidelines, but they are expected to last up to 30 years.

Building a WoodBlocX retaining wall requires no specialist skills so you can build them yourself saving on hiring a tradesperson. There is no heavy lifting involved in a WoodBlocX build, and all the parts fit into an average-sized car.

We ensure each customer receives a step by step guide that is tailored to their project before they begin their build. We have also created a series of quick how-to videos which cover every part of the build to assist you, plus our friendly customer service team is on hand to help via phone, email or live chat.

Attractive and sustainable
The rough-sawn wood provides an attractive finish which looks great in both contemporary and traditional gardens - customers can choose from flush capping for a modern finish or overhanging capping for a traditional finish - the wood will naturally fade to a grey over the years and whilst our structures don't need any annual maintenance or treatments you can choose to paint them to suit your garden style.

We source our timber from sustainably-managed forests, and our treatment process involves no chemicals that might leach from the wood, unlike the heavily treated sleepers. The dowels are all made from recycled plastic too, and we continue to work hard to reduce our carbon footprint in everything that we do.

Awards & Accreditations

  • WoodBlocX Queen's Awards
  • Made in Britain Badge
  • feefo Platinum Service Award