Decking membrane. All your questions answered about landscape fabric

Last Updated on 08/07/2023 by Barney

When asked customer advice and information on this subject, the short answer is most definitely YES.

The use of a quality membrane under decking will prevent weeds from taking root whilst letting water permeate into the ground below.

The UK has the perfect weather conditions weeds to take hold. Not using a suitable product is just asking for a future problem. All professional landscapers in the UK install this as standard, as a customer, always ask and check with the contractor if using one for the project .

Q.) Do I need membrane under my decking?

lay membrane on bare soil

When decking is not being installed over a solid concrete surface then yes, a heavy duty weed control sheet is needed. Once decking has been installed it is impossible to use weed killers.

Even when installing over an old patio, growth can occur in failing pointing gaps between paving slabs. Better safe than sorry and at less than £1 per metre it is not worth taking the risk without one.

Q.) What can I put under my decking boards to prevent weeds?

Water permeable weed control fabric is the only landscape solution to prevent weed growth under decked areas. Gravel can be placed on top (highly recommended) which still allows water to pass to the ground. This weighs the barrier down preventing those stronger weeds from pushing the ground barrier upwards.

Q. Should you put membrane under decking?

If the area to be decked is over garden soil, grass, an old patio, then it is important to install a heavy duty weed fabric over the ground before installing the deck.

Seeds from weeds carry in the wind and find themselves dropping between the gaps. Once the seed finds contact with the soil surface it will germinate and grow.

No one wants unsightly and problematic weeds growing through

Q. What is the best material to put under a decking.

There are many membranes available but it is very important to choose the right one. It needs to be heavy duty as it will need to last on the ground for many years to come. Heavy duty weed control fabric & woven membranes are the right product for this purpose.

Q.) Where can I buy and how much does it cost?

Compared to the cost of building a deck, weed control fabric is inexpensive . Expect to pay around £1 per square metre in the UK for a decent product that will last and prevent weeds from growing.

You can find a whole range of suitable weed membrane products with differing sizes and prompt delivery times here on our best weed membrane page.

Q.) Do I need to use weed killer before laying the membrane?

remove all perennial weeds before laying membrane
Remove perennial weeds

Not necessarily. Check the area where the decking is to be constructed. If it is clear of weeds and grass, you are good to go.

Give perennial weeds an application before the weed control fabric is laid.

Q.) What is the difference between weed control fabric and weed membrane?

Weed control fabric is a membrane with a fabric like material, a bit like felt. Weed membranes can be either fabric or woven versions. Both do the same job, prevent weeds from growing.

Ensure a heavy duty version is purchased.

Q.) What tools do I need?

To install correctly I would advise a good pair of garden scissors for cutting to size and around posts. A mallet (preferable) or a hammer for securing the pegs into place (quite essential on stony – hard ground).

When using gravel a wheelbarrow is useful to haul it front the delivery location. Apart from that, this is all the materials you are going to need for a successful installation.

Q.) How to lay heavy duty weed control fabric under decking?

This is a very simple process, not hard work, easy to accomplish and difficult to make an error.

Once the subframe is constructed the sheet is cut to size allowing for a 10cm overlap. Slits are cut to allow for any bearing posts.

Once in position use the proper pegs to hold into place . Whilst not absolutely essential, it is good practice to spread a layer of gravel on-top, 5cm will suffice (this is where willing friends might be able to help)

Q.) Do I need to lay gravel on top of the weed control fabric?

gravel laid directly onto the membrane
Do it right first time

This is good practice and gives as extra level of protection. The gravel will not be visible so not necessary to purchase a decorative one. Standard 10mm pea shingle is perfect and available for delivery from most builders merchants.

Q.) How do I keep grass from growing under my deck?

If the deck has been installed without a made for purpose sheet covering the ground below then one needs to be installed to prevent this from occurring.

This involves lifting the boards, using a suitable glysophate product to kill the existing grass and installing the sheet.

Thanks for reading, I hope this advice has been useful, answers any questions and provided the information needed for a successful landscaping project.