How Do I Stop Weeds From Growing Through My Decking Boards?

Weeds can be an issue for garden decking if the installer did not take measures to avoid weeds growing through the decking boards.

Weeds and Garden Decking
Weeds and Garden Decking

Every installer should take measures before they lay the decking boards across the joists/frame. There are a few methods you can use to stop weeds from taking hold after your deck has been installed.

Like all weed solutions, there is the chemical version that will slowly destroy the soil around your decking project or the safer methods.

Here at Wezaggle, we believe you should not be destroying the area with salt or weedkiller, there is a very easy method that will take a few hours to organise and install underneath the decking boards.

Using salt or strong weed killer can harm the local wildlife, ruin your soil and could make your pet sick if they digest it.

Installing A Weed Barrier

The decking installer should have installed a breathable weed barrier straight under the decking.

Some installers will cover the area in a salt mix or use enough weed killer to destroy the soil for many years.

A breathable weed barrier will stop any weeds from growing up through the boards, you can also double these weed barriers giving you that extra protection against weeds.

You must not use plastic sheeting because you will find that rainwater puddles and becomes stagnant.

Another issue with using plastic sheeting is the rainwater runoff, which can destabilize foundations and other parts of the garden.

If your decking has already been installed then you can still use a weed barrier.

Fitting Your Weed Barrier

Here is the method we use when installing a weed barrier under an installed decking.

Because the boards have been installed in can be hard to spread out the weed barrier underneath the decking boards.

You can remove a section of the boards and gently spread it underneath.

Fitting Your Weed Barrier
Fitting Your Weed Barrier

Cut your weed barrier into sheets and overlap by 2 feet or cut a sheet big enough to cover the decking.

Cutting sections and overlapping by 2 feet is just as effective once you have pinned and covered with sand to hold in place.

  1. Cut your weed barrier into section
  2. Remove one decking board closest to the wall
  3. Drop two lengths of rope through the void
  4. Use a long pole and pull the rope underneath
  5. Tie the rope to the edge of the weed barrier and pull it through
  6. This method will bring the weed barrier right back to the wall without taking up all the decking boards

Once you have pulled the weed barrier to the back of your decking you should use some tent pegs to hold it in place. Continue doing this until you have covered the area under the decking. Remember to overlap the weed barrier by 2 feet.

I then cover the weed barrier with sharp sand so there is no room for weeds to grow and take hold underneath the weed barrier.

You can also use rocks, bricks or anything heavy to keep everything close to the ground. Sand is heavy and offers drainage so you will not get puddles and a lot of runoff when it rains.


Not many people think about weeds when they install their decking only to discover a few months later that green shoots start to pop up.

You can just use a salt or weed killer mix and that area will not see any weeds for many years. But this method will do more harm than good once it starts to spread around the garden and onto the lawn and the flower beds.

The weed barrier is safe and just as effective if you cover the area with a breathable barrier to stop rot, puddling and water run-off.

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