Install mulch under your deck by first removing any plants, dead leaves, and other debris from the soil under the deck. Then, cover the soil under your deck with water-permeable landscape fabric. Next, install a border that will keep the landscape fabric in place and contain your mulch. Then, spread a non-wood mulch such as gravel or rubber under your deck. Finally, check the mulch thickness to ensure it is 3–5 inches (7.5–13 cm) deep at all points. Add more mulch as necessary to reach the proper depth.
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What are the Benefits of Putting Mulch Under a Deck?
Spreading the right type of mulch under your deck is one of the best ways to prevent weeds from growing under your deck. You can also use mulch under your deck to decrease soil erosion and encourage proper water drainage. This means fewer weeds under your decks, less animals making homes in this space, and fewer insects breeding underneath your deck.
- Fewer weeds.
- Prevent soil erosion.
- Discourages invading animals.
- Improve water drainage.
- Eliminate insect breeding grounds.
If you do not mulch the area under your deck, standing water can sit there. This not only encourages mosquitos and other biting insects to breed there, but it also may draw unwanted animals such as raccoons and possums. A weedy, unmulched under-deck area can also attract pests.
What Type of Mulch Should You Use Under a Deck?
Gravel, stone, and rubber mulches are the best for use under your deck. They will suppress weeds without encouraging rot. Avoid using wood chips, bark mulch, leaves, straw, or nut hulls as mulch underneath a deck. These natural materials will soak up water under your deck and the shady conditions won’t allow the mulch to dry out. This will lead to fungus growth and rot, which can damage your deck posts and home foundation.
- Gravel and rock mulches, including river rock.
- Rubber mulch.
- Avoid wood, bark, and other natural mulches—they invite rot and fungus.
Gravel is our choice for mulching under your deck. Make sure to choose the best gravel for drainage. This will prevent flooding and standing water. While gravel is best under most decks, if it is a high deck with ample room underneath, you may choose to use rubber mulch to make the space a safe area for children to explore.
5 Steps to Install Mulch Under Your Deck
If the area under your deck is overrun by weeds, insects, or pest animals, mulching is a great choice. The job is simple. Just follow these steps:
Clear the Area
Begin by using a garden rake to remove all dead leaves, twigs, and loose plant material from under your deck. If you have some stubborn plants growing there, attack them with a garden hoe to destroy them at the root, then rake the area again until it is smooth. At the end of this step, you should have bare soil under your deck that slopes slightly away from your home’s foundation.
Install Landscape Fabric
Lay this water-permeable landscape fabric over the soil under your deck. Lay the fabric in lengthwise sections to minimize the number of cuts you have to make. Overlap the pieces of landscape fabric by 6 inches (15 cm) where they meet. Then, drive these landscape staples through the fabric at the edges and overlaps. The staples will hold the fabric securely to the soil to create a weed-proof barrier.
Add a Border
Put a border in place on all sides of your landscape fabric. This border will contain the mulch and help prevent the landscape fabric from being disturbed. Our top choice is this wood-style border, but you can use borders made of metal, plastic, or even stones. Just make sure the border follows the lines of the deck for a uniform, neat appearance.
Spread Your Mulch
Use a wheelbarrow to pour your gravel or rubber mulch in different areas just inside your border (since it won’t be easy to reach the center of the space). Then, use a garden rake or hoe to pull the mulch from the edges toward the center of the space. Work carefully to avoid tearing the landscape fabric with your tools. It is often best to add a little bit of mulch at a time and gradually build up the mulch layer under your deck.
Check Mulch Thickness
To prevent weeds but still encourage optimal drainage, your mulch should be 3–5 inches thick (7.5–13 cm). After spreading your mulch, stick a ruler into the mulch in several places to measure the depth. Wherever the mulch is too thin, add more, or move some from an area with too much mulch. Create a mulch layer that follows the slope of the ground to encourage good drainage.
Is Plastic Better than Landscape Fabric Under Your Deck?
Plastic should never be used in place of landscape fabric under your deck. Unlike landscape fabric, plastic retains water. This means the area under your deck will become filled with stagnant water. This creates the perfect environment for mosquitos, gnats, and other insects to breed. This water can also become foul-smelling over time, which can make your deck area unpleasant to use.
- Plastic is not a suitable replacement for landscape fabric.
- Sheets of plastic under your deck hold water, which allows mosquitos to breed.
- Stagnant water trapped in plastic sheeting can produce rotting odors.
- Landscape fabric allows water to pass through and enter the soil.
- Weeds cannot sprout through landscape fabric.
Landscape fabric is essential because it allows water to permeate down into the soil, but is too tightly woven for weeds to sprout through. This means the water will trickle down through your mulch and enter the soil, but any weed seeds that sprout will be smothered by your layer of landscape fabric.
What Can You Put Under Your Deck Instead of Grass?
Instead of allowing grass and weeds to conquer the area beneath your deck boards, you can add mulch. Here’s how:
- Use a rock mulch or recycled rubber.
- Avoid using organic material such as wood and bark mulch, since it encourages wood rot.
- Clear all debris and plant material out from under your deck.
- Spread landscape fabric on the soil under your deck.
- Add a border around the landscape fabric to keep the mulch contained.
- Pour mulch inside the border and spread it with a rake.
- Make sure the mulch is 3–5 inches (7.5–13 cm) thick at all points under the deck.
This process will create a long-lasting barrier that deters weeds and insects while also preventing erosion and rot. Your deck and home will be preserved by adding mulch with these steps.
