Under Deck Weed Barrier: What to Put Under a Deck to Stop Weeds (Plus Sheds and Pavers)

Under deck weed barrier: what to put under a deck to prevent weeds

For an under deck weed barrier that works, put a woven landscape fabric over cleared, leveled soil under the deck, cut it snug around every post, and cover it with 2 to 3 inches of gravel. The fabric blocks the light weeds need, the gravel holds it down and shades it from the sun, and water still drains through. Under a deck nothing heavy sits on the fabric, so SHIELD 3.2oz is enough; step up to XBAR 5oz if the gravel will take foot traffic or storage. Skip plastic sheeting: it traps water and stays damp under the boards.

Weeds pushing up under a deck are the hardest kind to reach, so do it before the boards go down if you can. The same idea works under pavers and sheds, with a heavier fabric where there is load, covered below. Size the run with the DOTDAY Fabric Calculator. Free US shipping, no minimum.

The under-deck weed barrier layer stack

Which weight for which structure

Step-by-step: installing fabric under hardscape

1. 1
   Prepare the area

   Clear the zone for your deck, pavers, or shed. Remove vegetation, rocks, and debris, and aim for a level surface for stability.
2. 2
   Lay the fabric

   Roll out the fabric across the cleared area for complete coverage. On larger areas, overlap sheets by at least 6 inches so weeds cannot find the seams.
3. 3
   Anchor it

   Secure the fabric with landscape pins every 12 to 18 inches along seams and edges so it stays put, especially in windy conditions.
4. 4
   Excavate where needed

   For pavers or deck footings, dig to depth carefully without tearing the fabric where it needs to stay intact. Around posts and supports, cut the fabric to fit snug against each footing and overlap the cut flaps a few inches so weeds cannot work through the gap.
5. 5
   Layer and finish

   For pavers, add crushed stone or gravel on top for drainage and a stable base. For sheds, follow the foundation guidelines, then secure any exposed fabric edges.

Get the weight right for the load

The most common mistake is using a light fabric under pavers. Under a compacted base and foot traffic it tears and lets aggregate sink, so paver areas need XBAR 5oz dual-layer. Decks and shed floors put no real load on the fabric, so SHIELD 3.2oz is the cost-effective choice there for weed control and airflow. For a drainage trench beside the structure, TERRA non-woven geotextile filters and flows water. For pavers specifically, see our guide on weed barrier under pavers, and for a gravel drive up to the shed, read landscape fabric for gravel driveways and our gravel driveway weed barrier guide.

Do you need weed block fabric under a shed foundation?

Yes for gravel pads and for blocks or skids that sit on grade. Not as a weed barrier under a poured slab. The fabric always goes at soil level, under whatever carries the shed, and it gets cut to fit around anything that goes down into the ground. Here is how that plays out by foundation type.

Gravel pad. Lay XBAR 5oz dual-layer over the compacted subgrade, then put all of the stone on top of it. The fabric separates stone from soil so the pad stays firm, and blocks weeds from coming up through the gravel.

Concrete blocks or deck blocks on grade. Fabric goes under the blocks, over leveled soil or a thin compacted base. The blocks sit on the fabric, never the other way around.

Skids. Skids rest on the gravel pad, so the fabric is under the stone, not under the skids directly. Build the pad first, then set the skids on the compacted gravel.

Posts, piers, or pillars set in the ground. Set the piers first. Then roll the fabric out, X-cut it at each pier, and lap the flaps back over each other so no soil shows at the base of the post. Never drape fabric over the top of a pillar. If the shed stands on piers over open, shaded ground and nothing sits on the fabric, SHIELD 3.2oz is the cost-effective choice. If stone goes on top, use XBAR.

Poured concrete slab. A slab blocks light on its own, so fabric is not needed as a weed barrier. Some installers spec a separation fabric under the gravel base of a slab. Follow that spec if it applies, and skip the fabric if it does not.

Where the fabric goes for each shed base

Why the fabric never goes over the pillars, and the order of work

A shed pillar, pier, or block exists to carry the structure down to firm ground. Anything draped over the top of it sits between the load and the support, where it gets crushed, shifts, and does nothing for weeds. Weeds come up from the soil, so the barrier belongs at soil level, below whatever you put on top.

For a shed on a gravel pad, the order of work is: mark and square the footprint, extending the pad a little past the walls so roof runoff lands on stone. Strip grass, roots, and topsoil, then level and compact the subgrade. Set any in-ground piers now, so the fabric can be cut around them. Roll out XBAR, overlap seams at least 6 inches, pin every 12 to 18 inches along seams and edges, and X-cut around each pier. Spread the gravel without driving on bare fabric, then compact it in lifts to the depth your shed maker or local code calls for. Set the blocks or skids on the compacted stone and level the shed on top. Size the pad with the DOTDAY Fabric Calculator.

Frequently asked questions