AllPondSolutions Pond Underlay 2 x 8m 150gsm Non-Woven

AllPondSolutions is proud to offer our own branded pond underlay. This is 150 grams per square metre of 100% virgin non-woven polypropylene, and it is the layer that stands between your liner and whatever is buried underneath it.

This piece is 2 x 8m and covers 16 square metres, enough on its own for a 4 x 3m liner with room to spare, or combined with a smaller piece for a larger pond.

Why underlay matters

A pond liner rarely fails because the material is poor. It fails because something sharp was left underneath it. As the pond fills, the weight of the water presses the liner hard onto whatever is below, and a stone, a root or a fragment of glass will work through it over a season or two.

Underlay is the cushion that stops it. It also lets gas from the soil escape sideways rather than collecting in bubbles beneath the liner.

Check the weight of "free" underlay

Pond liners are often sold with free underlay included. It is usually around 60 g/m2, which is thin enough to tear on the first sharp stone it meets. Ours is 150 g/m2, two and a half times the material, in the place it matters most.

How much do I need?

Allow the same area as your liner plus about 10% for overlapping the pieces. It does not need to be a single sheet: lay pieces side by side, overlapping each by 5 to 10cm, and work outwards from the deepest part of the pond. Do not tape or glue the joins, as the overlap is enough and it lets trapped gas escape.

Laying it

Clear the excavation of every stone, root and sharp edge you can see, then run your hand over the surface to find the ones you cannot. Start at the bottom and work up the sides, carrying the underlay past the rim so the liner never touches bare ground. Lay the liner on top, then trim both back together once the pond has filled and settled.

Use it on top as well

If you are adding gravel, cobbles or rock, or building a stream, lay a second layer over the liner first. Sharp stone dropped onto a bare liner is one of the most common causes of a leak.

• Size: 2 x 8m, covering 16 square metres
• 150 g/m2 non-woven polypropylene
• 100% virgin fibre
• Rot resistant and permeable, so gas and groundwater can escape
• Inert and safe for fish and plants
• Overlap pieces to cover a pond of any size or shape
• Required for the guarantee on AllPondSolutions HDPE pond liners