How to measure your pond for a box welded liner

The three key measurements

Every box-welded liner is defined by three dimensions: length, width and depth. All measurements should be taken from the inside of the pond walls, at the maximum dimensions of each.

• LengthThe longest internal dimension in metres
• WidthThe widest internal dimension in metres
• DepthThe deepest point, measured vertically from the base to the top of the walls

Lip allowance

The lip allowance is the amount of liner that extends beyond the top of the pond wall — to fold over the coping or be hidden under the edging material. Our standard allowance is 300mm per side. This is included automatically in all our liner calculations. If you need more, note it when you request your quote.

The diagrams below use “Flange” to label the lip overhang (F) — the amount of liner that extends beyond the top edge of the pond.

Square and rectangle

Length (L) and width (W), both measured internally at the maximum extent. For a square pond, one side measurement is sufficient — we use the same figure for both dimensions.

Circle

Measure the internal diameter at the widest point. We calculate the liner size from this, plus depth and flange allowance.

L-shape

Measure each section separately — W1 and W2 for the two widths, L1 and L2 for the two lengths. Provide a sketch with all dimensions labelled, or call us and we'll walk you through what we need.

With steps (multi-depth)

For ponds with planting shelves or stepped depths, measure the overall length (L1), the shelf length (L2), the main depth (D1), and the shelf depth (D2). Width (W) is the internal measurement at the widest point.