A pond measuring 4 meters by 3 does not require a 4-by-3-meter liner. The membrane must descend along the banks, follow the shelves, cover the bottom, and retain a margin for finishing. It is this developed surface area that must be calculated before ordering.
For products sold by the square meter, a second step is required: converting the dimensions of the piece into the quantity to be ordered. Measure first, choose the membrane width, then calculate the corresponding surface area. Here is a method with a concrete example and points to check to ensure you receive a piece adapted to your pond.
Wait for the final profile before taking measurements
A plan helps to estimate the budget, but final dimensions should be taken on the finished and prepared excavation. An increased depth during construction, a widened shelf, or a relocated edge can change the amount of membrane needed.
Take the maximum length, maximum width, and maximum depth. Draw a sketch with the shelves, angles, water inlets, and any potential pipe penetrations. Also indicate the planned water level: it serves as a reference for depths and finishing the perimeter.
If a waterfall or stream joins the pond, measure this part separately. Its waterproofing, connections, and potential overflows must be included in the project. A margin intended for finishing a bank does not automatically become large enough to cover a waterfall.
The formula for a first estimate
The method presented by Aquiflor uses the maximum depth and a margin of 50 cm at each edge:
- Estimated liner length = maximum pond length + 2 × maximum depth + 1 meter.
- Estimated liner width = maximum pond width + 2 × maximum depth + 1 meter.
This formula provides a benchmark for a simply shaped pond. The 50 cm per side corresponds to a starting margin; the actual finishing planned may require a different reserve. Walls, anchors, and specific details must be taken into account before confirming the dimensions.
For a complex shape, always compare this calculation to the actual profile. The elasticity of EPDM is not meant to compensate for ordering a piece that is too short.
Confirm with a rope or a flexible tape measure
Place a non-stretchable rope on the prepared ground, from one edge to the other, following the slopes, the bottom, and the rises. It must conform to the contours without cutting straight across a hollow. Repeat in the other direction and on sections likely to be longer.
Add the necessary reserves for finishing. Then measure the rope laid flat and note each path on the sketch. For an irregular pond, a single line in the center might miss a wider or deeper section.
Taking measurements with two people makes it easier to keep the rope against the shelves. Take the time to double-check before choosing the roll width. A small difference in measurement can have a significant effect on the format to be ordered.
Example: 4 × 3 meter pond with 1 meter depth
Using the previous formula and a total margin of one meter in each direction, the estimate gives:
- Liner length: 4 + 2 × 1 + 1 = 7 meters.
- Liner width: 3 + 2 × 1 + 1 = 6 meters.
- Minimum estimated rectangle: 7 × 6 = 42 m².
Suppose the on-site measurement confirms these dimensions. A width of 6.10 m with a length of 7 m covers this rectangle. The surface area of this piece would then be 42.70 m², not 42 m².
You must still confirm the proposed cut lengths and how the site accepts decimal quantities. If a surface area must be rounded for the order, have the resulting length validated before payment. A quantity in m² does not replace the specification of the expected dimensions.
Choose the available width without multiplying seams
The Aquitechnics EPDM sold by the m² offers several widths, including 3.05 m, 4.27 m, 4.58 m, 4.88 m, 6.10 m, 7.62 m, 8 m, 9.15 m, 10 m, 12.20 m, and 15.25 m. Check the selected variant and cutting possibilities when preparing the order.
Compare the two possible orientations of the piece. Depending on the dimensions, rotating the rectangle may allow you to choose a better-suited width. The goal is to cover the profile with the necessary margins and avoid unnecessary joints.
Large pieces require handling organization. Prepare the path to the construction site, a clean place to unfold them, and enough help. A flexible membrane can remain heavy and cumbersome, especially when it needs to be moved around obstacles.
Square meter, linear meter, and pre-cut format
| Sales method | What the quantity represents | To check |
|---|---|---|
| By m² | The surface area of ordered membrane | Chosen width and corresponding length |
| By linear meter | A length within a defined width | Fixed roll width and unit of sale |
| Pre-cut format | A piece with announced dimensions | Full dimensions, thickness, and profile coverage |
On the Aquitechnics product page cited here, the quantity is expressed in m². Therefore, do not enter only the desired length. For example, "7" does not automatically mean a 7 m long piece in the chosen width.
For a custom cut request, provide both dimensions, the unit of sale, and the variant reference. This verification is particularly useful if the requirement exceeds the proposed formats or if the pond has an unusual geometry.
Plan for the underlay at the same time as the liner
The protective underlay is placed between the prepared ground and the membrane. It limits abrasive contact and risks related to small irregularities, but it does not remove the need to clear away sharp objects or address ground stability issues.
The Aquitechnics Premium 400 g/m² underlay is sold by the m² in a 2 m width. Its surface area is calculated by taking into account the profile, the layout of the strips, and the necessary overlaps. A sufficient total surface area alone does not guarantee a practical layout.
You can also consider the Aquitechnics EPDM liner and underlay pack. Check the contents and layout of the pieces so that the protection correctly covers the bottom, shelves, and sides.
Think about details that require accessories
A wall penetration, a bottom drain, a connection to a waterfall, or fastening to a wall may require a specific assembly. Identify these details on the plan before installation. Accessories must be compatible with the membrane and the intended function.
Manufacturers provide procedures for joints and singular points. Products meant to glue a membrane to a substrate do not all serve as a watertight seal between two strips. Have complex cases validated before cutting the liner.
A decorative stone-effect strip does not necessarily replace the waterproofing membrane. OASE makes a clear distinction between these functions in its presentation of liners and underlays. Therefore, prepare the bank finishing as a whole, with clearly defined waterproofing continuity.
Checks to perform before confirming the order
- The excavation matches the final profile.
- Measurements follow the shelves and include the finishing.
- The selected width covers the confirmed requirement.
- The quantity respects the unit of sale on the product page.
- The dimensions of the expected piece are explicit.
- The underlay and necessary accessories are planned.
- Access and handling are organized.
- The terms for cutting, transport, and delivery have been verified.
Keep a copy of the sketch and the order confirmation. Upon receipt, check the reference and dimensions before any finishing cuts. The installation must allow the membrane to follow the relief without excessive tension.
Prepare your EPDM order
With your measurements and your sketch, choose the appropriate width and confirm the surface area to order. For a specific format, the Aquiflor team can assist you with this calculation.
Sources
- Aquiflor — Waterproofing tips, calculating liner dimensions: formula and field checks.
- Aquiflor — EPDM liner for pond: project support.
- Aquiflor — Protective underlay: role and format of the geotextile.
- OASE — Liners and underlays: protection and distinction from decorative elements.
- Elevate — PondGard EPDM: installation and system accessories.
- Aquishop pages for Aquitechnics EPDM, the pack with underlay, and the 400 g/m² underlay: variants and units of sale.
