Liquid Membrane Waterproofing Calculator

Guided By Adam Paul - Waterproofing Expert

A liquid membrane waterproofing calculator is a tool designed to estimate how much liquid-applied membrane and primer you’ll need for a specific surface area, based on real-world jobsite conditions like number of coats, substrate absorption, vertical surfaces, and product specifications.

The liquid membrane calculator helps you to avoid material shortage during application, prevent over-purchasing and minimize wastage, and plan primer and coating coverage accurately based on surface type.

How to use the liquid waterproofing membrane calculator?

1. Measure the surface: Enter the length and width of the waterproofing surface in meters (or feet if the unit switch is added).
2. Add number of coats: Add the recommended number of Liquid membrane coats. Typically requires 2 coats for waterproofing. The number of coats can be found on the manufacturer’s/application guidelines.
3. Enter product coverage rate: Use the value provided by the membrane manufacturer (e.g., 1.5 m²/L for 2 coats).
4. Choose a substrate absorption modifier: Different surfaces absorb liquids membranes differently.
   • Smooth concrete: 1.0
   • Screed or brick: 0.8
   • Very porous surfaces: 0.6
5. Include vertical surfaces if needed: If you install liquid waterproofing on walls, skirting, or parapets, enter their height and length.
6. Add primer calculation (optional): If the product requires a primer, enable the primer option and input its coverage rate and container size.
7. Set wastage allowance: Typical jobsite wastage is 5-15%, depending on application method and surface roughness.
8. Get the result as per the provided data

You can use liquid waterproofing calculator on any kind of membranes, such as acrylic waterproofing, bituminous liquid waterproofing, epoxy waterproofing, polyurethane, and paints.

Surface Length and Width of Liquid Membrane Calculator

Surface length and width of the liquid membrane calculator represent the horizontal dimensions of the area you want to waterproof using a liquid membrane. These measurements are typically taken in meters (m) or feet (ft), depending on the unit system you choose.

Surface length and width define the total surface area of the horizontal floor or deck that will receive the liquid waterproofing treatment. You should always use accurate measurements because the liquid membrane quantity depends directly on the total area.

You can measure the longest side as the surface length and the shortest side as the surface width.

Example:
If you have a terrace that is 10 meters long and 5 meters wide, your surface length is 10 m and surface width is 5 m. The total horizontal area is then 10 m × 5 m = 50 square meters (m²).

Number of Coats of Liquid Membrane Calculator

The number of coats of the liquid membrane calculator is how many layers of liquid membrane you will apply on the surface.

Applying multiple liquid coats increases waterproofing durability and effectiveness. The total amount of liquid membrane required is multiplied by the number of coats because each layer consumes material.

You should check the product guideline to make sure, how many liquid waterproofing coats you should apply on the surface before starting the calculation of the amount of liquid membranes.

Most of the liquid waterproofing membranes recommend 2-3 coatings. Some liquid membranes require primers also. We have also included that function also in the liquid waterproofing calculator.

Coverage Rate of Liquid Membrane Calculator

The coverage rate of the liquid membrane calculator is how much area (in square meters or square feet) one liter (or gallon) of liquid membrane can cover in a single coat.

This value is crucial because it tells you how efficiently the membrane covers the surface. It varies based on product type and surface condition.

You can find the coverage rate from the manufacturer’s guidelines. Coverage rate of the liquid waterproofing is denoted by m²/L or ft²/gal, but it can be varied with the surface absorption rate.

Example:
If the coverage rate is 1.5 m²/L, one liter of membrane will cover 1.5 square meters for one coat.

Surface Absorption Modifier of Liquid Membrane Calculator

The surface absorption modifier of the liquid membrane calculator is a factor that adjusts the amount of liquid membrane required based on how much the surface soaks up the product.

Different surfaces absorb liquid membranes at different rates. For example, porous concrete soaks up more material than smooth tiles. This means you’ll need more membrane for highly absorbent surfaces.

In the liquid waterproofing calculator,

• A modifier of 1.0 means average absorption, no adjustment needed.
• Values above 1.0 increase the membrane quantity; values below 1.0 reduce it.
• Smooth, non-porous surfaces: 0.8 to 1.0
• Porous concrete or plaster: 1.2 to 1.5

Example:
If your base coverage rate is 1.5 m²/L, and the absorption modifier is 1.3, you divide the coverage rate by 1.3 to find the effective coverage rate. This means more liters are required per square meter.

Wastage Percentage of Liquid Membrane Calculator

The wastage percentage of the liquid membrane calculator is the extra liquid membrane that may be lost during application due to spills, overspray, tool absorption, or uneven surfaces. You should assume the wastage amount of liquid membrane waterproofing before calculating it. The wastage amount of liquid membrane depends on the expertise and site conditions.

In real-world applications, some material is always wasted. Including a wastage allowance ensures you purchase enough membrane to complete the job without running short.

• Liquid membrane wastage percentage is usually between 5% and 15%, depending on the complexity of the job and the applicator’s skill.
• More complex or textured surfaces often require higher wastage allowances.
• You add the wastage percentage to the total material required by multiplying the base amount by (1 + wastage_percentage/100).
• For example, if you calculate 10 liters needed and expect 10% wastage, you should buy 11 liters.

Example:
For a project requiring 20 liters of membrane, a 10% wastage means purchasing 22 liters total to cover losses.

Container Size of Liquid Membrane Calculator

To calculate the liquid waterproofing membrane, you should know the container size of the liquid membrane. Container size of the liquid membrane calculator is the volume of liquid membrane per packaging unit, typically measured in liters (L) or gallons (gal).

Knowing the liquid membrane container size helps you determine how many containers to buy to cover your project’s total membrane requirement.

• Common liquid membrane waterproofing container sizes are 1 L, 5 L, 10 L, 20 L in metric, or 1 gal, 5 gal in imperial units.
• After calculating the total liters or gallons needed (including wastage), divide that number by the container size.
• Always round up the container sizes because you can’t buy partial containers.

Example:
If you need 22 liters of liquid membrane and the container size is 5 liters, you buy will buy (22 ÷ 5) = 5 containers.

How Accurate is this Liquid Membrane Waterproofing Calculator?

The liquid membrane calculator gives a close estimate based on the surface area, number of coats, and product data you input. However, actual usage may vary due to surface texture, on-site conditions, and workmanship. Always follow your product’s technical datasheet and add a safety margin.

How do I know the Correct Coverage Rate to Use?

Use the coverage rate provided by your membrane’s manufacturer. It’s usually listed on the container label or in the product datasheet. If unsure, contact the supplier or refer to product-specific documentation.

What is the Absorption Modifier, and How Should I Set It?

The absorption modifier adjusts for how much the surface soaks in the liquid.

• For smooth tiles or coated surfaces, use 0.8-1.0.
• For rough concrete or blockwork, use 1.2-1.5. You can also do a small patch test to observe absorption.

Should I Always Include Primer in the Liquid Membrane Calculator?

Yes, you should include it If the manufacturer recommends priming, it helps with membrane adhesion and reduces absorption. Most cementitious and polyurethane membranes require priming over concrete or porous substrates.

Can I Use this Calculator for Terraces, Balconies, or Bathrooms?

Yes, you can, it’s ideal for all flat or slightly sloped surfaces where liquid membranes are used: roofs, terraces, decks, balconies, toilets, and kitchens. Just enter accurate dimensions and details for the area you’re treating.