▽ +09.00Engineering Hub · Calculator

Membrane roll calculator

Work out the real coverage of each roll after side and end laps, then the number of rolls and a suggested order quantity.

Inputs

The values shown are an illustrative example, not product data; replace them with your project values and the approved TDS.

Area

m²

The net area to be treated, without waste.

Roll width

From the TDS of the approved product.

Roll length

From the TDS of the approved product.

Side lap

The overlap along the long edge, as the TDS and specification require.

End lap

The overlap where one roll ends and the next begins.

Waste

An allowance for cuts, overlaps, details and site losses.

Recommended order quantity32 rolls

Results

Result of the example values

Net area: 250.0 m²
Effective coverage per roll: 8.87 m²
Rolls for the net area: 28.20
Waste: 25.0 m²
Recommended order quantity: 32 rolls
Membrane supplied: 320 m²
Share lost in laps: 11.3 %

Estimate only — final quantities depend on the approved specification, the product TDS and a site survey. No prices are given.

Send with a quotation request

+01.00Formulas

How it is calculated

Coverage per roll = (roll width − side lap) × (roll length − end lap)
Rolls = net area ÷ coverage per roll
Order = round up [ area × (1 + waste %) ÷ coverage per roll ]

QQuestions

Questions clients ask

How many membrane rolls do I need for a roof?

Add the roof area and the upstands on the parapets and walls, multiply by the number of layers, add the side and end laps and a waste allowance, then divide by the roll’s net coverage from the manufacturer’s data. The calculator on this page does exactly that.