Waterproofing
Waterproofing Material Calculator
Pick the product and enter the area. This works from the manufacturer’s own published consumption figure, allows for coats, substrate porosity, wastage and the perimeter fillet, and tells you how many tubs to order — not just a kilo count.
Your area & build-up
Measure the surface actually being tanked — the deck plus any upstands, not the room footprint.
m²
m
kg/m²
: 1
What this assumes
- Consumption figures come from the technical data published for the membrane or coating you select, and the exact sentence is shown underneath every result with a Manufacturer figure tag. Nothing in the waterproofing set is an interpolated value — if a product carried no published figure it is simply not in the picker.
- Published consumption is theoretical — an even film on a sound, primed substrate. The substrate control moves the working figure across the published band; the porous setting deliberately leaves the band, adding an indicative 40% for an absorbent or textured deck. That uplift is labelled as an allowance, not a manufacturer value.
- Wastage covers decanting, roller and brush retention, and the loss on detailing around outlets, upstands and pipe penetrations. 10% suits a flat terrace; vertical work — basement walls, tank sides — loses more, so 15% is the default there.
- The coving allowance assumes a 40 mm fillet at the wall–slab junction at roughly 0.15 kg per running metre. It is a standard detailing figure (IS 3067 practice), not a product datasheet value, and is added on top of the coating quantity.
- Pack counts round up to whole tubs, preferring the largest pack that does not overshoot — a part-used tub of two-part membrane is a tub you paid for and cannot store open.
- This estimates the membrane or coating only. Primer, protective screed, reinforcing mesh or fabric, and the fillet mortar itself where it is a separate product are costed separately.
Where these figures come from. Consumption, pack sizes and coat counts are parsed from the technical data published for each waterproofing product and are shown verbatim with every result. Substrate, wastage and fillet allowances follow standard Indian waterproofing practice — IS 3067 for design and detailing, IS 2645 for integral compounds, ASTM C836 for liquid-applied elastomeric membranes — and are shown as editable, clearly-indicative inputs rather than manufacturer figures.
Questions
How much waterproofing membrane do I need for a terrace?
Multiply the terrace area by the product’s consumption per coat, by the number of coats, then add wastage and the perimeter fillet. For a typical acrylic or cementitious membrane at around 1.4 kg/m² per coat over two coats, a 100 m² terrace works out near 308 kg before the fillet — pick your actual product above and the tool uses its published figure, not a generic one.
Why is consumption shown as a range instead of one figure?
Because the deck decides it. A steel-trowelled, sealed slab takes the low end of the published band; an old, open-pored or textured screed takes the high end, and a genuinely porous substrate takes more still. A single average would over-order for one and run short on the other, which on a tanking job means a cold joint in the membrane.
Does the calculator include the coving or fillet at the edges?
Yes, if you enter the perimeter. A 40 mm fillet at the wall–slab junction is added at about 0.15 kg per running metre. It is the detail most terrace and basement leaks trace back to, so it is counted separately and shown as its own line rather than absorbed into the area figure.
How do I handle a two-part (liquid + powder) membrane?
Two-part products are supplied as pre-batched kits, so order against the total the tool gives and against the kit pack size. If you want the site mixing split, switch on the base-to-liquid breakdown — the ratio there is editable and marked indicative, because published component ratios are not in every datasheet.
What wastage should I allow for basement or water-tank walls?
More than for a flat roof. Vertical and overhead work loses material to sag, re-coating and heavier detailing around construction joints and pipe penetrations, so the tool defaults vertical-heavy zones — basement, tank — to 15% rather than 10%. Raise it further for a congested tank with many outlets.
Can I use this for a tender or BOQ?
Use it to size an enquiry and sanity-check a quantity, then confirm against the current datasheet and a site trial before it goes into a contract. Formulations, pack sizes and the condition of the substrate on site all move the real consumption.
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