About this calculator
This calculator works out the materials for bituminous waterproofing of foundation walls below ground: primer, a thick bitumen coating (polymer- modified bitumen thick coating, PMBC, or a bitumen mastic) and/or torch-on or self-adhesive membrane rolls, the treatment of the wall-footing junction, and the dimpled membrane that protects the waterproofing from the backfill.
Enter the perimeter (a rectangle or a list of walls), the height of the waterproofing on the wall measured from the top of the footing, and — optionally — the footing's ledge and side if they are waterproofed too. For a coating enter its consumption per m² per 1 mm of dry layer, the number of layers and the dry thickness of each.
Formula
wall area = perimeter × height
footing ledge = ledge × (perimeter + ledge × outside corners)
footing side = side × (perimeter + 2 × ledge × outside corners)
primer (l) = area × l/m² × (1 + waste %)
coating = area × consumption (per m² per mm dry) × layers × layer thickness
with waste = coating × (1 + waste %); containers = ceil(with waste / container)
membrane courses = ceil((height covered − side lap) / (roll width − side lap))
membrane rolls = courses laid round the perimeter off the rolls in order,
a new piece lapping the last by the end lap where a roll runs out
fillet (kg) = perimeter × kg/m × (1 + waste %); tape rolls = ceil(perimeter / roll)
protection = courses over the wall height, laid the same way as the membrane;
a roll at least twice the wall height is ripped lengthwise
into floor(width / height) strips
Worked example
A 10 × 8 m foundation, 1.5 m of wall to waterproof, two coats of 2 mm dry thickness at 1.25 l/m² per mm, 10 % waste:
area = 36 m × 1.5 m = 54 m²
primer = 54 × 0.2 = 10.8 l; +10 % = 11.9 l → 2 × 10 l
coating = 54 × 1.25 × 4 mm = 270 l; +10 % = 297 l → 10 × 30 l
fillet = 36 m × 1.7 kg/m = 61.2 kg; +10 % = 67.3 kg → 3 × 25 kg
dimpled membrane = one 2 m course of 36 m → 2 rolls of 20 m
FAQ
Why consumption per mm of dry layer? A thick coating shrinks as it dries, so data sheets state the dry thickness the waterproofing must reach and the material needed for it. BKM's PMBC-2K, for example, gives 3.75 l/m² (3.75 mm wet) for a 3 mm dry layer — 1.25 l/m² per mm of dry layer.
How thick must the coating be? The design decides. Manufacturers' data sheets quote the German DIN 18533: at least 3 mm dry against ground moisture (class W1-E) and 4 mm against pressing water, with a reinforcing fabric embedded. The calculator warns below 3 mm. DIN 18533 is not a Lithuanian standard and was not read directly, so it is named here as the manufacturers' reference only.
What is the fillet for? A rounded fillet (radius about 4–6 cm) in the corner between wall and footing lets the coating run round the corner without a sharp bend where it would crack; Remmers' specification gives about 1.7 kg of mineral fillet mortar per metre. A joint tape is the alternative for some systems.
Can I use membrane rolls instead of a coating? Yes — tick membrane rolls, untick the coating (or keep both for a combined system). The courses run horizontally round the building; laps are inputs you should take from the membrane's laying guide.
Which standard applies? None is cited. EN 15814 is the product standard for PMBC and gives no quantities; the take-off is area × thickness × consumption.
Assumptions and limits
No standard is cited: see above. The waterproofing system itself (type, layers, thickness, reinforcement, drainage) must come from the design.
Defaults to replace: coating 1.25 l/m² per mm dry (BKM PMBC-2K), primer 0.2 l/m² and fillet 1.7 kg/m (Remmers), membrane rolls 1 × 10 m (TechnoNICOL), dimpled membrane 2.0 × 20 m with 200 mm overlap (DELTA-MS) are product figures; the membrane laps (100 / 150 mm), containers, fillet bag, tape roll, heights and 10 % waste are placeholders.
Geometry: one waterproofing height all round; the footing ledge and side are uniform. Inside corners, pipe penetrations, reinforcing fabric, the scratch coat some systems apply first, and the drainage are not counted. The dimpled membrane covers the wall height only.