DPC, membrane, coatings and tape for the areas you actually identify.
Painting, tiling and finishes. 5 questions answered below, each with the arithmetic behind it and the limits of what the tool decides. Open the Waterproofing Materials tool.
Waterproofing is bought by area, by coat and by detail. A tanking membrane, a cementitious coating and a liquid applied system all cover a stated area per unit, all need more than one coat, and all need tape and reinforcement at the corners and junctions where water actually gets in. The calculator handles those three separately because they fail separately. The area gives the bulk material, the coats multiply it, and the details are counted from the junctions you list. Where the area of a detail is not measured, it is reported, because a waterproofing estimate with an unmeasured wet room corner is an estimate that has left the hardest part out.
A bathroom with twelve square metres of floor and eighteen of wall to be tanked is thirty square metres of treated area. A liquid system at one point five kilogrammes per square metre per coat, in two coats, needs forty five kilogrammes per coat and ninety in total. Tape for the floor to wall junction runs the room perimeter, fourteen metres, plus the internal corners, plus two pipe collars. A sheet membrane instead needs the same area in square metres of membrane with laps, and its tape only at the joints. The same room, two systems, two different orders, and both from the same measured area.
Liquid applied coatings, sheet membranes and cementitious systems, each with its own coverage and detailing. The one you choose follows from the substrate, the water pressure and what will be laid over it, and that is a specification decision. The calculator asks which family you are using, because a sheet membrane is ordered in square metres with laps and a liquid is ordered in kilogrammes per coat.
Coverage per coat from the product, multiplied by the area, then multiplied by the number of coats you enter. Both figures are shown, because the per coat number is what tells you whether a tin is enough for one pass and the total is what you order. Coats are never assumed: a two coat system specified by a manufacturer and applied as one coat is the most common way a waterproofing job fails.
Both are counted from the details you list rather than from the area. Tape goes at the floor to wall junctions, the internal and external corners and the pipe penetrations, which means a small bathroom can need more tape than its area suggests. Sheet membranes also need their joints taped. Reinforcement fabric goes where movement is expected, and the calculator counts it from the runs you describe.
A blank area is reported as missing and left out of the total, so an incomplete scope is visible rather than invisible. Treating a blank as zero is how a tanking estimate comes to look complete while missing a wall. The same applies to a detail with no length, which is reported rather than assumed to be a metre.
No. It calculates materials for a system you have specified. Whether the detail is watertight depends on the substrate, the preparation, the number of coats actually applied, the laps and the workmanship, and none of those can be verified from a quantity. What the estimate does is make sure the material to do the job properly is on site, which is the part that can be arranged in advance.