Craft Quantities
Plan & Takeoffs

By trade

Waterproofing calculators

Waterproofing is the trade where a square metre missed is not a shortfall but a leak. It is also the trade where the flat area is the smallest part of the work: the upstands, the corners, the penetrations and the terminations are where the material goes and where the failures happen.

  • 19Calculators
  • 2Parts of the site

How waterproofing is measured

Square metres for sheets and coatings — always plus laps, upstands and returns — and linear metres for tapes, fillets, termination bars and waterstops. Liquid systems are bought by the kilogram at a wet film thickness, which is a different calculation from an area and a coverage rate.

What gets left off a waterproofing order

  • Upstands. A tanked floor with a 150 mm upstand around a small room can add a fifth to the area.
  • Laps on every sheet joint, at the lap width the manufacturer specifies rather than a nominal 100 mm.
  • Reinforcement at corners, movement joints and penetrations, which is a separate material from the membrane it reinforces.
  • The protection layer before backfill or screed, without which the membrane is damaged by the next trade.

Job takeoffs13

Where tankers and wet-room fitters meet the rest of the job: each runs one of these calculators, with every other trade in the same job beside it.

Worked examples1

A real job estimated step by step, with this trade's steps counted.

Comparisons6

Two ways of doing the same work, weighed against each other.

Planners1

Work this trade out from a space rather than from a job.