Bathroom Tanking & Waterproofing Calculator – Materials & Cost

MEASURE · WATERPROOF · ESTIMATE

Bathroom tanking calculator for membrane, tape and sealing details

This free bathroom tanking and waterproofing calculator turns measured wall and floor areas into an estimate of membrane packs. Add primer, joint tape, internal and external corners, pipe collars and drain seals when those components are part of your chosen system. Optional labour and job pricing produce a free printable estimate.

The calculator starts with product coverage rather than an assumed bathroom specification. Waterproofing systems vary in application method, substrate preparation, coating thickness and compatible accessories. Measure the work and use current instructions for the exact product; a quantity estimate cannot establish that an installation is suitable or watertight.

How to use the calculator

1. Select metres and square metres or feet and square feet.
2. Add a rectangle for each wall, floor, niche or return to waterproof.
3. Deduct excluded areas per copy and enter repeated surfaces if useful.
4. Choose the coverage basis printed in the system instructions.
5. Add a deliberate reserve and any complete matching packs already available.
6. Enable only the primer, tape and sealing details needed for the specified work.
7. Add optional prices and labour, calculate, then review and print.

Measure the actual waterproofed surfaces

For each rectangle, the calculator multiplies width by height or floor length, subtracts the entered deduction and multiplies by identical copies. Use separate entries for surfaces with different dimensions. A floor can be entered exactly like a wall: the second dimension is simply its length.

Do not assume the whole room is treated to the same height. Enter the extent required by the selected design and product instructions. Niche sides, window returns, shelves and other small faces may add area that a simple room perimeter misses. Add those as separate rectangles and avoid counting the same face twice.

Deductions describe areas excluded from the particular rectangle. Enter them per copy. If two matching walls each have the same opening, enter the opening once and set copies to two. A deduction must remain smaller than the gross rectangle. Where the waterproofing continues around an opening, include the returns separately.

For an area already measured accurately, enter that area as the first dimension and one as the second, using the matching measurement system. Give the row a clear name so the printed breakdown remains understandable. Bulk entry supports the same five fields when there are many surfaces.

Per-coat consumption versus complete-system coverage

The most important purchasing choice is the coverage basis. A manufacturer may describe square metres covered by one tub for the finished system, product consumed per square metre over all coats, or product consumed per square metre for each individual coat. These are different inputs.

Complete-system area mode divides the planned area by the stated area per pack or kit. It does not multiply by coats. All-coats consumption mode multiplies area by the total stated consumption and divides by pack quantity. Per-coat mode also multiplies by the entered coat count. The retained coat count is ignored when you switch to either complete-system method.

For example, 10 m² at 0.5 kg per m² per coat over two coats requires 10 kg before reserve. A total-system rate of 1 kg per m² gives the same result. Entering 1 kg per m² as a per-coat rate and then adding two coats would double that estimate. Always check the wording surrounding a coverage figure.

Some systems use one coat and others use a different application build-up. BAL Waterproof 1C, for example, is described by its manufacturer as a one-coat system. This illustrates why the calculator leaves coverage to the specified product rather than prescribing a universal coat count.

Keep kilograms and litres separate

Consumption mode lets you identify product quantities as kilograms or litres. Rate and pack quantity must use the same unit. A 5 kg tub does not automatically contain 5 litres, and changing the quantity label does not convert mass to volume. Use the manufacturer’s stated quantity and consumption basis.

Changing the measurement system converts surface dimensions, area coverage, tape lengths and relevant rates between metric and imperial. The product quantity remains in the explicitly selected kilograms or litres. Currency selection changes the displayed symbol only; it does not perform an exchange-rate conversion.

Reserve, full packs and existing stock

The membrane reserve percentage adds to the measured net area before purchasing quantities are calculated. It can represent assessed handling losses or additional allowance for the particular job. It starts at zero so there is no hidden waste assumption. An allowance cannot compensate for missing surfaces or the wrong consumption basis.

Required quantities round up to complete purchase packs. The calculator then subtracts complete usable matching packs already owned. Count stock only where the product remains suitable for use and matches the selected system. Partly used tubs are not represented by a fractional whole-pack entry.

A kit may include more than membrane. Check its primer, tape and detail contents before ordering additional items. The calculator’s kit coverage mode evaluates membrane-covered area; it does not automatically know the component inventory. Avoid charging for accessories already included, while checking that the included amounts are sufficient.

Optional primer quantities

Primer is a separate optional calculation because its need and coverage depend on the system and substrate. Leave the primer area blank to use the total net surfaces, or enter a measured override for only the areas to be primed. Enter coverage per purchased pack for the complete primer application, including any required coats.

If a primer is diluted, use the supplier’s coverage for the purchased concentrate and the appropriate application. Do not treat added water as extra purchased product. The primer reserve and stock are separate from the membrane allowance. Different substrates or primers may be clearer as separate estimates.

Joint tape, corners, collars and drain seals

Measure the tape required by the selected joint and junction details. The calculator does not assume that every perimeter, seam or corner uses the same treatment. Enter splice count and extra overlap per splice if those lengths have not already been included in your measurement. Its separate reserve is applied after measured length and overlaps are added.

Tape rolls are pooled by total length. The result is a purchasing estimate, not a cut plan proving that every continuous piece can be obtained. Check long uninterrupted lengths, minimum overlaps and usable remnants against the installation layout.

Internal corners, external corners, pipe collars and drain seals use explicit piece counts and pieces per purchase pack. Count the details shown by the system design. A drain seal or collar must match the compatible connection; an item with a similar name or size is not automatically interchangeable.

NoMorePly’s waterproof tanking kit is an example of a supplier offering membrane, primer and tape together. Use the current contents and instructions for the exact kit you are buying when checking quantities.

Optional labour and project costs

Area labour uses the net waterproofed surface once, without reserve and without multiplying again by coats. Enter a rate covering the intended work or choose hours or days for more variable preparation and detailing. Other costs can include separately assessed preparation, delivery and tools.

All prices start at zero and labour starts at None. Closing a pricing section retains its entries. Turning an accessory checkbox off excludes that accessory’s quantity and price, while retaining its values for later use. Keep input prices on a consistent pretax basis; markup adds to cost and the entered tax applies afterwards.

Frequently asked questions

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