Tanking Slurry Explained

Cellar and basement waterproofing, step by step

Kingfisher Building Products · Ulverston, Cumbria

What is tanking slurry?

A cement-based coating that is brushed onto walls and floors to form a continuous waterproof barrier.
In BS 8102 terms it is a Type A (barrier) system: it resists water rather than draining it away.
Mixed with water and a polymer admixture, it reacts with water and free lime in the substrate to form pore-blocking crystals.
It suits refurbishment of existing cellars and basements because no pump is needed.

Slurry (Type A): suits retrofit, but it relies on thorough preparation and careful detailing at every joint.
Cavity drain (Type C): relieves water pressure, but needs a pump, maintenance and specialist design.
If there is structural movement, running water or a habitable conversion, get specialist advice first.

BS 8102 waterproofing types at a glance

Kingfisher's Aquatech Premium Tanking Slurry is a cementitious tanking slurry supplied in 20 kg tubs.

Remove all plaster, rendering, paint, limewash, bitumen and other coverings, back to a sound substrate.
Rake out mortar joints to a minimum of 13 mm and brush out loose material.
Floors must be concrete. Aquatech cannot be applied successfully to timber or floating floors, tiles or stone slabs.
Stop active leaks first with Tank Plug.
Treat sulphate-contaminated walls with Anti-Sulphate (two coats, the first diluted 1:1).
Form a 45° fillet at the wall/floor junction with Barrier Mortar. The junction is the weakest point.

Mix a gauging liquid of 3 parts clean water to 1 part K-X11 (usually about 5 litres per 20 kg).
Add the powder to the liquid while mixing with a low-speed paddle until it reaches a thick batter consistency.
Leave to stand for 10 minutes, then remix, adjusting with more gauging liquid if needed.

Pre-wet the prepared surface, then spread the slurry with the brush, keeping a flowing edge. Do not brush it out thin like paint.
Coat 1: brush on in vertical strokes at about 10 m² per 20 kg. Leave at least 4 hours and no more than 36 hours.
Coat 2: brush on in horizontal strokes at about 12.5 m² per 20 kg.
Walls: carry the treatment 200 mm onto the floor. Floors: carry it 100 mm up the wall.
Always follow the data sheet for the product you are using.

Aquatech tanking slurry: application sequence (summary of the data sheet)

Let it cure slowly. In hot conditions, mist-spray with water or cover with polythene. Do not use hot-air dryers or dehumidifiers in the early stages of curing.
Do not apply below 5°C or if frost is expected.
Droplets on the surface during curing are normally condensation, not a leak.
The product is an irritant: wear eye protection, gloves and overalls.

Walls: use a cement/lime renovating plaster (not gypsum-based backing plaster), thermal laminated plasterboard fixed dot-and-dab (not standard plasterboard), or a stud dry-lining system.
Floors: lay a screed at least 50 mm thick over the tanking.
Decorate with matt emulsion or stone paint. Do not use impermeable decorative systems.

Measure the wall and floor areas, including the 200 mm floor and 100 mm wall laps.
Use the Kingfisher tanking calculator to estimate quantities.
Read the full Aquatech technical data sheet before starting.

Technical data sheets and brochures from Kingfisher Building Products

For complex or high-risk basements, use a specialist. The Property Care Association is the UK trade body for structural waterproofing.
Kingfisher Building Products manufactures tanking, damp proofing and masonry protection products in the UK and offers free technical advice.

Kingfisher Building Products Cooper Lane, Ulverston, Cumbria LA12 9RA Tel: 01229 869100