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.

Is slurry the right system?

• 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

Aquatech at a glance

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

• Pack size: 20 kg
• Colour: Cement grey
• Coverage: 8–10 m² per 20 kg on a 2-coat application
• Thickness: Damp-proofing: minimum 2.0 mm · Waterproofing: minimum 4.0 mm
• Mixed with: Gauging liquid of clean water and Kingfisher K-X11
• Application: Brush, two coats

Preparation is everything

• 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.

Mixing

• 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.

Two-coat application

• 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.

The full sequence

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

Curing and safety

• 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.

Finishing a tanked room

• 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.

How much do I need?

• 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

Get advice before you start

• 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