ALKA product reference
ALKA 305
Solvent-Based, One-Component Polyurethane Primer for Waterproofing Membranes
Alka-305 is a high-performance, hand-applied, solvent-based, single-pack polyurethane primer for bonding waterproofing membranes to concrete.
It also acts as a concrete sealer.
Pack size: 15L Drum

Overview
Usage
Alka 305 is a multipurpose waterproofing primer that can be used in:
- Showers, Bathrooms,
- Under Tiles,
- Balconies, terraces,
- Planter Boxes,
- Roofings,
- Flower Beds,
- Kitchens,
- Pools.
Advantages
- Polyurethane modified for fast-re coating and easy film build,
- Permanent flexibility with high elongation.
- Suitable for use in conjunction with all cement-based tile adhesives that conform to AS2358.
- Dries to a keyed finish to promote direct tile adhesion
- Seamless application for leak-free performance.
Packaging
15 Litres / 15 Kg drums
Colour
– Grey
Product Details
Shelf life: 9 months
Storage conditions
Store away from direct sunlight and away from naked flames, sparks, and heating.
Flash point >25 C
Density: 0.98-1.02 Kg/L
Application
Curing time
Cured Overnight
Cured Overnight
Waiting time for overcoating
Between 4 – 48 hours after application
Between 4 – 48 hours after application
Consumption
2 coats of a minimum of 0.8L/m2 (1.04 kg/m2) each are required to achieve a 1.2 mm dry film thickness (DFT).
2 coats of a minimum of 0.8L/m2 (1.04 kg/m2) each are required to achieve a 1.2 mm dry film thickness (DFT).
Coats – 2 to 3 normally
APPLICATION INSTRUCTIONS
Alka 305 is supplied in ready-to-use pails.
Alka 305 is supplied in ready-to-use pails.
Preparation:
Surface must be clean, sound, smooth and dust-free as well as oil-free.
A compatible primer. Epoxy should be applied to ensure membrane adhesion to the substrate and to prevent outgassing from the concrete.
In the case of high porosity, wet concrete (humidity >5%) or in any doubt, it is recommended to use a hydro-epoxy primer. Compatibility of the primer with the membrane must be checked prior to application.
Surface must be clean, sound, smooth and dust-free as well as oil-free.
A compatible primer. Epoxy should be applied to ensure membrane adhesion to the substrate and to prevent outgassing from the concrete.
In the case of high porosity, wet concrete (humidity >5%) or in any doubt, it is recommended to use a hydro-epoxy primer. Compatibility of the primer with the membrane must be checked prior to application.
Alka 305 can be applied with a brush or a roller to the desired thickness.
2 coats of 0.8 L/m2 (1.04 kg/m2) are required to achieve a dry film thickness (DFT) of 1.2 mm. For UV resistance, coating thickness must abide by the numbers given on this Technical Datasheet. A thinner coating will result in premature degradation. Application temperature of Alka 305 is >5°C to 35°C.
Alka 305 can be subject to light foot traffic after 24 hours.
2 coats of 0.8 L/m2 (1.04 kg/m2) are required to achieve a dry film thickness (DFT) of 1.2 mm. For UV resistance, coating thickness must abide by the numbers given on this Technical Datasheet. A thinner coating will result in premature degradation. Application temperature of Alka 305 is >5°C to 35°C.
Alka 305 can be subject to light foot traffic after 24 hours.
Clean-up
Reusable tools should be cleaned carefully with Xylene or MEK before curing.
Reusable tools should be cleaned carefully with Xylene or MEK before curing.