Description
Crommelin One Coat Rapid is a heavy-duty, liquid-applied waterproofing membrane that goes down before tiling, supplied here in a 1L pail for showers, laundries and other small wet-area jobs. It is a polyurethane-modified grey membrane that cures into a seamless, flexible layer under tile, so there are no laps or joins in the finished surface.
About the formula
The membrane is polyurethane modified for high flexibility and reinforced for strength and durability. Crommelin states it stretches by more than 300% and stays flexible over time, which helps it cope with minor substrate movement. It dries to a keyed, slightly textured surface that gives cement-based tile adhesive something to grip. It is made to be used with cement-based tile adhesives that comply with AS 2358, and it is designed to meet AS 4858 and AS 3740. It is water based, so tools clean up with water.
Where to use it
Indoors: showers, bathrooms, laundries and kitchens, on both walls and floors, before tiling.
Outdoors: balconies, patios and podiums under tile, where the membrane is covered by the tile finish.
Suitable substrates include concrete, cement render and screeds, plasterboard and wet-area plasterboard, suitably prepared compressed fibre cement sheet, timber, plywood, wet-area particleboard and steel.
How to use it
Surfaces need to be sound, clean and dry, with loose or crumbling material removed first. New concrete should have cured for at least 28 days before coating. Where the manufacturer's data sheet calls for a surface primer, use a 1:1 dilution of the membrane with water and let it dry. On walls, one coat is enough, and Crommelin quotes coverage of up to 2m² per litre. Floors need more material per square metre, and complex or irregular surfaces may need extra coats, so check the technical data sheet for your job. Allow good airflow while it cures. Once the membrane has cured, a flood test is described in the manufacturer's data sheet: water about 25mm deep for 2 hours, removed straight afterwards. Clean tools with water before the membrane dries. Uncured material can be removed with warm water and detergent.
Important notes
This membrane is not designed to go directly onto white-set plaster. Prime that surface first with a coat of Crommelin Next Day New Concrete Sealer and let it dry. Full cure takes about 7 days. Re-coat and cure times get longer in cold, humid or still conditions. Tile over the membrane so it is not left exposed. Waterproofing wet areas is regulated work in many parts of Australia, so check local requirements and follow the manufacturer's full instructions.
Specifications
| Brand |
Crommelin |
| Product |
One Coat Rapid Under-tile Waterproofing Membrane |
| Pack |
1L pail |
| Colour |
Grey |
| Base |
Polyurethane-modified, liquid applied, water clean up |
| Elongation |
Over 300% |
| Coverage |
Up to 2m² per litre (see data sheet for floors and irregular surfaces) |
| Full cure |
About 7 days |
| Standards |
Designed to comply with AS 4858 and AS 3740 |
| Use |
Interior and exterior under-tile applications |
Safety
Use it with good general ventilation, avoid prolonged skin and eye contact, and wash your hands after use. Store the pail sealed in a cool, dry place. Refer to the Safety Data Sheet (SDS) for full details.
