How to choose a waterproofing product: membrane, cementitious or bentonite

The choice depends on where the water to be stopped is coming from. On roofs and terraces an elastic liquid membrane is usually used, applied in several coats with a reinforcing mesh. Under the tiles of bathrooms and balconies you need a two-component cementitious waterproofing product, recognisable by the EN 14891 marking. Against groundwater on foundations and basements, bentonite sheets are laid against the pour, overlapped. Packs range from 10 m rolls to 25 kg bags, from 20 kg tins to 60 kg drums: the type of product matters more than the size.

The types

• Liquid membrane: a paste or liquid product that forms a continuous membrane. In the collection there are water-based bituminous liquid membranes, like the one by Edilchimica, and the liquid membranes of the Kimicover line. It is used on roofs, terraces and exposed surfaces.
• Cementitious waterproofing: it is prepared with the stated mixing ratio, for example components A and B in a 3:1, 4:1 or 1:1 ratio. It is used on substrates to be tiled, such as bathrooms, showers and balconies.
• Water-repellent waterproofing: it treats the surface without forming a truly thick layer. It suits walls and materials that must repel rain water.
• Bentonite waterproofing: sheets or rolls based on bentonite, laid against the pour of foundations and below-ground structures.
• Bituminous spray paint: for touch-ups and small surfaces, where a tin would be wasteful.
• System accessories: primer, joints and stabilising mat. They do not waterproof on their own, but they are needed to make the system work.

How to choose by job

If the roof will not be walked on and stays exposed to the sun, choose a suitable colour: the collection has grey, black, red, clear and paintable black products. The Kimicover line has several models, including Duo, Blindo and K80: read the data sheet of each one to find out which substrate it should be used on.

The features to look at

• Standards: EN 1504-2 (concrete protection) and EN 14891 (waterproofing under tiles) appear in the collection, sometimes together on the same product. If you need to tile on top, look at the second.
• Mixing ratio: for two-component products it appears as A : B = 3 : 1, 4 : 1 or 1 : 1. Follow it by weight, without estimating by eye.
• Product type: liquid membrane, cementitious adhesive, liquid coating or bituminous paint. They are different families, not interchangeable.
• Pack size: tin or pail of 20-25 kg, 60 kg drum, 25 kg bag, 320 ml cartridge, 10 m roll. Choose according to the surface: too much leftover product dries out.
• Colour and finish: it matters whether the surface stays exposed or is to be covered or painted.
• Made in Italy: some lines state 100% Italian production, a useful fact if the specification requires it.

Common mistakes

• Applying on a dirty or friable substrate: the layer comes off together with the dust. The substrate must be clean and sound.
• Skipping the primer when the data sheet calls for it.
• Forgetting mesh and sealing tape at corners, joints and junctions: that is where the water gets in.
• Applying a single thick coat instead of several criss-cross coats, respecting the thicknesses and times on the technical data sheet.
• Working when rain is imminent or in frost.

Frequently asked questions

Can I tile over a liquid membrane?

It depends on the product. To tile you need a waterproofing product designed for this use, usually cementitious and with the EN 14891 marking. Check the technical data sheet.

How many coats are needed?

Usually several criss-cross coats, but the number and thickness depend on the product. Follow the technical data sheet.

Is the reinforcing mesh needed?

Yes, at corners, joints and junctions, where the substrate moves or changes direction. Mesh or sealing tape is used.

Can I use the same product on a roof and on foundations?

Generally not. A membrane for roofs and a product for below-ground structures work differently: check the intended use on the technical data sheet.

What is it applied with?

By brush, roller, trowel or spray, depending on the product.

You will find all the products in the waterproofing products collection: if you do not know which one suits your substrate, request a quote or advice from the AMES technicians.