Waterproofing a wet room before tiling: the Kerakoll way

Why this brand · Kerakoll #2 · The brands Saniso stocks, and why  

Waterproofing a wet room before tiling decides how long the wall and floor behind your tiles stay dry. Tiles and grout look after the surface. What protects everything underneath is the waterproofing layer, and it only works when the corners, drains and joints are sealed as carefully as the flat areas. In this second edition of our series Why this brand we look at how Kerakoll builds that layer for a shower, a bathroom or a full wet room: a membrane, tapes and corners for the joints, flanges and drains for the details, and a gel adhesive made to go on top. You'll see which products Saniso carries, which ones have a listed price today, and how it all connects to tiling, grouting and sealing.

Why does a wet room or shower need waterproofing under the tiles?

In a shower, water hits the walls and floor every single day. Tiles shed most of it and grout joints are made to cope with it. Corners, wall-to-floor junctions, drains and pipe penetrations are the places where water can still reach what is behind the tiles. A waterproofing layer under the tiles keeps the substrate dry, and that is why it is added before the first tile goes on. The Nanodefense Eco product page describes its use for absorbent substrates in damp environments, a good reminder that the substrate matters as much as the tiles. Planning a whole bathroom? Start with our guide on planning your bathroom renovation.

What does the Kerakoll waterproofing system look like, layer by layer?

Here is how the layers fit together. How to lay the tiles themselves (layout, notched trowel, spacers, grouting) is explained in our guide on how to tile a wall, step by step, and the Kerakoll tile system as a whole in Why Kerakoll? The system behind a tidy tile job, so we keep this to the waterproofing part.

Which Kerakoll waterproofing product fits your situation?

The overview below uses the descriptions on the product pages at saniso.nl. The Aquastop products are listed without a fixed price: open the product page and use the quote form to ask for a price for your quantity. Nanodefense Eco has its own product page, where you can check the current availability and price.

What are Kerakoll's strengths and opportunities for waterproofing your wet room? (a positive SWOT)

A SWOT usually looks at a brand from a boardroom. We wrote this one for the person holding the trowel: what the range does well, where it opens doors for you, where it fits best and why we stock it.

How do you go about waterproofing a wet room before tiling, step by step?

This is the general order of work. It is an overview, not a replacement for the technical data sheets: layer thickness, number of coats, mesh and waiting times depend on the product and the substrate, so read the sheet of each product before you start.

1. Check the substrate. It should be sound, clean and flat. Remove dust and loose material.
2. Prime where the sheet asks for it. Dusty, porous or smooth substrates benefit from a primer such as Active Prime Fix or Active Prime Grip.
3. Seal the joints. Tapes and corner pieces (Aquastop 120, Aquastop Plus 120) go on the wall-to-floor junction, the inside and outside corners and the movement joints, bonded as the product sheet describes.
4. Seal pipes and drains. Flanges (Aquastop Flangia, Aquastop Plus Flangia) go around pipes and drain outlets, and the drain itself connects to the membrane.
5. Apply the membrane. Nanodefense Eco is applied with a spreader or roller. Aquastop Nanoflex and Aquastop Flex can be combined with the Aquastop AR1 mesh, which also helps you check that you applied the right amount.
6. Let it dry. Wait as long as the technical sheet says before you tile.
7. Tile with a Biogel gel adhesive. The method is the same as for any wall or floor: see our guide on how to tile a wall, step by step.
8. Grout and seal. Finish the joints with a water-resistant grout and close the corners with a sealant in the grout colour.

How do you seal drains, pipes, corners and joints?

The details are where a waterproofing job succeeds. For the joints, Aquastop 120 and Aquastop Plus 120 are the tape and corner pieces: Aquastop 120 is described as continuous waterproofing even at expansion joints, and Aquastop Plus 120 as a three-layer tape with an alkali-resistant TPE core. Around pipes and drain outlets, the flanges Aquastop Flangia and Aquastop Plus Flangia come in 120×120 and 350×350 mm (Flangia) and 200×200 and 250×250 mm (Plus Flangia). For the drain itself, Aquaform SD and VD are a lateral drain (74 mm high, 50 mm outlet, removable siphon) and a vertical drain (141 mm high, 75 mm outlet) whose connection membrane is described as fully compatible with the Aquastop waterproofing systems. Aquastop Fix is the waterproof sealant for Aquastop tapes and membranes, and Aquastop Nanosil is a neutral silane waterproof sealant for through elements and installations.

How do you prepare the substrate with a Kerakoll primer?

A primer is the step people skip most often, while it decides how well the next layer holds. It binds dust, evens out how much moisture the substrate draws and helps on smooth surfaces. Check the technical sheet of your waterproofing product for the substrates that need one.

Which tile adhesive goes on top of the waterproofing?

The Kerakoll waterproofing pages point to the Biogel gel adhesives: Aquastop Nanoflex is intended for tile laying with them, Aquastop Flex lists excellent compatibility with Biogel cement-based adhesives and Aquastop Nanogum names Biogel Extreme. Both are in the shop at a listed price.

Which grout and sealant suit a shower?

In a shower the grout has to cope with water every day. Fugalite Color is a waterproof, non-absorbent resin grout in 50 colours, and Silicone Color is the sealant in the same colours for corners and movement joints, so everything matches. Which colour suits your tiles, and how the Color Fill range fits together, is covered in Kerakoll Color Fill: grout and sealant.

Can you waterproof a shower yourself?

Yes, many DIYers do. The Biogel adhesives and Aquastop products are made to be applied with a spreader, roller or trowel, and the product pages explain what each one is for. The key is to follow the technical sheet exactly and to take your time with the corners, the drain and the wall-to-floor junction. If you are unsure about a detail, ask us before you order or have a tiler check the plan.

How much material do you need?

The product pages give the coverage. A worked example for 10 m² of wall and floor: Active Prime Fix covers about 0.1–0.2 kg/m², so 1–2 kg, and one 5 kg bucket is enough. Biogel Ready covers about 1.6 kg/m², so about 16 kg, which is one 17 kg bucket. For the membrane, the quantity depends on the product and the thickness that its technical sheet prescribes, so send us your surface in m² through the quote form and we help you work it out.

Which tips help you get the most out of the Kerakoll waterproofing system?

• Read the technical data sheet of every product before you start.
• Seal the corners, the wall-to-floor junction and the drain first, then the flat areas.
• Order tapes, corner pieces and flanges together with the membrane, so the whole job arrives in one go.
• Choose the grout colour first and order the matching Silicone Color at the same time.
• Take photos of the sealed corners and the drain before you tile: you will be glad you did.

What is the delivery time at Saniso?

Order on a workday before 15:00? Then your order is delivered the next workday, as long as it fits in a parcel. Pallet shipments have a different delivery time. Saniso has thousands of products in stock in the Netherlands. Saniso is on its way to becoming the e-commerce platform for construction across Europe, and already delivers to more than 20 countries.

How do you order at Saniso if you're not a customer yet?

Your first order is easy to place:

1. Create an account via register. Already have an account? Log in here with your email address or phone number.
2. Choose your product and click "Add to cart", or go straight to "Buy now". For products with a quote form, send your request on the product page.
3. Check out: all prices at checkout include VAT.
4. Choose delivery or pickup: have it delivered, or pick up your order for free in our showroom.

How do you stay up to date on offers?

Want to know when there are new offers? Sign up for the newsletter: scroll to the bottom of any page on saniso.nl, enter your email address under "Newsletter" and click "Subscribe". You'll get updates on offers and discount coupons, and we don't spam. With an account you also collect loyalty points for a discount on your next purchase.

More about this in the Saniso FAQ under "How do I sign up for the newsletter?". Questions about ordering, payment, shipping or returns are answered there too.

Frequently asked questions

Header photo: Neil Cooper (the19doors), Unsplash / Wikimedia Commons, CC0. Product images in the header: Kerakoll.

Next in Why this brand: more Kerakoll, starting with levelling a floor before you tile.