Bathroom waterproofing in Batumi: showers, WCs and balconies

Where an apartment needs waterproofing

The layer is needed wherever water can end up on the floor and soak through the slab to the neighbours: in the shower and by the bath, across the bathroom floor, under the washing machine, in a storage room with a water heater, and on the balcony. We take it 20–30 cm up the walls in the bathroom, 15–20 cm up the walls and under the door threshold on the balcony, and up to the height of the shower head in the shower and above the bath.

The layer has the hardest job in a walk-in shower without a tray, where it is tied up with the fall, the floor drain and the floor height. How we work these out is covered on the page about the walk-in shower with a floor drain, and the full order of work is described in the section on complete bathroom renovation.

Polymer membrane, cementitious coating or liquid rubber

The polymer membrane works indoors only and copes well with a floor that gets wet from time to time. In a walk-in shower without a tray, water stands on the floor every day, and on a balcony the layer has to take sun, rain and swings in temperature. In both places we use a flexible cementitious coating: it is thicker, at least 2 mm, and bridges cracks in the slab. The fall, the drip profile and the threshold are covered on the page about balcony renovation.

Preparing the base

Before the first coat:

• we measure the moisture with a meter: the screed and plaster must be dry for any compound. For the cementitious coating we also dampen the surface before application, without leaving puddles, so that the concrete doesn't draw the water out of the layer;
• we remove the dust, cut back lumps and ridges, and fill voids and cracks;
• in the shower area we replace gypsum plaster with cement plaster, and only moisture-resistant plasterboard is used there;
• we chamfer external corners and form a fillet or lay tape in internal ones: on a sharp corner the layer tears first;
• we prime with a product from the same system.

How long we dry the screed before waterproofing is explained on the page about screed for tiles.

Tapes, collars and the floor drain

Screed settles, the floor slab deflects, and over time the joint between floor and wall opens up by fractions of a millimetre. A continuous layer cracks at such a joint, so we cover corners, junctions and pipe penetrations with tape and preformed parts.

We bed the tape into the fresh first coat and press it down with a trowel so that no air is left underneath, with an overlap of at least 5 cm. On corners we fit preformed corner pieces: tape folded by hand leaves a crease, and water travels along it under the layer. The collars on the water outlets and the drain flange are bedded in the same way, between the first and second coats.

Along the rim of the bath and shower tray we bond a tape that the tiles later cover. Silicone on top of it is only the second line of defence: in a damp bathroom it ages faster than anything else.

Two coats and drying times

We apply the compound in two coats, the second at right angles to the first, to close up pores and missed spots. We check the thickness by consumption. According to the technical data sheets of the products we use, two coats of the polymer membrane take about 1.4 kg per m², and the cementitious coating at 2 mm takes about 3.2 kg. If noticeably less has gone on, the layer is too thin, and we apply another coat.

The polymer membrane needs about two hours between coats, and tiles go on it the next day. The cementitious coating needs about three hours between coats at +20 °C and three days before tiling, and all that time we keep it covered from sun and rain. So in a bathroom with the polymer membrane, application and the water test usually fit into 2–3 days, while in a walk-in shower without a tray and on a balcony, where the cementitious coating goes on, the stage takes longer, especially in cold, damp weather.

Water test and sign-off of the layer

Once the layer has cured, we plug the floor drain, put a temporary upstand along the edge, at the bathroom door or along the edge of the balcony, and flood the floor until the water covers the highest point. We mark the level on the wall with a marker and check it against the mark 24 hours later. At sign-off, on site or by video, we check that:

• the base doesn't show through anywhere, and there are no pinholes or bubbles in the layer;
• the tapes are embedded in the compound, their edges aren't lifting and there are no creases;
• the layer goes up the walls to the agreed height and runs under the threshold;
• the collars and the drain flange are coated over with compound;
• after 24 hours under water the level hasn't dropped and it is dry below.

We fix any fault straight away, while it isn't under tiles yet. Tiles go on a flexible adhesive compatible with the compound; more on this in the section on tile laying.

How much bathroom and balcony waterproofing costs in Batumi

Labour for a two-coat liquid waterproofing membrane costs from 30 ₾ per m², and up to 42 ₾ with our materials. Waterproofing tape at corners and junctions is a separate line, at 14–18 ₾ per linear metre.

A complete 4–6 m² bathroom, with the floor, walls up to 20–30 cm and the shower area, comes to 750–1,080 ₾. Balcony waterproofing with a cementitious coating or liquid rubber costs 69–96 ₾ per m² with materials. Screed, if we redo it, is priced separately.

A walk-in shower without a tray, many pipe outlets and corners, and cracks and gypsum plaster in the wet area all push the price up. The final cost is set after the site measurement and once the estimate is agreed, and the price of the stage in the contract doesn't change unless the scope does.