Foundation waterproofing in Batumi: new houses and wet basements

Foundation waterproofing in Batumi: what water we protect against

The waterproofing material is chosen by the water that reaches the foundation. You can see it in the ground survey report and on site after a good downpour. There are three cases, and in Batumi you meet all three, sometimes on neighbouring plots.

If the house will have a basement or lower ground floor below ground level, we design the waterproofing for the worst case: the water level after the autumn downpours is higher than in the dry month when the survey boreholes were drilled.

How the external layer is built

We apply waterproofing on the outside, the side the water pushes from. Before that the concrete is cleaned, nibs chipped off, honeycombing filled with repair mortar and corners rounded with fillets: membranes do not like sharp edges. Then primer and the layer itself, reinforced at corners and junctions. On top goes protection: a dimpled membrane or insulation boards, so stones in the backfill do not tear the waterproofing.

At the top the layer is taken up the plinth above the splash line from the paved apron and covered with a drip or cladding. Under the walls, along the top of the foundation, we lay a horizontal damp-proof course so moisture does not rise through the concrete into the masonry.

The weak points: joints, entries, corners

Water almost never passes through an intact membrane. It comes through construction joints, pipe entries and corners where the layer was not pressed home. So:

• waterstops go into construction joints between pours before the concrete;
• water, sewer and cable entries pass through sleeves with seals, not sealant smeared round the pipe;
• an extra strip is bonded onto inside and outside corners;
• the vertical layer laps over the edge left out from under the slab.

Every detail is photographed before backfill. For a strip foundation, a slab and ground beams on piles the layer follows the same logic but sits in a different place: for a slab the main sheet is underneath, for a strip it is on the sides.

Drainage and the paved apron work together with the waterproofing

Waterproofing holds water back, drainage carries it away. Perimeter drainage goes below the foundation footing in crushed stone and geotextile, falling to a chamber or discharge point. The paved apron slopes away from the wall with a movement joint at the plinth, and roof downpipes are connected to the storm drains rather than discharged onto the apron. On plots by the sea where the water sits high, even a good membrane works under constant pressure without drainage. How this works for a house on the seafront is described on the page about seaside houses.

If the house is built and the basement gets wet

First we look for where the water comes from: a leaking pipe, a downpipe discharging at the wall, a paved apron sloping towards the house, or groundwater. Sometimes it is enough to correct the apron and lead the downpipes away. If water comes through the wall, we dig the foundation out from the outside in sections, dry it, repair it and lay a new layer. Where digging outside is impossible, cracks and joints are sealed by injection from inside. For old houses this is often part of an old house renovation.

How much foundation waterproofing costs

Foundation and plinth waterproofing costs from 78 ₾ per m² of surface: cleaning, primer, a torch-on or coating layer and protection. Plinth insulation with XPS boards is from 75 ₾ per m², perimeter drainage from 87 ₾ per linear metre, the paved apron from 93 ₾ per m², injection of a crack or joint from 155 ₾ per linear metre, and digging out at an existing house from 39 ₾ per m³. The final cost is set after an inspection and agreement on the estimate.