House foundations in Batumi: chosen by the ground, built and priced

Where choosing a foundation starts

The foundation type is chosen by the ground, not by the site foreman or the client. Along the Adjara coast neighbouring plots can be completely different: one has dense clay a metre down, the next has fill and sand with water, a third is a slope where the layers lie at an angle. So we start with a ground survey, and only from its report does the structural engineer design the foundation for the weight of the house and the seismic load.

We design to the Georgian seismic building code. In an earthquake the foundation works together with the frame, so sections, reinforcement and the connection to the columns come from the calculation, not from what the neighbour did. We explain what keeps a house standing in an earthquake on the page about earthquake-resistant construction.

Which house foundation in Batumi suits your ground

How a concrete slab foundation differs from piles in ground, water and cost is covered in the comparison of pile and slab foundations. If the plot has a level difference, read separately about the foundation on a slope: most of the money there goes not into piles but into retaining walls and drainage.

Groundwater, salt and downpours

By the sea the groundwater sits close to the surface, and after the autumn downpours it rises further. If the ground survey shows water that is aggressive to concrete, the engineer specifies a more resistant concrete and a thicker cover over the reinforcement. This is not the place to save: rust inside concrete splits it from within, and the only repair is to open it up.

The second thing we settle at the design stage is where water leaves the plot. Perimeter drainage, stormwater drains and the paved apron are cheaper at foundation stage, while an excavator can still get round the plot. We apply foundation waterproofing on the outside, the side the water pushes from, and take it up the plinth above the splash line from the apron.

What goes into the foundation before the pour

Drilling concrete later is expensive and risky, so everything that passes through the foundation is placed in advance, following the services layout:

• sleeves for the water supply, sewer, power cable and communications;
• starter bars for columns and walls, from the setting-out drawing;
• the earthing loop, if the design includes one;
• vents for a ventilated crawl space under a pile foundation;
• cast-in fixings for the staircase, porch and terrace.

Before the pour the site foreman photographs the reinforcement and sleeves, you get the photos in the weekly report and can ask to see any detail on video. Until the reinforcement is signed off, we do not order concrete.

How the work goes on site

A surveyor sets out the house grid from points tied to the plot boundaries. Then come the excavation or trenches, a compacted bed and concrete blinding, on which the formwork goes up and the reinforcement is tied. Concrete comes from a plant with a batch certificate and is pumped in one shift, so there are no cold joints where the engineer did not plan any.

We do not plan a pour for a downpour: rain washes cement out of the surface and leaves the top layer weak. After the pour the concrete is kept damp for several days and not loaded, and the formwork comes off once it reaches the strength set in the design. In summer heat we water and cover it, otherwise the surface cracks before the concrete has gained its strength.

If another contractor has already poured the foundation

Sometimes a plot is bought with a foundation in place, or the first contractor left after the pour. Before putting the shell on such a base we check it: geometry and levels, starter bars, the concrete at broken edges, the waterproofing, whether there are sleeves. If there is a design we compare against it, if not we measure it and show it to the structural engineer. Whatever we find goes into a report with photos. Sometimes improvements are enough, sometimes foundation underpinning is needed, and that is decided before the first course of blockwork, not after the cracks.

How much house foundations in Batumi cost

A strip foundation costs from 660 ₾ per m³ of concrete with materials, a concrete slab from 390 ₾ per m² of house footprint, a pile and ground beam foundation from 300 ₾ per m² of footprint, and a single bored pile from 540 ₾. These prices include formwork, reinforcement, concrete and sleeves. Excavation, drainage, waterproofing and insulation are separate estimate lines, and the ground survey, from 3,000 ₾ per plot, is separate too.

The estimate depends most on the depth of dense ground, water, the level difference and access for the concrete truck and the drilling rig. For a two-storey 150 m² house, a slab on a level dry plot and piles on a slope can differ several times over. We send a preliminary estimate from the house plan and photos of the plot within 24 hours on working days; the final cost is set from the design and ground survey, after a site visit and agreement on the estimate.