Strip foundation in Batumi: design, reinforcement, price per m³

Where a strip foundation fits

A strip foundation runs under all the load-bearing walls and columns of the house as one closed reinforced concrete band. It works well where dense ground lies shallow and level and the water stays below the footing: on the terraces above the coast, in the foothills, on older plots with clay. For a two-storey house of blocks in a cast-in-place concrete frame it comes out cheaper than a slab, because concrete goes only where there is load.

On the seafront with sand and high groundwater the strip loses out. A narrow footing presses on weak ground harder than a continuous slab, and the ground floor still has to be built separately. There the engineer more often chooses a slab foundation or piles.

Strip foundation in Batumi: depth and width

Frost hardly penetrates the ground in Batumi, so the depth of the strip is set not by freezing but by the dense layer from the ground survey. We take the footing below the fill and topsoil onto ground that carries the load. The engineer calculates the footing width from the weight of the house and the bearing capacity of the soil, and for seismic loads adds reinforcement and a connection between the strip and the frame columns.

A shallow strip without a calculation, the kind sometimes poured under block houses, does not suit us in a seismic area. In an earthquake such a strip can open up at the corners, and cracks run up the walls. So every corner and junction is reinforced to the drawing, and the strip is closed all round.

Reinforcement, sleeves and vents

The strip cage is tied from longitudinal bars top and bottom and transverse stirrups, with L-shaped bars at the corners so the sides work together. Starter bars for columns and seismic ring beams come out where the setting-out drawing shows. Before the pour we place sleeves in the formwork for water, sewer and cable. If there will be a crawl space under the floor, we build in vents, otherwise damp stays trapped under the house.

Before the concrete arrives we photograph the cage on every side and at the corners. If you are far away, the site foreman walks the strip with you on a video call.

The ground floor on a strip foundation

The strip carries the walls, and the floor between them is built separately. There are two ways: a cast-in-place ground-bearing floor on a compacted bed with insulation and waterproofing, or a cast-in-place floor slab spanning the strip over a ventilated crawl space. The second costs more, but the floor stays dry and warm and the pipes under it remain accessible. On damp plots by the sea we more often recommend a crawl space or a slab.

Waterproofing and water at the strip

On the outside the strip is waterproofed and the plinth insulated with XPS boards. Round the house we lay perimeter drainage below the footing and a paved apron sloping away from the walls. How this layer is built and what to use on wet ground is described on the page about foundation waterproofing.

How much a strip foundation costs

A strip foundation costs from 660 ₾ per m³ of concrete: setting out, formwork, reinforcement cage, vibrated concrete and striking. Earthworks are priced separately, from 39 ₾ per m³ including soil removal, the bed under the strip from 51 ₾ per m², waterproofing from 78 ₾ per m², plinth insulation from 75 ₾ per m². If there is no ground survey yet, it costs from 3,000 ₾ per plot. To compare other options, see the pier foundation for light buildings and the main foundations page. The final cost is set from the design and the volume of concrete, after a site visit and agreement on the estimate.