Expanded clay block house in Batumi and Adjara

An expanded clay block house is built from wall blocks made of cement and granules of expanded clay, which is clay fired until it swells. These blocks are heavier and stronger than aerated concrete, masonry laid on mortar is forgiving of irregularities, and an anchor holds firmly in the dense block. On the other hand, it is noticeably colder, so the wall needs an insulated facade. In Adjara this method has one more peculiarity: the blocks themselves are harder to find here than aerated concrete, and that is where we start any calculation.

Expanded clay concrete in Georgia: where to get the blocks and what can replace them

We don't usually find expanded clay concrete blocks in Georgian builders' merchant chains. A batch for a house is ordered from a manufacturer for the specific project or brought in from far away, and that time has to be built into the schedule before the foundations. So before the design we check who has blocks of the required density, whether there will be enough for the whole house from one batch, and whether test reports come with them.

There is a close local equivalent: pumice blocks. They too are made of lightweight concrete with a porous aggregate, only instead of expanded clay they contain volcanic rock, pumice or slag, and Georgia has deposits of these. Hollow pumice blocks are made by Georgian manufacturers and are easier to find than expanded clay concrete. Switching from one block to the other usually doesn't require changing the layout, but the structural engineer checks the density and strength of the new block against the batch test reports. If you'd like a warmer wall, we price an option in aerated concrete in a frame.

How an expanded clay block wall is built

The standard wall block, 390×190×188 mm, comes solid or hollow. The thickness of the masonry and insulation for an external wall is set by the thermal calculation, while internal walls of the same blocks come out heavy and good at stopping voices. In a guest house you notice this between rooms: you hear the neighbours less through a wall like this than through aerated concrete.

We lay the blocks on cement-sand mortar. The joint is colder than the block, but under a layer of mineral wool on the outside this matters less. On hollow blocks the mortar goes in strips along the outer shells, and the top course under a ring beam or floor slab is covered with mesh so that the concrete doesn't run into the voids.

Wall weight, the frame and seismic loads

An expanded clay concrete wall is often twice as heavy as an aerated concrete wall of the same thickness. In an earthquake the force acting on a house grows with its mass, so the structural engineer designs the frame and foundations under such walls for a greater load. On weak ground and on a slope this shows in the estimate straight away.

The voids in the blocks offer a convenient way to strengthen the masonry. If their size allows, the voids at the corners, by openings and next to columns are reinforced with vertical bars and filled with concrete, which gives cores without separate formwork. Where they are needed and how many is decided by the calculation. We tie the masonry to the columns of the cast-in-place concrete frame as the design specifies, and build a single-storey building without a frame only with a seismic ring beam along the top of the walls.

Moisture and an insulated facade

Expanded clay concrete takes up water more slowly than aerated concrete and releases it faster, so it copes better with building in the rainy season. Its weak point is a different one: without insulation the wall is cold. In winter, in a heated room, warm humid air touches the cold surface, and mould appears in the corners and behind cupboards along the external walls.

We put the insulation on the outside, not the inside. That way the cold zone moves into the layer of wool, and the masonry itself stays warm and dry. Usually this is mineral wool with a vapour-permeable render, or a ventilated facade for walls facing the sea. How to choose between them is covered in the comparison of the two facade types. Insulation fixings and subframe anchors for hollow blocks have a long expansion zone, so that they don't end up in a void and spin.

Fixings, chases and building services

In solid blocks, heavy items hold on ordinary expansion anchors. Hollow blocks need long anchors that expand in several shells at once, or chemical anchors with mesh sleeves. We try to hang the water heater and kitchen cabinets where the masonry is solid or the voids are filled with concrete, and mark those places on the plan before laying starts.

Chases for cables and pipes in expanded clay concrete are cut with a diamond disc: the block is dense, and the expanded clay granules crumble unevenly, so a chase cut by hand comes out ragged. We lay the runs to a diagram and photograph them before plastering, and these photos then go into the handover file.

Where expanded clay concrete fits

• a house with an insulated facade, where the owner wants a heavy wall that holds fixings and stops voices;
• walls between rooms and between guest rooms you rent out;
• a garage, workshop, boundary wall or outbuildings, where warmth matters less;
• a house whose design has already been done for lightweight concrete with a porous aggregate.

We don't recommend it for uninsulated walls in a house lived in during winter, or for plots with weak ground, where every tonne of wall makes the foundations more expensive. Clay blocks also give a warm masonry wall: they are lighter and warmer than expanded clay concrete, but brittle, and they should be laid by a crew that has worked with them before.

How much an expanded clay concrete house costs

The shell of an expanded clay concrete block house costs from 720 ₾ per m²: foundations, masonry with ring beams or in a cast-in-place concrete frame, floor slabs and roof. The insulated facade is not included in this price, and neither are windows, building services or finishing, yet in a home a wall like this doesn't work without a facade. A turnkey ETICS facade costs from 205 ₾ per m² of wall.

Laying an expanded clay concrete block wall with materials starts from 150 ₾ per m², and a seismic ring beam on the masonry from 100 ₾ per linear metre. For comparison, an aerated concrete shell starts from 750 ₾ per m², and 30 cm aerated concrete masonry from 145 ₾ per m². An expanded clay concrete shell comes out slightly cheaper, but insulation over the whole wall usually eats up that difference, so we compare the options on a finished wall with its facade. A turnkey house costs from 1,200 ₾ per m² at economy level and from 1,680 ₾ at mid-range level.

The price depends on how available the blocks are and on delivery, the ground, the facade type and how complex the plan is. We'll send a preliminary estimate from the house plan within 24 hours on business days. The final cost is set on the basis of the design, after a visit to the plot and once the estimate is agreed.