House construction methods in Batumi and how to choose one

Almost any construction method you know from Europe or from your own country can be used here too. But house construction methods in Batumi have to be judged with the location in mind. A house here is designed to the Georgian seismic building code PN 01.01-09. It has to stand up to more than 2,400 mm of rain a year and 70–80% humidity, and, by the sea, to salty air as well. So for every method we ask two questions: how it will behave in an earthquake, and what water and salt will do to it over the years.

What narrows down the choice

We choose the wall material last. First we look at the plot and at how the house will be used, and these conditions rule out some of the options:

• The heavier the house, the greater the force acting on it in an earthquake, and the stronger the frame and foundations have to be. Light systems have a different weak point: the anchoring to the foundations and the bracing.
• Timber, aerated concrete and wood-chip concrete absorb moisture, and moisture makes steel rust. Damp is less of a threat to concrete and fired clay, but they too need a facade that doesn't hold water.
• Closer to the sea, salt speeds up corrosion, so a steel frame, light gauge steel framing (LGS) and any fixings need more protection than usual.
• On a slope, every tonne of the house shows up in the foundations and retaining structures, so a light frame often turns out simpler there.
• In a house you rent out, heavy walls and a solid floor slab stop voices between rooms, and a floating screed deals with footsteps. In a frame house, sound insulation comes from layers of mineral wool and double boarding.

Then there is maintenance. If you live abroad, the house spends the winter without its owner. A masonry house copes with this more easily, while a timber facade and steel joints need someone to inspect them every season.

Cast-in-place concrete and masonry

In a cast-in-place concrete house, the concrete is poured on the plot, and the walls and floor slabs work together as one rigid box. Solid concrete walls are heavy and need a lot of reinforcement, so they are usually kept for the lower ground floor on a slope, where the wall also holds back the soil. In a house with a concrete frame and block or brick walls, only the columns, beams and slabs are concrete, and the wall material is chosen separately.

Precast concrete and panel houses are assembled by crane from factory-made elements. This suits a series of identical houses, but not a single house on a slope: the panels have to be delivered, and in a seismic zone the joints need their own calculation.

Blocks and brick

Aerated concrete and foam concrete blocks make a warm wall that weighs little. Both are porous and take up water, so they need a facade on the outside, and a wall left uncovered before the long rains takes a long time to dry out. Expanded clay concrete is heavier and stronger, but colder. Wood-chip concrete, a mix of wood chips and cement, behaves almost like timber if nothing protects it on the outside.

Porous clay blocks are brittle. They are cut with a saw and laid with thin joints or a thermal mortar, and the crew needs experience with this particular material. By the sea, facing brick can develop white salt deposits (efflorescence) if there is no damp-proof course at the plinth. And in a seismic zone, any blockwork is held in place by a frame, or by reinforced ring beams and cores, as the calculation requires.

Frame systems: steel, LGS, aluminium and timber

A frame house is assembled from posts and beams, and the walls are filled with insulation and covered with boards. It is light, there is almost no wet work, and rain disrupts the schedule less than on a cast-in-place concrete build. A frame of hot-rolled steel sections spans large spaces, so it is used for commercial buildings and houses with panoramic glazing. LGS, made of thin cold-formed steel sections, comes from the factory galvanised and cut precisely to size.

By the sea, steel needs hot-dip galvanising or a thick zinc coating on the sections, durable paint and treated cut edges, and the joints should be inspected regularly. Aluminium does not rust, and it works well for pergolas and glazed terraces. But near the sea bare aluminium develops pitting corrosion, so the sections are anodised or powder-coated. They are also kept apart from steel fixings with isolating pads, because in salty air aluminium in contact with steel breaks down faster.

Timber frame and SIP panels

Timber frame and prefabricated panel houses are possible here if the timber is kiln-dried and treated with preservative, and the layers of the wall go in the right order. When the air conditioning runs in summer, moisture moves into the wall from outside, and in winter, with the heating on, it moves outwards. So an ordinary vapour barrier on the inside does not always work, and sometimes a membrane with variable vapour permeability is needed. SIP panels, two OSB boards with expanded polystyrene in between, go up quickly, but the wall lets almost no vapour through, and without mechanical supply and extract ventilation the house stays damp.

Solid wood: profiled timber, logs, CLT and half-timbering

Solid wood works in Batumi, but it needs more care than masonry. Profiled timber and machine-rounded logs at natural moisture content shrink, so windows and doors are fitted in special frames that allow the walls to move, and some of the finishing has to wait until the log walls have settled. Glulam and CLT panels made from dried lamellas hardly shrink and keep their shape, but the material costs more and the design has to be precise, because the parts are cut at the factory.

Any timber house here needs a high plinth, wide roof overhangs and a protective finish on the facade that will have to be renewed. In an earthquake a light, flexible timber house behaves well, but the structural engineer still calculates how the walls are fixed. Half-timbering, a frame of visible beams with infill between them, needs more attention: the beams take the rain and sun, so they have to be inspected more often.

Fast and experimental methods

A modular house is made of factory-built units, which are lifted into place on the plot by crane and connected to the utilities. In Batumi the road decides: a module has to get down the street and turn at the gate, and on a slope the crane needs a level standing area. Quick-build steel-frame buildings with sandwich panels suit a warehouse, workshop or shop that needs a large open space without wet work.

Containers, unusual shapes and 3D printing

A shipping container house by the sea has two problems: the steel rusts, and condensation collects on the cold walls inside. It needs anti-corrosion protection, insulation without gaps and ventilation, and every window opening is reinforced with a frame.

Domes, A-frames and barn houses are more about shape than construction method, and they are built on a timber or steel frame. A dome has many joints where water can get in during wind-driven rain. In an A-frame the roof also forms the walls, and a barn house usually has no overhangs, so only the facade protects the walls from rain.

Permanent formwork made of expanded polystyrene or wood-cement blocks, once filled with reinforced concrete, gives what is essentially a cast-in-place wall with built-in insulation, and the engineer calculates it the same way. 3D-printed houses are an experiment for now. The walls are printed from a concrete mix, but seismic loads still call for reinforcement and calculations, so we first check whether the mix and the structure have been tested.

House construction methods in Batumi: how we choose

We follow the same process for any method. First come the ground survey and the brief: who will live in the house, whether it will be rented out and whether you come in winter. Then the structural engineer outlines two or three schemes that meet the code on this ground, we compare their estimates and timelines, and you decide on the basis of the figures.

Energy-efficient and passive houses

Energy efficiency can be added to any of these methods. In Batumi that means continuous insulation without thermal bridges, well-installed windows, sun shading on the south and west facades, and mechanical ventilation with heat recovery, which may need dehumidification in the humid months. A passive house also needs an airtight envelope, which is checked with an air tightness test.