Dome house in Georgia: a geodesic frame for the climate of Batumi and Adjara

A dome draws people in with its shape: a round living room, sky in the windows overhead, a house unlike the ones next door. Technically it is a light, rigid shell that, for its weight, stands up well to wind and snow. Its difficulties lie elsewhere: in the joints, in the roof, and in furniture that has no straight wall to stand against.

How a geodesic dome is built

The sphere is assembled from triangles. Struts of several lengths meet at hubs in fives or sixes, and the finer the subdivision, the smoother the dome and the more parts it has. The hubs are steel connectors to which timber struts are fixed, or the frame is assembled from ready-made triangular panels. Every strut has its own number and its own length: a mistake in one part distorts the geometry of its neighbours, and trimming on site can no longer put it right.

At the bottom, the dome bears on a ring plate, and the ring plate on the foundations, with an anchor at every bearing hub. Windows and doors are cut into the facets or built as vertical dormers, and the structural engineer checks each opening separately: a triangle that has been cut out takes part of the shell out of action.

Dome house in Georgia: where to get the frame

We don't know of any manufacturers of dome house kits in Georgia, and a permanent dome house is a rarity here. In Adjara you will come across tent domes for glamping, but these are seasonal structures, not houses. The frame for a permanent house has to be ordered from a manufacturer abroad, together with the drawings, the cutting list and the assembly instructions.

Before the order, our structural engineer checks the kit's calculations against the Georgian seismic building code PN 01.01-09 and against the wind and snow on your plot. If the manufacturer doesn't provide calculations, or has designed the dome only for its own conditions, we settle this first and only then pay for the kit. We design the foundations, junction details, roof, windows and building services ourselves, and assemble the frame to the manufacturer's scheme. While the kit is on its way, we build the foundations on the plot.

Joints and roofing: the main risk of a dome

An ordinary house has two roof slopes and one ridge; a dome has dozens of facets, and each one meets its neighbours at an angle. Wind-driven rain pushes water up the surface, and through a weak joint it gets into the insulation. So under any covering we lay a continuous underlay with every seam sealed, and water-test the dome before the interior finishing.

Asphalt shingles lie well on the facets, but they have to be trimmed at every edge, so there is more waste and more labour than on an ordinary roof. The other route is a continuous welded PVC membrane, as on a flat roof: there are fewer seams, and all of them are welded, but the dome takes on a more technical look. The most vulnerable spots are the windows and dormers. A sloping window in a facet needs a factory flashing kit or precise hand-made flashing, and a vertical dormer also needs a small roof of its own. Water from the whole sphere runs down to the bottom ring, so around the perimeter we fit a flashing and drainage.

Heat, vapour and condensation

Warm, moist air rises to the very top of the dome, to the facets that are coldest in winter. If the vapour barrier lets vapour through in even one triangle, water settles in the insulation of the upper facets, where it stays hidden longest. We tape the inner membrane at every joint between facets, and cut the mineral wool to a template so that the triangles fit without gaps.

We design the ventilation with extract at the highest point and supply at the bottom. In summer windows in the upper facets heat the house more than vertical ones do, so we keep them on the north side or cover them with external blinds. The outdoor unit of an air conditioner has no secure place on a curved shell, so it goes on a stand or on the wall of an annexe.

Floor area and layout inside a sphere

The floor area of a dome is that of a circle: an 8 m diameter gives about 50 m², 10 m about 78 m², 12 m about 113 m². An upper level usually takes up half the circle or less, because towards the walls the ceiling comes down to the floor. So a dome for a family is either large in diameter or comes with an annexe.

Kitchen units and wardrobes are designed for straight walls, and a dome has none. So the kitchen, storage and bathroom go against internal partitions or into a rectangular annexe connected to the dome, which is also a convenient place for the appliances and service risers. A sphere gathers sound at its centre, and an empty dome echoes. Textiles, rugs and acoustic panels on some of the facets damp the echo.

Foundations and earthquakes

A dome is light, and on a level plot piles with a ring of ground beams are usually enough. The piles go under the bearing hubs of the shell, with an anchor in each hub. On a slope the dome stands on a platform on piles, without excavating the whole footprint. When a slab makes more sense than piles is decided by the ground survey, and this is covered in the comparison of pile and slab foundations.

In an earthquake a light, rigid shell takes a small load and works as a single whole, as long as the hubs are intact. So the site foreman photographs every connector and anchor before the sheathing goes on. How we design a house in any material for seismic loads is described on the page about earthquake-resistant construction.

Glamping dome or permanent house

A tent dome 6–7 m in diameter, with a frame, insulation, a timber platform and installation, costs from 25,200 to 36,000 ₾ per unit. It is a quick way to launch a glamping site, but in a humid climate a tent needs looking after: it has to be dried, washed of mould and inspected after storms. Power, water and a bathroom for each dome are connected under a separate estimate.

If the domes are going to be let by the night, we design them for running a rental from the start: a bathroom for each unit, a separate meter, space for linen. How to arrange accommodation in separate cabins on one plot is described on the page about guest houses.

What you can build instead of a dome

Alongside a dome we always price options that are simpler to build and maintain in Adjara:

• an A-frame house: also an unusual shape with a glazed gable, but with a roof of two slopes, and the materials for it are sold in Georgia;
• a timber frame house with a polygonal living room and a roof lantern: a similar character, and the furniture stands against straight walls;
• a modular cabin with panoramic glazing, which is set on piles and connected within a few days;
• a tent dome on a platform, if what you need is seasonal glamping rather than a house.

How much a dome house costs

A turnkey dome house costs from 2,520 to 3,120 ₾ per m² of floor area. The price includes the foundations, a geodesic timber frame, insulation of the triangular sections, flexible roofing over the facets, windows, building services and interior finishing. The plot, the design and connection to external utilities are not included. The shell, with the frame, insulation, sheathing and windows, costs from 1,320 ₾ per m².

That is noticeably more than ordinary lightweight houses: a turnkey timber frame house starts from 1,620 ₾ per m², an A-frame from 1,860 ₾. The difference comes from cutting the triangles, roofing over the facets and the openings, each of which has to be flashed on site. Asphalt shingles with materials cost from 270 ₾ per m² of dome surface, and a pile and ground beam foundation from 300 ₾ per m² of house footprint. Delivery and customs clearance of the kit are not included in the price per m² either: in the estimate they are a separate line based on the manufacturer's quote, and you see the amount before ordering.

We send a preliminary estimate from photos of the plot and the diameter you want 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.