Log house in Adjara and Batumi: machine-rounded logs, settling and cost

Machine-rounded logs are made on a machine that strips the bark and the uneven outer layer from the trunk, so that all the logs come out the same diameter. A log house built from them goes up quickly, the walls are straight from the start, and the log ends projecting at the corners give the look people choose such a house for. You can build a machine-rounded log house in Adjara, but compared with square timber it settles more and has more places where water gets in.

How a machine-rounded log wall is built

Along the underside of each log runs a lateral groove, a half-moon channel cut along its whole length. Each log sits with this groove on the log below, insulation between the courses is laid between them, and the rows are fixed together with dowels. At the corners the machine cuts saddle notches, and the logs are joined with their ends left projecting: they extend beyond the wall and keep the corner from shifting.

Along the top of the log, in the part hidden under the next course, a relief kerf is cut. As the log dries, the stress goes into this kerf, and fewer large cracks appear on the visible faces. How warm the wall is depends on the width of the lateral groove rather than the thickest part of the log, so at the joint the wall is thinner than the log's diameter. The first course, the sill log, is often made of square timber or of a log sawn lengthwise, so that the log walls sit flat on the plinth.

Green or dried logs: ordering and acceptance

Rounded logs are more often made from timber at natural moisture content: kiln-drying a trunk of that diameter is slow and costly, and dried logs are noticeably more expensive. For a house on the coast we still recommend kiln-dried logs, and we keep green logs for the mountains and for small buildings: in the humid air by the sea a green log house takes too long to dry. We order the logs from the manufacturer to the design, with the notches already cut and every log marked. Where the batch comes from and who makes it is stated in the estimate, as some of these logs are imported. We ask the supplier for the moisture content before dispatch and measure it ourselves on acceptance.

The machine removes the outer layer of the trunk, the densest and most resinous one. Without it a log soaks up water more easily and turns blue faster if it lies in the rain. So straight after unloading, the logs are treated with a preservative that protects against beetles, the ends are sealed with an end-grain sealer, and the logs are stacked on spacers under cover, with gaps between the rows.

Settling of a log house: what we allow for

A log house settles noticeably more than kiln-dried square timber, especially one built from logs at natural moisture content, and in Batumi's humid air the settling drags on for months. So the order is this: we assemble the walls, put on the roof, and the house stands under it and dries. Windows, building services and finishing are done after settling, and that is how the scope of the shell is written.

• Gables are more often framed: a log gable is tall, stands up poorly to wind and settles along with the walls.
• The rafters go on sliding brackets, so that the wall can move down under the roof without dragging it along. We use a light roof covering, and our comparison of metal roof tiles and asphalt shingles will help you choose between the two.
• Openings are cut with grooves for the settling frames, and the windows go into these frames after the settling period.

Screw jacks under the posts and slip joints on the partitions work the same way as in a house built from profiled timber, only a log house needs a larger height allowance. After the main settling we seal the joints on the outside with chinking, the “warm joint”, and in a log house it matters more than in a timber one: on a rounded joint, wind-driven rain gets into the groove more easily than on a flat one.

Log ends, notches and projections: where a log gets wet

At every corner of a log house the log ends stick out, and the rain hits them on the end grain. End grain soaks up water much more than the side of the log, and rot in log houses often starts at the projecting ends and the bottom notches. So:

• we make the roof overhangs deep enough to cover the projecting log ends at the corners;
• the ends get a separate sealer that slows down their drying and keeps the rain out, so they crack less;
• during assembly the notches are treated with preservative and lined with insulation, so that water doesn't sit in the corner;
• under the windows we fit drip sills that project beyond the face of the log.

The sill log goes on damp-proofing on top of a plinth 30–40 cm high, and for a log house we stick to the upper figure: the projecting ends and bottom courses are bare wood in the splash zone. The foundations for a log house are chosen according to the ground survey, usually a strip footing or a slab, and piles on a slope. A log house is light, and in a tremor the main danger for it is sliding: the wall can shift off the plinth or come apart along the courses. So the anchoring to the foundations and the dowels up the height of the wall are calculated by the structural engineer.

Delivery and assembly in the mountains and by the sea

The logs for a log house are long and travel on a long-bed lorry. Such a vehicle can't always reach a plot in mountain Adjara: hairpin bends, bridges and narrow village streets mean the logs have to be transferred to a smaller vehicle, and sometimes unloaded further down and lifted with a lorry-mounted crane. We check the access, the unloading area and the storage space before ordering.

A small crew assembles the log house following the markings, and heavy logs are lifted by crane. We start assembly in spring, so that by the autumn rains or the first snow the log house stands under its roof. What else changes when building high in the mountains, from snow loads to off-grid utilities, is described on the page about building a house in the mountains.

Finishing inside a log house

Inside, the logs are usually left exposed. After settling they are sanded, large cracks are filled, and then the walls are coated with an interior oil or lacquer. For the kitchen, the bathroom tiles and built-in wardrobes we put up a separate frame with a gap at the top, as in a profiled timber house, only for logs we leave a larger settling allowance.

A round log is poor at hiding cable, so the wiring in a log house is more often surface-mounted: retro twisted cable on ceramic insulators, or steel conduit along the wall. It can be concealed only in steel conduit inside a channel drilled during assembly, and then the socket positions are marked as early as the design. The floor is laid on joists, and under the bathroom tiles we make a separate waterproofed base that isn't connected to the logs.

Machine-rounded log house: where it fits

A log house suits a plot in the woods or in the mountains best, one the owner visits often: a mountain village, a wooded slope above the coast, a country plot by a river. Logs also work well for small buildings, such as a bathhouse or a guest cabin. The steam room, stove and drainage in a stand-alone bathhouse are covered on the page about building a bathhouse.

A log house is a poorer fit for a narrow town plot: the log ends at the corners project beyond the wall, and there may not be enough room left for the setbacks from the neighbours. Right by the sea, the projecting ends and end grain under wind-driven rain need frequent care. If you need a timber house for living in all year round without a long settling period, glulam behaves more predictably: it costs more, but hardly settles.

How much a machine-rounded log house costs

The shell of a machine-rounded log house costs from 1,620 to 1,980 ₾ per m² of floor area. That covers the foundations, the assembled log walls, the floors and the roof with rafters. Windows, utilities and finishing are not included in this price: they are done after settling and priced separately, as is the design. A turnkey log house starts from 2,610 ₾ per m².

The biggest line in a log house estimate is the wall: from 390 ₾ per m² including the logs and assembly. Everything else is inexpensive taken separately, but it adds up. Sealing the joints between the courses starts from 17 ₾ per linear metre, and a log house has a lot of joints; preservative and fire-retardant treatment from 20 ₾ per m² of surface; a finishing oil or lacquer from 27 ₾. A profiled timber shell is cheaper, from 1,200 ₾ per m²: a metre of wall takes more log, and the notches and offcuts add to the price.

Costs go up with kiln-dried logs, a larger diameter, a roof with several gables and a road where the logs have to be transferred to another vehicle. A simple log house with a gable roof and framed gables, and a plot by the road, cost less. We send a preliminary estimate from a sketch and photos of the plot within 24 hours on business days, and the final cost is set on the basis of the design, after a visit to the plot and once the estimate is agreed.