Round log: a guide to building a traditional, characterful home

Round log is solid log with a round or nearly round cross-section. Machine-turned round log typically measures 150–230 millimetres in diameter; heavy speciality logs are thicker still. Today the round- log house is above all a solution for cabins, saunas, outbuildings and traditional-style holiday homes – new detached houses in Finland are almost always built from rectangular laminated log. It is rarely chosen on technical grounds: people pick round log for its atmosphere.

What kinds of round log are available?

• Machine-turned solid round log: the most common, 150–230 mm in diameter; uniform and dimensionally accurate, with standard ranges typically 170–230 mm.
• Hand-hewn log: the most traditional method, where every log is shaped individually and the surface stays lively.
• Laminated round log: a glued round profile that moves less than solid timber; some manufacturers also offer it as settlement-free.
• Round aihki log: a heavy log turned from slow-grown northern pine, around 240–250 mm in diameter.

Kelo or round log?

Kelo is pine that has died standing, dried naturally and weathered to a silvery grey. Genuine kelo is scarce and expensive, so the kelo-holiday home market has largely shifted to heavy round aihki log. Aihki gives the same massive look with better availability and a lower price. Kelo has already dried in the forest, so its moisture movement is minimal; fresh turned log, by contrast, settles and checks like any solid timber, which must be allowed for in the design.

What does round log suit best?

Round log's strengths are its traditional appearance, massive character, and the timber mass's good heat and sound retention. It is a natural choice for a lakeside cabin, a garden sauna, a storehouse and a traditional-style holiday home.

A round surface has more joint length and collects more weathering stress than smooth square log, solid timber checks as it dries, settling is the greatest of any log type, and modern architecture with large glazed areas is harder to achieve in round log. None of these is a deal-breaker, but they should be accepted knowingly before the material decision.

Round log in a cabin, sauna and dwelling

Log size is chosen by use. For a winter-use cabin or sauna, a log thickness of at least 70 mm is recommended – heavy round log exceeds this many times over, so thermal insulation is no problem in leisure use. A solid-log sauna buffers steam-room moisture with its whole timber mass, but settling must be handled with tension rods and adjustment allowance on doors. For year-round residential use, a solid-timber wall must average at least 180 mm thick to qualify for solid timber's own U-value reference of 0.40 W/(m²K) – in a round profile the average is less than the diameter, so a dwelling calls for the heaviest logs in the range.

How much does round log settle?

A solid-log wall settles about 30 mm per metre of wall height after erection. Settling is not a defect but a characteristic, managed through the structure:

• Settling allowances are left above windows and doors – in the region of 60–70 mm for a two-metre opening.
• Opening jambs are fixed with a sliding key batten, never rigidly.
• Load-bearing posts are fitted with screw jacks, adjusted as settling progresses.
• Dowels stop the logs twisting; their maximum spacing is 2,000 mm.
• Internal walls settle slightly more than external walls, because indoor air is drier.
• Cupboards are fixed to one log course only, and roof connections get sliding brackets so the roof structure cannot push the walls outwards.

Surface treatment and maintenance of round log

A fresh log surface outdoors should be protected as early as possible, since UV radiation greys the surface quickly and moisture exposes it to blue-stain and mould fungi. For exteriors, choose a tinted translucent or opaque wood protection – a colourless treatment does not give sufficient UV protection. Solid log needs a vapour-permeable treatment that lets moisture escape; film-forming products trap it and flake. Maintenance intervals are 3–7 years for translucent finishes, 7–10 for opaque; south- and west-facing walls take the most punishment and set the pace. Annual maintenance covers the tension rods, joint tightness, and the eaves and splash zone around the plinth.

Who is round log the right choice for?

Round log suits a builder who values a traditional log surface and accepts the character of a living material. Profiles and joint solutions vary by manufacturer, so ask for profile drawings with every quote and compare log sizes. Take settling and maintenance seriously at the design stage and a round-log building serves for generations. If your goal is a modern house with large windows, square-profile laminated log or settlement-free log is the easier path.

• Machine-turned round log is typically 150–230 mm in diameter; heavy round aihki around 240–250 mm.
• Kelo is naturally dried, standing-dead pine – scarce and expensive, which is why round aihki log now replaces it.
• Round log suits cabins, saunas, outbuildings and traditional-style holiday homes best.
• A solid round-log wall settles about 30 mm per metre; leave 60–70 mm settling allowances above openings.
• Protect exteriors with a tinted, breathable treatment; translucent finishes need renewal every 3–7 years.
• Laminated round log is also available from some manufacturers as settlement-free.