Building a log house: forms, joints and why the wall settles

DB David Bohler · 2026-08-22

From the raw trunk to the machine-milled profile — a log house lives on three cuts in every log and on the fact that fresh timber moves. This guide explains the forms, the lateral groove and the corner notch, the main corner joints and settling — plainly, and without inventing standard figures.

What sets a log house apart from timber framing

In log construction the horizontally stacked timbers are the load-bearing wall — there is no stud frame to be sheathed. Two wall planes meet at right angles in the corners, and there the corner joint alone holds the house together. Almost everything else follows from that single principle: the shape of the cuts, the choice of timber, and the fact that a newly built log house visibly settles in its first few years.

Lateral groove in section: the upper log’s concave cope seats on the back of the log below, with the gasket in the joint.

The forms: from natural log to milled profile

“Log house” is not one method but a whole family, reaching from the raw tree trunk to the machine-milled square beam:

Natural log (round log): a real trunk, debarked only, keeping its grown taper. Entirely handcrafted, every log unique.
Milled round log: timber turned to a constant diameter. Looks round and rustic, but the taper is gone.
Squared log (D-log): sawn and planed flat inside and out, with tongue and groove. Allows precise assembly and freer floor plans.
Glue-laminated beam: very dimensionally stable, little settling and hardly any checking — the other end of the scale.

Behind this lie two fundamentally different worlds. Handcrafted building (Scandinavian, Canadian, “full scribe”) works with round logs of differing thickness, each one individually fitted to the one below. Machine-profiled building stacks evenly milled beams like prefabricated parts with a fixed tongue-and-groove geometry.

Taper: why natural logs are laid alternately

A real trunk is thicker at the butt than at the tip. Softwood counts as full-bodied as long as the diameter decreases by no more than about one centimetre per metre. Over six metres that quickly makes five or six centimetres of difference. To keep the wall level, natural logs are laid course by course alternating butt and tip. With machine-turned round logs this is unnecessary, because the taper has been milled away.

Corner notch: the saddle notch interlocks the crossing logs, the heads project past the corner.

The three cuts on every log

One distinction is kept strictly in the trade and is easily confused: the groove runs lengthwise, over the whole log; the notch sits crosswise, only at the corners.

1. The lateral groove on the underside

A concave channel is worked into the underside of each log over its full length — the lateral groove (also called the Swedish cope). It seats on the rounded back of the log below and at the same time holds the gasket. In section it is classically V-shaped or rounded. On a natural log it is not a standard shape: a log scriber traces the contour of the log below, and the channel is cut to exactly that curve (round on round). On a milled profile it is an exactly cut, usually double tongue and groove.

2. The corner notch

Where two logs cross, a notch takes the place of the groove and interlocks them. The main forms on round logs:

Simple saddle notch: a crescent-shaped notch in the underside of the upper log, sitting on the lower one like a saddle. Simple, but loosens as the timber shrinks.
Double saddle notch and the Canadian notch common in the trade today: here the lower log is shaped to a ridge as well. The point of the Canadian version is that the joint pulls itself tight as it dries instead of gaping open.
Dovetail: a wedge-shaped joint, usually flush without overhang — typical for squared timbers.

The overhang is a matter of its own: with projecting ends the log heads reach past the corner — the classic log-house look — while flush corners are cut off level.

A note on dimensions: notch depths (“about half the diameter”) and flank angles (“around 45°”) circulate as rules of thumb, but they depend on the workshop and are not standardised construction dimensions.

3. The first course: the sill log

The bottom course — the sill log — is worked flat underneath so it beds fully on the foundation, and has no lateral groove: there is nothing beneath it to fit to. Only the logs above it get the groove. And one more common mix-up: on a handcrafted natural log the top stays round — flattening on top happens only with machine-milled profiles.

Why a log house settles — and why that governs the shapes

Fresh timber holds a lot of water and shrinks as it dries. A whole log wall sinks measurably as a result; the trade calls this settling. Figures of roughly five to six per cent of wall height are quoted, finishing after about two to three years; on a height of 2.70 m that is easily around 16 centimetres. The key point: timber shrinks strongly across the grain and hardly at all along it. Settling therefore affects the height of the wall, not its length.

The whole geometry follows from that movement:

Self-closing joints: notch and groove are scribed so that shrinkage makes them tighter rather than opening them up.
Controlling checks: a natural log contains the pith and will inevitably check as it dries. A fine saw kerf on the hidden side steers the crack to where it will not be seen.
Sliding connections: above doors and windows and at posts, room must be left for settling — with sliding fixings, never rigidly screwed.
Gaskets: groove and notch almost always hold a concealed gasket — once moss or sheep’s wool, today pre-compressed sealing tape. “Chinkless” only means no visible joint from outside, not the absence of sealing material.

Which timber

Softwoods dominate: spruce and pine as affordable, readily available standards, larch and Douglas fir for greater natural durability in the wall, and in North America often cedar. Whether timber is built in green or kiln-dried decides how much the wall will still shrink afterwards — and therefore how much settling allowance has to be planned in.

In short

A log house is not a wall with a cladding laid over it, but a stack of load-bearing timbers worked in three places: the lateral groove underneath, the corner notch crosswise, the flat sill log at the bottom. All of it is designed around the fact that timber moves. Once you understand that, you can look at a finished log house and see why every cut sits exactly where it does.

Sources and standards

Standards are not free to read and are named here for verification only. What applies is always the edition in force at the building location.