Different Cuts of Tree Trunks, Different Aesthetics and Uses

Wood is one of the most common materials in the world. Architects usually obtain sawn wood at a nearby store, but many of us know barely anything about its manufacturing process and all the operations that determine its appearance, dimensions, and other aspects that affect its performance.

The wood we use to build is taken from more than 2000 tree species all over the world, each with different densities and humidity levels. Also, the way the trunk is cut determines the functionality and final characteristics of each wood section. Let’s take a look at the most used cuts.

Parts of a Trunk

A trunk is composed mostly of cellulose fibers joined by lignin. We have identified the outermost and innermost part of the trunk:

Bark: irregular layer of dead cells which protects the layers inside.

Cambium: the second outer layer that adds on the trunk diameter when new cells are generated year on year.

Sapwood: young, lighter-coloured wood that are constantly growing. It has a high water content and little lignin.

Heartwood: adult, dark wood, harder because of its high lignin content.

Pith: innermost part of the trunk, very rigid and tightly knitted, without humidity.

Wood for building is typically classified according to their hardness for both soft and hardwoods—it is essential to specify the proportion of Sapwood to Heartwood inside the trunk. Softwoods (from fast-growing tree) are cheaper and easier to process but are less resistant, hardwood (from slow-growing trees) are stronger but more delicate and more expensive.

The growth rings inform us of the tree’s age while the medullary rays move the sap along the tree vertically and is perpendicular to the growth rings. These two elements make a difference in the look and characteristics of the resulting wooden board.

 

The Many Ways to Saw a Trunk and Their Results

Although sawing techniques may differ depending on the type of use, the three main ways to cut a log into boards are: Rift, Quarter and Flat Sawn- and a series of variations that evolved from these techniques:

 

Rift Sawn

This cut is made perpendicular to the growth rings. It results in visible wood grain and avoids warping (deformations in the shape of the board) or fissures (longitudinal cracks), but more material are wasted than other cut types.

 

Quarter Sawn

Cuts are made parallel to the four axes of the trunk so that cut pieces are not too prone to warping with a large number of visible rings.

Flat Sawn/Live Sawn

A widely used method but it results in pieces that are not of the best quality as most contain a certain percentage of the Sapwood and the Heartwood. The centrepiece that meets with the core is also likely to break, while the remaining pieces are prone to warp and curl.

Parallel Boards

Cut similarly to the Flat Sawn system, but only pieces of a smaller section are taken, resulting in les  warping problem.

Cantibay Method

This method results in wide boards without much waste, at the same time eliminating the core of the trunk.

Quarter Sawn (Alternative Method)

The trunk is cut into four quarters to extract good quality pieces with good strength and appearance.

Whole Piece

The trunk is used to its maximum potential, ridding the bark to extract a single square log.

Cross Cut

This cut uses the heartwood to the full by obtaining very resistant pieces. With the remaining sapwood, smaller pieces are cut.

Interlocked Cut

The boards intersecting the core of the trunk are first cut out. The remaining wood are cut into thinner boards that are quite resistant to deformation.

Deformations

When wood—which has a high moisture content as it grows—dries, different contractions occur depending on the cut made and the resulting arrangement of the growth rings. Although this varies in different species, the deformation is always greater in the direction tangential to the rings than in the radial direction.

 

*All images are credited to José Tomás Franco

Source: Archdaily