Hardness, Durability, Grain, and Lamination Explained
There are several factors to consider when selecting wood for stair treads that will be used on floating steel stringer stairs. They include the species of wood, the method of sawing the wood, and the construction of the stair treads. The species of wood selected will vary in hardness, durability, and grain. In addition, how the wood is sawn will affect the appearance of the grain, and the construction or lamination of the tread will have an effect on the appearance of the finished product. In addition, the construction of the wood tread must take into consideration the code requirements for open risers.
The hardness of wood is measured using the Janka scale. This scale helps you to understand a wood’s relative hardness.
Why is wood hardness important? Softer woods are more prone to dents or dings than harder woods. Also, softwoods are not suitable for use as handrails since they may not hold up under the typical forces required to meet building codes.
The chart below shows the Janka Scale rating for several of the popular types of woods our clients choose for their stair and railing projects. IPE is one of the hardest of the hardwoods and Eastern White Pine is among the softest.
Janka Scale Rating of Several Types of Wood
Durability is the wood’s ability to resist natural elements of decay. Durability is critical when choosing wood for an outdoor application. Environmental elements that affect the degradation of wood include fungus, destructive insects, and weather. For exterior use, the wood’s ability to resist weathering such as photodegradation from UV rays, contraction and expansion, warping, surface checking, and decay will affect the longevity of the wood. The wood’s durability is based on the use of the heartwood. It is important to note that sapwoods are not durable. Hardwoods like Teak and IPE are among the most durable woods for outdoor use.
Note: Shown in green in the chart above are woods recommended for outdoor use.
The grain is the natural cell pattern of the wood. The natural pattern of the wood combined with the method used to cut the wood will affect the overall look of the finished product.
- Straight Grain – runs in a single direction parallel to the axis of the tree.
- Wavy Grain – runs in irregular directions from the vertical access of the log.
- Spiral Grain – follows a spiral twist around the axis of the tree
- Interlocked Grain – spirals around the axis of the tree and reverses direction resulting in the alternating of direction.
- Irregular Grain – is many different patterns of the grain as it twists or swirls. Often times it is the result of knots deformed growth, or crotch wood.
Examples of Flat Sawn, Quarter Sawn and Rift Cut Lumber
There are three main methods for cutting lumber and each method has a different appearance of the finished board. Flat Sawn is the most common and has a flame appearance. Quarter Sawn results in a straight grain appearance with a flame effect. Rift Cut results in a straight grain pattern.
Also known as plain sawn is the most common method of milling logs and the least expensive. The boards are cut from the log in a way that maximizes the use of the wood and minimizes the amount of waste. Flat Sawn wood is more likely to cup and warp over time.
Flat Sawn wood boards result in a flame look.
Just as the name implies the log is cut into quarters then it is flat sawn. This method is more expensive than flat Sawn wood since it requires more labor and produces more waste. Quarter Sawn wood is more resistant to warping, cupping, and twisting than flat sawn wood.
Quarter Sawn wood results in a straight grain pattern without the flame effect on the front of the board. The oak will show flecks or rays in the grain on the face of the board.
The boards are cut radially around the center of the log. Rift Sawn lumber is the most stable and the most expensive since it does not utilize the entire log, therefore, having the most amount of waste.
This method results in a straight grain pattern with a clean consistent look on the front of the board.
Note: Wood is a natural product, therefore the grain does not always grow in one direction. This may result in some boards having variations in pattern and appearance.
Wood Tread Construction Solid, Laminated and Boxed
Solid Wood Treads
As the name implies are made from a solid piece of wood, they are generally considered timbers and are often difficult to source. As the piece of wood gets thicker, it becomes less available and more expensive. Solid wood although beautiful, is more likely to twist or crack than laminated wood.
Laminated Wood Treads
Laminating is a method used to create a thicker piece of wood. It is made of multiple layers to improve overall strength and stability. Shown below are two wood stair tread styles with two different lamination styles Butcher Block and Random Stack.
Box Stair Tread Construction
This example of a box stair tread construction has lock mitered corners on the edges and a layered laminated plywood core for stability. This technique of construction makes it possible for all the faces of the tread to have the same grain pattern. In addition, a boxed tread can be constructed to hide the stair stringer mounting attachments, resulting in a minimal refined appearance. Concealing the steel stair tread supports makes the wood treads appear to float in thin air.
End View of Boxed Stair Construction
Floating Stair Rise Construction Requirements
It is also important to understand the code requirements for floating stairs when choosing your tread material and construction. The open risers on floating stairs are required to be a space of 4 inches or less. There are a variety of ways to design the stairs to meet this requirement. They include Solid treads, L-shaped treads, and added L-shape toe kick on the tread. Examples are shown below.
Now that you have an understanding of various wood characteristics and construction techniques for wood stair treads it should be easier for you to make a selection for your Keuka Studios floating stairs.
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At Keuka Studios, we custom fabricate residential and commercial stairs and railings to fit your style, space, and requirements. To learn more about how each stair and railing project moves from vision to reality. Take a look at our custom stair design process. We take pride in building craftsman-quality and commercial-grade stairs and railings for interior and exterior applications. Contact us to get started on your project.