All About Big Timber Beams
Updated: Mar 23
Bigger is better, right?
If you are going to build with timbers, then build with big timbers!
Big timbers definitely have their own unique characteristics that can either make a project work or make your visitors scratch their heads. The difficult part is that the same size timber will feel different when used in different applications. It’s not about the absolute size of the timber but rather the proportional scale to the other items around.
The above timbers are 12x18. These will look great on the hotel porte cochere they are intended for, but probably not so great on a homes’ back patio.
Since scale is specific to each project, it is impossible to have any rules for when a timber goes from aligning with the design, to an oversized aesthetic, to overkill. With that being said, below are some “most common” rules that can be used as a starting point.
Generally residential applications use 8x8 posts. 10x10 posts are also used for taller posts (>14’) or to achieve an “oversized” aesthetic. Commercial projects typically use 10x10 posts and larger, based on the size of the project.
Each member of a truss will typically have a different height dimension but most will share the same width dimension. By far the most common width dimension for timber trusses are 8x. Decorative trusses will sometimes be built with 6x timbers. It is also common to mix and match 8x and 6x beams in the same truss to provide a depth dimension to the truss.
The most common size of box beams are 6x8. Some architectural styles lend themselves to a wider beam such as a 6x10 or even an 8x12.
In an ideal world the size of the beams would be dictated entirely by the architectural design but sometimes we need to look for a few cost saving areas on a project. Timbers have a significant change in cost when changing the sizes. This is due to two factors that move in the same direction. The first factor is the amount of board feet present in the timber. The second factor is the cost per board foot. The below exercise will demonstrate how these two factors compound on each other.
Example: 10x10 Post versus 8x8 Post
In this example there is over a 40% savings by moving down the post size! It is common for a project to have 10-20 posts so you can begin to see the cost difference really start to add up.
Width and Height versus Length
The above discussion was focused on the width and height of the beams. The other dimension worth discussing is the length. Just like beams will cost a premium with each increase in width and height, they will also fetch a premium at certain length thresholds.
In regards to length, keep these general rules in mind to manage costs and lead time conflicts.
The cost per board foot ($/BDF) is generally the same up to 20’ lengths (i.e. there is no length premium).
From 22’ to 30’ in length the increase in cost per board foot is generally linear (i.e. an increase of $0.10/BDF for each 2’ increment).
Beams greater than 30’ begin to experience a more exponential increase with each incremental length increase (i.e. 32’ to 34’ is a $0.20/BDF increase whereas 40’ to 42’ increase might be a $0.60/BDF increase)
The above timber is a 10x20x46’ beam. Beams of this size and length are increasingly more difficult and more costly to get.
People love to build with timbers because they evoke an emotion. This emotion can range from warm and nurturing all the way across the spectrum to stately and intimidating. The design and scale of the timbers will largely dictate what emotions are felt. At Northern Timber Crafters, we facilitate the planning and practice our craft to bring natural beauty into your home. Homeowners who partner with us have an extraordinary home that they love and are excited to share with others.