In this article, we talk about designing with reclaimed timber beams. If you’re considering using salvaged timber for your home or small project, follow along as we share our journey through the design process of our Fombell Addition in western PA project.
Introduction: Questions About Reclaimed Timber Beams
Typically, when reclaimed timber is used from a project’s structural design, it is sourced from a supplier who has access to a variety of wood species at a wide range of sizes and lengths to fit your needs. Designing with a nearly unlimited supply of wood is one thing. Using salvaged timber from a stockpile of existing beams is something else! It takes a lot of careful planning, coordinating, and creativity to get the design you want from the usable inventory you have available. But it’s not every day that you are lucky enough to have access to century-old timber beams from a nearby barn to design with!
When you decide to use locally sourced timber beams for the structural system of your new house, addition, or renovation, you’re probably wondering “Where do I start?”
If you’re anything like us and our project, you will have a stockpile of timber of unknown species, unknown quantities, unknown strengths, and unknown sizes and lengths to contend with. At this early stage in the game, there are many questions and very few answers. Some of the questions we wrangled with were:
- What is the quality of the timber available?
- What are their sizes and lengths?
- Are they sized for post and beam framing?
- Are a majority of them in good shape to potentially use for the project?
- Are the timber pieces structurally sound? How do we get them tested?
- What species of wood are they?
- Does the wood need fumigated?
- How else might we need to prepare the wood for use?
Sound overwhelming? It doesn’t have to be. Let’s take it one step at a time.
Follow along and we’ll show you what our process was and how we learned answers to these questions.
Are Reclaimed Timber Beams Right For My Project?
First and foremost the most important consideration when designing with timber is to decide whether reclaimed timber beams are right for your project. Would your project benefit from the look of exposed antique timber beams? Do your project goals present the opportunity to showcase the timber in the spaces? Do you like the look of exposed timber as a structural system? To read more about whether reclaimed timber is the best choice for your project, check out our post: Reclaimed Timber: The Benefits & Challenges.
For our house addition in western PA, we were tasked with incorporating the Pennsylvania barn framing typology that is prevalent in the area into an otherwise modern house addition. An important design decision that was established early on was that we wanted to use materials in an honest way. We wanted to avoid using materials as decorative elements, and instead, try to highlight materials in their true form. Also, we were fortunate enough to have access to some really interesting old timbers from a dismantled barn built in the 1800s. It became apparent early on that using reclaimed timber as the main structural system for the project was the right way to go.
Our Design Process:
Taking Inventory of Our Reclaimed Oak Timber
At the beginning of the design phase, the first thing we needed to do was consider the quality and quantity of available timber in our inventory. While we knew we had a large supply of salvaged timbers available, we also knew a certain percentage would be unusable, either due to rot or size limitations. However, we had no idea how many this could affect.
The first thing we did was lay out all the pieces to see what we were dealing with. We had a rough tally of the pieces and used this to start to conceptually design our structural system but we really needed a detailed assessment of the sizes, lengths, and quantities of our timber to dig into the design and understand what spans we could achieve.
We found a testing lab who could send someone to our site to visually inspect the timber for structural soundness (we cover this topic in more detail in our post: Reclaimed Timber: How to Prepare Reclaimed Wood for Reuse) but we had to contend with the unpredictable onset of winter weather and the inspector’s schedule. This process actually took longer than expected, which caused us to push through design without having a finalized tally of inventory of usable wood until close to the end of the design process.
Structural Timber Design & Material Inspection
With antique timber beams acting as the main structural system for the addition, we already had a few design decisions made for us. We wanted the timber to be exposed with the roof framing spanning over it. We knew rough spans for the framing based on our inventory assessment.
Because it took us a while to locate and schedule a company to come and inspect the timber, we actually were midway through design by the time this happened. Obviously, it would have been best to have a detailed inventory before we started designing, but it just didn’t work out that way for us.
We knew the lengths of the longest beams for a general idea of the possible spans we could achieve, but we didn’t know if those few precious long beams were structurally sound. We crossed our fingers and keep making assumptions as we went along.
During the design phase, we came up with a few different timber frame designs for the addition. We considered different roof geometries, different timber frame configurations, and different connection types.
About the time we selected a final design to move forward with, we received news on the species of our wood. (Our structural engineer helped us locate a testing lab where we sent core samples for species identification.) The report came back confirming our stockpile of wood was white oak.
So with a design in hand, we worked with our engineer to confirm the spans and sizes of our wood would work with our intended design. (Our engineer used conservative assumptions when calculating the loading conditions for our white oak timber frames just to be on the safe side.)
It was near the end of design when we were finally able to schedule someone from the testing lab to come and visually inspect our timber beams. We started with 144 pieces of wood and after the inspection, we were down to 106. (For more on the visual inspection process, see our post on preparing reclaimed wood for reuse.) While we knew we didn't need all 144 pieces for our design, there were probably a few longer pieces in that bunch that probably didn't make the cut. We were bummed! We could always find timber for our shorter lengths, but for the longer spans, we really needed those long members because hated the idea of slicing two beams together midspan.
One final tally of the usable timber confirmed our suspicion. We wouldn't have enough good pieces at the right lengths and sizes for the whole project.
After considering our options, we decided to use the antique timber for only part of our project. Luckily for us, the design of our project lends itself nicely to this approach. Our design called for two separate additions on either side of the house. Using these timbers for one side and not the other wouldn't be the end of the world since they are not in direct proximity to each other. Secretly, we hoped that the selected contractor would be able to find a supplier who could source antique white oak to match our timber for the other addition, but we didn't know if this was possible. All we could do was hope!
Designing Timber Frame Connections: Splices, Joinery, and Post Bases
After determining the overall timber framing design strategy for the additions, we narrowed our focus to the smaller elements of the timber frame design: the connection details. There were slice connections, joinery connections, and base connections at the posts. As an overarching design move, we decided to use modern bolt connections and steel splice plate detailing for the project. We thought these types of connections would play to the more modern design goals of the project as opposed to more traditional post and tendon connections. We reviewed all the connections to confirm that our design rationale would work for each location. We also had to meticulously decide how the plates and bolt connections would look.
There were 3 types of connections; wood to wood, wood to steel, and wood to "other". This was our opportunity to focus on the number of bolts for each connection, the bolt spacing, the shape of the splice plates, how visible the splice plates would be, whether the plates were exposed or concealed, how the timber members were pieced together, etc. We looked at various detail options for each condition. Of course, we worked closely with our engineer during this entire process. He needed to confirm loading, bolt and plate size, dimensions, and overall geometry of the connections. In the end, we were all happy with the final details of the connections.
At this point, the timber design was finalized, the timber pieces were assigned to specific locations in our design, and our connections were detailed. We now had a real idea of what our final timber design would look like. All there was left to do was build the additions!
If you’d like to learn more about timber framing, check out our Timber Framing Design Resources.
This article follows the use of reclaimed timber in our Fombell Addition in Western PA project. For more information, check out our introduction and design process for this specific project.
