Many people love the look of reclaimed timber beams in their homes. The character of the beams, the story they tell, and the structural integrity they represent are all important features that many homeowners appreciate. Working with reclaimed wood on any design project can be a very rewarding process but it’s important to remember that it also takes careful planning, preparation, and patience.
In a past article, we shared our design process using reclaimed timber for our Fombell Addition in Western PA. In this article, we dive deeper into the process of preparing reclaimed wood for reuse. We share how the species and strength of the reclaimed wood were determined and how it was cleaned and fumigated for our project.
Determining the Wood Species
In order to use our stockpile of reclaimed timber for our project, we needed to figure out the strength of our wood. Our structural engineer could then use prescribed strength charts (based on the specific species of our reclaimed wood) to confirm that the size and lengths of our timber were adequate for our intended design. To do this, we first needed to determine what species of the wood we were dealing with.
With the help of our engineer, we found a testing agency who agreed to test our wood. The testing agency requested 3-4 sample borings of the wood (about 3″ diam. pieces) to test in their lab to determine the wood species. Shortly thereafter, we learned that our reclaimed timber was
White Oak.
Knowing that we now had a stockpile of White Oak timbers, our structural engineer could use reference the strengths noted in the White Oak strength charts for his loading calculations and confirm our previous assumptions.
Staging & Material inspection
We staged the timber on-site nearby. Thankfully our project is located in an area where there is plenty of space to lay out all the wood for inspection. This was the first time we had a chance to see all the timber. Prior to this, the timber was stored away in stockpiles.
Some of the timber had some real character. Some beams had notches and irregular cuts. Others had the old metal tags from when the barn was dismantled. And interestingly, a few had remnants of barn hardware and tools. What a great find these were!
We made sure to note which beams had the iron hardware intact in hopes that we could keep these treasures and highlight them in the finished house addition.
The next step in the process was to find a professional to visually inspect the old timber beams to determine the structural grade of each piece.
Visual grading consisted of 4-5 hours of poking and prodding each piece of wood – sometimes removing chunks of dry rot, sometimes taking a chainsaw to the ends to get down to the inner part of the wood.
As the inspector examined each side of each piece of wood, we stood nearby with tape measures and clipboards in hand, diligently taking inventory of the usable timbers. We noted lengths, widths, and depths of each. We labeled each beam with chalk as to where we thought they might go in our project. (We did this for our own reference so that later we could access whether we had enough of each size for our design.)
(As we mentioned in our previous post on our design process using this reclaimed timber, ideally the material inspection process occurs before design begins. Finding an inspector and scheduling a site visit took longer than expected which forced us to start the design process before we determined which timber was good to use.)
We knew that a certain percentage of beams would be rotted or unusable. But we had no idea how many this would affect. In the end, out of the 144 pieces of timber, we found out that 106 were still usable. Unfortunately, some of the longer timbers were unusable and would have design implications. This forced us to consider splicing timbers together to make the longer spans that our design required.
The inspector issued a formal report noting which members were of Grade #1 (based on visual inspection only). It’s worth noting that they do not certify anything. They specifically note that the report “does not constitute a certification of the grade of the material herein described. The only objective of this inspection was to make the best possible observations – under the circumstances – comparing the visible wood members to defined grade categories.”
So basically, they are saying that the visual grading is subjective and that they are not certifying the strength or grade of the wood.
We made sure our engineer was present for this visual inspection. He would be the one ultimately calculating the loads and capacities of the beams (and stamping drawings) so it was important to include him in the process so he could have the reassurance that the beams we were documenting were of an acceptable quality to him.
Now that we actually knew which beams were good (Grade #1), we had to go back to our original design and confirm the assumptions of lengths and widths for each of our structural design were actually available. As you can see in the image below, the blue text designates beams that we still needed.
Now, what?
We decided we would leave the design as is and hope that our contractor could source some antique White Oak timbers.
Corn Cob Blasting & Fumigation
After the design drawings were finalized and the construction contract was awarded, it was time to start cleaning and fumigating the timbers. Preparing reclaimed wood for reuse in any project is an important step that is not to be forgotten.
When you spend so much time designing a project to highlight hundred-year-old beams, you want to make sure they are clean and free of loose debris and bugs. You don’t want to have any loose organic (or other) particles constantly falling from the beams once they are erected!
We found a local company, calledBlastmasters that agreed to come to our site to treat the wood. The treatment was a 3-step process that took about 2 days for the amount of timber we had.
First, the beams needed to be manually scraped to remove any loose bark or wood chips.
You can see in the image at the right that there is loose sapwood on the surface. Using a pry bar tool, excess sapwood and bark were removed from the wood surfaces, which is what is shown below.
Next, the wood is corn cob blasted.
Corn cob blasting is powerful enough to remove the excess bark, dry rot, and debris from the surface, but gentle enough to not destroy the wood surface.
The corn cob blasting process is much like it the name suggests.
Bags of tiny corn cob chips are fed into a hopper and are sprayed at high velocity onto each side of the timber beams.
After the corn cob blasting, the timber beams have a nice clean appearance.
Here is a short 30-second video of the corn cob blasting process. You can see in the video the white residue and excess wood particles are getting blasted off the wood.
The final step in treating the wood is the fumigation process.
The process involves spraying a borate glycol solution onto the wood surfaces. The borate solution penetrates the wood and kills any remaining bugs. It also preserves and protects the wood from any future risk of bug infestation.
Once the timbers were fumigated, they were left to dry for about 24 hours before being handled or moved. Below is an image of the timbers a few hours after fumigation.
This concluded our on-site wood preparation process.
The next journey for our reclaimed barn wood is a trip to Lancaster, PA where the individual pieces of wood get fabricated into timber frames based on our design drawings.
If you’d like to learn more about timber framing, check out our Timber Framing Design Resources.
