Tuesday, February 20, 2007

Timberframe bloopers and practical fixes

We notched and stacked hundreds of timbers for over one year before assembling our frame. Occasionally, self-doubt would creep in and I would wonder if we were ever going to get the frame to fit together. Just how many stinking timbers were sitting in the barns, with grievous errors in the joinery... waiting to rear their ugly heads when it came time to raise the frame? The stick-frame carpenter who took the timberframe course with me, and eventually notched more timbers than me (and drank a whole lot more beer than me... every day... while working) claimed that he was going to be on vacation some where far away when I tried to put the frame together. That did not instill much comfort. "Oh well," I would tell myself, "I can always cut the tenons off and put it together with lag bolts if the wooden joinery thing doesn't work out." You must always have a plan B.

Fortunately, there were not many mistakes lurking in that pile of timbers, but it would dishonest not to admit to at least a few. In fact, there was on average, one small mistake in every bent of our house. As we progressed from bent to bent, I found comfort when we located the error in each bent - surely there couldn't be more than one mistake in a bent!

All of the mistakes were minor, none required scrapping any of the timbers, and any visitor in our house today would have a very hard time locating any of the faux paus. One common mistake (I think it happened 4 or 5 times in the frame) was the "misplaced brace mortise mistake." My drawings, I decided, were to blame for this mistake. You see, I would dimension two sides of the mortise with respect to one edge and one end of the timber. Then I would call out the dimensions of the mortise. It was very easy during "layout" (the process copying the drawings to the timbers) to draw the mortise on the wrong side of the dimensioned lines. In fact, the mortise in the picture above was cut on the wrong side of both lines!

I came up with two different fixes for the "misplaced brace mortise mistake." Fix #1, shown in the first picture, was to 1. cut a piece of wood from scrap, 2. plug the errant hole with this piece of wood, 3. sand to fit, 4. cut a new, correct, mortise in the timber. The plug stands out like a sore thumb in the first picture because the wood for the plug was not as seasoned as the wood of the timber. Also, you can see that I took time to cut a plug with matching grain to the timber. The piece of wood in the foreground is the scrap from whence the plug came. Eventually, the two woods (both white oak) achieved the same coloration and it would take a forensics expert to spot this boo boo today. :)

Fix #2., sometimes used in conjunction with or as an alternative to fix #1 was to make a custom brace with an offset tenon. That's what's shown in this picture. As a final note, make sure you know where all of your mistakes are if you're paying to rent a crane. I paid for my crane by the gallon (I own it, it is old, it leaks), so fumbling to fix these mistakes didn't cost as much as it could have.

3 Comments:

Anonymous glenn steimer (eujenius2@yahoo.com) said...

Tom--I took the "Timberframe 101" course with you in Paris, Tenn, with my son. (I was the "special ops" lawyer). After being deployed a second time, I came home resolved to at least get my shed built (same plans as the student shed). I cut a bunch of Amish-cut oak timbers, but found that most of my rafter pieces (cut green) had warped too much out of shape to be useful. With your massive project--have you had this problem? If so, how did you solve it?

February 27, 2007 at 10:59 AM  
Blogger oldmilwaukee said...

Hey Glenn!

Yes, I had some warpage. Some of the timbers were not too bad, and we just built with them. Some could be pulled into stratightness (and kept there), depending on their location in the frame. A few just had to be culled. I took the culls, and recut them to smaller timbers on my band-mill, or cut them for shorter timbers so the bow was not as significant.

Preventing the bow starts with making sure the heart is in the very center of the timber when it is cut at the sawmill. Then it is important to keep the sun or moisture from hitting one side and not the other - which will cause significant warpage.

I don't know what to tell you about the bowed rafters. Did you already notch them? If not, and you plan to use them, remember the crown always go up (but I'm sure you remember this from Scott's class).

In any case - CONGRATULATIONS on starting your frame! When do you plan to raise it?

February 27, 2007 at 1:33 PM  
Anonymous Glenn Steimer said...

Thanks so much for the reply. I forgot to congratulate you--not only for the incredible workmanship and ingenuity you have displayed throughout the project, but your prose is terrific as well. I had to put the shed on hold last summer while I converted my basement into a usable workshop. I now have about 750 sq ft of shop, along with a lot of new toys--I mean tools, including an 18" Jet bandsaw. It will give me a place to work out of the sun and rain. I hope to raise the shed late spring or early summer. I will have to buy several new timbers--at 62 cents a bd foot for white oak (from the Amish) that's not too bad. My longer term goal is to raise a considerably larger building (I purchased the plans from Goshen Timberframes)which is much smaller and simpler compared to what you are doing. It will become a garage and studio space, and I want to make it "off the grid" even though it will be on my own two acre plot that my house occupies. I intend to exploit my gas well to a) drive a stirling engine to heat the building, the water, and generate electricity; and b) to power the CNG engine Honda I plan on purchasing (you can buy a garage-installed gas compressor that Honda sells with the car). Anyway--thanks for the answer to my question, and continue to march on!!! PS--If you ever need a gang of warm bodies to do a weekend raising or something, give me a holler and I'll come down! Glenn

March 5, 2007 at 1:50 PM  

Post a Comment

<< Home