Hi,

There is currently a good challenging thread posted on The Carpenters Fellowship website featuring photos of a tie beam break and an old repair to same that is currently somewhat difficult to explain.

Your ideas and contributions would be much appreciated. Check out :-

http://www.carpentersfellowship.co.uk/forum/index.php?showtopic=363

or go to the "discussion forum" and select "Tie beam Failure - high strength gaffer tape" posted by Lui Rocco on 02nd October 2009.

Regards

Ken Hume

"Blimey" all right, it looks like rot form here but the chap says it isn't? The grain runs off and the horizontal check formed first, some one removed the bracing and did I see an extended mortice below the brace in the bent next to the broken one? Could there have been a lower connecter as well which was removed along with the bracing? Is this a stand alone building? It appears to be a smaller structure 20' or such.

Tim

At first I would have thought that the tie was overloaded with a guess of someone lifting something using the tie. But upon looking at the close up picture, and seeing how cleanly the upper portion separated so clean and evenly, definitely tells me this was a material problem, as in defective. Obviously the grain run out was too excessive, but the upper portion was defective in that it could have been a weak section to start with or could have acquired a fungal infection while drying. Could have been excess sap there trapped... But it looks like a material issue as opposed to a loading issue. Shrinkage could have started the failure, but insufficient quality of material looks like the downfall. With that kind of run-out, that stick should have been culled before cutting joinery. I'd want to replace it with a good stick and move on if feasible.

At first I would have thought that the tie was overloaded with a guess of someone lifting something using the tie. But upon looking at the close up picture, and seeing how cleanly the upper portion separated so clean and evenly, definitely tells me this was a material problem, as in defective. Obviously the grain run out was too excessive, but the upper portion was defective in that it could have been a weak section to start with or could have acquired a fungal infection while drying. Could have been excess sap there trapped... But it looks like a material issue as opposed to a loading issue. Shrinkage could have started the failure, but insufficient quality of material looks like the downfall. With that kind of run-out, that stick should have been culled before cutting joinery. I'd want to replace it with a good stick and move on if feasible.

My first though after seeing the cross grain shear at the top portion of the beam suggest there was a force from below. Who knows what may have happened in that barn in the past. I would replace the beam if it were mine.

But.... you would be removing the historic fabric. The fix that was used has stood the text of time. Improve the fix perhaps while retaining the fabric.

Tim

Hi Thane, Brad & Tim,

If this building is "listed" by English Heritage as a historic building then straightforward swap out might not be acceptable and instead a repair might have to be made to try and preserve as much of the historic fabric of the building as possible but really I shouldn't second guess the opinions of English Heritage. Their architectural historians may take a different view.

This is quite an unusually severe break which is why I brought it to the attention of forum regulars. Its hard to believe that a tie beam of this section could just break all on its own but once again the facts surrounding this break are not known.

This break might go some way to explaining why so many cambered tie beams can be seen in SE England. i.e. experiences like this where the bottom of the beam has been artificially flattened resulting in the cutting through of too many wood grain fibres. Carpenters may have learned early on that they should try to limit the possibility of incurring a failure like this by endeavouring to stick with the natural shape of a log when it was being converted.

This failure goes some way to explaining my own dislike of empty "leggy" frames where there is little in the way of a second line of defence if a major failure is encountered.

Regards

Ken Hume

This same conversation goes round when it comes to classic cars. Where do you draw the line? If the original engine was gone but you find a replacement with all the correct date codes, but you re-stamp it with the numbers the car would have had. Is that restoration or deception? Does it restore it to what it was or is it a fake? Depends on what viewpoint you decide to take, not clear cut.
With structures like this, the goal should be preservation(where possible), and restoration when needed for safety or practicality. If you replace this beam with a good one, done the way the original was, be it sawn or hewn or whatever, I'd call it restoration, thus preserving the rest of the structure. Some might also argue that if you repurpose a classic stucture, like a barn, even if it gets a little modified for the new use, at least it may be preserved instead of being allowed to deteriorate any further. In the US we have more structures(barns) than we have people to preserve or restore or repurpose them, so I welcome their reuse.

Like I said, if it were my barn I would replace the beam.
In doing so, the structure can still be considered authentic.

Ken,
What do you mean by "Leggy" when refering to this building?

From what I see there was nothing to resist any appreciable load. A seaoning check started as the timber dried in service at the bottom where the heart is running out. The check ran up along the badly sloping grain till it got to the decayed upper portion which popped short and brash under some moderate load. No matter what else, it was a poor timber choice. Not shaping the bottom of the timber would have left a continuous strap of unbroken fiber so I do agree that not shaping something with other than straight grain has a lot to be said for it.

For most mechanical properties there is no strength difference between sapwood and heartwood, hardness and compressive strength would be exceptions in some cases. The fiber is the same in either, heartwood is backfilled with nonfiberous extractives. Sapwood is not decay resistant, heartwood contains widely varying amounts of decay resistance, but, if there is food there is something designed to consume it.

The brash break reminds me of "brown rot", a "pick test" of the upper portion would confirm this if its the case. The class basidiomycetes is generally responsible. Beefsteak, mentioned by one person is one of the many basidiomycetes. Different fungi contain enzymes to break down different parts of the wood and convert those portions to simple sugars for their use. In an attack by brown rot fungi the cellulose rich S-2 layer of the cell wall is often the first to be degraded. From our previous discussions on cell structure, this is the widest layer of microfibrils within the cell wall and are predominantly responsible for mechanical properties and shrinkage... the critical fibers. Even a small weight loss or microscopically slight looking amount of decay can cause widely varying strength loss.
I did a quick search on the FPL website for "brown rot" and came up with many hits, this is a good overview paper;
http://www.fpl.fs.fed.us/documnts/pdf2001/fpl_2001_curli01a.pdf

It might be worth considering a tie rod through from post to post buried in the upper part of the new masonry wall.