I'm with Tim, From your previous description, I thought the roof system in question was one of simple rafters, which is why I floated a canted purlin post / plate system as a potential repair scheme...

This does much to drive home and emphasize why it is not just unwise, but not particularly useful to discuss these matters without photographs and dimensions.

Tim has the key there, are the rafters one piece ? And how do they join the purlin plate ? Is there an abutment of some sort ?

I'm guessing there is, and I'm almost certain the frames problem is not that of a thrust issue, at least not in the way you believe it to be. If it were, that massive drop and the resulting moment (were the thrust left unchecked) would have broken those spindly posts which are incredibly weakened by section removed in joining braces at the same locale (really really poor design) long before pegs sheared or relish popped.

Are any of the tying joints pegged ? Missing pegs may have ironically helped save the posts when the dynamic changed.

I'm thinking, the geometry was lost when that tie fell away and some thrust from the section of the roof above it (part of two bays) was redirected to the plates. And that who ever placed those cables did not have anything with enough uumph to pull it back together completely, ( neither do truck straps nor typical cable comealongs - Just because TF'ers use them does not mean they are appropriate rigging for tweaking buildings in restoration applications ) and called it done, short of being done. Something that is typical of stopgap repair. They did however, fix the leak and stabilize the situation, which ultimately did save the barn.

You need to hire in a consultant that knows what they are looking at, and can recommend the right equipment to pull things back into contention and help you choose a proper tension scarf for the tie.

As an aside - Restoration is as much about rigging as it is about carpentry, which is to say it is as much or more about knowing how to read a frame and realign the geometry a frame was built to, than it is about cutting the repairs, and knowhow is as important as skill. It is a demanding business on multiple levels, and often entered into by those who are under-equipped and think they can just wing it.

It is typical of hungry carpenters to turn to barn repair during downturns in the economy, often as much bad as good is the result.

Tim,
I did not look for a break in the rafters but I would suspect they are continuous as well. Only the one tie has rotted. Ties are missing pegs/withdrawing at the corner post and at both sides of bents 2 and 3. In total 5 of 8 ties are withdrawing from posts. I did not check the foundation with an instrument, just visually, your suggestion is well noted. I could see now that what appears to just be outward thrust could have a couple of contributing factors. I'll check with my water level next time I am back at that barn. I agree with the new pegs in any open hole. Even if the forces in this barn are beyond the shear strength of pegs they have to provide some additional strength to the structure.

Mike,
This is the fifth barn I have run into in SW Michigan that has a collection of sawn and hewn beams. I have not run a study yet to see if there was a size limit for local saw mills above which beams need hewn but it does seem to be the larger beams that are hewn. As an alternative to a "size restrictions at a mill" theory I should say that Jack Sobon mentioned he had run some numbers on his apprentices hewing work vs sawn timbers and found that timbers 3x5 and smaller were more economical to have sawn and anything larger his apprentices could manufacture for less than a mill. It looks like just the plates, ties, and purlins are the only hewn members in this barn. I would suggest it was a length issue not size. The center and corner posts are sawn. I can not offer any information about the pictured corner post being potentially replaced.

As far as history in SW Michigan. This area was settled in the 1830's and was known for it's hardwood forests. Forestry gave way to agriculture as the trees disappeared. TF building slowed by the 1900's and was extinct by 1930, having been replaced by pole barn and stud construction.

Hi,

Just stepping in and out with a question. These last few posts in here are great. Will's post attempt to answer the "Why" of the situation. I find this part the most interesting.

Will, when you say the "tie fell away". What do you hypothesize caused this. If I am understanding correctly, the canted posts are supposed to negate the thrust, which would in turn negate the tension in the "tie". Is this thinking right? If it is right why would the tie fall away? That midspan post I expect contributes to this equation in some way.

In the second picture, you can see the tie is away from the housing and it appears that the tie has dropped from the force of the strut and canted post. I can see this making the post bend above the tie (extremely it looks)from the rafters falling with. So does that mean the ridge is dropping in the middle bays? Does the ridge have a concave sweep to it when looking at the barn from outside? Would looking at the plumb cuts of the rafter at ridge, give an indication of how much this ridge has fallen?

Sorry to butt into this great topic. Im a firm believer in answering Why before What to do now.

Really appreciate everyone's knowledge around here.

Mo

I find it interesting that the braces weren't pegged. As they work in compression, and in pairs, I guess you can get away without pegging, but it is certainly not common in the barns around here. The tie beam pegs being missing is a real mystery. Not much to hold the frame together without those. Good job on the pics, my interior barn shots always come out very dark.

My horse barn is a mix of hewn and vertically milled timbers. All of the scantlings and at least one of the posts was sawn on an up and down mill.

I agree that a hewer can match some timbers in cost, depending on the labor rate of the hewer. Over length and larger cross section timbers demand a higher bd/ft rate at the mill, especially the long stuff, requiring specialized equipment. Three years ago Jack mentioned the turning point was an 8x9 timber over a certain length, probably over 24'. Most mills get about $1.50 a foot for pine/hemlock in that dimension. That's a $216 timber.

Hi Shawn:

Nice to see more details.

The vertical ridge supports I suggested would be convenient w/ posts already there at midspan of the building. Of course the existing posts need to be sound enough / large enough and on footings capable of handling the added compression.

Will's advice on getting some professional opinion is wise. Though there's nothing wrong w/ offering up suggestions here--many forum members have a lot of experience--there of course could be more issues at play.

And I also see a lot of mixed hewn and sawn stock here in Maine. I agree that it's a length issue. Most mills could only handle about 24' of length, which is why the longer members were typically still hewn.


And no dovetailed/wedged tenons on those tie beams? That really is a poor design. Not much stopping any withdrawal.

Good luck; keep us "posted."

Mo – You have it there, the thrust was redirected away from the wall plates and the tying joints, and perhaps completely negated, until the Tie fell away, (rot took it, a spot leak high in the roof, guessing water ran down the strut and sat in its mortise, the adjacent purlin post and its connection to the Tie and the Purlin Plate likely warrant close inspection, a resistance drill might be in order) when the Strut and Tie were lost, everything changed about the way the loads traveled through the frame. This dynamic changed again when the cables were placed.

And there are potentially, and more than likely, other things at play in there, which is why a trained eye should be brought in.

Ok, so I have met Tom Nehil, of Nehil-Sivak Engineering in Kalamazoo, through a timber framing course at Tillers International. I imagine he would be an acceptable trained eye for such a project and familiar with the local timber building styles and structural requirements. What services should I be requesting from an engineer for a project like this? Any guesstimates as to the cost of such a request? I imagine the benefits would certainly be worthwhile and valuable though there is a limit to the repair budget for this simple barn.

-Shawn

i buy the whole 'length' argument on the hewn vs. sawn - but there are other posts in the frame that are hewn. is that post the only sawn post? or are there others? if it is the only one, it may be a clue to the history of the structure... or maybe the hewer bought stock in a local mill by the time he got around to that post.



as to questions to an engineer - be careful here. find someone first that does barn repair work - then perhaps they can recommend an engineer sympathetic to your needs. otherwise you may end up with more steel cable, flying buttresses, or a sky hook.

kidding aside - a tension scarf may be tricky to pull off in situ, so you'll have to get creative with how it gets pulled together. will t. is right - correcting / repairing a barn like this is as much about rigging as it is about woodworking.

based on what i've seen (and i'm no engineer, just dangerous enough with how it all works for people to think i might be) i agree that the geometry changed and developed outward thrust at the plate. if i have time i might model it as an FEA just for fun to see what comes out.

Shawn – I can appreciate budgetary concerns, but there is much there, and it is probably an easier chore to bring it back to its intended working configuration than you might imagine. I also have met Tom, he and his partner were guest speakers at the PDW a few summers back. While I'm sure they could be of great help, it may be less expensive and answer more questions if you brought in a timber restoration specialist, as they might provide more insight as to rigging scenarios, they may also have a better eye or methods for finding signs of rot ( a timber that has been wet over a sustained period, will often look relatively sound on its exterior but be compost inside – look for water stains, mold and listen for hollow thuds – And that resistance drill was not a stretch, perhaps IML can point you towards someone in the area that has one ) in the rest of that Tie or adjacent members,.

http://www.imlusa.com/html/products.html

Though...

Running calcs on that tension scarf will be in order, the dueling struts will see be having it doing its duty.

Speaking of the struts, they usually fall over braces, I can't tell for certain from the photos, but have some of the Tie to post braces been removed ?

You should expect to pay their going day rate plus mileage, plus a fee to prepare a report if one is desired.

Best with it -

Will,
Regarding struts and braces. In the first photo you can see in the bottom right a brace but in the third photo (which happens to be the opposite side of the same tie in photo 1) no brace. It is literally hanging on by a wire. The owner was installing some romex and happened to attach to that brace with a staple. Soon after the brace fell out, remember no pegs, but has not been lost due to its connection to the electrical wire.

I'll try to catch up to Steve Stier this week since I'll be back in Lansing for another job. He should qualify as one who has barn restoration experience.