Newbie - monitor barn build

[Cornhusker]

Greetings!
I have been lurking on this forum for about 2 years, trying to get my terminology correct, and learn as much as I can for my first timber-frame, a monitor-style barn, approximately 40' x 60'.

I'm planning to have 6 bents, spaced 11' 6" apart, and 3 bays aisles: a 16' wide, taller, central bay aisle that includes a loft at each gabled end, but an open "cathedral" ceiling in the middle; and two 12' wide side bays aisles, with shed-style roofs.

The central (taller) bay aisle would have a row of small (2' tall x 4' wide) windows, running just below the eaves of the central bay aisle roof, for natural lighting.

The 12 big upright posts will be 8" x 8", Douglas fir, 16' tall, milled out of some high-voltage power poles that were 80' tall and about 18" wide at the base (must have been some amazing trees).

Those upright posts will sit on poured concrete piers, reinforced with rebar. The rest of the floor will be a poured concrete slab, with recycled red bricks for the main center aisle.

The main, horizontal tie-beams that run under the lofts will be 16' long, 8" x 10", cut from ash that is dying in our area from the emerald ash borer. The bottom of those beams will be 9' above the floor.

I plan to use an 8" x 10" top plate, on top of the posts, perpendicular to the tie beams, mainly ash and hackberry.

I've spent quite a bit of time working out roof-load calculations, using the calculator on this site. I plan to use a metal roof, fixed to tongue-&-groove boards (for the look from inside the barn), with some kind of foam insulation in between, but I still have quite a few details to work out yet.

I will use common rafters, probably 3" x 7",  for the roof, which will be a 10/12 pitch, over the central bay.  The common rafters will be cut from doug-fir telephone poles (used, but in great shape).

Then, the side (shed) roofs, will probably be 6/12 pitch, also using another set of top plates at the eaves, and also using common rafters.

One of my main questions involves these shed roofs: how to tie the upper end of these roofs into the central bay aisle frame?  Should I timber-lock screw them to the top of large girts, which would run below (but parallel to) the top plates?

I have the main posts and tie-beams milled, and I'm ready to start cutting mortises and tenons, but I'm still unsure about this girt/shed roof connection, and would appreciate any advice, or any other observations, whether simple or complex.

I'm also in the process of collecting TF tools.  I don't have a good chisel yet, and I'm still trying to decide whether to buy an old-school beam boring machine, or to try to build a jig for a hand drill and buy a good Wood Owl forstner bit. I can't afford a chain mortiser.

Also, if any of you are in the vicinity of Nebraska and have already built a TF barn, I would love to come see your work and bend your ear for advice.  I'm in the south-central part of the state, not far from Grand Island.

I'll post some photos of my drawings/designs in the next day or two.

Thanks!

[scsmith42]

Welcome Cornhusker!

I look forward to seeing pix of your progress.  Monitor style barns are amongst my favorites.

Scott

[Crusarius]

I have one I am planning as well. Would be great to see your progress 

[Jim_Rogers]

how to tie the upper end of these roofs into the central bay frame?  Should I timber-lock screw them to the top of large girts, which would run below (but parallel to) the top plates?

You can lag bolt a ledger on the side of the posts so that you can cut a birds mouth on the shed rafters and attach them with timberlok screws similar to this:



 
You'll have to do the load calculations to make sure that the ledger is big enough to handle the load. I put these on this building as the rafters lined up with the posts and we had to have some way to support them.

Also, just to help you to understand terms, bays are between bents, aisles are between posts. So you have a long center aisle and two outer aisles.
Bays go eave to eave, aisles go gable to gable. Not a big deal just wanted you to know.
Jim Rogers

[Cornhusker]

Thank you for the reply, Jim. That's exactly the kind of advice I was looking for. It does seem like the ledger would need to be quite stout.  In fact, it seems to me like the ledger would need to be even more beefy than the top plate supporting the higher, central roof, since the shed roofs have a longer span, (12' vs. 8') and the shed roofs also have to withstand snow drifts dropping onto them from the upper roof.  I'll run those calculations on ledgers and see what I get.  

But I understand that you don't recommend resting those shed rafters on the girts, correct?

Thanks so much for the illustration, too - super helpful.

[Jim_Rogers]

You can rest them on the girts if they straddle the posts. But sometimes they are in line with the posts and that creates a problem.
This added snow load from the upper roof is why we hire engineers to verify our loads and joints.

Jim Rogers

[VictorH]

Welcome Cornhusker!  Nice to see another Nebraskan here.

[Cornhusker]

So, I have 12 upright 8"x8" posts, 16' in length, and I am getting ready to start cutting mortises into them. 

The next decision I have to make is: how to bore the holes for the mortises? The mortises will be 2" wide.  I cannot afford a chain mortiser.  So, I have thought of buying an antique boring machine, plus ship auger bit (at least $500, I think); 

Or, I could buy a 2" ship auger bit or a 2" forstner bit (probably Wood Owl) that I can use with a heavy-duty corded drill that I already own.  This is probably my most affordable option, (less than $100), although I really like the idea of an old boring machine.  

I realize that some of the difference is basically philosophical / aesthetic / preference.  

One question I had for those of you who are experienced: is a forstner bit going to be able to make deep enough holes for the mortises in an 8" post?  If not, I assume that I'm limited to the 2" ship auger bit?

I'd appreciate any feedback, on these questions, or anything else that I might be overlooking.

(Oh, I also plan to make a 1" x 1" story pole, also 16' long, so that all of my cuts will be exactly the same).

[classicadirondack]

I've use a Milwaukee 2 in self feed bit and a "Hole Hawg".  Be cautious, there's a lot of torque

[Ljohnsaw]

With Forstner bits, you need to withdraw them often to get the chips out.  Otherwise you will get it stuck down the hole (don't ask me how I know...).

I have two antique boring machines.  GREAT tool!  Keep the bit sharp and away you go!  WAY easier on the wrists/body than trying to use a power drill.  Also, makes nice straight holes right where you want them.

[alecs]

I've looked at used chain mortisers on ebay, with the thought that if need be, I could sell it again as a little bit more used after being done with it.  Think of it as a long term rental.  

[Troy Schon]

Well yesterday was a beautiful day for timberframing in Nebraska. We got a lot of work done on the posts and a plan for the next step. Thank you for food, fun, and fellowship. Hopefully we can get some more Nebraska boys together for a workshop or raising next spring.