Arcade Posts

Hi All:

I think this subject might be interesting to discuss. It's not particularly common from what I've seen.

The big old 1885 New England barn that I was in the other day had these posts lining either side of the barn's center isle. I believe the correct term is "arcade post."

They run floor to rafter, maybe 24 feet long. I'm curious about a few things:


1. Does this long arcade post method pre-date typical floor-to-crosstie arcade posts, or is it vise-versa?

2. Was this style developed for space/ height advantages in a building's interior. (getting rid of continuous ties) It seems cathedral-like.

3. Do you only find this in really big buildings?


4. Is roof spread more or less likely w/ this system?


5. Is raising a barn w/ this frame situation more problematic? It seems to interrupt the whole concept of "bent raising"




I have posted a couple photos to show what I'm referring to:

Hi Don,

This is not an arcade post but it might well occupy the position where one might expect to find an arcade post. An arcade post rises to join with an arcade plate, running parallel with the wall plate and it is set horizontally i.e. not in the plane of the roof like a purlin. This barn has no arcade plate.

I rather suspect that this is another form of debased carpentry in that the only thing that appears to be preventing spread is the tops of the two principal rafters and in reality only the peg that joins these rafters together.

Is there a connecting floor lower down ?

Regards

Ken Hume

In the top photo there appears to be a hay track. This barn could be a custom design for the hay track system....

Jim, there is a hay track. I agree that this might be one of the reasons behind the design. With no crossties, a big mound of hay could be lifted from a wagon and ride down the length of the barn w/out needing to be hoisted above the ties.

But many, many barns have these tracks w/ out this post arrangement so I'm puzzled that it didn't "catch on" because it affords that option.

Thanks Ken,

No-- not another debased form! Is there no end to them?!?!

Anyway, so I'm wondering what kind of post is this if not an arcade? They are on either side of the center isle.

As far as roof spread, I'm not an engineer like yourself, but I tend to think there are two (three, if you count buttressing) ways to prevent roof spread in a gable roof:

1. tie the walls together
2. stop the ridge from sagging.

Either method works, correct?

This barn is quite square and true given its 120-odd years. Roof spread didn't seem to be an issue. the ridge is good and straight, as are the walls.

These posts, which are attached to the major rafters nearer the ridge side of their span, appear to be holding the major rafters vertically, thereby prventing sag (and thus spread).

I'd like to think this has held the walls in check far better than pegs at the ridge... I don't think there is a connecting floor further down.

I attached another picture:

just a quick additional thought.

There are ties going to the walls. You probably saw them...check the 2nd picture of the first posting. These no doubt help tie the building as well...

Don, the strut and brace going from the post to the interrupted tie may form a truss which can help with the spread. On second thought it doesn't work that way, something would have to be switched.

I also see a open mortice in the forward post on your recent post (that's too many posts), do the other post have the same open mortice or is it a oddity. More mortices could mean a tie was removed to make room for the hay rack.

The building is square ruled, did you notice that, on the second photo. The tenons are through, is that only one peg I see at the tie to post connection? How about a wedge on top of the same joint?


There is something going on with the rafter tops as well. The the not so well placed collar board jammed into the peak (hay rack). It appears there are two types of rafter peak joints, the tongue and fork and a plumb cut butt joint? Could just be the photo.

And standing outside you see no bow at the eve?

In the last photo isn't that a center isle connecter about 3' below the interrupted tie, between the two posts?

What is the size of the "arcade" post?

And lastly how is the interrupted tie connected to the exterior post? Tim

Tim

that's a tall order to check. I'll likely go back sometime. I presumed it was square rule first of all because of its age (1885). And saw housings as well.

Your post-tie-strut suggestion of forming a truss works for me. In order for the walls to spread, the "arcade" posts would be have to bow considerably... the interrupted tie would pull on them, etc.

But these tall posts hold the ridge up via the major rafters, thus preventing ridge sag and the resulting wall spread, so these two factors probably keep the walls plumb. (that my take).

I noticed the open mortise only after I saw it in the photo, so not sure if ties were removed. And yes, just one peg. Didn't see any wedges. You must be thinking dovetail tenons...

The walls are pretty straight, no bow. In fact the barn is pretty stout overall. Nice building.

I noticed the "gussets" tying the rafters at the peak. I would have expected a ridge beam w/ major rafters. And I think that is a tie over the center isle in the last photo. This is the second-to-last bent of the barn.

The posts are 8x8 w/ some taper I think.

And the interrupted ties connect to the exterior posts like all crossties in the other CGs here: on top of the posts and cant past them a bit to catch the flying plates (in this case).

Have you ever seen this post style in the center isle?

More pictures here, just scroll down a ways:

http://www.tfguild.org/forums/ubbthreads...16&fpart=15