Gambrel Barn designed by Architect

[kettleviewtimber]

This is a design of a gambrel style barn.   The size is 20' x 30'.  

Any suggestions or possible issues you see with the design?

All members are 8" x 8" white pine, even the knee braces.  Tenon length is 3" with 1" dowels.

None of the Joints are housed.  The timbers are coming from reclaimed barns in the area.

The rafters are all 2" x 8".

[Jim_Rogers]

That link was useless to me..... what are you having problems with?
Be specific....

Jim Rogers

[Thehardway]

Most engineers would need windload, snowload and floor loads to do anything meaningful.

From a layman's point of view the 8X8 is way to small for a 20' span on a barn, especially with recycled white pine timbers. Additionally the joinery for the second floor posts appear to fall directly over the knee braces and would cause a serious weakening of the beams.
I can't tell for sure because of size of the drawing about the post/plate joinery.  Is that to be a continuous plate with a traditional English tie joint or is it bent style construction with plate broken at posts? Is this to be all common rafters for roof or principles with commons or rafter/purlin

Additionally I would want some bracing on the second floor posts to beam and post to plates.  There is nothing to prevent racking or twisting of the second floor structure.

I would not be real happy with this design from a structural standpoint.

What would the tenon width be? 1.5" or 2"?

Forgive me if this critique sounds harsh.  I like barns to be able to hold LOADS as you never know what someone down the road will try to park or put in it.

[Jim_Rogers]

Unless this architect has timber framing experience then the design would/could be questioned.

Such as 8x8 braces.....

Normally with 8x8 timbers the tenons should be 2".

And having the second floor posts over the braces from below isn't necessarily a bad thing.
It is true that there will be some lost in the strength of the tie beam where the brace pocket enters, but the sub tenon pocket for the second floor post won't weaken it much. And right at this point where the tie maybe weaken, it is supported by the brace, so that may offset the weakness point.....

Please post another link so that I am able to view whatever the html page shows.....

[Brad_bb]

Yeah, the middle bents need more knee braces.  And with recycled timbers, you should probably be using square rule and housing at least the knee braces and anything else you want a good looking joint.  Tie beams should be taller and sized to support expected floor loads(live loads) plus all the structure above etc.
   8X8 knee braces is not necessary or normal practice, unless that is a look you are going for.  You can use smaller stock.  I like oak for knee braces; you can use 4X6 inch stock.  Or if you use pine, it needs to be beefier, and it's got to be very good quality stock though.

[kettleviewtimber]

Here is the post to connecting girt connection. Bent style construction with common rafters for roof. One 1" dia. dowel.  The tenon length is 3" and width is 2".

[Jim_Rogers]

I can understand what you mean now, but seeing that joint.

This is the case where you may need to use a spline piece to go from one timber through the post to the other timber.

The current tenons aren't long enough to provide enough relish for the pegs and they will most likely blow out depending on the loads placed on the frame. And or what type of enclosure system is used to hold it all together.

Will this frame need to be engineered?

An engineer, who is familiar with timber framing, would/should see this right away. And may make proper suggestions for improving joints like this.

Jim Rogers

[swampfox]

Jim, brings up a good point about the enclosure.  If there are sips (but is says barn in topic) than you can get away with the frame being weaker from a racking point of view.  Anything else and this needs more.

The plates not being housed from a structural stand point looks weak to me.  That is a big load that is going to be transferred to that point.
I agree with the others about the posts being to small in X-section.  It looks as if the wall post tenons have no relish to the outside of the tie?
This doesn't seem right.

In my opinion, there are two options, have a continous plate (with scarfs over wall knee braces, or posts) that rests on the posts, drop the tie, and common rafter the slope.  Have the same relationship with the loft posts (dropped tie).  Or drop the ties, Principal rafters, common purlins, common rafters.

At least an 8x10 for ties?