I still am unsure of how to have a queen post act as a truss as opposed to just transferring the load to the tie beam. Using a typical 30' x 40' (american)English barn,as an example. that are dotted all over the landscape in New england. I see that the gable end bents typically have a center support post for the tie beam with girts that tie lower on those posts to the corner posts. The interior bents seem to be able to structurally do away these interior support posts and the girts , allowing a clear span under them. In most of the house frames I see plans of that are basically, even sometimes smaller, versions of this typical English barn I describe, the queen posts are acting only to transfer the load to the tie beam. I am really unsure as to what would allow one queen post frame to allow a clear span under it and another to recquire the support under the tie beam. I am generally thinking of frames that are using principal- common rafter system( no ridge beam) and both continous top plates and purlin plates, if that has any bearing. My other thoughts are that the bottom tenon of the queen post is perhaps joined in a similar way like the king post to become a proper tension joint. Also perhaps if there were a 2nd floor load being supported on these tie beams as well. tb

TB,
Hey I think I know what you are asking about...my question is...are you opposed to having large queen truss diagonals on the first floor level/under the tie beam?....or....Do you want to have the queen truss be above the tie in the upper/second level? Now I am not an expert, but have you thought about having a second tie beam 6-9ft above the first one? Could you use the purlin posts also as the Quess truss rods/posts, and have the second tie-beam be used as the compression member of the Queen-truss? I wish I could draw you a picture of what I am thinking.
Let me know what you think.

Rooster

...Or have it all and go with a hammerbeam truss...

I agree with your observations... queen post bottoms are in tension, for long-span internal trusses w/o support under the tie-beam. It is my understanding that the purpose of the queen posts in those internal bents/trusses is to keep the long tie beam from sagging - similar to the function of the king post in a king-post truss. The collar tie would be in compression, keeping the rafters from sagging. I believe the design is different in the gable ends because it can be. If one can include support for the tie beam (in the gable ends or anywhere in the structure), then the whole structure will be stronger, over-constrained, and somewhat redundant. Now I think I'm being redundant. What was your question exactly?

thanks all. to answer a few questions , I was relating the barn more specifically to a basic high posted cape house frame of 24 feet wide and a one and a half story( 3-4 feet post extension), so the second tie beam is not an option. I just would like to have a bit more freedom by not having the support under one of the tie beams on an interior bents. Of course my gable end bents would be built up because they can be. Thomas in Kentucky , my question was what makes the queen post act as a truss as opposed to just transferring the load to the tie beam? It does seem that it is much like the king post , but I have never seen an example of queen posts in these barns of a wedged and pegged through dovetailed tenon as you see in king posts( which seem to be ideal in this type of tension joint)? I wonder if there is any joinery or sizing of member and also tenon accomodations I would make differently if I needed the queen to perform its truss duties. I also wonder if the purlin plate is essential to a queen post truss or might you be able to join the rafters directly to the post tops and run intermediate longitidinal plates between the bents as Steve Chappell does in his sample frame in "timber framers workshop", as you know continuous top plates of such lengths of 36' and more are difficult and expensive to obtain. Since the barn frame I describe seems to always have these continuous purlin plates, I wonder if they are somehow imperitive to allow such clear spans as 30 feet or more. By the way I do like the idea of using longer braces , perhaps from the lower third of the posts and also using a larger size on them. Not such a fan of hammer beam trusses, they are beautiful but, they seem to be suited best to superiorly butressed masonry buildings , other wise they seem to be doomed. Thanks again guys. tb

TB, I am familiar with the frame type you speak of. In all of the ones I have seen in the Hudson Valley, the queen post arrangement is not acting as a truss, but transferring vertical load. I have occasionaly seen braces to the outside of the queen posts going down to the ends of the tie beam, which could help make it act like a truss. I think I have seen this in newer barns though where the queen post tie was omitted to accomodate a hay track, (there goes the truss action.) Usually the interior bents have a center post too. Some times in carriage barns, one bent doesn't have a center post and instead has an oversized tie beam going full width. This was so the carriage could be pulled in and turned (swung)around. The huge tie beam in this case is called a swing beam. Some of the old mill buildings in the area have real timber queen post trusses to provide column-free space below. There is one on Columbia Street in Hudson that has an attic or third floor supported by the bottom of the truss, a second floor that is hung by rods from the trusss and a totaly column free first floor.
Best regards,
Chris

chris. Thanks for your help. If you get a chance check out the www.heritagebarns.com and look at their picture they show of a typical English barn. Or if you happen to have a copy of tf guilds red book page one "the evolved American frame" or in Jack Sobon's historic American timber joinery "tie below the plate design " page three(A great book by the way). All of these illustrate the example I speak of, though I have seen also many example of your swing beam barns. It is just puzzling to me why some of these barns were able to rid the support of the intermediate post while others were not?? . You are right the old mill buildings are wonderfully crafted. I also think that tying below the plate , while it is attractive in some respects, it already undermines the basic needs of a proper truss , the rigid triangle. Thanks again for your input. Sincerely tb

Dear TB:
Attached is a photo of a late model queen post bent, sans queen post tie as mentioned earlier. If a tie (top chord) were put in and the queen posts bottoms were morticed thru the tie beam to develop tension, it could act as a queen post truss and help support the second floor.