The Forestry Forum

Hi everyone.

Does anyone have a picture or info on a hammerbeam truss holding a structural ridge beam?

Thanks in advance

This link shows one that a student and I cut a few years ago.

http://www.timelesstimberworks.com/hammerbeamcape.html

This link will take you to one that you can modify and then, have checked by a PE.

http://sketchup.google.com/3dwarehouse/details?mid=cf9f785428222a63f49c12a531c40405



Regards,

jay

P.S.  Jim may have one to share.

Quote from: Jay C. White Cloud on April 03, 2013, 09:17:09 AM

P.S.  Jim may have one to share.

I do not...

I don't think that you can have a structural ridge and a hammer beam.  For the ridge to be structural, it needs to bear on posts, and having a post run through the middle of the truss, would make it not a hammer beam truss anymore.  The ridge that Jay shows is just a nailer.

i concurr with the last post, you can have a ridge beam and all such, but it is not a structural ridge.
the structural part is the hammerbeam truss, which supports a secondary ridge beam which i assume would then support common rafters.
a structural ridge is a complete system of posts and beams where the ridge beam bears the weight of the roof straight down through the posts beneath it into the foundation, or somehow into the walls as is the case in many strucural ridges on log structures
a structural ridge bears inward force against the walls at the rafter seats, whereas a hammer beam or other truss system bcreates outward thrust

That's why I said I didn't have one...... ;D

Hello Folks,

Well we may have gotten a bit off topic, but definitions and semantics can/are important.  (especially if you're trying your best to be accurate in your writing for publication as David and I both are.)  I will share the following for consideration, per Zelpatemot's origingal question,

QuoteDoes anyone have a picture or info on a hammer beam truss holding a structural ridge beam? 

First, I thought I should check myself, to make sure some of my old wires didn't get crossed along the way on this topic.  I don't sleep much and when I read late at night, things can get jumbled in my old head, but I think I kept it all straight on this one.

By the way of several dictionaries and reference sources, here are some definitions of value:
 
Structural member:

1.   Noun. Support that is a constituent part of any structure or building.

This went on to list everything from sill beams and braces, to post and ridge beams.  Some can be considered critical members, while others are minor members, but all are considered structural members.  In design, architecture and CAD work, it is used more so in the languages of different text.

Ridge, Ridgepole, Rooftree

A structural beam laid along the edge where two sloping sides of a roof meet at the top; provides an attachment for the upper ends of rafters

QuoteI don't think that you can have a structural ridge and a hammer beam.  For the ridge to be structural, it needs to bear on posts, and having a post run through the middle of the truss, would make it not a hammer beam truss anymore.  The ridge that Jay shows is just a nailer.

It is a nailer,  (as a secondary definition) but also a "structural member" or "structural ridge" as discussed in https://forestryforum.com/board/index.php?topic=48387.0 It is a "structural member" by definition, as it transfers it's load to the short king or ridge post to the straining beam between the principle rafters, and then down through the other structural members to the posts themselves.  I don't mean to sound too validating but I routinely have conversations with PE and this is their language as well.  Perhaps not all, but it is the general consensus.  I will expand on the topic of structural ridges, as considered by PE, that the lower the pitch of the roof, the more critical they become, especially so in "stick built," structures.. 


Handbook of Building Construction: Data for Architects, Designing and Construction Engineers and Contractors by George Albert Hool, Nathan Clarke Johnson (1920)

I should have been more specific, my bad.

A hammer beam truss, supporting a ridge beam that holds common rafters.

A modified hammerbeam with a *king post perhaps? Similar to the cape link above, but common not purlin rafters.

Thanks

QuoteA modified hammer beam with a *king post perhaps? Similar to the cape link above, but common not purlin rafters.

I can't find the link? Also, a principal rafter, (purlin rafter) is a critical component of a hammer beam truss system.  Now there are many variants of the Hammer Beam truss system as they have evolved from the archetypal Cruck Frame, and there are those with a more common rafter roof system.  Do you have any drawings you could post of what you are thinking about?

Regards,

jay

I drew this King-post truss in response to Dave's request for large timbered trusses.
Could it be converted to a modified Hammer-beam truss?

Rooster



 (https://forestryforum.com/gallery/albums/userpics/15824/Dave_s_shop02.jpg)

Perfect Rooster, I will respond in detail later...

this is kind of half way between roosters drawing and jays frame that he linked too...

it was the first idea that came to my head, so i don't think it is very traditional or i don't know if any previous examples of this method.

its just a rough sketch it leaves a few blanks to be filled in but it gets the idea across

(https://forestryforum.com/gallery/albums/userpics/27590/hammertime2.jpg)

Justin you got the idea, now just add braces to the main post of some configuration, then from the bottom of the short king post down to the other brace, and you are 90% there (the joinery can make or break this bent design.)  Many PE still feel the need to run a cable across this assembly to achieve the strength specification they require.  Hammer Beam Trusses are a real challenge on several fronts.  Just like the one that I helped facilitate, they stuck one on the end of the building, which is not a good practice, but what they wanted.

Hi,

Westminster Hall Hammer beam roof (1395) in London, England has a ridge !

Chilterns

I'm new as a contributor to this, can I interrupt to ask a question? I'm wondering if a Hammer beam roof system can be designed like Justin's drawing here but add only the brace from main post to hammer beam? I'd like to leave out the brace from king post down to hammer post if possible.  Thanks

A hammerbeam is usually a poor way to build a roof. They should really be on an immovable wall to restrain thrust. Leaving out components sure isn't going to improve upon that. If you can tolerate the steel rod or cable that forms a bottom chord that would work better.