Hello Timber-frame World,

This message comes to you from a relative novice. After many hours browsing the forum's pages and links, I would first like to thank so many folk for sharing their knowledge and experience.

We brewed up a construction project about six years ago, and originally thought to implement it with stud (stick) framing. That was before my brother-in-law handed me Tedd Benson's books and voila!, the philosophy changed.

I have spent many hours on this design, and followed every lead available. My source materials are the Benson books, plus TFG Workbooks 1&2. Beyond this, I have spoken with local artisans and am in dialogue with one in particular who can help me with technical info. Problem is, though I speak passable franglais, there is a language barrier and further, my designs of American origin may not be readily comprehensible to a native. So, I turn to you for advice.

The design is for a saltbox form with lots of plates supporting a common rafter roof system. My first inquiry relates to optimal positioning of struts and braces in the roof. The plan is accessible here:

http://informal.izaut-rustica.com/graphics/selfbuild/frame_west_sm.jpg

In respect of the braces supporting the queen posts, must these be angled at 45deg, or can I keep the aesthetic choice at 35deg?

In respect of the strut under the shed roof, should this remain perpendicular to the roof, or go more steeply to the midspan (option ghosted in)? Position of the foot strut is limited to allow passage with the inner two bents.

For complete overview of frame design, go to:

http://informal.izaut-rustica.com/selfbuild.htm

Perhaps I can get the ball rolling by giving my own thoughts.

Strut position Here it is without click:



Loading: moving the upper end of the strut will transfer loads from the LH post to the RH one; the latter is capable of such change. The loading on the supporting girt is close to a one point load at center, and will not differ. The rafter max span will decrease a little, but a 3x4 (actually 8x10cm, standard in this neck of the woods) is well capable of holding the present.

Tension and Compression: In present perpendicular position, the strut will fairly squarely be in compression from dead or live loads; the brace joints (to girt and to strut) also. If the move to right were large enough, then the brace joints would go into tension, undesirable. However,the queried change is about 1ft horizontal which will be counteracted by the down/outward thrust from roof slope.

Jointing: common rafter to plate jointing may be effected with a step-lap seat, where the former meets latter at an angle; current position denies this opportunity. This may be the deciding factor, though other joints are possible.

Brace (strut) to queen post angles:



Bracing in lower corners is usually impractical, but here is an opportunity where it isn't, in fact, it increases access to loft space (between QPs). Bracing in upper corners is practical at 45deg or steeper. In lower corners, the converse argument applies. So this is OK!

... no balls rolling. I'll just imagine I could possibly help someone else with the principal of discussion :rolleyes:

Here's another consideration; the wall system.

In the case where the strut remains perpendicular to the roof slope, the top of the strut (and plate) would coincide with the depth of the wall system (whatever that may be) making for some awkward fitting around braces etc. This does not fit into the context of an easy selfbuild !

Angling the strut 10deg steeper will allow it to remain wholly within the living space. The wall-fitting will be simpler, though it must still work around strut braces.

This design has moved on! I've specified timber sections and put a joint list together.

Click here to speculate. I will be happy to recieve comment or criticism

Thanks Derek. The main alternative to the strut would involve principal rafters which would crucially reduce headroom under the shed slope.

It isn't clear to me here whether you are still working on 'exchange and liability' or irritation at my dig at having an un-responded post here for 3 weeks. If the latter affends you I apologise; I've added a to that ff post.

Derek, I've read all your thoughts in the disclaimer discussion, and I appreciate that its safer to 'only talk amongst professionals'. So I'm privileged to have some of your remarks now, and BTW, Brits are regularly amazed at the sue-ing tactics which occur in the USA. Personally, I grew up with the philosophy of self responsibility. If I trip over somone's walking stick, its my fault for not lookin where I was goin

The strut holds up a plate, one of 4 on the long roof slope. Then common rafters above.

That is indeed interesting; you have given an identical response to that from a local designer here. I thought it resulted from the structure really being foreign to him.

There is (now) a good reason why I can't do away with it: the foundations are well started, a system of plots with 1ft sq pillars and variable area base. The plots to each side of that external wall are about 3ft sq, whereas that under the wall is only 2ft sq. So, the load needs to be directed away.

It isn't entirely clear, but your objection to the strut seems to be on aesthetic grounds. To be honest, the strut does bug me somewhat, but more in knowing that it can do the job. It looked more correct when perpendicular to the rafters. So long as there is no structural reason to discard it, it seems to be the best option. Once the cladding is on it won't be seen from the outside, and it won't be tripped over because it only sits next to intended walls. Have you ever implemented such a structure in your builds?

There is another reason to keep it of course: its more timber-frame than just using the stud wall. :rolleyes:

Its worse than that; I'm a mule

What I meant to ask was, have you ever implemented a canted strut system in a manner where it did look good, or are they simply out of favour with your style?

Here's my response to challenged aesthetics and 'stand-alone' capability:



I can't see the strut replacement as an improvement.

As for those big braces ... initially had a fit realising the point load at mid-beam, where some mortise wood will also go missing. In fact, those 4x8 girts are amply dimensioned for the job, since they carry only a small floor load. Three of the four bents could take the braces (continuous wall) while for the fourth, only the LH one would need reducing to admit a doorway. Shall I go for it?!