Cob Re: Timber framing, was 2 x 4 I beams

[Patrick Newberry]

I wanted to thank everone for  all the wonderful responses concerning the 2x4 I 
beams.

I've pretty much rejected the 2x4 I beam idea and have arrived at this point.

I checked out the homade trusses made with 5/8 plywood and 2x4's that is
decsribed in Reynold's earthship III book. I was receptive to this idea,

but there is still a nagging feeling that I'd like to use the natural timber
I have on the land. I'm on 150 arces of timber, mostly scrub oak but a lot of
pine and a few hicory and persimmion trees.

I've been mainly building with earth, so I've made a small foot print so far.
I have a budget of about $150 a week for building, so I started to figure:
If I build the trusses, the cost per 16 feet per Reynolds design, would be
1 sheet of 5/8 plywood (?) $10
6- 8ft 2x4'(@$2.50 each)   $15
total sans nails glue etc is $25 per truss. or I could build about 5 trusses 
per week(including the glue,nails etc) and keep within my budget. 

Now I figure I can cut and peal  a 12 to 16 foot viga in about 1 hour...
Well you can see where this is going, I'm thinking from a cost standpoint,
and based on the fact that I am blessed with having access to free timber,
it appears that this may be the way to go.(but then I'm always open to other
suggestions) I'd probably need more vigas than trusses due to the trusses 
strength being greater than my vigas. I don't get too large of logs due to not 
being able to move them when they exceed a certain size. 

McHenry in Adobe build it yourself quotes a 8 inch vigas has a maximum span of 
about 16 feet. I find the 8 inch size is about the largest  size I can handle 
by hand. Of course the distance between the vigas is a factor too! (that is 
place closer)

I've not done any timber (roof) framing before, so I'm sending off for the book
MoosePrints : holistic home building by Robert Laporte. It has some timber 
framing in it, but does anyone have any other recommendations in this area. I 
see a book called "Build a classic Timber framed house" by Jack Sobon. In 
any case (of the roof), the walls will be infill   made from straw and 
clay, so any framing will be within that context.


Well enough, 
Happy New Year to everyone!
Pat
http:www.gnat.net/~goshawk





Now





> You would be better-off making the beams 12" or 16" deep using
> plywood or OSB gussets to space the top & bottom chords. This has
> the added advantage of providing you with deeper cavity for
> insulation (in addition to the superior strength).
> 
> Also, steel gusset plates (20 gauge or so ?) should be applied to
> both sides of the butt-joint of the 2x4s used to make the 12'-16'
> chord members. The butt joints should NOT be placed at mid-span,
> but rather, at the 1/3 or 1/4 span points (ie points of zero
> moment). The grade of lumber used for the bottom chord (ie tension
> flange) is critical, and using a continuous member of #2 grade or
> better lumber would be prudent.
> 
> One of the beauties of box beams and plywood web beams is that they
> can be built in situ, making irregular profiles a breeze. ie The
> top chord & bottom chords can be propped-up to form wonky curves
> that would delight any funky-gooey-architecture fan and then one
> simply applies the joining web afterwards... and voila !... a truss
> (or box beam).
> 
> All that being said, I would strongly urge that you have an
> enginoidal sort look at your proposed beam design once you do get it
> drawn up.  Either that or do some Power Studying at your local
> university library to bone-up on beam and truss design.
> Collapsing masonry roofs are not a Good Thing.
> 
> Okay, now back to singing those carols. A one an' a two an' a three...
> 
> Thengya. Thengyallverramuch.
> --
> Rob  Tom
> ---------- * ------------
> be417 at FreeNet.Carleton.ca
> Kanata,  Ontario,  Canada
>