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Rammed Earth Truss Joinery  RSS feed

 
Sally Valley
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Is this the best method of fixing the truss for a rammed earth house? What is this method of joinery called?
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Bryant RedHawk
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Your picture shows a Brick (clay block) wall with recesses for Joists, the Joists form the roof sub structure, the recesses support the joists and hold them in line with their ridge plate connection point so they remain parallel top to bottom.
In some buildings with this sort of masonry support at the walls they will use a pin (usually rebar set in mortar) or wedges to secure the wall end of the joists.
Most references to joinery are about specific joints meant to hold either timber framing or furniture pieces together, such as finger joints, dovetail joints, mortise and tenon joints, lap joints. 

For most rammed earth building, a top plate (wood beam) is used to fasten the roof joists at the wall.
Some use just the wall as the structural support usually with wood dowels (pins) driven on each side of the joists (milled or round wood) to hold them in position.
 
Fred King
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One guestion, your post mentioned trusses but the picture seems to show rafters although its hard to tell only seeing them out side the wall. A truss has a horizontal tie at top of wall that keeps the angled beams from pushing out on the walls so truss would be easier to attach. The truss wouldn't try to slide out and down from the weight of the roof but I think Mr Redhauk is right about the use of a plate or beam well anchored to the top of the wall and if rafters rather than trusses are used a ridge pole or beam to support the peak might be a good idea.
 
Roberto pokachinni
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I would definitely go with a top plate on top of your rammed earth wall, as Bryant suggested, which will provide a secure way to join wooden trusses or rafters to your walls.

I'm not sure what you mean, exactly, when asking about joinery, Sally, but I'm going to go out on a limb with where my brain went when I read your thread.  My thoughts on it were that you were thinking of how those rafters are joined to the top of the wall, and you may be thinking that there is a joint hidden there by the brick work.  From the visible angle/trajectory and the existing dimensions showing, I'd say that that is not the case. 

In some cases, though, there is indeed a notch cut out of the rafter called a birds mouth, which technically is a joint as it joins the rafter and the wall.  Using a small birds mouth joint makes your roof system a lot stronger than laying your rafter's on edge with no grabbing support (as seems to be the case in the image you posted). 

Here are someimages of birds mouth joints that you might find useful, if that is what is on your mind.  A rammed earth wall with a top plate that had birds mouthed rafters coming down on it would be the best in my humble opinion.
 
Roberto pokachinni
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If you search 'birds mouth joint calculator' you can easily figure out the layout for cutting the angles of the rafters.
 
Sally Valley
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Many thanks. I am learning the lingo through your information prior to a workshop and a build.
 
I agree. Here's the link: http://stoves2.com
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