[Cob] Attaching a roof to cob columns

[Henry Raduazo]

Pictures available upon request

Kevin: This is an essay on dead man anchors:
	In the cob industry "dead man anchors" are commonly used to attach  
door frames or backings for door and window frames to cob and dead  
man anchors are usually used as hurricane ties.
	 There are two basic types of dead man anchors commonly used in the  
cob industry The first is the all wood dead man. Fig. 1 below shows  
the construction process where a pine dead man is attached to a  
slender oak tensile member. The oak has been pre-drilled to prevent  
splitting and both the oak and pine dead man have been roughened up  
to take glue then they are bonded together with glue and screws.  
(Note Fig. 2 below)




	Fig. 3 shows the dead man anchors in their final position in the  
wall.  The anchor near the fence must be cut shorter and the anchor  
closest to the camera must either be taller of placed at a higher  
position in the wall because because the roof will slope front to  
back at a 45 degree angle and the oak tensil member as shown in this  
picture is not long enough to to reach the and be secured to the roof  
beam.
	The roof beams will run from the L-shaped column in the background  
to the T-shaped column in the foreground and be secured to the dead  
man anchors which will be imbedded in the columns. A second set of  
roof beams will extend to a third L-shaped column not seen in this  
figure.


	An alternative way to make dead man anchors is using wire tensile  
members instead of wood. Fig. 4 shows such a dead man anchor with  
horseshoe nails used to attach the anchor to the roof beams. In use  
the dead man will be buried in the wall during construction and the  
two wires will extend above the top of the wall. The first wire will  
be wrapped clockwise around the beam and nailed to the front, top and  
back of the beam while the other wire will be wrapped counter  
clockwise and nailed to the back, top and front. The best way to do  
this is to have one person grip the wire with pliers and tension the  
wire while a second person nails the wire to the beam. Use lots of  
nails and pound them in far enough to firmly grip the wire but not so  
far as to cut it.

 

	I have selected oak tensile members for my roof because the slender  
pieces of oak will provide both tensile strength and shear resistance  
against wind forces.

Ed

On Jul 9, 2010, at 10:33 PM, Kevin Brown wrote:
Hey Ed,

Thanks for the response and info. Is there often some play in the  
wire? I'm having trouble envisioning how to secure it snugly.


<-----Original Message----->
 >From: Henry Raduazo [raduazo at cox.net]
 >Sent: 7/8/2010 7:43:50 PM
 >To: brownkc at care2.com
 >Cc: coblist at deatech.com
 >Subject: Re: [Cob] Attaching a roof to cob columns
 >
 >Kevin: I would suggest a dead man anchor. A dead man anchor is a
 >piece of scrap wood buried in the mud a foot or so below the cross
 >beams and attached to the cross beams by means of a wire cable or a
 >thin stick. The wire can be wrapped around the dead man and will
 >extend perpendicular to the dead man to the beam. It will be wrapped
 >around the beam and attached to the beam by wire staple or horse shoe
 >nails.
 > The thin stick is attached first to the dead man with screws when it
 >is buried in the wall and then attached to the roof beams by screws
 >when the pillar is high enough to support the beams.
 >
 >Ed
 >On Jul 8, 2010, at 3:10 PM, Kevin Brown wrote:
 >
 >> Greetings all,
 >>
 >> I'm building a gathering place of sorts in central Montana (Big Sky
 >> Country) and am building a roof with two cross beams attached to cob
 >> pillars. Any suggestions on how to attach the roof to the pillars?
 >> The surface area of the top of the pillars will roughly be 16-20" x
 >> 16-20". Thanks
 >>
 >> Kevin Brown
 >>
 >>
 >>
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 >
 >.
 >

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