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Re: Blind connection to roof sheathing

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The roof sheathing nails will indicate rafter or truss top chord locations, or you can use a stud finder to locate them.  I don't know what your tension loads will be but I wouldn't consider using plywood or OSB alone to fasten to for tension loads.  Use locations that have 2x rafters or truss chords below.
 
Ray Shreenan  SE


From: Joseph R. Grill <vveng(--nospam--at)cableone.net>
To: seaint(--nospam--at)seaint.org
Sent: Wed, February 24, 2010 1:17:21 PM
Subject: RE: Blind connection to roof sheathing

Yes, that is an option, although not in all cases (I am looking at an assembly that will be installed on any number of roof structures) as not all under sheathing spaces are readily accessible.  I would generally prefer that myself, although it may feasible in some situations.  On the other hand a connector like what I am looking for might require accessibility also if it uses a washer.  A blindsided connector would be ideal.  I would suppose that a flat 2x member below the sheathing with a nominal attachment to say top chord of trusses would act like a large “washer”.  That brings another question to me.  Has anyone ever run calculations on a “pull through” value of a washer through OSB or Plywood?  Is there any literature on something like that?

Joe

 

Joseph R. Grill, PE

Verde Valley Engineering, PLLC

2220 Sky Drive

Clarkdale, AZ 86324

Ph. 928-600-5459

Fax 928-649-3659

email: VVEng(--nospam--at)cableone.net

 

From: Drew Morris [mailto:dmorris(--nospam--at)bbfm.com]
Sent: Wednesday, February 24, 2010 1:50 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Blind connection to roof sheathing

 

Can you put some flat blocking against the bottom of the sheathing?  This would give you a deeper section to put the screws into.

Joseph R. Grill wrote:

I am looking for a connector to attach a small galv. Steel bracket to roof sheathing.  Understanding all the implications of weather and moisture protection and plywood stresses for the application.  I will deal with those a bit later as I am trying to come up with some ideas for a proposed project.  I would still like to find something if available.  The connector will have to be structural with available values, of course.  The bracket will be subject to a tension force (although fairly small and the sheathing will probably check out) therefore pull through will be one of the issues.  So something with some sort of washer type of backup would be nice.  Others have suggested a wood screw to the plywood and have justified with calculations, but I don’t think it is even close to being a good idea.  The diameter is small.  The wood screw ideas were #9 so that is the diameter that is what is being considered at this point.

 

Any help would be appreciated.

Joe

 

Joseph R. Grill, PE

Verde Valley Engineering, PLLC

2220 Sky Drive

Clarkdale, AZ 86324

Ph. 928-600-5459

Fax 928-649-3659

email: VVEng(--nospam--at)cableone.net