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RE: electronic stud finder to detect roof joists?



Everyone is overlooking the obvious.  The roof shingles are nailed to
plywood sheathing so it will detect solid wood wherever it is moved!  My own
experience with older homes is that a house that old probably has solid wood
planking laid across the rafters.  Not much plywood was in use at the
beginning of the last century.  Also, I have seen older construction in
which the lumber used for rafters was whatever was left over after the rest
of the house was framed.

The best thing to do is drill the holes where you need them, get long bolts
or threaded rod and go up into the attic and place lumber backers under the
roof sheathing.  Connect the backers to the rafters if the load is large.

Good Luck!
Frank
NF0K

-----Original Message-----
From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org]On
Behalf Of Estes Wayne-W10191
Sent: Wednesday, January 24, 2001 11:04 AM
To: amsat-bb@AMSAT.Org
Subject: [amsat-bb] electronic stud finder to detect roof joists?


This spring I will take down all my roof antennas in order to get a new roof
installed.  When I put the roof tripods back up, I want to ensure that the
lag bolts engage the roof joists whenever possible, not just the plywood
roof sheathing.  One tripod will be in an area where there is no attic
underneath because of a cathedral ceiling.  Consequently, I don't have the
option to add any reinforcement from underneath the roof.

Electronic stud finders detect a change in dielectric constant when you move
the stud finder to an area that has a wooden stud behind the wall.  I'm
curious if anybody on this list has successfully used an electronic stud
finder to locate the joists under a roof.  I think the change in dielectric
constant would be much more subtle when you have to sense through the
thickness of the shingles and a layer of 1/2 inch plywood (composition
shingles, not wood shingles).

I suppose I could just buy an electronic stud finder and return it if it
doesn't work.  But it would be nice to know in advance if it's likely to
work.

Wayne Estes W9AE
Mundelein, IL, USA
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