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RE: electronic stud finder to detect roof joists?

Murray Peterson wrote:

	I assume you have joists which are similar to those used to support a
	tile roof or a sheet metal roof. If the joists are straight, (I assume you
	would put plywood shingles on in a way similar to terra cotta roof tiles)
	why not place a small mark (using a felt tipped pen) on top of the bottom
	shingle when it is first put on (when you can see it) to indicate where the
	centre of the joist is and then again mark the top shingle indicating the
	centre of the joist before the ridge cap is put on while you can still see
	the joist. You could then located the position of the joist by pulling a
	string between the marks. If you mark the joist locations in this way in all
	the likely locations you would mount your antennas it should be quite easy
	to bolt into the joists.

Wayne replies:

I may do something like you described, but I can't see the nails going into the joists when the first shingles are applied because the nails are obscured by the felt layer.  I have thought about marking the joist locations on fascia boards before the felt is applied.  The fascia markings would be visible after the new shingles are applied.  To do this, I would have to be there when the roofing company rips off the old felt.

By the way, the roofing shingles in the U.S. are typically asphalt composition, not plywood.  From bottom to top, the typical roof layers are joist, plywood, felt, and then shingles.  Most houses in the U.S. use asphalt composition shingles.  Some upscale houses have wooden shingles which are somewhat of a fire hazard even when treated with fire-retardant chemicals.  Tile roofs are rare in my part of the country, but common in regions that get much less frozen precipitation.

Wayne Estes W9AE
Mundelein, IL, USA
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