Finding steel behind aluminum panels

[ajk1]

Anyone know how to find light gauge steel channels that are located 40 mm (1.5") behind aluminum panels? Electromagnetic instruments (such as cover meters to locate rebar) will not work because the electromagnetic field will set up eddy currents in the aluminum (we have already tried various electromagnetic instruments). I am told that a simple magnetic stud finder should work, but I am not sure if it is strong enough to find the steel that far away (40 mm). Pilot holes are a way, but would be nice if there were some non-destructive means. The flange of the steel to which we want to screw with Hilti self drilling screws, is only 40 mm (1.5") wide, so the locating device would be best if it was reasonably accurate.

 

[ChipB]

I would think just a regular strong magnet would work. Are the Al panels attached to the steel studs? If so, just find the screws.

 

[ajk1]

yes a magnet might work. That was suggested already by the contractor who is about to start work, but it wouod need to be a powerful one I think. No the aluminum is not fastened to the steel. If it were, iot would of course be very easy to find!!!!

 

[ChipB]

So is 1.5" the depth of the flutes in the aluminum panels?

Are the flutes running vertically?

Are the Aluminum panels the exterior siding?

 

[racookpe1978]

Use a bigger magnet: try one of the "pickup" magnets from the hardware store that pulls steel scrap and grit off of the floor.

 

[ajk1]

to racookpe - thanks for the suggestion. I will pass it on to the contractor. he is starting work this week, so will be interesting

to Chipbe -
It is a 3/4" deep aluminum panel ceiling.
Immdediately on top of the ceiling panels are 3/4 x 3/4" galvanized steel carrier channels to which the aluminum ceiling panels are clipped; these of course run at right angles to the span of the ceiling panels.
Immdediately above that are the main galvanized light gauge steel channels running at right angles to the carrier members - these main channels are the elements to which we want to fasten the ceiling (because the carrier channels have insufficient strength.
So the 1.5" = 3/4" ceiling panel plus 3/4" carrier.