On Sep 28, 5:13*am, stryped wrote:
I planned to use a motion detector with the two flood lights centered
above my garage door. I started cutting thinking I would put a plastic
box behind the metal siding inside the garage.

Probably there needs to be a box outside, where the lights are?
So, find a place where a hole can be drilled big enough for
1/2" plastic conduit (the gray stuff is outdoor-rated), and run it
to your box. Either a straight run into the back of the box, or a
right-angle (with one of those panel-over-the-bend fittings, so you
can
run the wire by hand-feeding) will be weather-proofable. Just
use a bit of flashing and a bead of caulk.

Most flood fixtures use a box-cover-size mounting plate, match the
box size and shape to the fixture. I sometimes cut wood blocks
(cedar for weather resistance) to mate the vertical back of a
box to the irregular exterior surfaces; put your mount screws through
the wood into the steel, of course

I like to drill a weep hole or two (small, 1/8" will do) in the bottom
of
any box that lives outdoors. Don't know if it's allowed by code, but
it soothes my moisture-corrosion hackles. Insects like it, too!