Mounting outside GFCI to vinyl siding

[deerhunter5555]

Need help from all you residential guys. I built a detatched garage with vinyl siding exterior. For the rough in on my outside recepticles I just stubbed out the romex through the osb and coiled it up for later. Well, the siding guy has come and gone and he left me with one of those square vinal trims for electrical. I had planned on just putting on a GFCI and a weather-proof cover but am stumped on how to mount it. Did I screw up by not roughing in a box? I didn't put in a box at rough in because I didn't know how much it should stick out to compensate for the thickness of the vinyl siding. Help me please!
Erich

[Sparks]

Just cut in the box and fasten it to the framing members with a bracket, nail on box, old work box, whatever the situation warrants. Outline the box on the vinyl plate and use a roto, jig saw, etc to cut the hole. Then, install the Nec compliant, 'while in use' receptacle cover and GFCI receptacle, AKA, the bubble cover. No big deal.

[TnAndy]

Use an "old work" box. They have a couple of plastic 'flippy' ears on them that as you tighten up the screws, the ears flip out and hold against the backside of your wall surface, which in this case would be the back of the vinyl mount box you have.

Cut the hole in the vinyl box first.......Just be real careful as you cut the hole ( a rotozip tool would work good...make sure the vinyl isn't cold
though ).....don't over cut...the flanges on the box MUST be able to stay out on the front face !!........then reach thru that hole with something like a straight keyhole saw and cut the OSB ( or the box won't fit.....you only have about 3/4" from the vinyl box face to the OSB....over cut the hole in the OSB if you can to give you some working room.

Once you have the holes cut, stick your wire in the box, slide the box in the hole. Tighten the screws....the 'ears' will flip out and hold the box in place.... and you're in bizness.