Z-wave relay range

Oddball question... If I have a metal building that can't get Z-wave reception from the house only a short distance away, how big of a hole would i need to cut get reception on a plug in Z-wave relay? Or are there any relays that would allow me to have a pair of antennas, one inside and the other outside?

Good suggestions by lanbrown above. I'd just add that if there aren't any outside outlets you could put a z-wave device (motion sensor <not battery powered> or smart plug) on an extension cord and place that in a window facing the house/out-building. That might give you the range you need.

The detached garage is 18 feet from one wall of the house that has a USB powered Aeon 6 in 1 multisensor set just inside the door of the house. The problem is that the garage has no windows or plugs on the side facing the house, and one of the low priced Monoprice 4 in 1 motion/light/temp/humidity sensors can be seen if set on the outside of the garage or inside the garage IF the door facing the door where the Aeon is set is open, but not if that standard sheet metal exterior door is closed, making me believe that it's the sheet metal wall that's the problem, so somehow I need to get an opening just big enough to get the signal through or a relay that can send/receive on both sides of the wall. Even if I did have an outside plug to put a relay on, wouldn't it have the same issues receiving the signal from the Monoprice that the Aeon in the house does? I guess I'm spoiled by the Insteon signal over powerline with RF bridging between phases, meaning the light switches in the garage all work perfectly... but unfortunately, Insteon motion sensors suck.

Would it be possible to put a device under the eaves of the roof? It would take only a small hole in the soffit to run a LV cable through.

LV cable? If you're talking power, that's not the issue; I need RF on both sides of the heavily grounded steel wall. As I've said before, it sure would be nice if someone could figure out how to decouple the Z-wave transmitter from the receiver and build a pair of devices that pass the data over ethernet or WIFI at the same time they increment the hop count.

[jay (support)]

Just FYI, Battery powered Z-Wave devices can't really route, so if you're trying to route a signal through one that will also be a problem.

Just FYI, Battery powered Z-Wave devices can't really route, so if you're trying to route a signal through one that will also be a problem.

That's specifically why I went to the trouble to USB the multisensor... according to Aeotech, that should make it a relay device... and the battery powered Monoprice can see something on the network well enough to talk to it as long as it is outside the garage, although I haven't tried any of the netowrk mappiing and routing reporting tools to see who it's neighbors are. But given that the building inspectors demanded that the garage have it's own ground rod and all the metal conduits are tied to that rod and brackets secured to the pearlings with screws, I suspect that those walls are pretty much a perfect RF ground plane.