The slightest gap or join will make it useless. To be effective it must be very heavy foil with welded or bolted seams, and no wires passing through. And contr

The slightest gap or join will make it useless. To be effective it must be very heavy foil with welded or bolted seams, and no wires passing through. And contrary as it seems, earthing it won't make much difference. Especially as any earth wire will be many wavelengths long at VHF/UHF.