I am building a new home here in Costa Rica. What should I be using for switch and receptical boxes, plastic or metal. The ground wire doesn't seem to be very popular here as you have to buy each wire individually so that increases cost. I am working on getting some Romex sent down. The lower walls are concrete block and the upper will be framed in wood. I've seen both used but not sure the advantages and disadvantages of each. Also what is the proper method for the main ground?