When it comes to installing exterior trim over a rainscreen, penetrations are an area that you need to pay a little extra attention to. What we’re going to need to do is create an escutcheon block for each pipe or wire that exits the sheathing, but we need to provide solid backing for this to be affixed to—in this case we’re going to cut small pieces of our 1 x 3 strapping and install them as support for the block.
After the backing is installed I can go ahead and install my block. It’s not a bad idea to add a piece of rigid metal head flashing over the tops of your escutcheon blocks for extra protection against water infiltration. Instead of screws, in this scenario I’ve installed the block with 15-gauge stainless finish nails, which are perfectly acceptable for small pieces of trim like this.
When there’s a wire coming out of the sheathing for a future lamp installation, we clearly have to pad out in order to bring the block out to the face of the siding. I’ve simply added some pieces of 1×3 around the wire in order to create that needed depth. One of the benefits of having a space in between the sheathing and the back side of our block is it allows us to move our block a little bit when it comes to making our install to align it with the courses of siding. Another step I like to take is to make sure when I’m installing my blocks before doing siding is that I level them up so that when any of my cuts come into the sides or over the top they’re square and parallel for a nice install.