Z-Wave networks are unique in wireless protocols in that it's designed to be continuously improved and modified. Here are a few steps you can take to get the most out of your Z-Wave system:
Make sure your Z-Wave controller is placed centrally in your home
The easiest thing you can do to maximize Z-Wave coverage in your home is to place your Z-Wave Hub in a central location so it's equally distant to all of the furthest away devices. Try to avoid storing your Hub near your networking equipment, as this is usually in a cramped closet where Z-Wave signals will be blocked by walls and doors. Instead, place it on a shelf or other open area where it has a "line-of-sight" perspective of a central location in your home, like in your living room or main hallway.
Use Plugged-In Z-Wave Devices Everywhere
All Z-Wave devices that plug into mains power (like light switches, on/off plugs, or our water main shut-off) will repeat Z-Wave signals to carry signals from far away devices back to the main Hub. Make sure there are plenty of plugged in device in your Z-Wave network, and make sure signals have multiple paths to travel back to the Hub. This is important so that if something changes in the network, the whole network won't crash because everything was relying on a single device for connectivity. Also, it's very important to stay less than four "hops" total between the device and the main controller.
Migrate to Z-Wave Plus Devices
Even though your old Z-Wave devices are fully compatible with more modern devices, they could be seriously slowing down or otherwise diminishing your network health. To make the most out of your Z-Wave plus devices, make sure all devices (especially the plugged in ones) are Z-Wave plus. Not only do Z-Wave plus devices offer better range and responsiveness, they also have a feature called "network-wide inclusion" which is very handy in larger installations. Without network-wide inclusion, you have to bring devices near the MAIN Hub to include into a network. With network-wide inclusion, the device can be installed at the final location, even if the signal has to "hop" through a repeater before reaching the main hub. That way, you can be sure your installation location has Z-Wave coverage during installation instead of finding out afterwards.
Avoid Walls, Corners, and Tight Spaces
Avoid placing devices near walls, corners, and tight spaces, especially if surrounded by metal. These surfaces will interfere with the Z-Wave radio waves and diminish performance.
Avoid Aquariums, Plumbing, and Appliances
Similar to the point above - appliances usually contain lots of metal, which will block radio waves, and aquariums and plumbing contain water, which also block radio waves really well. These objects will interfere with Z-Wave radio waves and diminish performance.