We have a steel-frame home that is about 4000 square feet.
We use Google Wi Fi system and have six pucks. However, because of the steel studs, coverage is still spotty.
I am considering the addition of three more pucks.
Is there a maximum limit to the number of pucks I can have on the Mesh system?
Here's the official support page that talks about this issue: https://support.google.com/wifi/answer/7182840?hl=en The short version is that five is the recommended maximum.
But, you may find you have enough, depending on where they are placed and how they are connected. The optimal placement advice is to put the primary unit as close to the center of the home as possible and place any wireless secondaries around that, close enough that they can get a strong 5GHz connection for themselves. From there, they will provide 2.4GHz and 5GHz coverage to more distant clients.
If you find that arrangement doesn't work in your environment due to the construction of your home (and I would be a little worried about steel studs, but not as much as concrete, brick, or plaster), then you may need to consider using Ethernet to connect the secondary units back to the primary's LAN Ethernet port (use one or more inexpensive unmanaged Ethernet switches to make ports available to connect all of them). They can then be placed further away from the primary since they won't be relying on the 5GHz mesh connection to the primary any longer. In a large home, I would definitely try to use Ethernet as much as possible, especially for any streaming video devices/TVs, gaming systems, or fixed computers. Here's the support page with the details for building something like this: https://support.google.com/wifi/answer/7215624?hl=en
I just wanted to check in real fast to see if you saw MichaelP's reply as he covered this really well and to see if you still needed anything else resolving this. If you still need help, just let us know.
As we have a solid answer to the question and activity has slowed down, I'm going to go ahead and close the thread. If you have more to add, feel free to start a new discussion.