How to extend Airport Express Wireless Network to guesthouse?

To begin with, it may be wise to test different locations for the existing base station. Temporarily, connect a long Ethernet cable for the incoming Internet. Try to move the base station to various places. Avoid interfering objects/structures (Wi-Fi and Bluetooth: Potential sources of wireless interference - Apple Support).

If necessary, an extension of the network (Wi-Fi base stations: Extending the range of your wireless network by adding additional Wi-Fi base stations - Apple Suppo…) could be considered. The best way of doing this would be through an Ethernet connection to the extended base station (placed in the main building, if possible). Alternatively, you may want to test whether a powerline network adapter connection could be used instead of an Ethernet cable to the extended base station.

I am assuming that your existing AirPort Express...centrally located in the home....needs to stay in that location to provide adequate coverage for devices in the house, correct?

If that is the case, the simplest solution in terms of time and equipment would be to add another AirPort Express to "extend" your existing wireless network. The second Express would need to be located within your home, but as close to the guest house as possible. Ideally, the Express would be located on a window sill such that it had line-of-sight.....or as close as possible to that goal as possible....to the guest house.

I think that there is a good chance that this type of setup will do what you want....but with wireless, it is never possible to predict how well....or even if....things will work until you try things out. Buy from Apple and you have a 14 day return privilege.....just in case.

After I plug it in....does this airport need to be connected with another ethernet to the first airport (after configuring, which opens another can of proverbial worms?)

My suggested setup assumes that you want to leave your "main" AirPort Express located right where it is now......centrally in the house.

A second AirPort Express would connect to your "main" AirPort Express using wireless and then wirelessly "extend" the network.

What is really happening is the 2nd AirPort Express receives the wireless signal from the first and then broadcasts it again. So, the result is a much stronger signal at the guest house.

If I understand you correctly, then, getting another AE (Airport Express) and plugging into the back room of the main house, would get me some WIFI in the guest house

Please review what I wrote originally.......

I think that there is a good chance that this type of setup will do what you want....but with wireless, it is never possible to predict how well....or even if....things will work until you try things out. Buy from Apple and you have a 14 day return privilege.....just in case.

Now, if I purchased a third AE, and plugged that one into the GUEST house....would that help boost wifi in the guest house (away from the garage door?)

No, since Apple's extend a wireless network feature will only allow wireless extension of the network one time.....not two.

And will I be able to keep that window closed?

I think that there is a good chance that this type of setup will do what you want....but with wireless, it is never possible to predict how well....or even if....things will work until you try things out. Buy from Apple and you have a 14 day return privilege.....just in case.

Good luck! This worked for me to a workshop that was about 150 feet from the main house, but as I said.....what works for me may not work for you.

The more that you have a line-of-sight relationship between the "main" router and the extending AirPort, the better the network operate.

Even a normal wall in a home will absorb about 10-15% of the signal on average, so if the wireless signal must pass through 3 or 4 walls to reach the extending AirPort, more than half of the signal will be gone.

Tip.....The extending AirPort can only extend the quality of signal that it receives.