@A-Bru it depends on how far your chicken house is, you mention that it is 10-15m too far away letting me believe that it is under 150m. For such a short distance you do not need two cpe devices, it would be sufficient to use two eap225-outdoor and extend your network. Recommended is so far I remember max. 150 or 200m, if your chicken house is up to 150m away, then I probably would go for eap225-outdoor. If you do not want to spend anything, additional option for you is to take any openwrt capable router and run it as a client connected to your network. If you use cpe devices, the one you link is very good and runs on 5Ghz, but if it is just for a chicken house where no real bandwidth is required, two old cpe210 running on 2Ghz would probably be enough, two cpe210 cost like one cpe710 where cpe710 is really a good device and would be more than sufficient for your needs, I would go for two eap225-outdoor if distance is 150m or below.

  @A-Bru 

May not be what you had in mind, but Ihad a similar problem getting WiFi my pump house. My solution was to install a Shelly Relay that has the capability to repeat a wifi signal. I put a Shelly Plus 2PM Relay outside the pump house and it's signal made it through the 1 foot thick masonary wall.  

While I was at it I used the Shelly to control the inside and outside light on the building.

Hope you find this helpful.

  @A-Bru 

It looks like the Pharos series antennas you mentioned should work as a bridge for your chicken home door controller. The product includes an antenna and a router, so all you would need to do is connect the router to your WiFi network and then connect the antenna to the router. You will not need additional antennas, as the antenna included in the product should be able to cover the 10 meters of distance you need to connect your chicken home door controller.