A house has 3 floors, with thick floors and around 350m^2 total. The person responsible for setting up the electricity and networking in the house recommended to have the router and then 3 ZyXeL NWA APs (one per floor) - that was the only thing he wrote on the quote for the work.
But I am confused because APs are basically wireless switches, which as far as I understand they just relay an existing wifi signal. So if I have a wireless router, looking at NetGear NightHawk R7500, on the ground floor, I won't need an AP on that floor. I would need one probably on the top floor and cellar to extend the wifi range only. Is my reasoning not correct?
What would the recommended setup be for a situation like this?