You are grossly underestimating the force of sustained 250kmh winds (cat 4 hurricane), let alone the 400kph winds present in an F4 tornado. Even if your 900 year old building's walls could withstand that it would likely have no roof and be unlivable for an extended period of time.

Modern residential buildings in Florida etc are built to withstand these kinds of forces with hurricane glass and beefed up structures.