The improvement card says you need 5 clays + 2 reeds to turn your wooden house in clay house.
If I have 2 wooden houses, and only 5 clays+ 2 reeds does it mean :
If I have 2 wooden houses, and only 5 clays+ 2 reeds does it mean :
- that I can change 1 house and wait later to change the other one
- or that I must wait until I have 10 clays + 4 reeds to improve the 2 houses at the same time ?