Any change in the structure of a house will typically affect the roofline. That's why checking the roofline is a very good thing to do when purchasing a house, if the roof is straight that is an important data point about walls and foundation supporting that roof. A sagging roof is a sure sign of problems in the rest of the building, rarely a sign of trouble with the roof itself.

I understand your logic about the house but I don't see why it is an apt analogy. It would help to explain what kinds of problems you are imagining for the house and what they could correspond to in the food web, both at the lower and upper levels.

Thanks! I'll remember that if I'll need to buy a house.