What do upstairs walls sit on?

[Glastoun]

Our upstairs walls are not built directly over the downstairs walls. One is offset around 50cms from its downstairs equivalent, and the other about 80cms. So what are they resting on?

Floorboards and joists? Surely that would make joists part of the structural elements of the house, which I didn't think should be the case else how would they be replaced if they ever rotted?

It's a 1930s brick house - a builder knocked on the upstairs walls and said they were stud, but they feel much more sturdy than the modern thin plasterboard walls.

Are they likely to be bearing much weight from the loft/roof? I guess one of them is, because the cold water tank is sitting on it....

 

[kazuya]

its not unusual to find a block wall built off a wooden floor

 

[catlad]

Internal Joists should not be prone to rotting.

 

[noseall]

3" partition block walls were usually built up off a timber sole plate and not necessarily over any downstairs walls.

 

[mfarrow]

Ours are T&G, built off joists and bonded/toothed to inner leaf. Wo betide anyone who removes the joists!