Sloping floors

[raithrovers1]

I have a two story house built in the 80's. Ground level floors are very true and level. Upstairs the floors have quite bad slopes in them. This is partly caused by a wooden beam spanning my living room (downstairs) which is bowing in the center by about 2-3 inches.
I am trying to put my mind at ease that there is no subsidence. My question is if my ground floor is level does that rule out subsidence?
Also how big a job is it to replace a wooden joist with a steel support? and will jacking the roof up to its correct level cause me any other issues?
Cheers for any help.

 

[Static]

Check all your doors fit perfectly in their door frames (as would have when house was first built.. hopefully).. if they are all tight and not fitting the frames then go check the external brickwork for signs of cracking.. especially near the windows..
Subsidence is pretty rare.. dont jump to conclussions.. if the timber beam is bowing thats probably nothing to do with subsidence.. replacing a timber beam with a steel one is pretty easy in the scheme of things..