Does heightening a sofa increase strain in the centre?

[Est30]

Hi, I was wondering... if by heightening a sofa (150cm in length approx) from floor level by about 20-30 centimeters, would increase, or could potentially increase the strain in the centre of a sofa when people sit on it?
I have a long sofa, that was raised and I notice that my sofa is sagging in the middle when my boyfriend and I sit on it- this has only happened since it was raised. Is this because it has been heightened?
It reminds me a bit of physics and bridges I did at school a while ago-but I can remember very little and I was never very good at physics! I need expert knowledge- obviously, I won't have my sofa heightened in future, if it is more likely to sag and break when sitting on it!

Thanks

 

[chickenwing71]

First of all, it depends on how your sofa contacts the floor. Is it just four feet, one in each corner? Or is there some support in the middle? If it is just four feet, then as long as all the feet are on the floor (supports, raises, whatever) then the amount it sags will not change when you raise it.

However, if it does sag, then it won't have the floor under it to stop the sagging after a few cm. Maybe you could consider improvising a simple support in the center of the sofa so it doesn't sag (whether you raise it or not).