Mark

If its a bungalow the chances are the roof trusses make up the ceiling joists and are engineered to span the 8m due to the construction of the roof.

The joists in my house are 7"x2" 13.5" c/c and span 4.8m ( this is ground floor ceiling/first floor floor ) they need support as they need to be a lot deeper to span that length.

It would help if you explained what your problem was?

J