Replacing supporting beam

[dicko]

I have just bought a house that I am doing up.
It has an extension on the back which has a flat roof. It was constructed by a local builder and so RSJ`s etc were used to knock through.
The extension itself is approx 15ft. long by 12 ft deep.
The supporting joists run from side to side ( across the 15ft) there is a breeze block wall, half way down this 15ft run, which sticks out into the room some 8ft and from that to the outside wall ther is a wooden beam supporting the remaining 4ft.
I hope from this you now have a picture of the room.
What I want to do is remove the block wall to open up the entire room.
Would a wooden joist be sufficient, across the whole 12ft span. If so what size of timber would be needed to support the weight of the flat roof!!!!!
I hope someone has the answer.

 

[Softus]

An architectural engineer will know the answer, and will be able to provide the drawings that your LABC will require from you, since this work is notifiable.

 

[^woody^]

I hope someone has the answer.

You may get lots of answers, but whether any will hold the roof up, or be an economical section size is another matter.

The 'correct' answer requires calculation, not guessing

 

[dicko]

Thank you both for your replies.
I have been in touch with an architectural engineer who is now working out the details.