You must raise the beam to sit within the floor zone to achieve a flush ceiling. A structural engineer will advise on the best way to do this, as it could involve cutting existing floor joists — not a job to be taken lightly! Another thing you need to consider is deflection in the beam, which over a 4,000mm opening could be more than 10mm. This deflection can cause significant cracking in the ceiling, spoiling the effect. To avoid this issue, follow the steps below: 1. Position the beam into place.  2. Fully load the floor. I.e. put all furniture back in place. 3. Remove the props and allow the deflection to take place.  4. Cover the beam with plasterboard and skim it.