Roof/ceiling: open verses closed

[fluffypenguin]

Ok, apologies for incorrect terminology but Im sure some one can correct me along the way.
We are creating an extension on a semi bungalow. It will come out 10m. Previous applications and research has told me that creating a low roof on the out side is favourable.
Now, what I would like to know is, in creating a roof (still giving full height rooms inside) where the ridge height is as low as possible for a pitch roof what can be achieved inside?
Instead of having a ceiling inside can it be open?
If it is open we could add skylights.
Cost is a big determining factor, which would be cheaper to achieve, a room without a ceiling or one that has a ceiling?
Can anyone point out any pitfalls to any of this?

Thanks all.

 

[freddiemercurystwin]

To create an open pitched ceiling you need to remove the ties.The ties stop the walls wanting to push out away from each other. Structurally this is achieved by having a structural ridge beam. At 10m long it would be a humongous beam and would likely make it impracticable.

A few other options including reducing the span of the ridge beam with columns or piers.

Or consider instead structural ties like this maybe http://www.s3i.co.uk/image/s3i/Tie-Bar.jpg so you can still achieve an open ceiling.

 

[tony1851]

The ties stop the walls wanting to push out away from each other.

(Other contributors to this forum should take note of this).

 

[r896neo]

Freddie is right, i worked on a fancy new build which had a vaulted ceiling like that. The span of the beam was about 13m with a padstone about 4m from one end.

The steel beam forming the ridge was enormous and it also makes forming the actual roof ridge a bit of a faff. Pretty looking trusses might be an option depending on pitch.