vaulting a cieling?

[middi]

Looking at the photos ( again) it should not be a major problem to add new purlins, as to removing the existing collars and replace by a collar or two it would depend on the solidity of your existing purlin. One thing is certain, fewer collars would weaken the structure as it exists.
I will PM my phone no. call me if you want to look at an example of what I am talking about.
You will also have a chance to see an early 15thC king post in my house.

Middi

 

[robgil]

That sounds interesting Middi, i shall certainly get in touch and we can arrange things, ive got a stinking cold at the moment but it shouldnt last too long.
would this type of roof structure originally have had ceilings then? the ceilings there now are (apart from this plaster board one) lath and daub, ive read somewhere that daub ceilings are now quite a rarity.

 

[middi]

It should be possible to find out if ceilings were added at the construction stage or at a later stage of the building's life. I all depends what the owners of the property were looking for as the dwelling was being constructed and to what use they had in mind for it. ceilings in the upper floors were rarely inserted in cottages.
There appears to be a " progression" stage before ceilings were inserted, from basic wattle and daub between the rafters onto lath and plaster up to any collars which were present and then " spiking" of collars at lower levels or " modern" ceiling.

Middi