Loft subframe vs. cross-battons in purling roof.

[wonderwire]

I've been reading about loft insulation and boarding as I'm considering what to do with mine. For reference; I have an old purling style roof.

Most of the posts on this forum suggest either insulate between joists and screw boards directly to them (assuming minimum of 7") or cross-batten and then screw to this.

1. Please could someone clarify does cross-battening just involve screwing additional battons to the joists, or are these also attached to the roof frame somehow?

2. Some other sites suggest the need to add a subframe connected to the purlins. Is this good advice, or does it risk the structural integrity of the building? See below for an example

3. How is the example above supported by internal walls? Is it also resting on the joists?

What are the advantages/disadvantages of each?

Thanks

 

[^woody^]

I dont know why cross battening would be necessary for your purpose as opposed to normal battening if the surface needs to be brought out to accomodate insulation. You need to decide what you are trying to acheive and why you would need to cross-batten instead of parallel batten. Either way, they are just screwed to the joists.

Ceilings beneath lofts are not designed to take loads. So if you are intending to load them and dont want the plaster ceiling to crack, then it will need a raised deck independently supported to the ceiling. How you support it depends on what you have available in the loft, and what loads you intend to put on the floor