Hollow soffits

[garyo]

My house has original lath and plaster soffits. These have been over-clad with a hollow plastic 'tongue and groove' style profile, identical to this:

I want my new extension to match the existing house. Are these kinds of hollow boards sturdy enough to be used without a back board - i.e. supported at 400mm centres on the rafter feet and a batten arrangement taking them back to the wall?

The site that the image is taken from has lots of technical detail bit it's not clear on whether these are designed for this kind of use.

Thanks

Gary

 

[jblack]

I have just fitted the same thing but in short lengths rather than long runs (so the groove ran 90 degree to the house not parallel). It is very flimsy stuff at only 9mm thick so definitely needs something behind it to firm it up a bit. Can't you get it in 18mm?

 

[garyo]

I've not seen 18mm. My gut feel is that 9mm should be okay given that it'll hang off the facia at the front and be fixed at 400c/c.

I'll email the supplier for a view.

Gary

 

[cumbrianroofer]

fitting as you have described will be fine i fitted the same thing a couple of months ago a slate lath fix to the wall would act as an extra fixing imo