Hi all,

I currently have an existing deck roof frame that only consists of 195 x 45mm rafters with no purlins installed. This is because the previous owners installed an arched roof which I need to replace due to hail damage and its frame is starting to rust.

I want to use the existing rafters to install polycarb sheets. The issue I have is that for some reason the rafters are at inconsistent centres, ranging from 1000mm to 1600mm. For polycarb sheeting would it be ok to use either H3 wood 70 x 35mm or steel "top hat" roofing battens for the purlins without adding more rafters in between the wider spans? These products are designed for roof tiles or colourbond sheeting - surely polycarb will allow a wider span?

TIA for any advice.