Best roofing options for low pitch ground floor extension?

[Jerrythezinc]

You could bolt timbers onto both sides of the purlins as you suggest as then build up a framework using joist hangers at 610mm centres and using 25mm ply for superior strength between purlins.

 

[ed110220]

You could bolt timbers onto both sides of the purlins as you suggest as then build up a framework using joist hangers at 610mm centres and using 25mm ply for superior strength between purlins.

That's pretty much what I was thinking, except with joist hangars rather than screws, which seems a better idea (I'm only used to building studwork walls so far, not roofs).

Is 610mm the maximum span for 25mm ply? Also what size timber would I use? 63x38mm like for walls?

I was thinking of prefabricating the framework and bolting it to the purlins ready made in panels (purlins are 1350mm apart, so say panels of 2400mm x 1350mm with noggins or whatever you'd call them about 600mm apart).

That way it would take a minimal number of holes drilled in the steel and could be put up quickly once the asbestos sheets are off to minimise the time we're roofless (kind of like how the house was originally dry-lined with prefabricated trelllis like studwork to save building time).

 

[davejaydj]

I wondered if you made a choice between Zinc or Colorcoat Urban? We have seen zinc roofs but only seen the Colorcoat Urban and the Home Building & Renovation show. We have the same decision to make on a low pitch roof (currently felt)

 

[hardmetalking]

We are approved installers for Colorcoat urban. The main difference is penetrations through the roof. On a zinc roof all penetrations have a soldered joint whereas you cannot solder or weld Colorcoat urban so the approved weathering of a penetration is sealant.

As I've said before on a straightforward table-top roof with no penetrations I can see Colorcoat urban being a viable option otherwise I would have to recommend zinc.
I have several clients that have debated the same scenario and I'm sure they could shed some light on what made their minds up.