75mm x 225mm purlins vs steel

[hog]

'lo ... 2nd opinion needed pls?

have regs signed off for 1 storey ext. having gable roof of ridge beam + purlins all 75mm x 225mm timbers

still considering a vaulted ceiling (as no rafter ties needed anyway) - but obviously purlins will be seen internally and 9" deep. is this acceptable depth for 'aesthetics' or should I be considering alternative material (i.e. steel) if it's possible to have the same strength but less depth?

cheers!

 

[noseall]

Steel will be smaller in section (depth) than a timber counterpart. However, by the time you have bolted a timber plate to the top flange, it will be nigh on the same.

At least with the timber you won't have any trouble fixing things to it.

Some of the purlin depth will be swallowed up by the insulation underdraw unless you are going for a warm deck....?

 

[hog]

thanks noseall, I'd forgotten my cold-deck insulation will bring the ceiling 4" down the purlins