Steel rafter selection

[Macsky]

Which is the better?

305x165x40 or 356x127x33?

they’re on two different quotes for a 120’x50’ cattle shed, both on 305x165x40 stanchions.

Thanks

 

[Doing it for the kids]

Join the gang!

i think the last figure is the weight per m 40 vs 33 kg

 

[RWG Contracts]

I’d rather have the 305x165x40. Purlin is sat on 82.5mm rather than 63mm

 

[335d]

what your man says above

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[Macsky]

I’m assuming the 40kg is the stronger?

 

[Mur Huwcun]

I’m assuming the 40kg is the stronger?

Well the other one is a deeper section so using all my knowledge (sod all) on the subject I’ll risk saying that there won’t be much in them regarding saging down but the wider beam should in theory withstand twisting better and as the expert has said it would be a wider face for the perlins to sit on albeit that all depends on the cleat size.

Interesting to see how much more steel is in a 50’ wide up North than there would be here!!

 

[RWG Contracts]

I’m assuming the 40kg is the stronger?

No. Ones short, fat and heavy, probably thicker gauge which gives it strength. The other is tall, thin and light. It’s the “tallness” that gives this one the strength

 

[Macsky]

No. Ones short, fat and heavy, probably thicker gauge which gives it strength. The other is tall, thin and light. It’s the “tallness” that gives this one the strength

Which would be the more expensive? Again I’m assuming the heavier? By my calculations there would be approx 55kg more in each (half of the span) of the heavier rafters

 

[RWG Contracts]

Which would be the more expensive? Again I’m assuming the heavier? By my calculations there would be approx 55kg more in each (half of the span) of the heavier rafters

you buy steel per tonne so the lighter should be cheaper

 

[JD6920s]

I’d rather have the 305x165x40. Purlin is sat on 82.5mm rather than 63mm

I have used unequal angle for the perlin cleats and cut them as long as you want for more support

 

[RWG Contracts]

I have used unequal angle for the perlin cleats and cut them as long as you want for more support

So have I. Used to do it a lot on 20’ bays to make the purlins a smaller span

 

[Skintagain]

So have I. Used to do it a lot on 20’ bays to make the purlins a smaller span

Just rebuilt one here with 20 ft bays and 3ft angle cleats. Timbers are 11x3” I don’t think they will be sagging someone built a proper building 30 years ago with that one.

Back to the op. Both meet spec but the 305 you are getting more meat