Rafter sizing
- Thread starter andyandy2
- Start date
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If Mr BCO is involved, and he asks for calcs Andy can say its ok Shytalks of this forum did them for me 
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Me to, but you know what Nob Heads we are
Another query for shytalkz if he's reading this.
I've just been offered some 8" x 3" purlins which have been taken out of a bungalow roof. Would I still need to fit them as a pair and is it acceptable to re-use them (won't know what grade they are, if any, and the bungalow would of been built probably late 50's )
I've just been offered some 8" x 3" purlins which have been taken out of a bungalow roof. Would I still need to fit them as a pair and is it acceptable to re-use them (won't know what grade they are, if any, and the bungalow would of been built probably late 50's )
Assuming C16 grade, which is probably reaso, singles don't work either inclined or vertical.
Doubled up works fine in either orientation.
Hard to believe, just shows the factors of safety prevalent in timber design these days....
If you're using slate, or other lightweight covering in comparison to concrete tiles, then singles should be ok.
Doubled up works fine in either orientation.
Hard to believe, just shows the factors of safety prevalent in timber design these days....
If you're using slate, or other lightweight covering in comparison to concrete tiles, then singles should be ok.
Thanks again shytalkz, I think I will risk using them singly, am i right in thinking vertically is the best option, also when birds mouthing the rafters on to the purlin is there a minimum or maximum amount to notch out
No problem. Vertically would be better, as the purlin is then only bending around one axis; and the birdbeak stops any eaves lateral movement (unless the purlin deflects excessively). Birdbeak is a max of 1/3 rafter depth, measured at right angles to the slope.
Thanks shytalkz. Forgot to mention in the last post that it will be slate roof covering, so i'm sure it will be ok. It does seem these days as though things are over engineered, the victorians seemed to know a thing or two about building work, I wonder how many of todays buildings will be around in 150 years
The Victorians did have the advantage of not living in such litigious times, of course - and didn't have to contend with HSE, British Standards, Building Control etc. They did make mistakes and they didn't understand materials and soils behaviour as well as we do, either; nor did they have access to the materials that we do.
But yes, a lot of over-engineering goes on these days and there are far more slaves to the calculation sheet than was the case back then.
We design to build in a totally different manner from the Victorians, with the use of much higher-stressed materials, slender construction, less in-built ability for movement and so forth. We don't build cold, draughty places these days; but then they don't look anything like as elegant as Victoriana. Pluses and minuses, but have we progressed? Overall, from a technical point of view, I would say yes; but, from an aesthetic viewpoint, it's entirely subjective....
Unfortunately, a lot of our cr ap will be around for future generations to "enjoy" .
But yes, a lot of over-engineering goes on these days and there are far more slaves to the calculation sheet than was the case back then.
We design to build in a totally different manner from the Victorians, with the use of much higher-stressed materials, slender construction, less in-built ability for movement and so forth. We don't build cold, draughty places these days; but then they don't look anything like as elegant as Victoriana. Pluses and minuses, but have we progressed? Overall, from a technical point of view, I would say yes; but, from an aesthetic viewpoint, it's entirely subjective....
Unfortunately, a lot of our cr ap will be around for future generations to "enjoy"
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