Structural drawings

[PeterW]

Quick Saturday afternoon question. 

Engineer has asked for "structural drawings" of the roof joists and I've sent the quite detailed section drawings over.

He's replied saying he needs the structural detail of the wall plate, joists and collar ties but I was expecting that a simple "A" frame drawing would be enough ..?

He is semi retired and only works a couple of days a week so I've got til Wednesday to sort - anyone got anything as an example that I can use as I'm lost, or has been asked for anything similar ..? He's calculating the collar ties so I don't see what I need to add to the party as he's doing the calcs..!

Even an architect friend has said he isn't sure what is needed either ..!

[Jeremy Harris]

There are approved details from some of the manufacturers of things like I beams, and I used these for the rafter to ridge beam connection detail and the rafter to wall plate detail for our build.  IIRC, I downloaded a PDF from the I beam supplier and then just cut and pasted the detail drawings that showed things like the ridge straps, wall plate attachments etc.  Off the top of my head I can't remember where I got them from, and don't seem to have kept a copy of the original document for some reason, but a poke around on the web site of whoever is supplying your bits may help.

Alternatively, I think there used to be lots of approved details for this both in the old version of Part A and in the TRADA stuff (which you now have to pay for).  You may well find the details you want there - there are old copies of Part A around I know, as I nicked the TRADA joist span tables from an old copy a while ago and saved them (they are another thing you now have to pay to get hold of from TRADA).

[ProDave]

Yes I too am confused. I thought the SE was the one that took a concept of what you want and produced the drawings and calculations to show how to do it correctly. 

[PeterW]

Thanks both - issue is (as usual..) the 50 degree pitch so everything has to be engineer sign off and not straight from a table !

I'm going to drop him a note and see if he picks it up before Wednesday - we've ended up with using "normal" timber much to my annoyance as I've struggled to get the off the shelf I-joist manufacturers to warrant their products at above 45 degrees, and I can also over engineer without the need to go to steels if I use 47x195 which also gives the depth for insulation.

All in all we will end up the same roof depth as with a 225mm I-Joist as instead of 225+15mm OSB Sarking, we have 195+40mm PIR insulation. I also save on the external counter batten but move it inside as a service batten !

BTW the Trada tables can still be downloaded from here - not a Russian scam site !!!