what do you reckon to my joist plans

[redtop]

I have asked the SE but wondering what your good self's think..  Planning on using C24 225 x 45 which more than meet the span requirements.  All joists centered at 400 (so ignore ragid spacing on diagram) with noggins to meet plywood edges at 1.2M (not shown on diagram), close double red lines indicate double joists bolted together.

 

Note the bit on the left, with the horizontal joists are roof joists as that area is single story only (flat roof).  Solid black lines are steel RSJs, frame is timber.

 

[redtop]

and architects 2nd floor diagram,

 

[tonyshouse]

I like RSJ to sit on post, joists notched into RSJ

 

cant see the point of the double joist across the middle 

[Dave Jones]

timber posi joists are much easier to work with i found, not to mention getting services through them. the other joists can be hangered off the doubler easily enough.

 

An RSJ at 7M is a big beast to manhandle and would be much safer to get in with a crane which all costs money.

[bassanclan]

The diagram has slightly misled you.

The rsj actually goes to the very end of the grey circle. The black line of the rsj stops short of the circle because otherwise you wouldn't be able to tell that there is 100mm square section there.

 

The location of the double joists around the stairs is determined by your design of the stairs. You should know the length and width of this.

 

Is the existing spine wall single brick, double brick or cavity wall? 

[Dave Jones]

you need to double check the stairs to make sure you have headroom when travelling up the run. May have to adjust those small joists to achieve it. You can put in the dimensions at stairbox and it will check it for you.

[bassanclan]

Personally I wouldnt notch the joists. Either have thr joists sit on the steel (no good if you want a flush celing). Or have 12mm holes at 400mm centres drilled into your steel and bolt a piece of timber into the web on both sides using threaded rod. Then fix the joists with joist hangers. You may want to use a 203 or 254 steel rather than a 178mm in that case.

[redtop]

thanks for the advice, as always I wish I had provided more info at the start!  Steels are already fixed in place (all manhandled, no access for a crane) and the area you can just see of to the left, kitchen / dinner single story only, has already been joisted using timber in-fill and joist hangers.

 

i will take a look at stairbox!