# Forum Home Renovation Sub Flooring  Attaching timber joists to a steel beam

## sama

The deck addition i am building calls for a steel 250mm parallel flange channel as the bearer..   (ie: big c shaped beam).im thinking of  attaching my 450mm x 50mm hardwood joist to it by bolting a 40mm thick hardwood strip along the length of the beam and then nailing the joists to this..would this be the preferred method?

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## Bloss

A 450mm deep joist? That's some big timber! And just one? Hope you've got a crane to lift it into place.  :Confused:  
Assuming the actual joist you use is a more reasonable size you could do what you say in part. You'll need to ensure the correct number of bolts to the steel beam and use triple grips not just skew nails to hold the joists in place. 
Better idea is to get whoever specified the steel beam to provide the specs for the rest of the sub-floor structure including how to attach the joists to that steel bearer.  :2thumbsup:  
The deck will need to be approved and constructed by a licensed person so they'll be able to advise you too.  :2thumbsup:

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## rod1949

As Bloss says 450mm :Yikes2: . 
Do you mean 150mm??? If so why don't you use RHS steel?  It'll always be straight, around the same price as timber, never get eaten by termites, just as easy if not easier to use as timber.

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## sama

sorry ment 150mm joists and i found this from a prefious post,the quote is from the framing manual.... 
"Floor joists shall be nominally fixed to bearers or supporting walls at every crossing using a minimum of 2/75 x 3.10 mm skew nails. In addition, where there is only a single joist span in the full width of a house, every second joist shall be fixed at its ends using a framing anchor with 3/2.8 mm nails to each leg."......................  
i find no mention of having to use "triple grips" anywhere p.s the deck has no roof

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## Bloss

I just like a bit of over-engineering especially if I am advising DIYers. Whether I use triple grips depends on the site a bit too - and sometimes on every 2nd or 3rd joist. Skew nails work fine - at 150mm deep you might want to look at some blocking as they can tend to lean over or twist a bit more than 90mm, but if they are not visible that's mostly an appearance issue not affecting strength. :2thumbsup:

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