Best way to hang posi joists into different materials

[Vijay]

Ah good point mate,  they have quoted 72mm wide even though I told them I want minimum deflection

[Russell griffiths]

as Long as you only need to plane the ends for a snug fit

my roof rafters required a plumb cut on both ends that I didn’t have a saw deep enough to cut through in one pass. 

[Vijay]

Mr Punter mentioned a deflection value of 8 which is a good guide now. Just wondered what others have achieved and have been happy (or unhappy) with?

 

[Vijay]

Trying to work out the height of various steels in relation to the floor joists. My joists will be 304mm deep webbed joists and my steels will be 203 and 254 deep. If the webs are filled with timber for joist hangers to fix to, do I line up the bottom of the joist/hanger to the bottom of the steel, as obviously the joists are deeper than the UB's. 

Do I pack the top of the steels for the rest of the hangers to fix to which would also give something for the top chord of the joist to sit against?

 

Cheers

 

Vijay

[Russell griffiths]

6 minutes ago, Vijay said:

Trying to work out the height of various steels in relation to the floor joists. My joists will be 304mm deep webbed joists and my steels will be 203 and 254 deep. If the webs are filled with timber for joist hangers to fix to, do I line up the bottom of the joist/hanger to the bottom of the steel, as obviously the joists are deeper than the UB's. 

Do I pack the top of the steels for the rest of the hangers to fix to which would also give something for the top chord of the joist to sit against?

 

Cheers

 

Vijay

Sounds good, how about services on the underside, would it be an idea to have the steels high so you get a gap under for services to run under the steels. 

[Oz07]

I think structurally you'd be better off flush at the bottom gap at the top. If you look at a joist hanger its not normally as crucial at the top. Hasn't this detail been specced by anyone though? Floor supplier? Steel design guy? Sometimes the posi's can have extended top chord which could work with your steel sizes?

[Vijay]

5 minutes ago, Russell griffiths said:

Sounds good, how about services on the underside, would it be an idea to have the steels high so you get a gap under for services to run under the steels. 

 

I think whether it's top or bottom, I'm gonna have a few issues getting services around, especially the MVHR ducting  

 

4 minutes ago, Oz07 said:

I think structurally you'd be better off flush at the bottom gap at the top. If you look at a joist hanger its not normally as crucial at the top. Hasn't this detail been specced by anyone though? Floor supplier? Steel design guy? Sometimes the posi's can have extended top chord which could work with your steel sizes?

 

I contacted a few companies for quotes but to be honest, I didn't ask them directly yet as I trust opinions on here more. I want the best way to do things, not that'll do which is what I've found from some suppliers

 

I just thought, I should email the hanger manufacturers, IIRC there were 2 main ones.

[Oz07]

Surely your posi supplier will give you a fixing detail. At end of the day they're the floor designer no doubt there is some excellent knowledge here but you need to be using an indemnified professional

[Vijay]

1 minute ago, Oz07 said:

Surely your posi supplier will give you a fixing detail. At end of the day they're the floor designer no doubt there is some excellent knowledge here but you need to be using an indemnified professional

 

they're also the ones who tell me that a 19mm deflection in the joists is absolutely fine lol

[willbish]

18 minutes ago, Vijay said:

Trying to work out the height of various steels in relation to the floor joists. My joists will be 304mm deep webbed joists and my steels will be 203 and 254 deep. If the webs are filled with timber for joist hangers to fix to, do I line up the bottom of the joist/hanger to the bottom of the steel, as obviously the joists are deeper than the UB's. 

Do I pack the top of the steels for the rest of the hangers to fix to which would also give something for the top chord of the joist to sit against?

 

Cheers

 

Vijay

 

For ease of installation you could hang the posi's by the top cord directly onto the steel. No need for any timber packing then. Top chords are 35mm deep. That will give a void top and bottom.

 

This is what I did and its worked well. My posi's were 195mm, steel was only 162mm. This means the steel is below the bottom of the joist by 2mm which will require a bit of work come plasterboarding time but I think that is easier than packing the steel and 60+ hangers.

 

I wouldn't worry about people telling you need a professional to spec this. My 'professionals' weren't paid enough to think about this level of detail.

 

[Russell griffiths]

Have you thought of planning your MVHR and getting holes cut in your steel before you fit them. 

[dpmiller]

^this. I had some holes designed into our steels that match in with the pozijoist webs.  Very handy.

[Vijay]

16 hours ago, Russell griffiths said:

Have you thought of planning your MVHR and getting holes cut in your steel before you fit them. 

 

I haven't looked at he MVHR but will get that looked at straight away

 

7 hours ago, dpmiller said:

^this. I had some holes designed into our steels that match in with the pozijoist webs.  Very handy.

 

I think that would be down to pot luck for me as I'm no where near getting the joists on site