178 rsj - fitting joists at a vertical offset

[OrangeJuice09]

Hi, I'm having a 178 x 102 rsj (160 x 45 internal web) fitted to support an existing wall and want the existing joists (50 x 150mm) to be attached slightly higher than the rsj.
The usual designs I've seen are where the joists rest on the rsj or the joists fit inside the rsj (sometimes with a nogging).

I would like the joint to be half way up the top of the rsj

I think possibly joist hangers may work to meet the scenario but I'm not sure. Is this possible ?
Above the rsj wil sit the wall so I cannot bend the hanger staps over the rsj to make a fixing on the other side.
See image of what I'm trying to achive when I refer to offset. Thanks

 

[noseall]

Fill out the webs with timber regardless, i.e. have M12 holes drilled along the web centre then fix timber into the webs. You may have to use build-in hangars depending how much meat of the hangar is fixable by the timber surface (regards jiffys).
A build in fella could also be supplementary fixed to the timber infill.

 

[^woody^]

Masonry hangers

 

[tony1851]

Screw or bolt some timber packing on the bottom flange and notch the top part of the joists.

 

[^woody^]

...... if you want to load the bottom flange and weaken the joist bearing capacity

 

[Dereekoo]

...... if you want to load the bottom flange and weaken the joist bearing capacity

Bearing stays the same, shear increases

 

[^woody^]

Bearing shear

 

[tony1851]

The weight of a domestic floor will hardly impact on the strength of the bottom flange.

The joist would be perfectly ok, even cut down to 75mm.

The only considerations for joists in a domestic setting at the bearing are 1. shear and 2. bearing capacity perpendicular to the grain.

Neither of these would be a problem in this particular case.

 

[AngleEyes]

Screw or bolt some timber packing on the bottom flange and notch the top part of the joists.

I suspect the existing dimensions will preclude that possibility.

Hi, I'm having a 178 x 102 rsj (160 x 45 internal web) fitted to support an existing wall and want the existing joists (50 x 150mm) to be attached slightly higher than the rsj.
The usual designs I've seen are where the joists rest on the rsj or the joists fit inside the rsj (sometimes with a nogging).

I would like the joint to be half way up the top of the rsj

I think possibly joist hangers may work to meet the scenario but I'm not sure. Is this possible ?
Above the rsj wil sit the wall so I cannot bend the hanger staps over the rsj to make a fixing on the other side.
See image of what I'm trying to achive when I refer to offset. Thanks

View attachment 254181

 

[^woody^]

The weight of a domestic floor will hardly impact on the strength of the bottom flange.

The joist would be perfectly ok, even cut down to 75mm.

The only considerations for joists in a domestic setting at the bearing are 1. shear and 2. bearing capacity perpendicular to the grain.

Neither of these would be a problem in this particular case.

But why would you want to do it your suggested way, which is by definition bad practice, when there are better ways, orthodox ways, which are no more difficult or costly? It makes no sense.

 

[tony1851]

I suspect the existing dimensions will preclude that possibility.

Why would they exclude that possibility?

 

[tony1851]

But why would you want to do it your suggested way, which is by definition bad practice, when there are better ways, orthodox ways, which are no more difficult or costly? It makes no sense.

It isn't 'bad practice'; notching to this extent is allowed by BS 5268 and can be proved quantitively. You are allowed a higher shear stress when the notch is at the top of the beam. And it saves the cost and faffing about with hangers.

 

[^woody^]

No it's a last resort option, not first or even second or third choice. Last.

 

[Dereekoo]

We have only discussed 3 options so where does last come from?

 

[tony1851]

No it's a last resort option, not first or even second or third choice. Last.

If it works perectly well structurally (which can be proved) and avoids the cost of hangers, why should it be a 'last resort option'?