RSJ installation cost

[Jblakes]

Hi all,

We have a very bouncy upstairs floor that is two kids bedrooms. Beneath is the living room, that has a wooden beam across the centre of the room. We have looked under the floor upstairs and the joists are very old and not up modern code.

Due to the beam across the living room ceiling, there doesnt seem to be much i can do, dont want to take it down. So my thoughts are rsj or seen i-joist, to fit underneath the current joists.

This a good idea? Anybody know rough cost. Room roughly 3.8m span, no brick wall to support above.
The first picture is the joists. Its looks like it resting on the beam

 

[Kearn]

The remedy depends on the issue - what is bouncing? And why?

There’s always more than one way to skin a cat… our place has 3 oak spine beams, at 6m, span, beyond what our structural engineer would normally be happy with! Two, one above the other, same section size, one flexes, one doesn’t. Normally that would indicate failure of the timber, given the deflection we had, but the timber hadn’t failed. The approach would be support from underneath, or above to shorten the unsupported span - we had no desire for posts in the middle of rooms, so effectively added two queen struts (luckily this was the tie, so in the attic space).

Old joists don’t need to compare to modern calcs - often over specced depending on anhe and oak does a grand job compared to today’s softwood.
If it’s the joist(s) then again depends why the failure, might be possible to sister, splint with metal work on the side(s) or if you can access from the top, then flitch into the top.

That said, we had a number of original oak joists which were no longer up to it, and the best approach to replace rather than bodge - ours were occasional examples of poor quality cross grained timber with shakes beyond structural capability, not worth the risk.

An initial site meeting with a good structural engineer comfortable with timber would be money well spent.

Inserting full steels could be overkill.

 

[Jblakes]

It hard to fully tell tbh want the issue is. The beam in the middle doesn't seem to move but if you put you hand upto the ceiling you can feel decent movement when walked on. The joist seem to be intact. I think it just has always bounced, but because we now have two kids stomping around it sounds like they are going to come through (highly unlikely)

 

[Jblakes]

Is there any reason why you can't just install joists cross ways under the floor upstairs, supported between two solid walls?