used 6inch floor joists instead of 9

murt007

Hi all,

I under took a building conversion on a budget and converted a large shed in to a livable space last year. My problem is that instead of using 9inch floor joists I used 6 inch ones ( 150 x 45 ) this was due to an existing loft in the building used for storage. I now have the ground floor complete etc but am trying to make an office up stairs. But the 6 inch floor joists are flexing ( i know this because I have a projector bolted to the roof of the room under neat. )
Does anyone have any solutions to fix my problem. i will upload some images

murt007

this shows the structure I build to take the floors. the building is 25 feet by 30 feet. my problem is that the 6inch joists are spanning sections 15 foot by 14 foot wide

slimjimmc

Can you stick another RSJ or two in to support the open span?

murt007

slimjimmc wrote: »

Can you stick another RSJ or two in to support the open span?

thanks for your reply but if i was to use more rsj i would have to damage the walls in the finished ground floor. which is not worth doing

galwaydude18

Personally I would be putting in more rsj's to take the flex out and then put right the ceiling and walls in the ground floor.

Would you be able to put in 9" joists from the room above and panel adhesive@bolt them to the 6" joists?

If you leave it the way it is you will end up with cracked ceilings due to the flex in the existing joists.

Max Moment

You could double up on the floor joists i.e. 2no. 6" joists every second one and bolt these together through the middle of the joists to act together. This would certainly reduce the deflection.

You could add 'ties' and partially suspend the floor at mid-span from the Roof beams above.

Alternatively, make the projector independent of the floor above if you can live with the deflection

gsxr1

You dont have to damage the wall.

You could run a 4x6 on edge under the 6" joists running the same direction as your steel and building a support column downstairs on each side. Taking the bonce out.

2 times.

captainzero

batten across the joists with 3x2 at 16" centres should give same strength or even a bit more as it binds everything together

Gary Busey

Hi, looks like your too far now to redo. Id only consider adding Rsj Or Glulam beams as extra load bearing members underneath. Only other option is running A second Layer of joists above or below the existing at 45 degrees diagnal to your joists span. Either on will give enough support to reduce the deflection. Both will be expensive enough or you coud try cross bridging in between your solid bridging to gain rigidity.