Floor joist size and spacing

[dowdings]

Hello
Hopfully this is in the right forum.

I have a house which had an extension before I moved in. The garage has been widened and another floor buildt above it making an extra bedroom.

The garage is 12ft (3.65m) wide.

The floor ceiling/floor joists are 6.5" (16.5cm) x 1 7/8" (5cm) and spaced at 16" (40cm) centres and mounted in metal hangers.

When a perons walks around the bedroom the floor can be felt by another person to move as they walk. Also there is an en-suit with the stud wall which forms it built above one of the floor joists. The door the the en-suit rattles when someone walks across the floor indicating to me that the floor is moving.

I do realise that some movement is always there but I'm concerned there is too much.
Are the floor joists used correctly sized for the span?
what could I do to reenforce the floor?
Any ideas or suggestions greatly accepted.

Thanks
Steve

 

[catlad]

If you want to stiffen the floor up you can take the floorboards up and put extra joists in the same size

 

[^woody^]

Much easier, would be to put in some timber noggins at the centre or one third of the span. And at the ends too if none there already.

 

[dowdings]

I can get full access to the ceiling of the garage rather than disturbing the above bedroom.

What difference would noggins make at the centre, thirds or at the ends?
Would they just assist by "bonding" all the joists together?

And when you say ends do you mean right at the end of the joist next to the walls?
If so, what difference would they make with the joists already fixed with the metal brackets?

Cheers
Steve

 

[^woody^]

Noggins prevent individual joists from flexing

//www.diynot.com/forums/viewtopic.php?t=142250

 

[JohnD]

is the floor made of chipboard?

you say the joists are 12ft long and 6.5" deep x 1 7/8" wide? Sounds to me like they were sized fora flat roof, not a habitable room above. I doubt the extension had building control approval.

If it is a garage below you might do a better job by taking down the garage ceiling and putting proper-sized timbers in. It might be no more trouble than trying to bodge it up.

 

[Blagard]

Although I would suggest your joists are just a hint undersized, I doubt that is the problem. I do wonder if the joists have actually been properly fitted, levelled and fully seated in the hangers? Is the chipboard screwed down solidly onto the joists? Perhaps the "flex" you feel is in the chipboard rather than the joist although I have never heard of such a problem, you need to keep an open mind when you investigate further.

 

[noseall]

The difference that 1/2 span or 1/3rd span noggings makes is huge.

We work on floors that are in pre-nogged and nogged states and the flex of un-nogged floors is disturbing particularly when you are loading out with blocks!

As Woodspar has said, this should be your first job.

 

[JohnD]

Chipboard, bah!

I'd prefer ply, well-screwed down with nogs under all unsupported joints

I wonder if herringbones would help?

 

[noseall]

I wonder if herringbones would help?

Does pretty much the same job a solid bridging.

Agree about chipboard, John, absolute garbage!