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Floor bounce - PosiJoist Floor Vibration checks


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21 hours ago, Oz07 said:

Is the sag static or moving depending on load? If it's a permanent sag could you not lift the underlay and carpet and latex floor?

 

The sag I measured is static

The bounce I get when someone walks around is too small to measure with my gear

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16 hours ago, PeterStarck said:

The joist sizes are in the second PDF file and the layout in the first PDF file.

My bad. Because the links are on the same line without even a space berween them I thought there was just 1 link.

 

I don't see the chimney in the joist layout, just a big opening that I assume is the stairwell.

 

I am wondering if the "problem" is just the size of the joists.  The smallest they could get away with that just about meet the requirements for sag? and perhaps my own joists (similar span and no walls above) have simply been over engineered to give a better result?

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8 hours ago, ProDave said:

 

I don't see the chimney in the joist layout, just a big opening that I assume is the stairwell.

 

We don't have a chimney and yes the opening is for the stairwell. It does seem, for my case, that it is well (over?) engineered  but it is rock solid. I can't understand why they would use only one metal strap in some places and narrow cords, but then I'm not a SE.

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I was getting slightly worried reading this thread as we are installing our wolf posi joist this week. Our joist are designed to hang by top chord on a 47mm wide batten one side and 100mm other side. Span is 5.6m WS250 joist that is 147mm wide @ 400 centres. No steel joist hangers. We have tightly packed the bottom chord between the chord and wall. The joist are solid. We don't have any strongbacks mid span but may add in for extra reassurance.

20180123_121734.jpg

Edited by Alexphd1
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3 hours ago, Alexphd1 said:

I was getting slightly worried reading this thread as we are installing our wolf posi joist this week. Our joist are designed to hang by top chord on a 47mm wide batten one side and 100mm other side. Span is 5.6m WS250 joist that is 147mm wide @ 400 centres. No steel joist hangers. We have tightly packed the bottom chord between the chord and wall. The joist are solid. We don't have any strongbacks mid span but may add in for extra reassurance.

No need to worry, ours are hung by the top chord on a 50mm ledger plate both ends. The span is 5.9m and the chords are 122mm wide and are at just less than 400mm centres. They are tied with a 100 x 50mm strongback.

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Right... Here is where a lot of your issues are :

 

issue_joist.JPG.ff634854f7a74a846a484cc2dd3227e9.JPG

 

The red circle shows two things. Firstly that the hanger is not connected at the base or the face so its free to twist when any load is put on the bottom.

 

The blue circle shows that the hanger and the posijoist are incorrectly fitted. The hanger should either fit the full face of the trimmer, or have a tab under the trimmer and "legs" wrapped over the top. It also looks like the hanger is missing a few nails.

 

Any weight on that joist is going to twist the trimmer out of line and allow it to bounce. Looking at it in detail you could potentially get a block down the side of FT02 and FG01 from your layout that would brace the trimmer against the wall and stop it twisting although that wouldn't sort that trimmer issue. 

 

I would be asking the builder what was supplied - and also checking if that came from the manufacturer as B01 definitely looks wrong !

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1 hour ago, Simplysimon said:

@PeterW and as stated previously, look to the top of the trimmer above your red circle, it's short there too, either that or it's a trick of the lens

 

I wondered that but if the joists are all the same depth then it would mean the middle joists were lower ...

 

But it’s still not right !!!

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I think B01 should be the same depth as the others but this was not supplied as part of the package so the builder got the nearest size conventional joist from a merchant, was unsure of how to make it fit, then sort of split the difference.  Also I would be interested to know if the decking was D4 glued and screwed?

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Thanks all, I've yet to try bracing that area from underneath to see what effect it has.

I did notice in a separate part of the building not all the holes in the hangers where filled with nails - so suspect this floor (fitted by same builder) likewise is missing nails - as pointed out by @PeterW

 

Nor can I see in my various photos any sign of packers to brace joist against the wall once installed. (If I understand correctly the implication is that there should be some).

 

I now have the 41 page pdf document of posi-joist calculations but I'm reluctant to post it publicly while this floor issue remains.  I would really welcome someone with a bit of posi-joist knowledge having a quick look through it if anyone has time, just to confirm the design is acceptable.  That would be really appreciated.

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MiTek have check all the calculations and the design and report 'Based on the loadings applied to the joists, which appear appropriate for a typical domestic dwelling, we have found that all of the joist designs conform to the relevant design codes.'

 

So they seem happy, suggesting manufacture or installation issue - or  'appropriate for a typical domestic dwelling' is below my own expectations 

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Normally the ends are packed to take the compressive load in the lower member, and the upper member has to be fixed so that it can take a tensile load.

 

If there are gaps like that at the bottom, then as I think I mentioned much earlier in this thread, that could well be a contributory factor.

 

I think one issue may be that some builders don't realise that any composite joist, like posijoist, I beam or whatever, has slightly different end fastening requirements to a solid timber joist.

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