Joists 100mm short of a picnic. Trying to maintain my sense of humour....

[mvincentd]

Damn...i've written at length then lost it all.

 

To cut a long story short;

There's a pre production drawing detailing a 3546 joist including ends constructed such that they can withstand 50mm trimming either side should it in some cases be necessary.

I'd guess they required you to sign this drawing off before production, particularly as I believe they didn't do the on-site measure?

So regardless of all other facts they are in the clear if the joists now actually measure 3546.

In any case 3546 seems correct to me given you supplied a 3646 measurement for wall to wall........you have 2 x 50mm wall plates and a designed hanging system requiring both top and bottom chord to fit between them, ie in a space of 3546.

Just go measure and find where the deviation (and liability) lies.

Edited November 28, 2018 by mvincentd
mistyped dimension.

[mvincentd]

12 hours ago, recoveringacademic said:

The wall-plate is 47mm each side. More than enough to allow the joist top chord to sit happily on the wall-plate

I believe minimum joist bearing is 90mm...so typical allowance 100mm in line with typical width of a block wall.

I'm concerned that theres a possible misinterpretation here (worth approx 100mm) that you carry into this 2nd joist order when you;

12 hours ago, recoveringacademic said:

check the first design, find a couple things need to be changed, send the plan back annotated with the 'worst case' width.

 ...is 3646 the physically measurable distance of durisol to durisol, or is it (for want of a better way of putting it) 'being expressed as such for simplicity having taken into account a couple of things'?

 

[ToughButterCup]

This isn't easy. I'll just have to suck this one up.

7 hours ago, mvincentd said:

[...]

So regardless of all other facts they are in the clear if the joists now actually measure 3546.

[...]

 

Psst! Need some lovely POSI joists? Never used, mint condition, always stored in the dry

Ian

[scottishjohn]

If you think you are going to have to pay for new ones 

you could make up end sections to extend them ,if you wish 

solid wood that , has same profile but also has a tongue that goes right into first vertical web  for extra fixing

glue and screw it all in --

If you really worried  make them up using good plywood layers to make solid end as  glue lam end extensions - if still worried add extra long outer plywood braces both sides spread load further down the joists - cannot be that much load  when you look at thickness of joists hangers--make the glumlam plywood pieces so they can be top hung if you like --no need for joist hangers then --not the simple job you wanted --but dam sight cheaper than new beams and probably stronger if you do it right

 

[Russell griffiths]

Looking at the original picture of the joist end I think they could be changed

if you removed the solid blocking at the end and had larger blocking added then had them add new gang nail plates, and then a plywood stiffener to the side that should be adequate 

[Gone West]

@recoveringacademic The metal web joists for our hall were too long because the stairwell was the wrong size. The timber frame company went back to the metal web joist company who told them how to alter the length. I would have thought yours could be lengthened as they are to sit in joist hangers. Have the company told you they can't be lengthened?

 

[ToughButterCup]

Thanks everyone for your input. I appreciate your support and kindness. I really don't know what I (we) would have done without it. Especially thanks to @mvincentd for cutting through the haze and telling it like it is. 

 

I will be talking today to the manufacturers and let's hope something can come of it. I must say the manufacturer has been very professional. Cheshire Roof Trusses. (Robinson Manufacturing) Let's hope @PeterStarck that they can come up with something.

[Russell griffiths]

I’m sure that if they collect them and reconfigured the ends and re deliver you may only be out of pocket for a few hundred. 

 

Get it sorted. 

Move on. 

Onwards and upwards. 

 

 

[jack]

1 hour ago, recoveringacademic said:

I will be talking today to the manufacturers and let's hope something can come of it. I must say the manufacturer has been very professional. Cheshire Roof Trusses. (Robinson Manufacturing) Let's hope @PeterStarck that they can come up with something.

 

I don't quite follow everything that's been going on, but why did you get what you wanted last time but not this? Surely that's the crux of the matter...?

[joe90]

I really hope the manufacturer delivers new ones, if not I would simply extend them by cutting a block like this each end and glueing it in place, add a plywood gusset either side after fitting in joist hangers if you want belt and braces.

[ToughButterCup]

The point made by the BCO is also important.

Since POSI joists are engineered, and there are no guidelines similar to those operating for timber (only)  joists - the TRADA Guidelines, then he has no guidance to follow. (See earlier post).

 

Why a problem this time, and not last? They are different products, and different designs. One (the first), top hung (on top of the wall-plate) Easy Joists. The second is joist hanger hung, fitted between wall-plates, not on top of them.

 

I didn't do enough research into the difference between the two If .... if.... if .  If I can't take a joke, then I shouldn't have started.

[jack]

6 minutes ago, recoveringacademic said:

One (the first), top hung (on top of the wall-plate) Easy Joists. The second is joist hanger hung, fitted between wall-plates, not on top of them.

 

Right, didn't pick that up until now. What a pain

[Nickfromwales]

My suggestion is to remove the wall plate and replace it with a glulam or 9x3” to reduce the span. 

That would require the left and right wall plates first being affixed, and bolted sufficiently, and then the 9x3 or glulam ( SE to specify ) hung off those. 

 

We had a brief phone chat about this and, if no dice with the supplier, then this is a good solution with near zero compromise. 

 

What gap would be left if each end was switched out to 9x3? 

 

Can a timber yard produce C24 or C16 at 9”x4” wide? Cheap quick fix, just have one each end. Or sister two 9x2”’s each end, cheaper and quicker yet. Downward rotational force with the deeper wall plates would mean the plates would have to be bolted top and bottom, but then you keep the beams you have with no jiggery-pokery. 

[joe90]

35 minutes ago, Nickfromwales said:

Downward rotational force with the deeper wall plates would mean the plates would have to be bolted top and bottom, 

 

@Nickfromwales not sure I agree with you (but I am not an S.E.) if the joists are a tight fit there can be no rotational force as it would compress the top cord of the joist.!

[Gone West]

4 hours ago, joe90 said:

I really hope the manufacturer delivers new ones, if not I would simply extend them by cutting a block like this each end and glueing it in place, add a plywood gusset either side after fitting in joist hangers if you want belt and braces.

That is similar to the recommended way of shortening my metal web joists where a timber batten, the same size as the cord, was fixed between the cords and covered both sides with steel connector plates.

 

[Nickfromwales]

1 hour ago, joe90 said:

 

@Nickfromwales not sure I agree with you (but I am not an S.E.) if the joists are a tight fit there can be no rotational force as it would compress the top cord of the joist.!

Exactly. I doubt if you’re allowed to compress them as that would compound deflection imo. 

As stated in my first, SE would need to sanction anything ‘off’ the original. 

[ToughButterCup]

Weeeeeeeeeeelllll now: just heard back from the manufacturers. Cullens (the joist hanger chaps) have come up with this approved solution, have a look

 

 

What do you all think? What sort of timber should I use? Treated C24?

Ian

[Mr Punter]

I don't quite get it.  It looks like the screws are going through the back of the hanger.  Also you would probably need to screw through the chords into the block first so it is set the right distance.  Fairly odd but I am sure they know what they are doing.

[Onoff]

19 minutes ago, recoveringacademic said:

Weeeeeeeeeeelllll now: just heard back from the manufacturers. Cullens (the joist hanger chaps) have come up with this approved solution, have a look

 

 

What do you all think? What sort of timber should I use? Treated C24?

Ian

 

You've got to do it?

 

How much are they paying YOU?

[joe90]

That’s nearly what I suggested.

[Nickfromwales]

Do you have to do both ends equally?

[Mr Punter]

Yours looked a bit better as it was the full height of the joist.

[Jeremy Harris]

Personally I prefer @joe90 's solution, with the "T" shaped infill, as structurally that it very much better, as is restrains the outwards load in the lower joist structural member.

 

When loaded, the upper member is in tension, so wants to pull away from the wall plate, and the lower member is in compression and wants to push in towards the wall plate.  Having end restraints positively stops the lower member from trying to cripple the lower edges of the hanger.

[joe90]

As an aside I wish I had studied stuctural engineering, I am pretty good at knowing what will work but don’t know the maths behind it. Perhaps night school?

[mvincentd]

Sorry to hear the outcome, but good that they have this suggestion for remediating the existing joists rather than entirely new ones.  Like others, I too think @joe90 has a better design...to the point that i'd bet this is what they really mean but have drawn badly.  Its a wholly unqualified opinion but i reckon their drawn idea won't work, but Joe's will.

Good luck.