The POSIs Picnic: a solution is in sight.

[Jeremy Harris]

7 minutes ago, scottishjohn said:

it will be minimal but to be super sure  i said double up on bolts and if ends of joists are packed after fitting they can go nowhere --no space means even if there is a twisting force it can,t move cos theres no where for the plates to go.

Isaw original spec was  one bolt every 600 but joist were 400 spacing --i would have done bolts at same as joists anyway ,and if you still worried about something that can,t happen apply a layer of no nails or whatever behind wall paltes then load is pread over total area

how many diff solutions do you want to a simple problem 

i suggested a soltion to fix it that way aswell

take your pick both will work fine and with double wall plates you got twiice the area to glue + double screw the floor too if you want

  engineers  have said you don,t need full support on the end of the joist anyway --so can,t be much load anyway--=if you believe them  

me igo for belt and braces always 

 

As someone with a fair bit of a structural engineering background (as in having designed a two seat aeroplane and put it through approval) I can say with certainty that the stresses in a doubled up wall plate would be far from "minimal".  Do the calcs and see how the stresses change with increased distance from the points of applied load and restraint and it's pretty obvious just how much the wall plate stresses would increase with such an option. 

 

This is the reason that the joist structural engineer hasn't suggested doubling the wall plates, but instead has taken the very sensible option of adding an additional thick end shear web, screwed into the existing end compression post.

[scottishjohn]

35 minutes ago, JSHarris said:

 

As someone with a fair bit of a structural engineering background (as in having designed a two seat aeroplane and put it through approval) I can say with certainty that the stresses in a doubled up wall plate would be far from "minimal".  Do the calcs and see how the stresses change with increased distance from the points of applied load and restraint and it's pretty obvious just how much the wall plate stresses would increase with such an option. 

 

This is the reason that the joist structural engineer hasn't suggested doubling the wall plates, but instead has taken the very sensible option of adding an additional thick end shear web, screwed into the existing end compression post.

 

both solutions will work  well as when it is finished and floor attached to both wallplates and joist it is basically  a solid lump

thats why your engineer is not worried about full support on the end of the joist ,cos the load is spread over all components joists ,wall plates and floor itself and the load path is directly up the vertical brace into top stringer of the joist ,the actual load on the end will be very little as it is not braced and will bend to a degree and  transfer the load up the vertical path of the brace that is there --If it was designed to be strong enough to start with  the ends trimmed off 

its  not on a wing where things are deflecting and bending all the time ,where a solid unit will just fracture -stresses are totally different .

I give up --you all want to make it more complicated  than it really is  ,the making up of end fitments will take much more time  and effort than a simple doubling up of beam and more bolts to wall

do what ever you like 

[Mr Punter]

1 hour ago, JSHarris said:

 

As someone with a fair bit of a structural engineering background (as in having designed a two seat aeroplane and put it through approval) I can say with certainty that the stresses in a doubled up wall plate would be far from "minimal".  Do the calcs and see how the stresses change with increased distance from the points of applied load and restraint and it's pretty obvious just how much the wall plate stresses would increase with such an option. 

  

This is the reason that the joist structural engineer hasn't suggested doubling the wall plates, but instead has taken the very sensible option of adding an additional thick end shear web, screwed into the existing end compression post.

 

But you would not need to double up the wall plates - just 25mm each side to match the add-a-lump-on-to-the-end-of-each-joist solution.

[joe90]

28 minutes ago, Mr Punter said:

 

But you would not need to double up the wall plates - just 25mm each side to match the add-a-lump-on-to-the-end-of-each-joist solution.

 

I think you will find the joists are 100mm short, that’s 50mm per end!.

[Mr Punter]

15 minutes ago, joe90 said:

 

I think you will find the joists are 100mm short, that’s 50mm per end!.

 But the proposal from Cullen only adds 25mm

[joe90]

@recoveringacademic have you got a resolution yet?

[ToughButterCup]

17 hours ago, joe90 said:

@recoveringacademic have you got a resolution yet?

OK, here goes.

• Lengthening the joist as per the SE's (Cullen's own SE) is acceptable.
• Packing out the top and bottom chords is acceptable (BCO and Cullen's SE)

And I had a really interesting discussion with the BCO yesterday.

 

I made the point that the bottom of the joist hanger extends below the bottom of the wall plate. And that my learning from this discussion group is that a  'floating' bottom chord, even if nominally supported by a joist hanger is undesirable. He agreed. I said I would replace the wallplate with one which supports the bottom chord of the joist directly. OK it's a PITA, but that's all.

 

Here's what really interests me: the BCO drew my attention to the tops of the UH hanger

I mentioned that  the designer told me that we are allowed to snap that top bit off if needed. The blurb here (page 49), (Cu Cullen technical Guide .pdf) talks about 

'... Elongated slots and unique snap off feature, allows for height adjustment and face fix only option...' 

And in the way of BCOs the world over, he asked for documentary evidence (sent)

 

So, it seems likely that I'll replace the wallplates, pack out the ends as directed, and put the joists up. We agreed that I'd do a small section of one room and then ask the BCO to visit to see how I'm getting on.

 

All in all, I think that between us, we have managed to pull my hand out of the fire.

Photos to follow later this week.

Ian

[joe90]

Really glad you have a solution that keeps the BCO (and yourself) happy. I didn’t realise the wall plate was not the same depth as the joists! I would always make the wall plate the depth of the joists, it gives you something to fix plasterboard edges too. Personally I like to wrap the top ends of the hangers over the top of the wall plate but I have been called “anal” by some!

Edited December 4, 2018 by joe90

[PeterW]

@recoveringacademic as the wall plate at the bottom isn’t supporting any weight, it’s just for compression purposes, you could ask the BCO if just adding a lower piece - bolted to the wall and screwed up into the wall plate above - would satisfy the request. 

[Mr Punter]

@recoveringacademic I just want to check that you are aware that the proposal from Cullen only allows an extra 25mm extension to each end of the joist - 50mm total.  In your earlier posts on this topic you suggested that the joists were 100mm short.

[ToughButterCup]

15 minutes ago, Mr Punter said:

@recoveringacademic In your earlier posts on this topicyou suggested that the joists were 100mm short.

Even I make mistakes... ?

The errors seem to vary a bit between joists... Roughly 20 - 30 mm generally 

This photo was taken with the other end hard up against the joist on the other wall, so here the error is 15 or 16 mm. 

Thanks for watching my back.