Joists: how level should level be?

[ToughButterCup]

This week has been difficult and pleasing in equal measure. Never installed a joist  before, but now 8 are up,  sitting there waiting to be nailed in place. No nails yet - just push fit.

 

Fussing them into level-ness was interesting. Mostly I managed to get them level enough to of split the laser beam - half on, half over the top.

But doing that job made me look at the joists in great detail. The top surfaces have some very small bumps and dips above and below  the laser line. Nothing substantial.

 

Since I don't know  what I don't know, should I get the belt sander out and make sure that the bumps are levelled out?

 

Planning to nail them in and then put temporary boarding on them tomorrow: quite exciting because it's a bedroom - somewhere to put up guests?

[TerryE]

Ian, I can't recall, but what type of joist are you using?  Solid timber, eco joist (that's the ones with the metal zig-zag web or the ones with the OSB web?

 

IMO you can tolerate a mm or two and there's little point in sanding.  Anything more than a mm or two would require a planer anyway.

 

The main annoyance that we had was that our Ecojoist had jointing plates occationally and these added 2mm or so over the joint.  We had 2400 × 1200  22mm boards, but these still had a very slight ripple over the jointing plates. 

 

Any small pimples will get squished into the floor or ceiling boards

Edited December 15, 2018 by TerryE

[TerryE]

The main PITA with boards IMO are (i) planning all of your rigid runs: potable water, foul water and MVHR as well as electric of course.  This is a LOT easier with eco joists but gets harder with the webbed and solid ones.   These runs need carefully designed and laid out. Foul water piping requires fall away within tolerances.   The joists require cross bracing.   Don't leave this to your trades as chaos can ensue.  Start will the fattest / stiffest and do the electricals last.  Remember that you will have to meet structural and fire BRegs when planning these penetrations as well of course the dynamic of putting the bloody things in in the first place.

 

So many houses have above-board boxing in along walls to accommodate horizontal foul water runs and these look totally naff IMO.  Non in our house -- though a couple of internal walls have been doubled up to hid a multitude of messiness without being obvious. 

Edited December 15, 2018 by TerryE

[ProDave]

Any surface imperfections are lost in the noise and can be ignored.  Just make sure you screw the boards down, not nail them if you want squeak free.

[TerryE]

Our ONE joist cockup was that one of the cross braces running through the joists was only nailed into the joists and obviously not spiral nailed.  When you walk across one joist (and only only one in the house that does this), it flexes a mm or two relative to the cross brace and this generates an audible creak.  This is half way between my bedside and the ensuite.  BUGGER.  I didn't notice until after our bedroom had been carpeted.

 

PS  In the case of PosiJoists, these are also called strongbacks.

Edited December 15, 2018 by TerryE

[PeterW]

If they are metal web joists with P5 or Egger boards then the D4 glue is your friend as it fills all the gaps anyway - just don’t walk below it when it’s going off unless you like cutting it out of your hair .... 

 

If you read the MIs you will find they say nail the first board only then the last - others just need glue. I tend to nail them about 100mm back from every T&G joint on every joist. No squeaks either. 

[joe90]

I agree, a mil or two is not a problem. Our flooring was glued only, d4 glue, not a squeak anywhere. This was recommended by our builder who is nearly as fussy as I am ?

[ToughButterCup]

1 hour ago, joe90 said:

[...]

who is nearly as fussy as I am ?

 

And there's me wanting to know what fussy is....

1 hour ago, TerryE said:

Ian, I can't recall, but what type of joist are you using?  [...]

 

POSIs... and of course I should have thought...

1 hour ago, TerryE said:

[...]

Any small pimples will get squished into the floor or ceiling boards

 

So, that's that sorted out in my mind.

 

1 hour ago, TerryE said:

[...]

BUGGER.  I didn't notice until after our bedroom had been carpeted.

 

Thats what interested me ... all the nails I bought are twisted

1 hour ago, TerryE said:

[...]

was only nailed into the joists and obviously not spiral nailed. 

[...]

 

Would not have been obvious to me

1 hour ago, PeterW said:

[...]

If you read the MIs you will find they say nail the first board only then the last - others just need glue

[...]

 

Whaaasan MI?

 

1 hour ago, TerryE said:

The main PITA with boards IMO are

[...]  The joists require cross bracing.   Don't leave this to your trades as chaos can ensue.

[...]

 

Why should they need cross-bracing? 

1 hour ago, TerryE said:

[...]

   These runs need carefully designed and laid out. Foul water piping requires fall away within tolerances. 

[...]

 

The longest foul water run for us is two meters

[PeterW]

1 hour ago, recoveringacademic said:

Whaaasan MI?

 

Manufacturers Instructions...

[TerryE]

2 hours ago, recoveringacademic said:

Would not have been obvious to me

 

The squeak occurs when one or more nails slip in the nail hole.  The spiral ones and screws are far less likely to pull and slip.

 

2 hours ago, recoveringacademic said:

Why should they need cross-bracing?

 

Joist spans over 2.5m need extra measures to prevent the tendency to twist when loaded.  Staggered solid noggins are typically used for solid joists.  In the case of PosiJoists extra lateral bearers. (I think our build two overlapped were 3×4s were slid in during erection for each long span to run the length of the room and then fixed in place before the floor was nailed in position.)

 

Re the carpetting issue, we screwed down all of our boarding before the room were carpeted as an extra precaution to avoid squeak.  The only one that we missed was one lateral to joist cross.  Bugger again.

 

2 hours ago, recoveringacademic said:

The longest foul water run for us is two meters

 

It's any lateral runs that are a PITA as you have to be physically able to get the pipe in there.  In a couple of cases we used straight - 45 - straight 45 - straight to form a nice  roddable slow bend and one that I could get into position and still solder fit.  We followed Nicks et all suggestion a radial HEP2O system with no hidden joints.  HEP20 has enough forgiveness to pull through though it is really a two man job.  Ditto the flexible radial MVHR systems. 

Edited December 15, 2018 by TerryE

[ToughButterCup]

11 hours ago, TerryE said:

[...]

In the case of PosiJoists extra lateral bearers. (I think our build two overlapped were 3×4s were slid in during erection for each long span to run the length of the room and then fixed in place before the floor was nailed in position.)

[...]

 

Thank God you wrote that.

What needs doing, how, when, where, to what spec ?

 

- Thanks Terry.

Another  'Oh dear what a pity ' moment avoided a few days before  it hits us right in the  bank balance

[TerryE]

Ian, to be totally honest, I only know because I said to our erection crew: "what are you doing that for?"  Maybe it helped that I had teas and bacon butties in my hands at the time, but the crew boss decided to explain to the child in the room.  I am being a little unfair -- they were bloody brilliant and always willing to explain.

 

I think my BInsp was a bit stunned when he looked around the build.  I can't remember the exact words, but his aside comment was very complementary about the build and sturdiness of the timber frame.  In most interviews / reviews I used to get a pretty good instinct if the project / project was solid or you needed to dig deeper.  I guess that in most cases the inspector are just the same: they get a good instinct as to whether the job is being done properly or not after the first few minutes looking around.

 

With these guys it is just simpler to stay on the right side of them and avoid setting off any alarms -- even if unmerited.

[PeterW]

1 hour ago, TerryE said:

guess that in most cases the inspector are just the same: they get a good instinct as to whether the job is being done properly or not after the first few minutes looking around.

 

 

I think that is very true. One I’ve dealt with for a while knows that corners are not being cut and that if something isn’t right then it will be coming back out to be redone ..!! Also there is no hiding stuff either as he’s happy that the job is as open as possible - the flip side to all this is when you do hit a snag, a quick call gets you an answer.