First Floor: wall plates, hangers and joists - connecting up

[ToughButterCup]

I think I have got my head round the principles of putting the first floor in its place (is that a pun?). I have read the relevant guidance (The POSI Joist Handbook) -  and see architects note top left below. I have also read the architects note (bottom -right) which shows me I need to use 200 by 50 treated softwood.

 

Here's our first floor

 

And here's how Durisol recommend I attach the wall plate to the wall

 

 

So far so good. POSI say I must use a hanger (and the architect says so too) because of air-tightness, and that means I need to.....

 

make sure the fixing for the hanger doesn't penetrate the wall (and so compromise air-tightness) or put air-tightness tape over the masonry hanger fixing.

 

• Hanger - to wall-plate: I have a strong feeling I can't  get away with 50mm screws for the connection between the hanger and the wall plate can I? What size will those screws need to be?
• Wall-Plate to wall: Self tapping M10 coach bolts at 400mm centers (architects note above) to attach the wall-plate to the wall? The key thing is that they connect with the concrete isn't it, even if the 400 mm centers guidance happens to fall outside the concrete core (i.e. into the 'wood' of the Durisol block?
• I think I'll probably need to embed the wall-plate fixing in resin won't I - for air-tightness?

 

 

 

 

 

 

 

 

 

[MikeSharp01]

Are the Durasol the air tight layer? If I were doing this I would put a layer of airtightness membrane behind the wall plate it will be forced against the blocks so should stay air tight there, you can then seal it to the wall around the wall plate (above and below) that way you don't have to seal the individual joists to the wall plate. Around the bolts I would just run a bead of silicone around the holes in the membrane that the bolts come through then squash the wall plate onto it.

 

Edited September 21, 2017 by MikeSharp01
Typo

[ToughButterCup]

2 minutes ago, MikeSharp01 said:

Are the Durisol the air tight layer?[...]

 

Durisol is 65% air. Bit like a bird's bone structure.

 

In relation to the bolts that fix the wall plate to the wall....

5 minutes ago, MikeSharp01 said:

[...]Around the bolts I would just run a bead of silicone around the holes in the membrane that the bolts come through then squash the wall plate onto it.

 

Sorry @MikeSharp01, how do I run silicone round holes in the membrane  that the bolts have come through before fastening the wall-plate?

[Mr Punter]

I have not heard of self tapping coach bolts.  Can you not use threaded bar and resin?  You may have to abandon some holes if you don't hit the concrete.

 

If you are using joist hangers you will probably need to use the square twist nails as screws do not normally meet the requirement of manufacturers.

[ToughButterCup]

1 minute ago, Mr Punter said:

I have not heard of self tapping coach bolts.  Can you not use threaded bar and resin?  You may have to abandon some holes if you don't hit the concrete.

 

If you are using joist hangers you will probably need to use the square twist nails as screws do not normally meet the requirement of manufacturers.

 

And I have got one hundred and thirty meters of threaded bar (from the shuttering). You are some kind of genius @Mr Punter. 

[Lesgrandepotato]

@recoveringacademic Let us know when you've prepped the hangers, I suspect we can round up a few bods to throw the joists in with you. Think there are a few of us in the area. 

[MikeSharp01]

57 minutes ago, recoveringacademic said:

Sorry @MikeSharp01, how do I run silicone round holes in the membrane  that the bolts have come through before fastening the wall-plate?

• Mark the holes with the pre drilled wall plate,
• make sure you drill the plate and then the wall square,
• blow the dust out of the holes although pull out is not a major issue here you won't tighten the plate if the studding (threaded bar)is not tight you can enlarge the wall plate holes afterwards if needs be,
• then mount the studding in the holes in the wall with the resin,
• let them dry,
• put the membrane on the studding
• then silicone around the studs,
• then mount the wall plate and do up the nuts.

Bingo

Edited September 21, 2017 by recoveringacademic
Typo, readbility

[ToughButterCup]

Hmmm,

@MikeSharp01, I'll do a little trial first, photograph that and put it in this thread.

 

Do I need to check with the BCO about using threaded bar rather than self-tapping (yes I haven't heard of them either @Mr Punter) coach bolts? Or do I just do it and see if he cares, and if he does, well, tough?

[jack]

How many self tapping coach bolts will you need, at what size and length? I've half a box of galvanised 110mm (from memory) self-tapping coach bolts lying around somewhere that you're welcome to, although I'm assuming these will be too short if you need to get through a layer of Durisol and 50mm of wood.

[MikeSharp01]

3 minutes ago, recoveringacademic said:

Do I need to check with the BCO about using threaded bar rather than self-tapping (yes I haven't heard of them either @Mr Punter) coach bolts? Or do I just do it and see if he cares, and if he does, well, tough?

Worth checking, but it won't be a problem if the basic dimensions are he same (diameter), the issue is shear and at 400mm centres cannot imagine you will have a problem. Self tapping coach bolts do exist I think they are called screws rather than bolts though and you need the ones specified for concrete, they will be quicker than studding but perhaps not as cost effective as the studding, what diameter is your studding (threaded bar)? 

[Russell griffiths]

Watch carefully the wording in some of that spec, it says masonry hanger, in my mind you will not be using a masonry hanger but a timber to timber hanger just be careful when buying. 

Regarding the threaded rod you would need to check the loading for the bolts specified and then look at the threaded rod. Some threaded rod is like cheese when it comes to strength. The bolts will be in a shear type environment so see what the se wants. 

[ToughButterCup]

9 minutes ago, jack said:

How many self tapping coach bolts will you need, at what size and length?[...]

 

Good question. Although @Mr Punter has come up with the perfect answer to what I should do with (the now extracted from the concrete) 130 meters of threaded bar....... (above)

[Russell griffiths]

If the threaded bar is a bit feeble you could ask if you can change the spacing to match the spacing of the concrete pads inside the blocks. 

 

 

How we fit the wall plate without struggling, mark its location on the wall and ping a chalk line to give you the bottom height. 

Fix a temporary timber roof batten screwed into face of block, you can now sit your heavy wall plate (rim joist) correct word in my book on top of the batten it will help support while you mark and drill all the holes. 

When all tight remove batten and use it on the other side. 

[ToughButterCup]

7 minutes ago, Russell griffiths said:

[...]The bolts will be in a shear type environment so see what the SE wants. 

 

Noted. 'Nother phone call to Hillard.

Ian

[ToughButterCup]

6 minutes ago, Russell griffiths said:

If the threaded bar is a bit feeble you could ask if you can change the spacing to match the spacing of the concrete pads inside the blocks. 

How we fit the wall plate without struggling,

• mark its location on the wall and ping a chalk line to give you the bottom height. 
• Fix a temporary timber roof batten screwed into face of block, you can
• now sit your heavy wall plate (rim joist) correct word in my book on top of the batten it will help support while you mark and drill all the holes. 
• When all tight remove batten and use it on the other side. 

 

[...] Rim Joist [...] Glad you told me that because that's what it is. 

And I've just realised that I'll need to seal the holes made by the screws from the temporary roof batten (or similar)

 

Thanks @Russell griffiths

Ian

[ToughButterCup]

9 minutes ago, Russell griffiths said:

If the threaded bar is a bit feeble you could ask if you can change the spacing to match the spacing of the concrete pads inside the blocks. 

[...]

 

So that would be two threaded bars per 500mm instead of 1 per 400mm (but twice the fitting time.... how else is Debbie to keep me off the streets?)

[MikeSharp01]

15 minutes ago, Russell griffiths said:

If the threaded bar is a bit feeble you could ask if you can change the spacing to match the spacing of the concrete pads inside the blocks. 

This depends on the threaded bar size. According to THIS table the shear (single - which is what you have I think) strength of M10 studding is 13Kn which is 1,300 Kg (approx) ask your structural engineer, but it should be good for a serious party on the first floor. (10 people to the ton + jumping up and down)  

Edited September 21, 2017 by MikeSharp01
typo

[ToughButterCup]

Wooooaaaah @MikeSharp01, yer not inviting yer-self round fer an Acid House party are ya?

 

Despite how daunted I feel about this task, it's bloody interesting

[MikeSharp01]

2 minutes ago, recoveringacademic said:

Wooooaaaah @MikeSharp01, yer not inviting yer-self round fer an Acid House party are ya?

 

Don't drop acid these days, last time was A level chemistry in 1976!

[Jeremy Harris]

Shear strength of the fasteners is almost certainly secondary; the critical factor is almost always the allowable bearing stress in the holes in the material through which the fastener passes.  This is why much larger fasteners are often used than would seem necessary from just looking at the max allowable single shear stress limit for the fastener itself.

 

What you need to know here is the max allowable bearing stress for the materials being joined.  That then gives you the fastener diameter needed.

 

[ToughButterCup]

Hmm,

Well, I am proposing two M12 threaded bars (encased in resin) per 500mm going through a wall joist hanger> wall plate (rim joist)> concrete

 

M12 is about double the diameter of any coach bolts I've seen. But I note the architect's reference to SE and Durisol approval. Had you not written your post @JSHarris, I would have missed that. Thanks indeed.

Ian

[Alexphd1]

We cast in a rim board with 12mm threaded bar at 400 centers then planning to hang the pozi joist off the top chord. We cut the icf so the concrete is providing a solid base for the rim board.

 

Edited September 21, 2017 by Alexphd1

[ToughButterCup]

13 minutes ago, Alexphd1 said:

We cast in a rim board with 12mm threaded bar at 400 centers then planning to hang the pozi joist off the top chord. We cut the icf so the concrete is providing a solid base for the rim board.

 

Ah, that's genius @Alexphd1. After curing, you've cut away the inside of the ICF to expose the concrete (and some more of  the threaded bar), but you had the foresight to embed your threaded bar during the initial pour.

Your method interests me  because (for different reasons) I embedded M12 bar into our last pour(s) and then took the bloody stuff out again. The process of taking it out again showed me that the M12 sometimes bends a bit during the pour (@Onoff is a bit skeptical about that), and so might well 'twist' (usually upwards because of falling wet concrete) your wall-plate a bit. Nothing a lump hammer couldn't cure, though, I expect.

 

Thinking about it for a bit.... what about cold-bridging? Might your wall-plate (rim joist) be subject to an increased risk of interstitial condensation?

Ian

[Alexphd1]

no we cut the icf and placed the rim beam before the pour, the middle photo is before pour. We also slid in cuttings of DPM between the the timber and the concrete before the pour. We have 220mm eps continuous on the outside of the concrete hopefully that will prevent condensation. Sitting the pozi joist on top chord saves on joist hangers.... every little helps

[Onoff]

I think some of that studding from the sheds is only Grade 4.6 mild steel. Years back we BINNED all our 4.6 stuff and from thereon in only ever use 8.8 min. The 4.6...well you can tell the difference when you hacksaw or file it it's so soft.