IWI Into Ceiling Service Void

[Gaf]

Is it typical, or recommended, that ground floor IWI continues up the into the service void to meet first floor precast concrete floor from beneath?

 

*Aware I'm posting a bit lately. Each post is related to a different specific query. Apologies if I should be merging the posts.

[Redbeard]

Why not?If you think a further 25mm PIR is worth doing on the walls then it is worth doing on as much of the walls as you can possibly access.

[Mr Punter]

As long as the service void is properly sealed and no outside air can enter, this will be fine.  Is the concrete floor really just sitting on half a block either side?

[Gaf]

39 minutes ago, Redbeard said:

Why not?If you think a further 25mm PIR is worth doing on the walls then it is worth doing on as much of the walls as you can possibly access.

 

That was my thinking. Builder and plasterer said they’ve never seen this ever. Builder said he touched base with his architect on it and he said they never do this, is unnecessary.

 

4 minutes ago, Mr Punter said:

As long as the service void is properly sealed and no outside air can enter, this will be fine.  Is the concrete floor really just sitting on half a block either side?

 

It has been parge coated.

 

No the drawing in that area is actually strangely inaccurate. The concrete slabs are sitting on the full block.

[jayc89]

Is that a cavity wall with additional IWI to hit BR requirements?

The precast floor will bridge your IWI and assuming it's sitting on the inner leaf of that cavity that's already on the warm side, so the impact is minimal. I wouldn't stress about insulating the service void. 

[Gaf]

21 hours ago, jayc89 said:

Is that a cavity wall with additional IWI to hit BR requirements?

The precast floor will bridge your IWI and assuming it's sitting on the inner leaf of that cavity that's already on the warm side, so the impact is minimal. I wouldn't stress about insulating the service void. 

 

Yes a 150mm cavity wall (bead insulation) and the IWI was needed for BR. 

 

When you say the floor will “bridge” the IWI, do you mean if the IWI runs up along the wall into the service void to meet the underside of the precast floor? As in, the IWI ‘touching’ the underside of the precast will effectively insulate the whole void?

 

That was my understanding of why the IWI runs up into the void. The builder and plaster (and builder’s architect, not my own) say they’ve never seen this done and have never done it, so they didn’t follow the plans and have not installed the IWI into the wall at the service void.

Edited January 5 by Gaf