Thermal Bridging on a door threshold - round 2

[SBMS]

Following on from my previous thread... Architect has designed this as a flush threshold detail to help minimise thermal bridging across our triple track sliders, but also provide the 'solid' base that the door manufacturers insist on (they had a wobble regarding having any PIR under it due to them being sliding and heavy).

 

What are thoughts on this as a detail? Not sure how the slab gets poured leaving the haunching in the concrete infill in the cavity - would it matter if it was continuous?

 

[Dave Jones]

sit them on marmox blocks. they are structural.

[SBMS]

33 minutes ago, Dave Jones said:

sit them on marmox blocks. they are structural.

Does the extra expense justify it? Is there much thermal bridging going on?

[Mr Punter]

Underneath the doors the haunched concrete makes no odds.  No water is getting down there at this stage.  I sometimes just omit the inner leaf under doors.

 

Where there are not doors, on site the haunched concrete fill gets filled with mortar from the brickies and sometimes bridges the cavity.  Looks good on the drawings though!

[SBMS]

51 minutes ago, Mr Punter said:

Underneath the doors the haunched concrete makes no odds.  No water is getting down there at this stage.  I sometimes just omit the inner leaf under doors.

 

Where there are not doors, on site the haunched concrete fill gets filled with mortar from the brickies and sometimes bridges the cavity.  Looks good on the drawings though!

So in practice you think just fill to the purple line and it'd be okay? I guess it's below the DPC? Any issues with thermal bridging as @Dave Jones seems to indicate a marmox block would be useful?

 

[Oz07]

Whats your floor finish inside? Youve got a 210mm wide bit of pir before door how will you cover?

[SBMS]

18 minutes ago, Oz07 said:

Whats your floor finish inside? Youve got a 210mm wide bit of pir before door how will you cover?

Probably LVT. I would imagine a bit of 9mm ply on top of the LVT then 3mm screed over the top and then the LVT?

Edited September 19 by SBMS

[Oz07]

Think you'd be best going for a solid timber threshold inside to bridge the pir if going that route. I wouldn't be confident with ply, thin slc then lvt ontop of pir. 

[SBMS]

6 hours ago, Oz07 said:

Think you'd be best going for a solid timber threshold inside to bridge the pir if going that route. I wouldn't be confident with ply, thin slc then lvt ontop of pir. 

Thanks @Oz07 what would you recommend? Would some 22mm chipboard flooring be more suitable? How would I attach it across/ over the PIR? 

[Oz07]

No i meant like a solid timber threshold like hardwood etc just to bridge the gap. Not sure how you'd fix it at the cill end some bracket id imagine?

[Dave Jones]

12 hours ago, SBMS said:

So in practice you think just fill to the purple line and it'd be okay? I guess it's below the DPC? Any issues with thermal bridging as @Dave Jones seems to indicate a marmox block would be useful?

 

[SBMS]

30 minutes ago, Oz07 said:

No i meant like a solid timber threshold like hardwood etc just to bridge the gap. Not sure how you'd fix it at the cill end some bracket id imagine?

I see - I'd have to reduce the height of the PIR to accommodate the height of the timber threshold? If I did a 50mm PIR and then a 25mm hardwood threshold (or increased the depth of the 75mm screed). 

 

Any ideas on how to fix the hardwood threshold to the PIR and the rest of the 75mm screed?

[SBMS]

1 hour ago, Dave Jones said:

Thanks @Dave Jones, yep undestand where they'd go. Would they make a big difference to heat loss to justify the cost? Would they negate the need for the 75mm x 210mm PIR edge insulation slab to threshold (and just bring the 75mm screen right up to the edge of the track?