Passive slab....questionable?

[mvincentd]

Just stumbled on this...maybe it's old news here but figured it might fuel some thoughts.

http://www.realreview.ie/architecture/2016/04/thermal-bridging/

[Calvinmiddle]

That's not the detail I've seen before, and looks like it is a brick/block cavity wall.  Don't think I've heard of anyone combining that with a passive slab.  TerryE may be the only one that have something similar.

 

[Jeremy Harris]

Interesting that they quote from a company that seriously misled us, cost us a great deal of money by getting us to visit them under false pretences, is misusing material that is my copyright on its website, that is using false information about our build on its website (and that company had nothing to do with our build) and which refuses to take that information down, despite repeated requests from me over the past year or more.

[jack]

49 minutes ago, Calvinmiddle said:

That's not the detail I've seen before, and looks like it is a brick/block cavity wall.  Don't think I've heard of anyone combining that with a passive slab.  TerryE may be the only one that have something similar.

 

There was a whole range of these details on their site a few years ago for different wall types, many including brick and/or block. I'm sure(?) it's been engineered properly, but it doesn't look/feel like very substantial support for two masonry walls.

[Barney12]

54 minutes ago, Calvinmiddle said:

That's not the detail I've seen before, and looks like it is a brick/block cavity wall.  Don't think I've heard of anyone combining that with a passive slab.  TerryE may be the only one that have something similar.

 

 

I'm pretty certain @TerryE has the same wall make up as me save for the fact he has a stone skin and I have block and render. In both instances they sit on the external brick/block footing:

 

 

(Image Credit: MBC Timber Frame Ltd)

 

 

[TerryE]

@Barney12, ours is slightly different in that Hilliard decided to link the inner and outer ring beams by dozens of 20mm rebar links so that they act as a single structure.  This was a flawed design thermally, but luckily I was able to mitigate the bridging as I described this in my blog post Coping with a Thermal Flaw in the Design.  If I hadn't done this then we might have had similar issues to those described in the Thermal Bridging article. 

 

This double skin also meant that the window and door treatments were somewhat different to those for a clad house as I describe in the next post.

 

The external stone skin has pretty much zero impact on U-values.  It's really there for looks and weather protection.  However, one major upside is that it's thermal capacity means that the decrement delay factor is measured in days on this wall profile.

[mvincentd]

@TerryE that's v interesting...in essence you had the same problem that i've got and it was while searching for info on how bad the thermal bridge's effect was that I found the article I posted.

Did you consider Marmox thermoblocks but favoured Foamglass.....if so what reason?

I had the detail below, where flint block external skin bears onto xps300.  No precedent can be found for it though so BC don't like it, even though the xps manufacturer 'imagines it would work'.  So now instead of that piece of 100mm xps there'll be a Marmox thermoblock followed by a 'customised' coursing flint block to bring internal/external skins into level line.  I just wish we'd arrived at this before pouring the slab so at least we could have modified the height of the cast upstand to aid coursing.

So my next problem is just as yours was.......bringing the doors and windows (all mine are floor to ceiling) forward to sit mid cavity ...I haven't gotten so far yet as to solve their currently 'levitating' condition.

 

[TerryE]

I used the engineering brick plinth to wrap the Foamglass and to ensure that there were no rodent entry points into my foam under-slab.

 

I used Foamglass because the SE "signed-off" on confirming that it could carry the external skin. It's only a 75mm high layer: this was enough to pretty much eliminate the thermal break, but also meant that the plinth was well proportioned.

 

I added extra shuttering and rebar at the door and French door positions so that the slab has a 45×50 tongue positioned to support the door and the door exteriors are flush to this.  You can see from the pictures at the bottom of the second blog post referenced above that the external cills are slated.  I put another row of Foamglass under the slate butting against the tongues, to act as a thermal break here.