Correct height difference between DPC overhang and drains

standardg60

https://www.boards.ie/discussion/comment/122800163#Comment_122800163

I don't know what that is, but I do know the dryer something is, the more resistant to cold it is.

Penn

https://www.boards.ie/discussion/comment/122800304#Comment_122800304

Well the fact that the standard details include insulation below DPC level implies it was studied and measured and gives a better thermal performance. But even then it wouldn't really need a study to be done on it. Both details could be easily modelled in PsiTherm (which many of the images in Calahonda's post are from which is a thermal modelling system) to show the difference between them.

That said (and I don't mean this to sound condescending or dismissive), anyone with knowledge or experience of such design could tell which is the better option based on logic (which comes from that knowledge and experience). If you externally insulate the wall only to DPC level and not below, you've created a part of the wall with less insulation than the rest of the wall, and it's also at the floor/wall joint which is already thermally weaker when compared the rest of the wall or the floor because of how the wall and floor have to tie in with each other which doesn't allow for as much insulation.

Honestly, the DPC is completely irrelevant when discussing the thermal performance of the detail. Water-proofing is essential, but is a completely different and unrelated matter.

Mellor

https://www.boards.ie/discussion/comment/122800342#Comment_122800342

That's generally true, but that's nothing to do with thermal bridging, it's thermal resistance.

And the thermal resistance of a materially, is always greater than zero. Which means that adding insulation, even if that insulation will be wet, will always have a higher thermal resistance and adding nothing. There is simply no way that adding insulation, or adding any material, can create a thermal bridge.

https://www.boards.ie/discussion/comment/122800304#Comment_122800304

Ingress of heat from outside is not really a concern, but even if it were. Then you'd still want to use insulatino to prevent the thermal bridge.

that's all fine, but in terms of thermal transfer the dryer it is the better.

That's incorrect. The more thermal resistant it is the better. An insulated damp will would perform better than an uninsulated dry wall. But we are never comparing a dry vrs a damp wall. In the example above, both walls are damp below the DCP. I've no idea how you got the idea that by not extending the insulation it would be dryer and perform better.

To be frank if you believe a dpc plays no role in thermal bridging you shouldn't be posting on the subject.

The irony here is amazing.

to99

My cowboy builder went less than 150mm and now I've to pay €20,000 in repairs after 11 years. Water seeped in under house, floor joists rotten, damp gone up to the walls.

The Continental Op

https://www.boards.ie/discussion/comment/122853023#Comment_122853023

Double and Triple check that another cowboy builder isn't charging you for repairs that aren't totally necessary, he might be exaggerating how bad it is.

to99

https://www.boards.ie/discussion/comment/122853570#Comment_122853570

I did, 2 engineering surveys, damp survey etc.