Posted: Fri Jun 15, 2012 7:15 pm 
^woody^ wrote:
The NHBC show an illustrative diagram with no supporting information to back it up
Wrong again woody, supporting information is in black and white.
Why not try reading supporting information?
Should a knowledgeable person require supporting information to understand a simple illustrative diagram or drawing?
Regards oldun
Did you not read the supporting information?
Posted: Fri Jun 15, 2012 8:05 pm 
^woody^ wrote
Err no, it does not detail the chances of the dpm tearing on the sharp arris, or the route for moisture. It's a poor detail.
Well, why not write and inform NHBC that it is a poor detail?
We would expect a first year apprentice to fully understand the diagram even without supporting information
Posted: Sat Jun 16, 2012 11:12 am
^woody^wrote
I've had a look at quite a few tech documents about this simple thing, and there is no definitive answer
Then you have not looked far enough woody.
Marley, Anderson, Rubberoid and Plysolene do not give any information..
Visqueen do give detailed instructions and a drawing in their BBA Certificate , however their method is no where near common day practice in as much that the sealed joint between dpm and dpc is below the thickness of screed and oversite concrete, whereby dpm does not turn up and over brickwork and lapped by the dpc.
As it would appear that NHBCs approach is an acceptable alternative, and is every day practice then the way to go is for dpm and dpc on top, all as our original post.
Could we now put this post to bed?
Regards oldun
.