Finish DPM on concrete base for wooden workshop

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Any help on this would be most appreciated; I have spent the past couple of weeks scouring the internet for a definitive answer on how to best finish the DPM on a concrete slab/plinth prior to the workshop being constructed this coming Monday.

Base is exact size to match the wooden workshop as the sole/base plate will sit on the edge of the slab/plinth and the bottom piece of shiplap will hang over the edge of the concrete slab/plinth. This is all straight forward and very standard but I have to decide what to do with the excess of DPM that I have currently poking out above the height of the slab by 120mm?

See drawings below of the 3 choices I have come up with, any other ideas would be welcome.

Thanks!

Screenshot 2022-01-04 at 11.50.42.png

Screenshot 2022-01-04 at 11.55.08.png
Screenshot 2022-01-04 at 11.55.18.png
Screenshot 2022-01-04 at 11.55.29.png
 
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Definately NOT 2. 3 is better. If I was doing the job my present thoughts would be to have the DPC between the sole plate and the shiplap. Trim the DPC off above the sole plate against the shiplap.
 
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Definately NOT 2. 3 is better. If I was doing the job my present thoughts would be to have the DPC between the sole plate and the shiplap. Trim the DPC off above the sole plate against the shiplap.

Thanks @wgt52

I agree with you on option 2, but this seems to be the most common way the DPM is finished. Many seem to lay a flat DPM up to the wooden formwork prior to pouring the concrete and not return it up the side of the slab.

I am having the workshop built by a company and it will arrive on site in completed panels, so I will not be able to fit it between the shiplap and the sole plate. Also, I am only 200mm from boundary fences so it will be a nightmare to get this bottom length of shiplap fitted after.

So it would seem option 3 is my best method and make sure that I have a good seal between the cut edge of the DPC and the top of the slab. I have bought a tin of Liquid rubber to do this.
 
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