Another DPM / DPC thread !

[rwhitts33]

Not wanting to hijack the other thread but I have a similar question - doing a part integral garage conversion ie insulated stud wall 1.5m behind the garage door to leave a small working area.

For the new habitable room on the inner side of the stud wall we want to use 220mm of PIR insulation to bring the floor level up to match internally - bit chunky I know but it's only a small area so is best way rather than trying to suspend floor.

(Edited to make more sense) Regarding the other existing 2 internal and 1 external walls - from the attached sketch - it's a 70's bungalow and I've had to assume what I can't see going on below - but is there an issue that the internal render / plaster looks to bridge the inner DPC and then if we lay the new DPM how best would we finish it off coming up the wall bearing in mind walls will be reskimmed and the small length of external wall section is having an additional layer of insulated plasterboard, then skimmed and skirting.

Builder from another job and a surveyor have previously checked slab and said in perfect condition, very dry etc so we're assuming there was an initial DPM under the old slab. Walls all clean and dry with no signs of any damp.

On top of flooring PIR will be slip layer, then floor boards, laminate etc.

Thks

 

[^woody^]

There is a path for moisture between the wall and the DPM.

DPMs should be built in to the wall

 

[Deleted member 292770]

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[Notch7]

chop the existing internal render off at dpc level and finish the dpm below dpc .

Exactly what I was thinking - the internal render creates a damp path, although I would chop off up to floor level and bring DPM up to that

 

[Dodgyrog]

There is a path for moisture between the wall and the DPM.

DPMs should be built in to the wall

That's what I was thinking so should the original builders not have bridged the inner DPC with that plaster coat that goes all the way down to the floor, maybe should they have only come down to just above the DPC? Or does it not matter as originally being an airy garage any moisture rising up that inner coat would just evaporate off?

But then how do I build the new dpm in to the existing wall, cut a notch so deep and then mastic it in somehow?