DPM for an existing Conservatory base?

[Cat-Kicker]

Hi,

I have an existing Conservatory base which I am re-using for a new Conservatory. The old Conservatory was full height glass, the new one is on a 600mm high wall. Builder has dug footing around the outside of my base and built cavity wall up (so inside blockwork face is hard up against the side of my existing base). He has put a sheet of DPM underneath the blockwork and carried it up between his blockwork and the base, then over the top of my base so the I have about 300mm laying around the edge of my base slab. The existing slab itself does have a DPM under it.

Questions:

1) Would it be a good idea to 'glue' the 300mm of DPM down around the edge of my base with bitumen or something?

2) Being that I don't know how good the existing DPM below my concrete base is, would it be a good idea to either bitumen the whole base?

3) Could I even by a sheet of DPM and lay this on top of my base? I am then laying 25mm Celatex to raise the floor level slightly, with an engineered timber floor on top.

Just want a belts and braces approach really....

Thanks very much.

Gary

 

[freddiemercurystwin]

Your new dpm above your slab (which is good sense) should be lapped up the inside of the cavity of the new walls and lapped under the stepped dpc in the walls which should be a minimum of 150mm above the external ground level.

A bit like this detail but your concrete slab and insulation are the other way round, makes no difference to the dpm though:

Untitled

• freddiemercurystwin
• 29 Apr 2009
• 2

 

[Cat-Kicker]

Hi,

Well pretty much, but I don't know what to do with the new DPM where it sits on top of the existing slab?

DPM

• Cat-Kicker
• 23 Mar 2010
• 1

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[freddiemercurystwin]

If it was me, I'd stick a new dpm over the top of the old screed (under your new insulation) and lap it up the wall above the new one the bricky installed. Ideally your new one would have laped up the wall and sat on top of the horizontal one in the inner skin but it'll just have to sit there if the blockwork above the horiz dpc has been laid.