Leaking dpm under slab - is it an issue?

[Dunc]

I hope everyone survived the storm!

We have some areas of slightly damp concrete around the edges of one room. Can anyone advise if this is a concern?

Buildup is Mot1, radon barrier, 150mm reinforced concrete slab.

(Eventually there will also be 200mm PIR, slip membremane, UFH pipes and 50mm screed.)

I can only imagine that the radon barrier is compromised somewhere around these 2 walls. Only fix I can see is dig up the slab. Which isn't ideal 😞

Other ideas could be lay another dpm over the slab and tape to the existing upstand?

Advice greatly appreciated.

 

[Redbeard]

Are you sure it is not condensation? Hypothesis: Cold wall, cold (impervious) membrane - condensation on membrane; droplets run down and permeate both the surface of the concrete and 'pool' within the depth of the slab where the membrane has pulled away.

[saveasteading]

You won't be digging up the slab. Put a pencil line round the damp, and let's look at it again later. Condensation seems likely but have a look outside for signs of splashing or puddles .

[Dunc]

Hadn't thought of condensation! Although the upstand of radon membremane is dry to the touch. Obviously no idea what it was like overnight.

No puddles outside.

[Nickfromwales]

1 hour ago, Dunc said:

I hope everyone survived the storm!

We have some areas of slightly damp concrete around the edges of one room. Can anyone advise if this is a concern?

Buildup is Mot1, radon barrier, 150mm reinforced concrete slab.

(Eventually there will also be 200mm PIR, slip membremane, UFH pipes and 50mm screed.)

I can only imagine that the radon barrier is compromised somewhere around these 2 walls. Only fix I can see is dig up the slab. Which isn't ideal 😞

Other ideas could be lay another dpm over the slab and tape to the existing upstand?

Advice greatly appreciated.

 

What stage of weathertight are you? 

[Dunc]

Roof on and fully functional. Windows in. Basecourse of blocks under the sole plate have been rendered.

Only have breather membremane and battens on the walls; timber cladding not done yet.

There is some damp at sole plate but I suspect this is water getting behind the breather membremane at windiw level (no cills yet so water puddling where the cill should be)

and running down behind the membremane.

No evidence of condensation or trickles of water down the radon membremane updstand though.

 

[Nickfromwales]

11 minutes ago, Dunc said:

Roof on and fully functional. Windows in. Basecourse of blocks under the sole plate have been rendered.

Only have breather membremane and battens on the walls; timber cladding not done yet.

There is some damp at sole plate but I suspect this is water getting behind the breather membremane at windiw level (no cills yet so water puddling where the cill should be)

and running down behind the membremane.

No evidence of condensation or trickles of water down the radon membremane updstand though.

 

Yup. 
 

So basically you’re at a stage that I refer to as ‘drip dry’, so no point in worrying about that little bit of wet afaic.

 

Wind-driven rain will get into every mm of available space, and capillary action can pull that along a membrane for meters and meters, so is also not truly representative of where you’re currently vulnerable to such ingress.

 

”Stand down red alert”