DPC & cavity wall penetrations

porrige

Hello,

Would anyone have any expert opinions to share on the following please?

For house cavity block wall penetrations from internal to external such as electrical cables - is it ok to penetrate the wall below finished floor level (screed) & below internal wall DPC layer (concrete slabs below all this) ?

If I penetrate above FFL / internal wall DPC, the exit point will be very high & well above any pathway/patio on external side. The DPC on external leaf is higher than on internal leaf.

Thank you.

Calahonda52

where is your floor DPC and /or radon barrier in all of this?

porrige

Calahonda52 wrote: »

where is your floor DPC and /or radon barrier in all of this?

Hopefully correctly applied under the hollow core slabs.

sydthebeat

porrige wrote: »

Hopefully correctly applied under the hollow core slabs.

Hollow core on the ground floor?

I think you need to do a sketch to describe what you are talking about here

porrige

sydthebeat wrote: »

Hollow core on the ground floor?

I think you need to do a sketch to describe what you are talking about here

Sketch attached.
Question: ok to penetrate (20mm duct) through blockwork & the DPC layer below FFL ?
Or better to go via nearby door thresholds?

Thank you.

Bonzo Delaney

I hope you've the inner and outer mixed up there in the sketch.
The dpc on the outside leaf of the cavity should always be lower than the dpc on the inner leaf to allow moisture in the cavity escape to the outside

sydthebeat

porrige wrote: »

Sketch attached.
Question: ok to penetrate (20mm duct) through blockwork & the DPC layer below FFL ?
Or better to go via nearby door thresholds?

Thank you.

answer: no its not

there is a high likelyhood this area will retain water at some stage.. and if you penetrate the DPC all your doing is allowing the concrete slab to soak it up like a sponge.

i assume the walls are already finished and this is an after thought?

Calahonda52

You said the slab is hollowware so how did the radon layer get done and whats supporting the hollowcore.
In any event keep up away from all or this: attic/soffit/ down the wall

porrige

Thanks for responses. I think I’ll put the armoured electrical cables out through the door thresholds - at least I’ll have access to see & repair DPC.

The external leaf is plastered.
Yes, the sketch is accurate in relation to inner & outer leaf.

Below the slab is radon/dpm. The slabs rests on compacted hardcore & foundation walls (flat blockwork on reinforced concrete).

The radon barrier is another hot potato - no radon sump. Is it normal practice to provision a standby sump with connecting pipe work ?

Thanks

Calahonda52

who signed off on the building work thus far

porrige

a member from a respected national institution.