Breaching damproof course? Ok or no or ways round it? - Tile Advice

[Raccus]

A customer wants a low profile shower in a downstairs bathroom on a concrete floor. The drainage chanell required would need penetrate the dpc on the outside wall and so presumably that of the floor inside the house too. (I assume they should be on same level?) Drainage would travel about about 1 to 2m into the house perpendicular to the outside wall. Are there acceptable ways to do breach and patch pdc, or is it best totally avoided?
Thanks

 

[WetSaw]

Are there acceptable ways to do breach and patch pdc, or is it best totally avoided?
Thanks

I would much rather it was totally avoided thank you very much!

 

[Slippery]

The concrete floor will be siting in a "bathtub" of DPM, the top of which is level with the DPC on the brickwork so you will only breech the DPM where you exit through the wall.
I wouldn't expect any problem with this, just be aware of it and try to invent some way of sealing the waste pipe to the DPM, you'll be fine

 

[Raccus]

Thank you for your replies, appreciated.
Slippery, if dpm is same level inside as outside, then it would also breach in about a 1m length inside, where the waste pipe will be travelling mostly horizontal with the 1:40 fall to the outside. Sounds like we either should raise the shower.....or what about the alternative, digging out a rectangle for the channel, then laying a dpm over and re-cementing?
Pdc, is a small breach really that bad? Im not disputing it, i have no idea, but practically would think if you recover with dpm and then waterproof overlying floor too, i cant imagine it would be problematic. So yes, trying to find out how critcial it is; if its completely untouchable or if a small hole here or there would even be ok.

 

[Slippery]

Raccus, I think pdc was just joking as you misspelt DPC in the OP.

Only the top of the DPM is level with the DPC in the brickwork so you would be above the damp , the channel would be in dry concrete, as long as you dont go too deep and be careful not to puncture it whilst chanelling out, you are only breeching the side of the bathtub

 

[Raccus]

ah well spotted about the typo lol. And "the dmp is only the top of the dpc"? I thought the dpc was just a layer of membrane, not that it has any depth to it. And if the top of the pipe exits just under dpm, then the pipe being 40mm diamter with a fall of 1:40, will mean the 1m channel inside would also have to breach the dpm the whole way along the pipe's length. So it would be very much puntured presumably. Am i misunderstanding your reply, or not explaining well?

 

[Slippery]

Here you can see what's going on.
As long as you don't cut right through the concrete, your pipe will exit the wall between DPC and ground level.
Depending on the age of the house you will have around 100mm (before 2010 or so) to 150 mm
A small hole in the side won't matter
I don't know how deep your trap is but the fall @1:40 only needs to be around 3mm over the meter so you should be fine.

 

[Raccus]

aha! i seeeeee, thank you so much for the pic, that is great! explains it nicely

 

[Raccus]

one more thing, the floor is different levels, im hoping to have thicker insulation where it can fit and non where the floor is much higher. Are any problems forseen if i put down the insulation backer boards first, then use levelling compound over the top? Was planing to use prowarm boards and bal level max.

 

[david mccullough]

if you are going through the dpc cut as tidy a hole as tidy as you can and then tank it