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Bitumen lining and dry lean

should drylean cement/screed go below the line of self adhesive bitumen or can it go above the bitumen line? We have damp going over the floor and it looks like it is coming from the edge of the cement which has been put over the bitumen.

2 Answers from MyBuilder Conservatory Installers

Best Answer

I’m not sure what’s actually being done, but if cement / screed is laid over bitumen, (not a good idea) it will probably hold water, it’s always a must, to lay a membrane below to stop any rising damp. If I had a photo, maybe I could help a lot more. Bitumen is not the answer, water will soak up from anywhere and cause damp.
Another reason for damp is that the room has not enough heating all year round and ventilation may help a lot.
Sorry I can’t help anymore with information provided. Good luck.


Answered 13th Jun 2019

3 coats of Liquid DPM underneath Screed is absolutely fine as long as it is also goes up the wall and laps the Damp course in the brickwork which will be approximately 150mm above external ground level unless it’s only single skin.
If single skin brickwork the liquid DPM would need to be apples will height of the masonry. If the liquid DPM has not been applied correctly moisture will penetrate through.


Answered 29th Jun 2019

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