Roofing bitumen as a sub floor damp proof membrane ?

[.]

I need a concise answer for this one, preferably before the mrs leaves the vicinity of B&Q / Wickes in about 30 mins !

can I use roofing bitumen as a continuation of a pitchmastic DPM which I've been forced to expose in order to build a step between a kitchen and a utility room, 300mm below the level of the kitchen floor ?

does bitumen dry hard to fix to with tile adhesive ??

the utility room and kitchen both have plastic DPM under concrete and both are finished in pitchmastic. it's just the bit between the two that I need to proof.

2 courses deep by 2 - 3 foot long.

thanks for any tips.

[Chris Bacon]

What is roofing bitumen? Lap adhesive? Hot melt?

Not very, no.

What - a "bitumen" layer on top of the concrete?

[.]

comes in a 5l paint like tin. apply with a brush.

didn't think so but I wasn't certain.

yup, called pitchmastic. applied with a trowel, highly exothermic, filled the house with smoke and the smell of fresh tar, sets rock hard and was passed by BCO.

I was also thinking of simply using waterproof floor tile adhesive reasoning that if it's waterproof from the top it's waterproof from beneath. never breached a DPM so I'm unsure as to how to proceed.

[.]

now called mastic asphalt - the contractor I had in many years ago called it pitchmastic and got a subbie in to do the job.

[Chris Bacon]

I don't see any reason why you shouldn't use a bitumen emulsion for a DPM, it's very good for that - but you'd need to protect it somehow.

[.]

thanks for that. I've decided to just fix the aereated concrete blocks with waterproof floor tile adhesive. it should do the job ok and if it isn't, by the time anyone finds out, the house will be someone elses.