Bitumen solum covering repair

[Tarkin]

I'm putting a new bathroom in my 1930's bungalow (cavity brick wall construction, suspended timber floors). The room has been stripped back to brick, and the floor totally lifted. There had been a bad leak under the floor for a while that rotted some joists, I'm replacing those.

The solum was full of debris, some of it very wet from the leak. I've fully cleared it out today and exposed it back to the bitumen DPM that covers it. There's a few patches of damage to this bitumen where it's degraded and the bare earth below is exposed. Not many, but maybe 5% of the covering has cracks from what I can see. Photos below, you can see the spots where it's cracked through, some in the middle and some at the edges.

My question is what should I do to repair the solum covering? I'm planning like to insulate this floor before I reinstate it, and the bathroom will have a tile floor - so it'll be tricky to get back down here after this.

I will be doing this to the rest of the house as well, but one room at a time after we've moved in as we are on a time limit to get moved in and need a working bathroom. The ventilation in the sub floor is already good, and I will improve it when I do the other rooms as well.

Thanks in advance for any help!

 

[larry]

I'm interested in others views but when we replaced our joists I left the solum uncovered. It wasn't covered before - just soil.
Logic being that if there's good ventilation then it would be better for any moisture in the soil to come up to th under floor area and be dispersed than be pushed into the walls either side. But, you have cavity walls, and, possibly substantially harder bricks than we do (which are presumably also less water permeable). I'm sure though there will be others on here who'd be able to tell you has the bitumen would be been detailed originally and give overall a more illuminative response.

I suppose if you did want to cover it any kind of DPC material would do it.