Sealing concrete basement roof?

Hello,

I have a concrete cellar next to the house. It is thermally separated from the house by an [Isokorb]. (6x3m, a carport is planned on top)

I have two questions about this:

1. The ceiling of the cellar is not even and especially has no slope. After every rain, several puddles remain on it and some water also flows into the house (unevenness approx. 7mm). Now I have read that standing water is not good for the bitumen membrane. My architect says it doesn’t matter as long as everything is first sealed with bitumen and then paved over.

What do you think? Do I need to model a slope here? (self-leveling screed?)

2. At the end of the week we want to waterproof the cellar. For this, the roofer will deliver the materials and I will install it myself according to instructions (my father-in-law will be with me, he has done this several times before). But it is unclear to me how we should lay the bitumen membrane on the [Isokorb]. The isomaterial will melt if I get too close with the hot flame.

Do you have any tips for me?

Regards
Roger

Regarding point 1, not necessarily. If you also want to protect the [Schweißbahnen], you can cover the roof with a 5cm layer of gravel, which protects the bitumen sheets from UV radiation and mechanical stress.