Basement floor in old heating room damaged?

Hello,

We replaced the oil heating with gas heating in our terraced house built in 1975, and among other things, had the approximately half a meter high wall next to the oil tank demolished. The craftsman also chiseled out part of the floor, and now we have a channel about 3-4 cm deep in the floor, which we actually wanted to fill with screed. We have now noticed that the bitumen membrane in this area was also removed. I cannot assess whether this means that our basement is no longer properly protected against moisture—and whether this can perhaps be fairly easily repaired. Thank you for your help!

Hello questioner. I unfortunately do not know what you mean by a "Bitumenbahn". If it is a heating cellar we are talking about here, it can only be a room with "secondary use". The sealing only served the purpose of preventing moisture rising through the floor slab. I would not overestimate the problem you see! For simplicity, I would proceed as follows (the affected area will be manageable in size): - Vacuum fine dust thoroughly from the gutter-shaped depression. - Moisten the exposed concrete (the floor slab), also spray the edges of the screed. - At the hardware store there are mineral waterproofing slurries for tile setters, get yourself a small pack of those. - The pre-moistened (not wet!!) floor slab is now coated with the mixed slurry about 5mm thick. - After curing (about 24 hours) the depression is sealed with a repair mortar (also from the hardware store). But ATTENTION: Good repair mortars set quite quickly. Pot life about 2 to 3 minutes. So you must hurry, everything must lie ready at hand (smoothing trowel or clean trowel for smoothing) ----------------------- Good luck: KlaRa

That could also have been a sealing material to block the floor against oil leaking from the oil tank. We had such a foil under the screed of the barn that housed the oil tank.

That could also have been a sealing material to block the floor against oil seeping from the oil tank. We had such a foil under the screed of the stable that housed the oil tank.

It is common practice in the construction industry that the more valuable component is always protected.
In this case, that would be the floor slab plus screed, whereby the latter is provided with a protective coating.
In the original post, it is noticeable that a "real surface sealing" (by this I mean the bitumen membrane) in subordinate rooms above a screed is never applied over the entire area, which also has never been the state of the art. If it were a sealing that truly deserved its name, it would have been applied beneath a "floating" screed equipped with thermal insulation.
What I strongly suspect in this case regarding the "bitumen membrane" is a horizontal damp proof course only beneath the (dismantled) masonry, which incidentally is still installed in strips today to prevent moisture rising through the masonry.
And in this context, during the filling (of the gap after masonry removal), a mineral sealing slurry is completely sufficient.
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Regards: KlaRa