Install new KG pipes, double floor and moisture

Hello,

the subject title may be a bit confusing, so I will try to untangle the mess a bit:

We have an extension on the main building with moisture problems and a large outbuilding with mostly exposed roof drainage. The moisture problems stem from the fact that the ground covering outside between both buildings was raised so much that the rainwater presses directly between the two horizontal barriers. A seal in the form of a thick bitumen coating is not really present - more on that upon request.

Since the rainwater pipes currently empty centrally under the terrace into an old well, I want to redirect them into a soakaway basin far away from the house.

For this, of course, new KG pipes need to be laid - and here I come to the actual problem:

The yard is paved with grass grid stones - about 200 sqm of it. Underneath is about 30 cm of topsoil. Below that is the ORIGINAL path - paved with fieldstones (10-15 cm).
Below that again is topsoil, then comes heavily clayey soil.

My question is: if I now dig up, the pipe should be laid in gravel. My wife would like me to use the excavated soil - but here I see problems with settling. What is your opinion?

Second question:
Would it make sense to remove the soil to the secondary level, meaning down to the fieldstone base? Then it would make sense to first remove the soil and then lay the pipe under the pavement - I estimate about 60-80 cm deep. Your opinion on this?

Unfortunately, the previous owner of our house was completely foolish. He simply clad the base of our bedroom outside with fieldstone slabs and then built up the ground outside by 30 cm. Although the edges of the fieldstones are grouted, we still have moisture and mold formation exactly up to the second horizontal barrier in the room.
For me as a layman, it would seem obvious to restore the original condition after construction so that rainwater does not come over the base at all. Additionally, a drainpipe (coconut) will also be laid.

Your opinions are very important to me. We are not super rich. The previous repairs were all necessary due to the previous owner's negligence, previously not visible and are straining the budget.

Best regards - Maik

You lay the kg pipes in a pack of fill level (5-10cm below, 5-10 above). The rest you can fill up again with the excavation. Compacted in layers (every 15-20cm) with a trench compactor, not much happens. You probably don’t have 40-ton trucks rumbling over it anyway.

As far as sealing is concerned, you can’t avoid proper sealing. Either bitumen thick coating up to the sole or grouting or or or... Whether the fieldstone slabs need to be removed for this should be checked by someone on site.

So the sewer pipe must be laid with a slope. In that respect, you have already predetermined control points in height. Generally, the pipes are first laid in sand, then gravel, because it can be compacted. Use the topsoil for the last few centimeters so that grass can grow again. And yes, you are of course right. The water has to flow away from the base!

Hello and thank you very much for your response.

Unfortunately, I don’t have a trench hopper - but I am getting a 100kg vibrating plate.

The fieldstone cladding is supposed to come off anyway. My plan was to "embalm" the masonry between the two horizontal barriers with bituminous thick coating.

What exactly do you mean by "down to the sole"? Down to the beginning of the foundation? As far as I have seen, it was poured into a trench - so the walls are very uneven and would have to be plastered thoroughly.

I forgot to write:
The walls above the plinth are built with insulating stones, the plinth itself with hollow pipe bricks. I wanted to compensate for this thermal bridge with an 80mm insulation - directly using the thick coating as adhesive. According to the manufacturer’s datasheet, this should work - but I am also happy to be proven wrong.

Sand is scarce here - I would have to order it.
What exactly do you mean by "Schotte"?

Kind regards - Maik

Laugh! The R does it! Gravel! I meant gravel. Yes, and come on, the ton of sand should be obtainable for around 10 EUR!

Yes, of course - you’re right.
Lol - a single letter typo...

Question:
How far must the thick coating be applied?

The problem is that the base below the first horizontal barrier has an about 5cm ledge protruding outward – perpendicular and about 50mm high.
Below that begins the foundation, but about 3-5cm inward below the ledge. In cross-section, one could say this ledge resembles a window sill between the base and the foundation.

I strongly assume that the moisture inside the room was rather caused by rainwater, as the path outside is about 10cm higher than the floor inside. The lower barrier is about 30cm below the outdoor surface of the ground. So far, a sealing was only marginally or not at all present.

Additionally, the thermal bridge caused by the thinner wall thickness of the base and a different building material with a worse U-value.

I would now slurry the wall between the 1st and 2nd barrier and apply bitumen up to the lower edge of the ledge, then set a fillet and apply perimeter insulation to the base.

What do you think?
Hit or miss?
Suggestions for improvement or better execution.
As said – the foundation is not exactly straight...

Best regards – Maik