A friendly hello to all helpful forum members...
Unfortunately, I have a somewhat unusual problem (hence the somewhat lengthy text), for which I have not yet found a well-founded or confidently feasible solution. I would greatly appreciate advice from experienced builders or renovators!
Background: Old building from the 1960s, no basement, concrete slab foundation (with 30cm (12 inches) of construction debris underneath), exterior walls made of brick, building-standard horizontal damp-proof course starting from the first row of bricks, fully renovated and converted, slight slope (the north-facing room is just above ground level, the south side about 1.50m (5 feet) higher), occupied by us for 2 years, no other issues.
Problem: Earthy smell and moisture since summer 2018 in the north-facing room (with mold on furniture and clothing, NOT on the walls) and bathroom, especially noticeable when opening the door thresholds.
Cause: Incorrect sealing compound recommended by a professional friend (PCI Lastogum; intended for splash water in shower areas, not for ground moisture penetration), used throughout the ground floor ("I've always done it this way; it has always worked").
Result: Compound detached and softened into a rubbery texture on the wall below the horizontal damp-proof course; floor structure (Fermacell dry screed; also poorly advised, as we now know, since it is partly organic) damp and bacterial contaminated.
However:
Lastogum on the slab remains tight/hard and well bonded to the concrete.
Problems occur only in the north-facing room and bathroom.
Plan: Remove the floor in the north-facing room and bathroom; apply proper waterproofing extending above the horizontal damp-proof course and rebuild the floor using inorganic materials; leave the rest of the ground floor floor intact as long as no manifest problems arise.
Current information: Several experts contradict each other in almost every aspect (procedure, affected rooms, materials, floor construction, exact cause, internal or external waterproofing, health risks...). At present, air quality is good again and moisture levels are low (due to winter season/correct ventilation as usual/dehumidifier).
Now my questions, hoping for your help:
- Can the intact Lastogum on the slab remain and the new waterproofing be installed on top, or if not, why must it be milled off?
- What is the best way to connect the waterproofing at the wall junction?
- Waterproof slurry or bitumen membrane?
- Where should a vapor barrier or vapor retarder be installed, and where not?
- Water-repellent dry screed or is flowing screed required?
Furthermore, I received a rather alarming statement from one of the professionals:
"There will always be water accumulating under the insulation layer, rotting there like a swimming pool" (due to condensation moisture/low dew point at the very cold floor—this topic is now very familiar to us). However, "this doesn’t matter; you wouldn’t notice anything."
...If it's just about not noticing it, then you could seal everything airtight and let it continue rotting underneath. That can’t be right, can it?
...If the insulation layer is well bonded, then water cannot accumulate there, but rather somewhere else in the floor construction, where it can evaporate again, right?
Looking forward to your advice; thank you very much!
Pajero
PS: We understand that not questioning the suitability of the sealing compound was a mistake, but at that time we had no reason to doubt the recommendation of the professional who otherwise provided excellent advice for the rest of the house.
PS: External waterproofing is planned in the medium term, but cannot be carried out before 2025 for several reasons. There are no subjective impairments on the walls or in other rooms; living comfort is good and the building structure is (still) not affected.
Unfortunately, I have a somewhat unusual problem (hence the somewhat lengthy text), for which I have not yet found a well-founded or confidently feasible solution. I would greatly appreciate advice from experienced builders or renovators!
Background: Old building from the 1960s, no basement, concrete slab foundation (with 30cm (12 inches) of construction debris underneath), exterior walls made of brick, building-standard horizontal damp-proof course starting from the first row of bricks, fully renovated and converted, slight slope (the north-facing room is just above ground level, the south side about 1.50m (5 feet) higher), occupied by us for 2 years, no other issues.
Problem: Earthy smell and moisture since summer 2018 in the north-facing room (with mold on furniture and clothing, NOT on the walls) and bathroom, especially noticeable when opening the door thresholds.
Cause: Incorrect sealing compound recommended by a professional friend (PCI Lastogum; intended for splash water in shower areas, not for ground moisture penetration), used throughout the ground floor ("I've always done it this way; it has always worked").
Result: Compound detached and softened into a rubbery texture on the wall below the horizontal damp-proof course; floor structure (Fermacell dry screed; also poorly advised, as we now know, since it is partly organic) damp and bacterial contaminated.
However:
Lastogum on the slab remains tight/hard and well bonded to the concrete.
Problems occur only in the north-facing room and bathroom.
Plan: Remove the floor in the north-facing room and bathroom; apply proper waterproofing extending above the horizontal damp-proof course and rebuild the floor using inorganic materials; leave the rest of the ground floor floor intact as long as no manifest problems arise.
Current information: Several experts contradict each other in almost every aspect (procedure, affected rooms, materials, floor construction, exact cause, internal or external waterproofing, health risks...). At present, air quality is good again and moisture levels are low (due to winter season/correct ventilation as usual/dehumidifier).
Now my questions, hoping for your help:
- Can the intact Lastogum on the slab remain and the new waterproofing be installed on top, or if not, why must it be milled off?
- What is the best way to connect the waterproofing at the wall junction?
- Waterproof slurry or bitumen membrane?
- Where should a vapor barrier or vapor retarder be installed, and where not?
- Water-repellent dry screed or is flowing screed required?
Furthermore, I received a rather alarming statement from one of the professionals:
"There will always be water accumulating under the insulation layer, rotting there like a swimming pool" (due to condensation moisture/low dew point at the very cold floor—this topic is now very familiar to us). However, "this doesn’t matter; you wouldn’t notice anything."
...If it's just about not noticing it, then you could seal everything airtight and let it continue rotting underneath. That can’t be right, can it?
...If the insulation layer is well bonded, then water cannot accumulate there, but rather somewhere else in the floor construction, where it can evaporate again, right?
Looking forward to your advice; thank you very much!
Pajero
PS: We understand that not questioning the suitability of the sealing compound was a mistake, but at that time we had no reason to doubt the recommendation of the professional who otherwise provided excellent advice for the rest of the house.
PS: External waterproofing is planned in the medium term, but cannot be carried out before 2025 for several reasons. There are no subjective impairments on the walls or in other rooms; living comfort is good and the building structure is (still) not affected.