Hello!
I’m interested in your opinion again.
In about one week, the screed will be poured (plumbers and electricians are currently busy). Now the following issue has come up:
- We don’t have a horizontal damp proof membrane on the slab (no basement) and the screed installer has pointed out that this apparently does not comply with the standards.
- We don’t have a horizontal damp proof membrane because the builder said it wasn’t necessary since we have a 40 cm (16 inches) capillary-breaking layer (Geocell foam glass gravel). This was also recorded in the contract protocol and the construction meeting minutes.
- The architect also confirmed the non-necessity with a building physics calculation, which is documented in the construction meeting minutes.
=> Our concern now is what, for example, the insurance company would say in case of a pipe leak. Could they refer to the standard and possibly reduce the payout in case of damage, even though the non-necessity was confirmed by our professionals?
Here is the structure again (as mentioned, no basement, so directly on the ground):
200 mm (8 inches) gravel
400 mm (16 inches) foam glass gravel (capillary-breaking)
200 mm (8 inches) concrete
110 mm (4.3 inches) EPS granulate
70 mm (2.75 inches) cement screed
10 mm (0.4 inches) tiles
What do you think? Should we definitely add a damp proof membrane?
Best regards
Jochen
I’m interested in your opinion again.
In about one week, the screed will be poured (plumbers and electricians are currently busy). Now the following issue has come up:
- We don’t have a horizontal damp proof membrane on the slab (no basement) and the screed installer has pointed out that this apparently does not comply with the standards.
- We don’t have a horizontal damp proof membrane because the builder said it wasn’t necessary since we have a 40 cm (16 inches) capillary-breaking layer (Geocell foam glass gravel). This was also recorded in the contract protocol and the construction meeting minutes.
- The architect also confirmed the non-necessity with a building physics calculation, which is documented in the construction meeting minutes.
=> Our concern now is what, for example, the insurance company would say in case of a pipe leak. Could they refer to the standard and possibly reduce the payout in case of damage, even though the non-necessity was confirmed by our professionals?
Here is the structure again (as mentioned, no basement, so directly on the ground):
200 mm (8 inches) gravel
400 mm (16 inches) foam glass gravel (capillary-breaking)
200 mm (8 inches) concrete
110 mm (4.3 inches) EPS granulate
70 mm (2.75 inches) cement screed
10 mm (0.4 inches) tiles
What do you think? Should we definitely add a damp proof membrane?
Best regards
Jochen
Why should a polyethylene (PE) membrane specifically have been installed under the slab in this case?
Although concrete slabs do not always require it, they are usually reinforced with steel. Where exactly would the PE membrane be located then? And what condition would it be in after the steel fixer has walked over it multiple times and sharp-edged reinforcing bars have been dragged across it? Who would take responsibility for ensuring that the PE membrane, if it was installed at all, is not punctured, torn, and properly overlapped at the seams?
All of this is speculation, much like looking into a crystal ball. However, the German construction regulations and technical standards do not cover such residual risks.
----------------------------------
Regards, KlaRA
Although concrete slabs do not always require it, they are usually reinforced with steel. Where exactly would the PE membrane be located then? And what condition would it be in after the steel fixer has walked over it multiple times and sharp-edged reinforcing bars have been dragged across it? Who would take responsibility for ensuring that the PE membrane, if it was installed at all, is not punctured, torn, and properly overlapped at the seams?
All of this is speculation, much like looking into a crystal ball. However, the German construction regulations and technical standards do not cover such residual risks.
----------------------------------
Regards, KlaRA
KlaRa schrieb:
@ "joho78":
Tip: Save the money for the alternative waterproofing (which is the correct term), because it cannot be successful!
The installations running through the structural slab must be secured against slipping.
This means: Necessarily drilling into the slab through the waterproofing.
This perforates it and prevents it from fulfilling its intended function. Hello KlaRa, I have a question: What you wrote makes sense—the waterproofing will be damaged by the pipe fixings. How is it ideally waterproofed so that this does not happen, only under the exterior and interior walls?
Hello "Paulus16".
The root of the problem in construction actually begins during the planning phase. You are certainly not the only property owner in Germany facing such questions! Unfortunately, the standard situation is that installations are laid out in a haphazard way, often overlapping and creating significant high points clustered on the raw concrete slab. In cases of extreme heights, the concrete slab is even chased to embed some of the conduits; and if you’re lucky as a screed installer, these installations at least are fixed to the raw slab (and not hanging mid-air with the slightest touch).
A method in line with current standards is to level this tangle with a bonded screed layer, meaning it is smoothed out up to the top edge of the highest installation. This now even surface is used for the area-wide waterproofing layer (membrane sheets). At exterior walls, the waterproofing is extended up to the horizontal damp-proof course in the masonry. This may be directly below the first course of bricks, but often it lies above that.
Once the waterproofing is done like this, the next steps are thermal insulation, polyethylene (PE) foil, and wet screed.
This would be the proper build-up within the chaos of installations. However, the required thickness often is missing, which means artistic carving of the insulation material is needed to fit the insulation heightwise to the irregular raw concrete slab. You are right to observe: there is no room for a proper waterproofing layer here, or the waterproofing is incorrectly applied on top of the thermal insulation that visually masks the chaos.
---------------------------------------------
Regards, KlaRa
The root of the problem in construction actually begins during the planning phase. You are certainly not the only property owner in Germany facing such questions! Unfortunately, the standard situation is that installations are laid out in a haphazard way, often overlapping and creating significant high points clustered on the raw concrete slab. In cases of extreme heights, the concrete slab is even chased to embed some of the conduits; and if you’re lucky as a screed installer, these installations at least are fixed to the raw slab (and not hanging mid-air with the slightest touch).
A method in line with current standards is to level this tangle with a bonded screed layer, meaning it is smoothed out up to the top edge of the highest installation. This now even surface is used for the area-wide waterproofing layer (membrane sheets). At exterior walls, the waterproofing is extended up to the horizontal damp-proof course in the masonry. This may be directly below the first course of bricks, but often it lies above that.
Once the waterproofing is done like this, the next steps are thermal insulation, polyethylene (PE) foil, and wet screed.
This would be the proper build-up within the chaos of installations. However, the required thickness often is missing, which means artistic carving of the insulation material is needed to fit the insulation heightwise to the irregular raw concrete slab. You are right to observe: there is no room for a proper waterproofing layer here, or the waterproofing is incorrectly applied on top of the thermal insulation that visually masks the chaos.
---------------------------------------------
Regards, KlaRa
Thanks for the quick response.
So the slab will not be waterproofed initially; instead, the installations will be attached to it, then the area will be backfilled until we have a level surface, which is only waterproofed afterward—is that correct?
What material is used for the bound backfill?
So the slab will not be waterproofed initially; instead, the installations will be attached to it, then the area will be backfilled until we have a level surface, which is only waterproofed afterward—is that correct?
What material is used for the bound backfill?
The fill materials can consist of various types.
For example, PERLITE is a volcanic, and therefore mineral-based fill, which binds together firmly solely due to friction forces between the granules.
Then there are cement-bound polystyrene beads from THERMOZELL, and the SCHUBO system offered by KNAUF, designed for low weight per unit area (for example, on wooden beam ceilings).
The most important factor is that the system is moisture-resistant, as it is used between the foundation slab and the waterproofing layer.
-------------
Regards, KlaRa
For example, PERLITE is a volcanic, and therefore mineral-based fill, which binds together firmly solely due to friction forces between the granules.
Then there are cement-bound polystyrene beads from THERMOZELL, and the SCHUBO system offered by KNAUF, designed for low weight per unit area (for example, on wooden beam ceilings).
The most important factor is that the system is moisture-resistant, as it is used between the foundation slab and the waterproofing layer.
-------------
Regards, KlaRa
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