ᐅ Concrete foundation grounding (frost protection skirt) improperly installed

Hi,

we are building a small single-family house. Strip footings (frost collar?) and the slab-on-grade are partially or fully insulated (see attachment). The shell construction work was completely contracted out to a construction company (roof excluded).

Information on the structure:
A type of leveling layer (slightly wider than the footings, interior space is free) made of concrete was placed on the soil beneath the strip footings. The strip footings were then installed on top of this. They were partially insulated on the outside (according to structural engineering requirements, concrete C25/30 XC2). A gravel-sand mixture was placed and compacted under the slab-on-grade. On top of this came a layer of crushed stone, followed by the perimeter insulation of the slab. The foundation earthing (done by the construction company) was executed as a type of ring earth electrode. However, it unfortunately only surrounds about 4/5 of the building and at one point is routed from outside through the strip footing up into the slab. The concrete was then quickly poured, and the slab completed. I was able to take 1-2 photos but no more. Upon later review of the pictures, I noticed that the earthing system has no connection to the reinforcement in the slab.

I now strongly suspect that the grounding system was incorrectly designed/installed.

After some research, I assume that actually a ring earth electrode outside the building with an equipotential bonding conductor (FPAL; fixed to the reinforcement every 2m) should have been installed within the slab-on-grade.

Am I correct in this assumption? If yes, are there any options besides demolition to retrofit an FPAL to the slab?

Regards
Mr Unkown

EDIT: Attachments had to be removed, sorry

The slab rests on insulation. A foundation earth electrode embedded in concrete (with connected reinforcement) would not function properly due to the lack of contact with the ground. Therefore, you have a foundation earth electrode installed in the soil. Placing it within the blinding layer is also standard practice.

Thank you for the quick response

Alex85 schrieb:
The slab is resting on insulation. A foundation earth electrode in concrete (with connected reinforcement) would not function properly due to lack of contact with the ground.

Exactly, that’s why I assumed the "ring earth electrode + FPAL" option would be the right one

Alex85 schrieb:
So you received a foundation earth electrode in the soil. Placing it in the blinding layer is also normal.

At least that would be the case here. It’s not a closed ring, but it is located in the soil.

But shouldn’t the earth electrode still be connected to the reinforcement? That is definitely not the case at the moment.

Regards

Yes, the reinforcement is connected, this is called potential control and has nothing to do with grounding sensitivity.
The grounding in V4A stainless steel should usually be carried out by an electrician, not by the builder.
It is best to discuss this with the electrician who will be working on your house as soon as possible.

• Since the replaced version of DIN 18014:2007-09, the installation of foundation and ring earth electrodes is exclusively reserved for licensed electrical or lightning protection specialists authorized by the distribution network operator (DNO).
• They must create a measurement documentation including plans and detailed photos with measurements of the contact resistances before concreting.
• Unlike a draft standard from 2012, the current DIN 18014:2014-03 no longer mentions delegating installation work to the structural contractor.
• In two-sided fully insulated frost skirts according to figure 13 of the current DIN 18014:2014-03, but also the slightly different figure 13 in DIN 18014:2007-09, even with loosely spaced reinforcement, a strip or round steel foundation earth electrode in the footing is possible if these are in direct contact with soil without a capillary break layer and without the use of waterproof concrete.
• With frost skirts only partially insulated on the outside and not insulated on the inside, a greater soil contact is to be expected, assuming standard concrete.
• For waterproof concrete, ring earth electrodes with a maximum mesh size of 20 m x 20 m (65 ft x 65 ft) are required with or without perimeter insulation, and for lightning protection systems a maximum mesh size of 10 m x 10 m (33 ft x 33 ft) is required.
• Where ring earth electrodes are required, equipotential bonding conductors with a maximum mesh size of 20 m x 20 m (65 ft x 65 ft) must be installed in the floor slabs, both with and without lightning protection systems, and connected to the ring earth electrode at every connection tab or every 20 m (65 ft) of building perimeter, acting as foundation earth electrodes.
• Where this has been omitted once again due to ignorance of the standards, it can no longer be economically corrected.
• I refuse to believe that at this project there is only a strip electrode running once across the frost skirt and then further into the floor slab without any connection to the reinforcing steel.

Knöpfchen schrieb:
Yes, the reinforcement is connected and it is called equipotential bonding; it has nothing to do with soil contact.
Earthing in V4A stainless steel is normally carried out by an electrician, not by the construction contractor.

DIN 18014 specifically refers to this in 4.3 Functional Equipotential Bonding and in 5.7.2 Combined Equipotential Bonding System (CBN). Also, for this and not only for ring earth electrodes made of stainless steel (V4A), only licensed electrical specialists with authorization according to NAV § 13 are permitted to perform the work according to the standard.

Dipol schrieb:
I refuse to believe that on this structure there is only a single perimeter beam running once across the frost skirt and then continuing through the floor slab without any connection to the reinforcements.

I quickly put together an overview of the installed grounding system with pictures from the day before the floor slab was poured, plus two photos taken during the pouring (see attachment).

If I’m interpreting this correctly, my grounding system is useless.

EDIT: Attachments had to be removed, sorry