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Expansion joints
Foundation earth electrodes cannot be passed across expan-
sion joints. At these points, they can be led out near walls and
connected by means of fixed earthing terminals and bridging
braids in case of e.g. concrete walls (Figure 5.5.2.8).

However, in case of foundation slabs with large dimensions,
the meshes of the foundation earth electrode must be led
through these expansion joints (sections or joints) without Figure 5.5.2.8 Bridging braid with fixed earthing terminals
leading them out of the wall. Special expansion straps, which
create cavities in the concrete by means of a styrofoam block
and an integrated flexible connection, can be used in this
case.
The expansion strap is embedded in the foundation slab in
such a way that the styrofoam block is situated in one section
and the other end is routed loosely in the next section (Figure
5.5.2.9).
expansion
Membranes in case of foundation slabs joint
Membranes made of polyethylene with a thickness of about
0.3 mm are often laid on the blinding layer as a separation
layer (Figure 5.5.2.10).
These membranes only slightly overlap and are not water-
repellent. foundation slab
They typically only have little impact on the earth resistance Figure 5.5.2.9 Bridging a foundation earth electrode by means of an
and can thus be neglected. For this reason, foundation earth expansion strap
electrodes can be installed in the concrete of the foundation
slab.

Dimpled membranes
Dimpled membranes are used to replace the blinding layer for
foundation slabs and often enclose the entire basement (Fig-
ure 5.5.2.11).
These dimpled membranes are made of special high-density
polyethylene with a thickness of approximately 0.6 mm (dim-
ple height of approximately 8 mm) (Figure 5.5.2.12). The
individual membranes have a width of about 2 to 4 m, over-
lap (about 20 to 25 cm) and keep water away. The foundation
earth electrode therefore cannot be effectively installed in the
foundation slab.
For this reason, a ring earth electrode made of stainless steel Figure 5.5.2.10 Membrane of foundation slabs
(V4A), e.g. material No. AISI/ASTM 316 Ti, with an adequate
mesh size is buried outside the foundation below the dimpled
membranes.
Concrete buildings with a high resistance to water penetra-
tion are built without additional extensive external sealing
Foundations with an increased earth contact and prevent the ingress of water solely due to the concrete
resistance and structural measures such as joint sealing and crack width
“White tank” made of waterproof concrete limitation. Particular care is required when erecting these wa-
Waterproof concrete has a high resistance to water penetra- terproof buildings since all building components such as joint
tion. In Germany, closed tanks made of waterproof concrete sealings, entries for water, gas, electricity and telephone lines
are informally also referred to as “white tanks”. (in the form of multi-line building entries), sewer pipes, other

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