https://doi.org/10.14311/APP.2022.33.0463
Acta Polytechnica CTU Proceedings 33:463–466, 2022 © 2022 The Author(s). Licensed under a CC-BY 4.0 licence

Published by the Czech Technical University in Prague

PARAPET STRUCTURE FROM SPECIAL SHAPED TRC BLOCKS

Jiří Pazderka, Petr Hájek, Michal Nývlt∗, Hana Žáková

Czech Technical University in Prague, Faculty of Civil Engineering, Thákurova 7 166 29 Prague, Czech
Republic

∗ corresponding author: michal.nyvlt@fsv.cvut.cz

Abstract.
The paper describes innovative parapet solution based on special shaped blocks made form textile-

reinforced concrete - TRC. The blocks are designed for a placement at the parapet of building with
a flat roof. The solution is appropriate for buildings with precast-concrete bearing structure by fol-
lowing the principle of precast technology (short construction time, minimal technological pauses).
However, presented parapet TRC blocks can be used for energy efficient buildings as well in combina-
tion with thick layers of thermal insulation. The technical solution was registered as utility model no.
CZ27642(U1).

Keywords: Concrete, parapet, prefabrication, roof, TRC.

1. Introduction
Nowadays, the emphasis is on energy savings in the
field of building construction. The solution of build-
ing envelope details is important for contemporary
design of buildings. An important part of this issue
is the solution of the detail of flat roofs of buildings in
the form of a low parapet wall. For buildings whose
load-bearing structure consists of precast frame con-
struction system, the parapet wall design is an im-
portant part of the overall design. The main advan-
tage of precast technology is the minimization of wet
processes on site which resulting to short construc-
tion time. In order to minimize the wet processes
in precast construction systems, it is desirable that
the parapet wall structure should also be prefabri-
cated. However, this assumption is often not fulfilled,
because at the present time the construction of the
parapet wall in precast frame systems is commonly
solved in the form of a masonry wall from various
materials. In some cases, the parapet wall is in the
form of a specially modified beam which combines
the function of supporting the ceiling structure (spe-
cially adapted bearing girder) with the function of
the parapet wall. However, such prefabricates usu-
ally represent a distinct architectural element (not
suitable for most buildings) and at the same time al-
most do not consider the problem of linear thermal
bridges (it cannot be used for modern energy effi-
cient buildings). However, the requirement to mini-
mize thermal bridges is one of the key parameters of
the design of building envelope structures in today’s
building construction.

The solution currently used for the construction of
a parapet wall on a flat roof in the form of aăma-
sonry wall (mentioned above), presents several disad-
vantages. This is especially addition of another wet
process into site construction which resulting to re-
duction of efficiency and speed of construction (not

exploiting the potential of precast technology). An-
other significant problem is the risk of deformation
of the masonry parapet wall (displacement due to
shear stress in masonry) over time, which is often
associated with aăfailure of the roof waterproofing
layer. The parapet made in the form of aăspecially
modified beam (specially adapted bearing girder) is
a more suitable solution in terms of in situ efficiency
but these elements are always part of standardized
construction systems with predefined dimensions (the
possibilities of using are limited due to architectural
design). Another problem may be the high weight of
the parapet bearing beam and the resulting compli-
cations in terms of handling the precast.

2. Parapet structure from
special shaped TRC blocks

The above-mentioned disadvantages of existing para-
pet structures of flat roofs of buildings based on
precast frame system (masonry and parapet bearing
beams) are largely eliminated using specially shaped
parapet blocks made of textile reinforcement concrete
(TRC) [1]. The essence of the parapet block is that
it is made of precast reinforced concrete with an op-
timized (lightweight) shape solution with aăcrosssec-
tion in the shape of the letter "L". The vertical wall of
the parapet block is formed by a thin plate (30ămm
thick), which is reinforced by reinforcing ribs (50×100
mm) at distances of 0.7 − 0.8 m. The stiffening ribs
comprise a bending reinforcement. The low plate
thickness between the reinforcing ribs is made possi-
ble using high-performance concrete (HPC) in combi-
nation with textile reinforcement (TRC). The bottom
horizontal slab of the block has a variable thickness
which increases towards the centre of the block (thick-
ness 30 − 80 mm). The lower horizontal plate is made
of TRC and, like the vertical plate, is reinforced with
reinforcing ribs (50 × 100 to 137 mm) spaced 0.7 − 0.8

463

https://doi.org/10.14311/APP.2022.33.0463
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J. Pazderka, P. Hájek, M. Nývlt, H. Žáková Acta Polytechnica CTU Proceedings

Figure 1. Special shaped parapet block (visualization).

m apart. These ribs, together with the ribs of the ver-
tical plate, form an "L" -shaped frame structure with
reinforcement in the centre of the block. The variable
thickness of the horizontal slab is advantageous both
in terms of precast technology (concreting will take
place from the outer surface of the vertical slab) and
in terms of better stability of the shaped piece (lower
centre of gravity).

The parapet block is equipped with a horizontal
cross rib (30×100 mm) at the top, which serves for an-
choring of the flashing structure (through the spacer
profile). The rib on the top of the parapet block also
has a reinforcing function in terms of the horizontal
load on the parapet wall (wind pressure, suction, an-
choring of other structures). To ensure the fixation of
the position, the block is equipped with three holes
in the lower horizontal plate, which are used for an-
choring the block to the ceiling panel of the frame
system.

The shape-optimized "thin-walled" design of the
parapet block is advantageous both in terms of mini-
mizing the weight of the precast element during trans-
portation and subsequent handling on site. At the
same time, it is also advantageous the reducing of
overall vertical load on the bearing structures and
foundations of the building. The subtle optimized
shape of the precast block using TRC is also advanta-
geous in terms of eliminating thermal bridges. Only
a minimal cross-section of a part of the supporting
structure penetrates the thermal insulation envelope
of the building. In fact, it is not a thermal bridge, be-
cause the parapet construction must always be thor-
oughly insulated around its perimeter. This design
predetermines the parapet block for use in energy ef-
ficient buildings. For handling by lifting means, the
block will be equipped with countersunk threads for
screwing in the anchorages. These threads will be
located on the upper surface of the horizontal rein-
forcing rib at the position of the vertical reinforcing
ribs.

3. Description of the functional
principle

Figure 3 shows the installation of the precast parapet
block (no. 1) on the ceiling structure of a precast
concrete frame construction system comprising ceil-
ing panels (no. 2) and beams (no. 3). The parapet
block (no. 1) is secured (fixed) against horizontal
movements by anchoring at the anchor holes (no. 4).
The lower horizontal slab of the parapet block (no.
5) is"weighted" by a layer of gravity concrete (no.ă6),
which thus acts as a stabilizing layer. At its lower left
edge, the parapet block (no. 1) is separated from the
concrete layer forming a gradient (no. 7) by means
of an inserted thermal insulator strip (no. 8), which
eliminates the transfer of horizontal deformations of
the concrete layer due to longitudinal thermal expan-
sion.

On the upper horizontal reinforcement rib of the
parapet block (no. 9) is an anchored construction of
the flashing (no. 10). The vertical panel of the para-
pet block (no. 11) is supplemented by an additional
thermal insulating layer (no. 12), which compensates
for the higher thermal conductivity coefficient HPC
(compared to the adjoining masonry of the external
cladding (no. 13)). An additional thermal insulation
layer (no. 11) is connected to the thermal insulation
system of the facade cladding (no. 14), which is tight-
ened up to the thermal insulation under the flashing
(no. 15). From the inside of the roof, a vertical layer
of thermal insulator (no. 16) is anchored to the para-
pet block. This layer follows the thermal insulation
of the flat roof (no. 17). The thickness of the vertical
thermal insulation (no. 15) is designed to overlap the
reinforcing rib (no. 18) of the parapet block.

Figure 4 shows precast parapet block (no. 1) which
forms the supporting structure of the parapet shown
in Figure 3. The parapet block (no. 1) is character-
ized in that it is made in the cross-sectional shape
of the letter"L", where the thin vertical plate of the
block (no. 11) is reinforced with ribs (no. 18). The
vertical ribs are reinforced at the point of connection

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vol. 33/2022 Parapet Structure from Special Shaped TRC Blocks

Figure 2. Installation of special shaped parapet block on the building (simplified visualization).

Figure 3. Example of parapet block installation on the ceiling structure of precast concrete frame construction
system. Notes: 1 - parapet block, 2 - reinforced concrete ceiling panel, 3 - reinforced concrete beam, 4 - anchoring of
parapet block, 5 - horizontal part of parapet block, 6 - monolithic concrete - layer forming a gradient and stabilizes
the parapet block, 7 - monolithic concrete - layer forming a gradient, 8 - dilatation, elastic strip, 9 - the upper
part of the parapet block, 10 - anchoring of parapet block, 11 - vertical part of parapet block, 12 - lower thermal
insulation layer (compensation for reinforced concrete elements), 13 - filling masonry of perimeter wall, 14 - main
thermal insulation layer (ETICS), 15 - insulation of parapet extruded polystyrene (XPS), 16 - insulation of parapet
block, 17 - conventional roofing layers of flat roof, 18 - reinforcing rib of parapet block

465



J. Pazderka, P. Hájek, M. Nývlt, H. Žáková Acta Polytechnica CTU Proceedings

Figure 4. Precast parapet block. Notes: 1 - parapet block, 4 - anchoring of parapet block, 5 - horizontal part of
parapet block, 9 - the upper part of the parapet block, 11 - vertical part of parapet block, 18 - vertical reinforcement
rib of parapet block, 19 - horizontal reinforcement rib of parapet block, 20 - rib reinforcement.

to the ribs of the horizontal plate (no. 19) by triangu-
lar haunches (no. 20) and together with the reinforc-
ing ribs of the lower horizontal plate (no. 19) form"L"
frame structure. The solved parapet block (no. 1) is
characterized in that it comprises a lower horizontal
plate (no. 5) of variable thickness which increases
towards the centre of the precast. This plate is rein-
forced with ribs (No. 19) which have an increasing
thickness towards the centre of the prefabricated el-
ements. The lower horizontal plate (no. 5) has three
holes (no. 4) for anchoring the precast to the ceiling
panel of the framework system. The parapet block
(no. 1) is provided with aătransverse rib (no.ă9) at
the top of the vertical plate (no. 11), which serves
to anchor the parapet block flashing structure and to
reinforce it in terms of horizontal loading.

4. Conclusion
The technical solution of the parapet block for flat
roofs described in the paper was registered as a util-
ity model no. CZ27642(U1). The block is intended
primarily for energy-efficient buildings based on pre-
cast frame construction systems. However, it can be
used without further modifications for parapet solu-
tions in other building construction systems (e.g. ma-
sonry buildings with precast concrete ceiling), where
the advantage of the precast technology will be bene-
ficial. The parapet block is the next element used for
construction details in buildings, expanding the ex-
isting set of thin-walled precast elements, developed
at the Faculty of Civil Engineering CTU in Prague
[2–4]. A potential industrial partner for production

is currently being searched. Testing of mechanical
properties is planned after the production of the first
prototype series - based on the results, the final di-
mensions of the elements for serial production will be
optimized.

Acknowledgements
This work was supported by the research project
SGS19/145/OHK1/3T/11.

References
[1] J. Pazderka, P. Hájek.Utility model CZ27642(U1) -

Parapet structure, especially for building platform
roofs, CTU in Prague, 2015.

[2] J. Pazderka, M. Nývlt, H. Žáková. Underground
ventilated wall based on TRC blocks. IOP Conference
Series: Materials Science and Engineering 596(1),
2019.
https://doi.org/10.1088/1757-899x/596/1/012037.

[3] J. Pazderka, P. Hájek. Two innovative solutions
based on fibre concrete blocks designed for building
substructure. IOP Conference Series: Materials
Science and Engineering 246, 2017.
https://doi.org/10.1088/1757-899x/246/1/012046.

[4] J. Pazderka, E. Hájková, M. Jiránek. Underground
Air Duct to Control Rising Moisture in Historic
Buildings: Improved Design and Its Drying Efficiency.
Acta Polytechnica 57(5), 2017.
https://doi.org/10.14311/ap.2017.57.0331.

466

https://doi.org/10.1088/1757-899x/596/1/012037
https://doi.org/10.1088/1757-899x/246/1/012046
https://doi.org/10.14311/ap.2017.57.0331