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1 INTRODUCTION
To decide which constructive solution for a structure is more economical, regardless of the ar-
chitectural form, requires information and indicators that help to find economically sustainable
solutions. An instrument recommended by ISO 14040, that regulates internationally the envi-
ronmental assessment and life cycle of products, is the comparison of functional units. The
standard requires that for the functional units must be created equal conditions in relation to all
aspects of concern that may have an impact on the scientific comparison.
For this specific case, comparing conventional reticulated reinforced concrete structure and
unreinforced brick walls both with ceramic blocks, this means that the units must have the same
function regarding stability, thermal and acoustic behavior.
To compare the two constructive solutions, exterior and interior walls are defined as func-
tional units, with spans of 4, 6 and 7 meters and a ceiling height of 2.7 meters. The comparison
is carried out between the functional units of the same span.
Figure 1. Brick wall as functional unity
COMPARISON OF COSTS OF BRICK CONSTRUCTION
AND CONCRETE STRUCTURE BASED ON FUNCTIONAL
UNITS
Soheyl Sazedj
University of Évora, Department of Rural Engineering, Évora, Portugal
sazedj@uevora.pt
António J. Morais
Architecture Faculty – Technical University of Lisbon, Department of Technology, Lisbon, Portugal
ajmorais@fa.utl.pt
Said Jalali
University of Minho, School of Engineering, Guimarães, Portugal
said@civil.uminho.pt
ABSTRACT: In the context of economic sustainability of building construction, it is an issue to
decide which constructive solution is more reasonable without loosing quality. This study is
about the comparison of the costs of construction of structural walls; conventional reticulated
reinforced concrete structure filled with ceramic blocks versus unreinforced masonry with ce-
ramic blocks. Functional units are defined as inner and outer walls to enable a further specifica-
tion of the costs in order to perform a more detailed comparison without having designed a spe-
cific architecture. The results show a lower cost of unreinforced masonry construction,
especially in the case of small buildings, whether for home or public services.
2.7 m
Span of 4, 6 or 7 m
Figure 2. Wall of conventional reticulated reinforced concrete building filled with ceramic blocks as func-
tional unit
2 CONDITIONS
The functional unit in conventional construction (CC) consists of side pillars and brick walls in
between. The pillars are counted as half, as the pillar also serves for the wall that continues. The
beams are considered in regard of the span. Therefore, the beam has a height of 40 cm, 60 cm
and 70 cm depending on the span range of 4 m, 6 m and 7 m. As the slab is considered equal in
both solutions, in case of CC the slab height of 20 cm is reduced from the beams for the quanti-
fication of the materials. For each level is just considered the lower beam as the upper beam
serves for the upper level. In case of the masonry solution (M) the functional units consist simp-
ly of brickwork without columns and beams with equal dimensions of the CC solution.
The functional units are treated uncoated considering that in both solutions the coating will be
the same to safeguard the same quality, concluding that the price of the structure is of interest.
For the same reason the slabs are also equal for both constructive solutions. To avoid lost of
quality on the thermal and acoustical behavior, the masonry units are considered without rein-
forcement. According to the National Laboratory of Civil Engineering of Portugal, for safety
reasons and the weak seismic behavior of masonry, it is advised not to construct masonry build-
ings more than 3 or 4 floors. Suitably this comparison is limited to all the aforementioned condi-
tions.
Regarding the thermal behavior, a simplified model of calculation is used to compare the me-
dium heat transfer coefficient in connection with the surface area of the functional units. In both
construction cases, CC and M, the walls are considered with 3 layers, from the inner to the outer
side a 29 cm thermal brick, 1 cm of air and 3 cm of insulation with a thermal conductivity of
0.033 W/mK. In case of CC, the surface is divided in brick and concrete zone, whereby the con-
crete zone, 30 cm pillars, has no layer of air. So both walls are geometrically equal and have a
thickness of 33 cm without coating. For the CC unite the medium value of the heat transfer co-
efficient must be considered, contrary to the M unite where the surface is equal and the coeffi-
cient can be determined directly. The comparison of the heat transfer coefficients shows that in
case of CC the value is 0.456 W/m2K and in case of M 0.422 W/m2K. As the difference is very
small, it can be concluded that both cases are very similar; as equality is technically impossible
adequate heat insulation is used.
Two different scenarios are considered. In the first scenario the functional units are consid-
ered for the construction of a building with 3 or 4 floors and in the second setting the building
has only one or two floors. It is noted that for both scenarios the beams have the same dimen-
sions, since the design is independent of the height of the building. The beams are designed with
an overload of 5 kN/m2, which permits the use of the building for public services.
In the first scenario the choice of the materials is guided by a study on the comparison of the
conventional structures and unreinforced masonry (Sazedj, 2012). According to this study, to
satisfy Eurocode 6, thermal bricks are used with a width of 29 cm for the outer walls and a re-
sistant clinker brick, 11 cm wide, for the inner walls. This configuration ensures the static and
dynamic stability, while satisfying the needs of the thermal and acoustic comfort, compatible
with a reticulated structure of reinforced concrete. The exterior walls of the conventional con-
struction have 29 cm width using the same thermal bricks equal to the masonry structure guar-
2.7 m
Span of 4, 6 or 7 m
anteeing the same thermal quality. Therefore the pillars with 30 cm width are well designed for
constructive reasons. As, previously mentioned, the comparison concerns a construction with a
maximum of 4 levels, the design of the pillars with 30 cm meets also the required resistance and
there is no need to consider a larger section for the lower floors. The functional units of the inte-
rior walls in case of conventional construction consist of lateral pillars, 30 cm width as men-
tioned, and a normal brick of 11 cm width.
In the second scenario in case of masonry the above mentioned structural requirements in re-
lation to the inner walls do not exist, since the height is limited to two floors, interior walls can
be built with sufficient stiffness using the common ceramic bricks used in the conventional con-
struction. Table 1 lists the materials used in the functional units in both scenarios.
Table 1. Used construction material
MATERIAL
DIMENSIONS (mm)
DENSITY (kg/m3)
Normal brick
290x106x189
700
Clinker brick
237x115x70
1300
Thermal brick
294x289x189
1300
3 COMPARISON OF THE RESULTS
The cost is calculated according to the functional units, referring to the structure, including costs
of materials, concrete, brick and mortar, and labor, considering one worker and a servant. The
foundation is not considered since the foundation template is equal to either conventional con-
struction or masonry.
3.1 Scenario 1
Table 2 shows the costs for the construction of the functional units for the first scenario. Varia-
tion is estimated as Variation = CC-M. Hence, the sign minus indicates lower costs for Masonry
option.
Table 2, Comparison of costs for scenario 1
Functional
units
Exterior wall
Interior wall
CC
M
Variation
CC
M
Variation
4 m
537.72
418.18
-22 %
278.66
237.60
-15 %
6 m
841.01
627.26
-25 %
486.06
356.40
-27 %
7 m
1011.00
731.81
-28 %
619.72
415.80
-33 %
For the functional units of exterior walls can be seen that the masonry construction is more
economic for spans studied and cost reduction increases with increasing span. Cost reduction
varies with openings 4 to 7 m settling for 22 to 28%. This is due to the change in the height of
the beams, which increases with increasing span. The span changes two meters, from 4 to 6 m,
and then one meter, from 6m to 7 m, however the cost variation is 3% for both intervals.
In the case of interior walls the tendency is more marked as the span range increases. There is
a cost reduction from 15% to 33% as the span increases from 4 m to 7 m. The variation appears
more linear than in the case of the exterior walls although there are only three data.
The detailed costs for construction materials and labor are shown in the Tables 3 and 4.
Table 3, Comparison of material costs for scenario 1 (euro)
Functional
units
Exterior
Interior
CC
M
Variation
CC
M
Variation
4 m
419.82
290.41
-31 %
201.66
163.51
-19 %
6 m
664.23
435.62
-34 %
358.79
245.27
-32 %
7 m
805.76
508.22
-37 %
464.75
286.15
-38 %
Table 4, Comparison of labor costs for scenario 1 (euro)
Functional
units
Exterior
Interior
CC
M
Variation
CC
M
Variation
4 m
117.89
127.76
8 %
77.00
74.09
-4 %
6 m
176.78
191.65
8 %
127.26
111.13
-13 %
7 m
205.25
223.59
9 %
154.97
129.65
-16 %
The trend in the cost of materials is in accordance with the total costs. The materials costs
have a higher weight than the labor costs. It appears that the labor costs in structural masonry
are slightly higher in the execution of the exterior walls and slightly lower in the execution of
the interior walls due to partial occupation of spaces for reinforced concrete beams.
3.2 Scenario 2
Table 5 shows the constructions costs of the functional units in the second scenario.
Table 5, Comparison of the total costs of the functional units for scenario 1 (euro)
Functional
units
Exterior
Interior
CC
M
Variation
CC
M
Variation
4 m
537.72
418.18
-22 %
278.66
107.14
-62 %
6 m
841.01
627.26
-25 %
486.06
160.70
-67 %
7 m
1011.00
731.81
-28 %
619.72
187.49
-70 %
In the second scenario the costs remain the same for the outer walls, while for the interior
walls costs become much more favorable for masonry construction. This means that small
buildings up to two levels may benefit more from ceramic masonry, with a remarkable reduc-
tion of the costs of the interior walls 62 to 70% as the span increases from 4 to 7 m due to less
necessity of structural stability in comparison to the first scenario.
The detailed costs for construction material and labor are shown in the Tables 6 and 7.
Table 6, Comparison of material costs for scenario 2 (euro)
Functional
units
Exterior
Interior
CC
M
Variation
CC
M
Variation
4 m
419.82
290.41
-31 %
201.66
33.05
-84 %
6 m
664.23
435.62
-34 %
358.79
49.57
-86 %
7 m
805.76
508.22
-37 %
464.75
57.83
-88 %
Table 7, Comparison of labor costs for scenario 2 (euro)
Functional
units
Exterior
Interior
CC
M
Variation
CC
M
Variation
4 m
117.89
127.76
+8 %
77.00
74.09
-4 %
6 m
176.78
191.65
+8 %
127.26
111.13
-13 %
7 m
205.25
223.59
+9 %
154.97
129.65
-16 %
In this scenario it becomes clear that the second scenario is more beneficial in the construc-
tion of the interior walls regardless of the outer walls as they must evidently have the same costs
either in scenario 1 or 2. The interior walls in case of conventional construction turn to be more
expensive because of the concrete used for the pillars and beams.
4 CONCLUSION
This study compares the costs of exterior and interior walls of conventional construction, reticu-
lated reinforced concrete structure and unreinforced masonry both with ceramic blocks. Func-
tional units are defined with the same functional and physical criteria, structural, thermal and
acoustic performance for walls with spans of 4 m, 6 m and 7 m. The results show that in small
buildings, up to two floors and spans up to 7 meters, the material costs can be reduced. Cost re-
duction is obtained for the outer walls at least 22%, while for the interior walls at least 62%. The
results are applicable in residential and public buildings, such as health centers or centers of
administration. The labor cost is slightly higher, indicating the more intense application of man-
power. In the high unemployment societies, such as Portugal at the time being, this can result in
higher rates of employment.
5 REFERENCES
Cundall, P.A 1988, Formulation of a three-dimensional distinct element model - Part I: A scheme to de-
tect and represent contacts in a system composed of many polyhedral blocks, Int. J. Rock Mech. Min.
Sci., vol. 25, pp. 107-116.
Hart, R.D. & Cundall, P.A. & Lemos, J.V. 1988, Formulation of a three-dimensional distinct element
model - Part II: Mechanical calculations, Int. J. Rock Mech. Min. Sci., vol. 25, pp. 117-125.
Morais, A.J. & Sazedj, S. 2012, Strengthening (post-stress) of masonry buildings – method of vericaliza-
tion of load, the Eleventh International Conference on Computational Structures Technology, Civil-
Comp Press, Dubrovnik.
Morais, A.J. & Sazedj, S. & Sazedj, Sh. 2012, The Macro Economy of Masonry and Reinforced Con-
crete, National Construction Congress 2012, Coimbra.
Sazedj, S. 2012, Analyses of Sustainability of Structural Brick Work, PhD theses, Faculty of Architecture
– Technical University of Lisbon.
Sazedj, S. & Morais, A.J. & Jalai, S. 2012, Environmental Comparison of Masonry and Conventional
Construction, National Construction Congress 2012, Coimbra.
