Costs of Timber Houses in Different Standards and Productions in Brazil

Workmanship standards for construction

The identification of differences among workmanship standards is a crucial topic in construction, given that the Brazilian real estate market was looked upon with suspicion until the 1960s. This, due to the absence of numerical standards regarding cost composition ¹⁷. According to Decree 4591 of December 1964 ¹⁸, the standard of a construction is defined as “low, average or high, taking into account the following applied aspects: finishing condition, raw material quality, comfort innovation, equipment, and number of lifts”. In short, a construction standard involves the average evaluation of a complete residence, according to its general particularities, which include its finishing and built spaces.

The Brazilian standard document titled NBR 12721 ¹⁹ prescribes three examples of standards for a single-family residence, which are identified according to its area and basic features (Table I).

As for the finishing of single-family housing, ¹⁹ regulates basic specifications in order to delimit budget estimation. The popular standard is usually classified into the lower level because of the large production of compact single-story houses without any relevant aesthetic and technological demand, although two-bedroom buildings can be produced in this category.

Table II outlines some specifications and examples of raw materials according to the expected workmanship standards for residences.

From a structural perspective, any masonry building following the simple and popular standard and placed in a low-income community and/or region requires and uses the same inputs (bricks, cement, sand, etc.) as a high standard edification in a high-income zone or gated community.

Regardless of the construction standard (i.e., from popular to high), all masonry houses are conceptually based on the same low-technology construction practices. Only in specific options, due to factors related to greater thermal and/or acoustic insulation, a greater robustness of the walls of these houses results in greater wall thickness and represents a differential possibility. However, this strategy is based on the same technology as conventional masonry building. In short, double wall layers or larger bricks can solve this demand. Therefore, only three basic factors are more perceptible in the differentiation of masonry housing examples: volumetry, size, and finishing standard. These attributes accentuate a greater visual and economic distinction, which makes them differ- ential aspects in identifying houses with different standards.

In contrast, a timber housing example may be structurally identified in at least 15 distinct construction techniques with singular features and many particularities, as defined by ^{15), (16}. For example, timber-based construction techniques such as half-timbered frame, post-and-beam, and stick houses have robust framing made of lumber (hand-hewn or sawn wood), which is exposed and freestanding, as well as sealed with non-essential structural materials. Meanwhile, log-homes and horizontal clapboards between studs have solid walls based on wooden logs with a double function: freestanding and sealing roles. Similarly, a modular construction with crosslaminated timber (CLT) is produced with three dimensional rigid panels, therefore classified as engineered wood products, whose walls serve for both sealing and structural support.

In contrast, different woodframe variations are known by lightweight compact framing, with varied prefabricated features, whose wall structure is formed by lumber studs and covered by structural panels applied in order to brace and seal the whole set, forming a ‘sandwiched’ wall. Another type is formed by two construction techniques based on industrialized lumber. Clapboard-and-wainscot and nailed clapboard (vertically and horizontally oriented) houses are prefabricated solutions formed by compact framing sealed by lumber from native or planted forests. In both examples, walls are integrally made from industrialized lumber of the same or multiple wood species, sizes and geometries. Lumber clapboards, wainscots (to seal wall spaces), and thin studs are used to form the structure and seal it. These elements are fixed by metallic nails. Wall constitution and finishing are two attributes that distinguish each example, since nailed clapboard houses are focused on noble markets and clapboard and wainscot buildings are oriented towards popular and rural demands. Thus, the structural concept of different timber buildings represents the main typical feature that contrasts each construction technique.

Unlike masonry houses, wood acts as a structural and sealing element ^15), and it is a suitable material for the composition of living spaces ²⁰. In addition, ²¹ stated that wood has elements of robustness, pleasure, singularity, rarity, and sophistication. Furthermore, wood surfaces are aesthetically pleasing ^22)-(24, which are associated with sustainable architectural materials ²⁵. Also, lower lifecycle costs compensate the higher costs of green buildings ²⁶. In fact, building costs should be considered as an important factor in timber construction, even though there are multiple alternatives to supply different markets. However, few studies have estimated the costs of different timber techniques as the comparison of prefabrication and conventional systems led by ²⁷.

Construction cost and its perspective in Brazil

Informality has been a sectoral problem that interferes with different stages of construction, such as provision and storage, delivery times, and costs ²⁸.

In Brazil, the construction sector concentrates a disqualified technical workforce, since it is focused on artisanal production of many construction techniques ²⁹. After years of adaptation and development in the Brazilian territory, structural masonry was widely consolidated in the 1980s, becoming the most traditional method ³⁰.

Timber houses are produced both in more rudimentary artisanal styles and modern modalities stemming from semi-industrialization and industrialization, which are based on partial and complete production of prefabricated wooden parts and elements, respectively. These elements are semi-finished and finished (off-site) in plants to be assembled at the construction site, as theoretically described by ¹⁵ and scientifically confirmed by ³¹.

In contrast to masonry markets, whose technique is supported only by a single typology with different finishing examples, wood-based houses should be singularly analyzed regarding their market costs, due to the attractive and technical attributes ensured by many structural concepts and standards of workmanship. According to ³, the best economy in timber construction is generally achieved when standard-size members can be utilized in a repetitive arrangement with simple connections. This is very important, as ³² verified that entrepreneurs should ensure the quality of the final product to be delivered on promised time intervals and with agreed-upon cost.

The overall construction cost corresponds to the minimum value attributed to a house, calculated from the basic unitary cost, which considers the full cost per square meter of a standard project ¹⁹.

In 1964, Decree 4591 established a unitary cost of construction to measure property costs ¹⁸, which became an indicator of sectoral cost over the years ³³. These basic unitary costs do not consider the following: groundwater retraction, projects (structural and architectural), ovens and stoves, lifts, electronic devices (ventilation, exhaustion, heating, etc.), urbanization and recreation, landscaping, taxes, ground, among others ¹⁹. The estimation of basic unitary costs of timber-based houses becomes important, as this activity could be exploited and absorbed by the construction sector (regardless of the forest-timber industry), which was about 10% of the Brazilian Gross Domestic Product in 2015 ³⁴.

From this domestic scenario, this study aimed to evaluate the basic unitary costs of timber houses produced in Brazil for each housing technique while considering three main finishing standards and three types of production. This is justified by the pricing omission of timber-based techniques in different regional studies such as ^35)-(37, among others. Thus, the following hypothesis is suggested: contrary to the impressions of Brazilians, timber houses may be economically competitive and, in some cases, cheaper than masonry buildings in the Brazilian market.

Statistical analysis

In order to validate the representativeness of this sectoral survey, the margin of error was measured and compared to literature values. The Raosoft Sample Size Calculator software ⁴⁰ was used, which prescribed values of 95% for the confidence level and 50% for the response distribution.

Statistical analysis of the surveyed sample

While this study integrated a series of different approaches developed to characterize the timber housing production sector in Brazil, ^{16), (31), (39}, and dozens of other approaches ascertained a domestic sectoral population of 210 producers, out of which 107 companies were randomly evaluated with a representative sampling rate of 51% and a margin of error of 6,65 %. This value is close to the ideal level of 5%prescribed by ⁴¹. Therefore, the costs presented in the next section may vary slightly by ±3,325% with respect to the margin of error for this sample.

Basic unitary costs of timber houses produced in Brazil

As Brazilian construction is widely dominated by structural masonry ³⁰, this study inserted the correspondent basic unitary cost of artisanal masonry estimated by the Brazilian Institute of Geography and Statistics (IBGE) in all figures. The data of ³⁸ considered the masonry costs for the macro-region under study. In view of the contrasts between masonry and timber houses, the outcomes regarding the basic unitary costs of each technique were organized under two parameters: production processes and workmanship standards. It is important to emphasize that an individual cost per technique is formed by a global fee that includes technology, raw material procurement and processing, parts production, and building assembly and finishing. To specify the sectoral results, the production techniques were grouped into three graphs for each finishing standard, according to the available processes: low (Fig. 1),medium (Fig. 2), and high (Fig. 3). The analysis of the basic unitary costs of timber housing produced in Brazil proved the studied hypothesis. Timber housing can be economically competitive with regard to masonry solutions, as there are timber techniques cheaper than this traditional method of bricks and concrete. This finding discredits Brazil’s popular perception about the higher costs of timber houses. Clap-board and wainscot housing with a low standard and an artisanal method was the cheapest technique (Fig. 1), and CLT modular housing with a high standard and an industrial process was the least viable model (Fig. 3).

Figure 1: Basic unitary cost (US$/m2) of timber houses with low finishing standard

Figure 2: Basic unitary cost (US$/m2) of timber houses with average finishing standard

Figure 3: Basic unitary cost (US$/m2) of timber houses with high finishing standards

For the low finishing standard (Fig. 1), 15 timber construction techniques demonstrated lower costs per built area than masonry housing: stick with masonry (in artisanal and semi-industrial production processes), post-and-beam (artisanal and industrial), modular for construction site (industrial), clapboard and wainscot (artisanal, semi-industrial, and industrial), nailed vertical and horizontal clapboard houses (both techniques in semi-industrial and industrial processes), log-home (semi-industrial), and mixed and platform woodframe houses (both varieties in semi-industrial processes). Apart from the platform and mixed woodframe varieties (which are modern, light, and efficient examples ^{15), (42), (43} and the post-and-beam technique, the general panorama found for the other wooden techniques matches some solutions with lower added-value and simpler technology. These exceptions were justified by their greater availabilities in the Brazilian market, as already stated by ^16). In addition, 17 construction examples were more costly than masonry housing (Fig. 1): clapboards between studs (all three production processes), balloon and platform varieties of woodframe (artisanal and semi-industrial), loghomes (artisanal and industrial), vertical and horizontal varieties of nailed clapboard and mixed type of woodframe (all three techniques in artisanal production), post-and-beam (semi-industrial), and CLT modular, stick with masonry, woodframe modular, and half-timbered frame houses (all four techniques only in industrial production).

For the average standard (Fig. 2), 14 techniques were cheaper than masonry housing: clapboard and wainscot (all three production processes), stick with masonry (artisanal and industrial), platform woodframe and log-home (semi-industrial), modular house for construction site (industrial), and nailed vertical and horizontal clapboard varieties (semi-industrial and industrial). However, 18 varieties exceeded the cost of masonry: clapboards between studs (all production processes), stick with masonry (industrial), post-and-beam (semi-industrial), half-timbered frame, CLT and woodframe modular houses (all three techniques in industrial process), balloon and mixed woodframe varieties (artisanal and semi-industrial), nailed vertical and horizontal clapboards varieties (artisanal), and log-homes and platform woodframe (both techniques in artisanal and industrial processes).

Regarding the high finishing standard (Figure 3), 11 techniques revealed lower basic unitary costs than masonry housing: clapboard and wainscot (all three productions), stick with masonry (artisanal and semi-industrial), post-and-beam (artisanal and industrial), modular for construction site (industrial), nailed vertical clapboards (semi-industrial and industrial), and log-home (semi-industrial). However, 21 construction techniques were more expensive than masonry: nailed horizontal clapboards, clapboards between studs, and platform woodframe houses (all three techniques in all productions), post-and-beam (semi-industrial), nailed vertical clapboards (artisanal), log-home (artisanal and industrial), mixed and balloon woodframe varieties (artisanal and semi-industrial), and woodframe modular, CLT modular, stick with masonry, and half-timbered frame houses (industrial).

The clapboards between studs technique showed basic unitary costs higher than artisanal masonry housing (Figs. 2 and 3), which is explained by the frequent consumption of native woods involved in this technology, as confirmed by ¹⁵. The higher costs of native species reposition their products for noble uses ⁴⁴, but timber from Brazilian native forests has higher costs due to complex transportation, as measured by ⁴⁵. Given this condition, the clapboards between studs technique is usually aimed at finer uses in lodges, chalets, and holiday homes ⁴⁶.

The clapboard and wainscot technique reported lower costs than masonry (Figs. 1 to 3). Popular in rural applications, this more viable situation was justified by the exclusive consumption of pine wood (whose silvicultural variety is cheaper than native species ^{44), (47}), affordable access for low-income people ⁴⁸, and better and simpler aesthetic, structural, and production features ⁴⁹.

In these three contexts (Figs. 1 to 3), the half-timbered frame, woodframe modular, and CLT modular construction techniques showed basic unitary costs above those of artisanal masonry housing. Higher industrialization and customization of these examples resulted in factors that confirmed the higher costs expected. However, modular houses for the construction site, which features less refinement and intense industrial and commercial functions, were cheaper than masonry due to the excessive use of pine woods and large-scale production.

The stick with masonry technique showed a higher cost than masonry in industrial production, as well as lower costs in the artisanal and semi-industrial methods. Post-and-beam was cheaper than masonry in artisanal and industrial models, and it was costly in semi-industrial production (Figs. 1 to 3). Despite the simplicity and low technological evolution of these two techniques, their higher costs were related to the use of noble woods and the customization of singular projects ^15).

Similar situations were observed for the nailed horizontal and vertical clapboards techniques (Figs. 1 to 3), as their artisanal processes were more costly than masonry, while their semi-industrial and industrial production models were relatively close. Greater rusticity and architectural simplicity justified these lower costs in industrial stages, while custom projects are more costly when produced manually.

The log-home technique showed a singular panorama: artisanal and industrial production models exhibited higher basic unitary costs in comparison to artisanal masonry(Figs. 1 to 3), while its semi-industrial process was cheaper. This scenario is due to the low presence of specific developers, despite the higher lumber and round-wood consumption.

Three varieties of woodframe technique (platform, balloon, and mixed) revealed higher costs in their artisanal processes than masonry. However, they were closer or slightly above the cost of masonry, both in semi-industrial and industrial models. The higher cost of woodframe could be attributed to the following factors: higher technological complexity ^{50), (51}, high production efficiency ^{42), (43), (52}, and the structural utilization of wooden composites and engineered products ^{52), (53}. But these materials have reported higher market costs ⁵⁴.

In fact, the modularization of timber construction was more costly than prefabrication in Brazil. As modern manufactures usually require more investment in technology and machinery for advanced production, this scenario is very plausible for the global progress and innovation in timber construction, despite the fact that lower longterm costs are expected for modular buildings. Even in Canada, where timber industry is widely known by its high technology, the modularization was marginally more cost-effective than panel prefabrication ⁵⁵. Still, panel prefabrication could be productively updated using automation-based improvements, as analyzed by ⁵⁶.

The results of the last question were described in Fig. 4. An important consideration is that the sampled companies could declare to offer one, two, or three finishing standards to supply any market demands. Regardless of the construction technique, this sector concentrates the supply of solutions with high and average finishing standards, focused on select markets and wealthy clients. Nevertheless, more than half of the studied sector offers low standards for popular use. The surveyed scenario showed that timber housing is diverse in Brazil because it is available to all economic classes.

Figure 4: Finishing standards available in the timber housing production sector

Most of the population is willing to pay slightly greater amounts of money for a higher-quality residence ⁵⁷. In this scenario (Fig. 4), the average- and high-standard classes may hold current clients and also attract a considerable share of future buyers for timber houses, i.e., if benefits and economic viability were better exploited. In the perspective of popular houses involving lower standards and thus lower costs, the large-scale production of standardized timber houses becomes a way to offer dwelling with acceptable quality and uniform features. This is assured by ⁵⁸, who confirmed that prefabricated buildings provide more environmental benefits than on-site construction, i.e., essentially in terms of waste generation, materials and energy consumption, and carbon emissions. Moreover, ⁵⁹ argued that engineered wood products arise as promising solutions to increase the efficiency and sustainability of the innovative construction. Therefore, companies must adapt their culture and processes to society’s demands, since an innovative organization will undoubtedly generate long-term value and will be better prepared to deal with the economic, social, and environmental challenges looming in this century ⁶⁰.

In general, when the construction of a green building is planned, it requires about 10% additional costs, yet it should offer more than 50% energy and water savings over its lifecycle ⁶¹. Design, materials, and tools are the factors that drive up costs in green projects ²⁶. In timber housing, greener projects really add more value from an environmental perspective, since buildings are built with lignocellulosic bioproducts, are strongly designed by those principles, and have several advantages.