2Barreiras, in western Bahia, sits in bioclimatic zone 7 of NBR 15220-3:2005 (the Brazilian bioclimatic zoning standard), and the construction guideline for that zone is direct: "Wall: Heavy; Roof: Heavy". FAD No. 070 (Ficha de Avaliação de Desempenho, a performance assessment sheet), issued in August 2024 for a Light Steel Frame (LSF) system, assessed thermal performance only for zones 3 and 6. Between the speed that steel promises and the mass that the climate asks for, the choice of enclosure begins before the budget.
In C&S Engenharia's reading, LSF speeds up the works when the project fits the assessed scope. Outside it, speed is paid for in another currency.
SiNAT, the technical assessment arm of PBQP-H (the Brazilian Habitat Quality and Productivity Program), lists among its guidelines SiNAT Guideline No. 003, Revision 03. Its object is systems structured in lightweight cold-formed steel profiles, with enclosures in thin sheets: the formal definition of LSF. The guideline says how to assess; approval comes applicant by applicant.
That approval takes the form of a Performance Assessment Sheet (FAD), issued after an assessment coordinated by IPT, or, in older documents, of a Technical Assessment Document (DATec). Each sheet is valid for one manufacturer's system. In C&S Engenharia's reading, LSF is not a generic product. It is a set of systems, each with its own document.
FAD 070 also cites NBR 16970:2022, a dedicated series on Light Steel Framing in three parts: performance, structural design and interfaces. The text, which is paid, was not read.
FAD 070 applies to "single-family, single-storey, detached and semi-detached housing units". FAD No. 072, from November 2025, covers single-storey houses and two-storey townhouses. DATec No. 049 A, from October 2024, reaches up to 2 storeys, with validity declared until September 2026.
Three exclusions repeat. Revision 01 of Guideline 003, from 2012 and already superseded, and FAD 072 rule out environments of high environmental aggressiveness, such as industrial atmospheres. No document assesses foundations. And FAD 070 records that the enclosures, because they have a structural function, "cannot be altered or demolished, whether totally or partially".
For agribusiness, the last sentence weighs heavily. In C&S Engenharia's reading, a support building whose use may change within a few years calls for a system that accepts change.
The territory began as a federal plan: Decree No. 8,447/2015 created the Matopiba Agricultural Development Plan, later declared revoked by Decree No. 10,473/2020. The delimitation by Embrapa (the Brazilian Agricultural Research Corporation), on which the decree was based, totalled 337 municipalities, 30 of them in Bahia, with Cerrado covering 91% of the area, Amazon 7.3% and Caatinga 1.7%.
In the 1981-2010 Climatological Normals of INMET (the Brazilian National Institute of Meteorology), Barreiras records 1,003.4 mm of rain per year. December alone adds up to 203.7 mm; June, July and August together, 5.9 mm. It is a cerrado climate, with well-marked rainy and dry seasons.
The annual compensated mean temperature is 25.2 °C, with a monthly minimum of 22.8 °C in June and July and a maximum of 27.8 °C in October, before the rains.
In C&S Engenharia's reading, the difference between semi-arid and cerrado is not semantic: the wall must endure the heat of October and a summer of concentrated rain, with the water it brings to the base.
NBR 15220-3 classifies 330 cities into zones numbered from 1 to 8. Barreiras is in zone 7; Correntina, in zone 6; Luís Eduardo Magalhães does not appear on the list. For zone 7, the standard recommends small, shaded openings, heavy walls and roof, evaporative cooling with thermal mass, and selective ventilation.
In C&S Engenharia's reading, the logic is physical: the heavy wall stores the heat of the day and returns it with a delay, when ventilation can already remove it.
FAD 070 assessed only zones 3 and 6. FAD 072 declares all zones, with a fibre-cement roof, plasterboard ceiling and glass wool, and indicates for townhouses light colours with shading and ventilation. DATec No. 014, from 2013 and no longer valid, also declared all of them.
FAD No. 073, from June 2026, already uses zones 1M, 2R, 3A, 4B, 5A and 5B of the new version of NBR 15575, which differ from the numbering of NBR 15220-3. Matching the zone of the site with that of the sheet now requires translation.
Two caveats keep the calculation honest. NBR 15220-3 has a scope of social-interest housing, and performance is verified under NBR 15575-4, which was not read in full text. And "all zones" holds for the roof assembly of each sheet, not for any roof.
Hence the thesis. In C&S Engenharia's reading, in Barreiras masonry or concrete is the prudent choice for housing, unless there is a valid sheet covering the zone or a performance demonstration under NBR 15575. LSF does not leave the table. It must prove, case by case, what the guideline attributes to mass.
Steel is a ferrous alloy; what protects it is the zinc coating. The 2012 Guideline accepts class Z275, of 275 g/m² summed over both faces, in rural or urban regions, and requires Z350 in a marine atmosphere, up to 2,000 m from the shoreline. The minimum nominal thickness of studs and tracks is 0.80 mm.
FAD 070 says that the walls "have the potential to meet the DSL (Design Service Life) of 50 years". That potential depends on protection against bimetallic corrosion, screws tested in salt spray, eaves of 600 mm, a waterproofing membrane up to 200 mm above the foundation, and a maintenance manual in accordance with NBR 14037.
NBR 15575-1:2013, in a table reproduced by the PARC journal, of Unicamp, sets a minimum service life of 50 years for the structure and of 40 years for the external vertical enclosure. No document read compares the service life of LSF with that of concrete. In C&S Engenharia's reading, the useful question is who will carry out the maintenance that the sheet presupposes.
In the cerrado, the base matters. In C&S Engenharia's reading, the rain from November to March tests precisely the membrane and the eaves, details that are cheap on the drawing board and costly once the wall is closed.
The example is hypothetical: it is neither a real project nor official data. It gives an order of magnitude for class Z275.
| Step | Calculation | Result |
|---|---|---|
| Studs | 6.0 / 0.6 + 1 | 11 pieces |
| Sheet for the studs | 11 x 2.7 m x (90 + 2 x 40 + 2 x 10) mm = 29.7 m x 0.190 m | 5.643 m² |
| Sheet for the tracks (bottom and top) | 2 x 6.0 m x (90 + 2 x 40) mm = 12.0 m x 0.170 m | 2.040 m² |
| Total sheet | 5.643 + 2.040 | 7.683 m² |
| Minimum zinc (Z275) | 7.683 m² x 275 g/m² | 2,113 g, about 2.1 kg |
| Steel of the sheet | 7.683 m² x 0.0008 m x 7,850 kg/m³ | 48.2 kg |
| Zinc over steel | 2.113 kg / 48.25 kg | about 4.4% |
That is 2.1 kg of zinc for 7.7 m² of sheet: the minimum defence of the steel in a rural or urban setting. The calculation does not measure durability: the documents make the 50-year DSL conditional on the whole of zinc, interfaces, screws, base and maintenance. In C&S Engenharia's reading, with so thin a layer the sensitive point tends to lie in the joints, not in the middle of the profile.
The structural walls of FADs 070 and 072 reached 30 minutes in testing, classification REI-30 under NBR 16945:2021. The 2012 Guideline already asked for that minimum in multifamily buildings of up to 5 storeys.
In Bahia, the yardstick belongs to the Military Fire Department (Corpo de Bombeiros Militar da Bahia, CBMBA). Technical Instruction No. 08/2016 (read in a copy) sets the required fire resistance times (TRRF) according to State Decree No. 16,302/2015, with NBR 15200 for concrete, NBR 14323 for steel and annexes for masonry and drywall.
The IT exempts from TRRF buildings of classes P1 and P2, up to 12 m in height, with less than 750 m². Single-storey buildings are also exempt with fast-response automatic sprinklers or a fire load of up to 500 MJ/m², with exceptions. Partitions between autonomous units of groups A2, A3, B, E and H, however, require 60 minutes.
In C&S Engenharia's reading, this is where the blind spot lies. The detached single-storey residence tends to fall under the exemption. A building classified in those groups requires, in the partition, double the REI-30 of the sheets read. That wall calls for its own solution and testing; the version of the IT currently in force should be confirmed with the CBMBA.
NR-18 (the Brazilian regulatory standard for construction safety) has items by system: 18.7.3 for carpentry and rebar, 18.7.4 for concrete structures, 18.7.5 for metal structures. Under 18.7.5.1, all assembly of a metal structure is the responsibility of a legally qualified professional, and the individual fall protection system (SPIQ) must be provided for in the PGR (risk management program) of the works.
In C&S Engenharia's reading, the structural LSF wall takes the site into the chapter on metal structures. Qualification follows: SENAI-SP offers the course "Builder of Light Steel Frame Buildings", of 160 hours, with no equivalent offering read in Bahia. The crew that assembles is part of the system, and the region must either train it or bring it in.
The schedule data comes from a study in Guarapuava, in Paraná, presented at CONTECC 2021 with SINAPI prices. The LSF residence took 58 days, against 96 for masonry: 39.6% less. The study concludes that the system, "despite being faster, is also more expensive"; since its monetary values have internal inconsistencies, only the direction is used here.
A 2017 work from UTFPR, in Campo Mourão, reached the opposite direction. Direct costs were R$ 39,265.32 for masonry and R$ 43,035.53 for LSF, 9.6% higher. With indirect costs, the totals reversed: R$ 47,304.69 against R$ 44,562.41, with LSF 5.80% cheaper. The authors point to indirect cost as the decisive factor.
Two studies from Paraná, opposite signs, none in Bahia. SINAPI, maintained by CAIXA with price surveys by IBGE, publishes compositions by state in monthly spreadsheets. It is in them, and in the budget of the case, that the regional calculation is made.
In C&S Engenharia's reading, the mechanism shows even without the number: LSF trades direct cost for schedule. It pays off when each week on site is expensive. In a short, lean project, the time gained has little to pay for.
| Criterion | Light Steel Frame | Masonry and concrete |
|---|---|---|
| Technical document | SiNAT Guideline 003 and the manufacturer's FAD or DATec; NBR 16970:2022 | No official data read |
| Assessed scope | Single-storey houses and townhouses; up to 2 storeys (DATec 049 A) | No official data read |
| Bioclimatic zone 7 | FAD 070 did not assess; FAD 072 assessed with defined roof and insulation | Zone guideline: heavy wall and roof; classification of each wall without official data read |
| Fire | REI-30 in testing (FADs 070 and 072) | IT 08/2016 adopts NBR 15200 and an annex for masonry; values without official data read |
| Aggressive environment | Industrial atmospheres excluded | No official data read |
| Later alteration | Structural walls cannot be altered (FAD 070) | No official data read |
| Safety during assembly | NR-18, item 18.7.5 | NR-18, items 18.7.3 and 18.7.4 |
| Schedule (Paraná, 2021) | 58 days | 96 days |
| When to indicate, in C&S Engenharia's reading | Project within the scope of the sheet, zone covered, schedule expensive | Zone 7 without a sheet, changeable use, short project |
The sheets read do not assess foundations, roofing, installations or frames, and the Guideline asks that these interfaces be considered. In C&S Engenharia's reading, the enclosure is a decision of coordination.
In the group, IncorpBuilding conducts turnkey development engineering. Its Integrated Design phase coordinates the disciplines in BIM and closes a detailed budget, and the verticalisation front brings together structure, enclosure, installations and finishes. It is at this point in a development that the choice between LSF and masonry is resolved with the data of the project.
The decision criterion fits in three questions. Does the valid sheet cover the zone, the size and the atmosphere of the development? Does each week saved pay for the difference in direct cost in the budget? Is there a qualified crew to assemble? With three positive answers, LSF enters the comparison. With one negative, masonry or concrete remains the baseline, and the next check is thermal performance under NBR 15575.
It can, with a condition. Barreiras is in bioclimatic zone 7 of NBR 15220-3, which recommends heavy walls and roof, a zone that FAD 070 did not assess. In C&S Engenharia's reading, use in housing depends on a valid sheet that covers the zone or on a performance demonstration under NBR 15575.
FADs 070 and 072 say that the walls "have the potential to meet" the design service life of 50 years. That potential depends on the right zinc for the atmosphere, on the interfaces, on the base and on maintenance. No document read compares this service life with that of concrete.
In FADs 070 and 072, the structural walls reached 30 minutes in testing, classification REI-30. In Bahia, IT 08/2016 of the Fire Department exempts several low and small buildings, but asks for 60 minutes in the partitions between autonomous units of some occupancy groups.
The studies read do not allow a claim. In Campo Mourão, in 2017, LSF had a direct cost 9.6% higher and a total 5.80% lower, because of indirect cost. In Guarapuava, in 2021, it was faster and more expensive. In MATOPIBA, the answer requires the SINAPI compositions for Bahia.
The documents read ask for a minimum thickness of 0.80 mm for studs and tracks and a Z275 coating, 275 g/m² over both faces, in rural and urban regions. In a marine atmosphere, up to 2,000 m from the shoreline, the requirement rises to Z350. Industrial atmospheres are outside the assessed scope.
By Raphael Schifino, CVO
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