Modular construction has experienced a boom due to increased worldwide demand for flexible and quality housing. With urban areas getting more congested and the necessity for rapid deployment increasing, modular integrated house solutions provide a way forward. This type of buildings not only means of short-term relocation, but they are an advanced combination of engineering and efficiency. This article discusses the technical benchmark and performance standards that characterize the modern prefab industry.
Fig. 1: A Two-Story Modular Container House Configuration Demonstrating Standardized Dimensions and Stackable Structural Design
I have written this article and I am the Senior Civil Engineer at ZN House. With over 10 years of experience in modular steel design and sustainable architecture, I have overseen the development of numerous high-performance fast-assembled box units. My work focuses on ensuring that every structure we produce exceeds national safety and durability standards through rigorous testing and innovative material application. I was part of the engineering team involved in the Qatar World Cup Fan Village project in 2022.
Structural safety is the foremost concern when assessing modular structures. Several recent inspections carried out with the help of MIDAS/Gen finite element software have confirmed that the Q235 steel frames in modular units are structurally robust. The units are built to resist very high vertical as well as horizontal loads, which means that they can be used in any climate.
Structural performance assessments are conducted using finite element modeling aligned with load assumptions defined in GB 50009 (Load Code for the Design of Building Structures). Simulation boundary conditions reflect modular unit anchoring and transport configurations. Results are used for internal design verification and are cross-checked against code-based load combinations rather than serving as standalone certification. Structural frame design considers lateral loads in accordance with GB 50009:2012, Section 6.3.2. Finite element analysis using MIDAS/Gen modeled lateral, vertical, and wind loads. Boundary conditions and material properties follow Q235 steel specifications and GB 50009 load combinations. Material classifications and component tests are verified per GB 8624 and GB/T 7106; project-specific certification may vary by local jurisdiction.
The infographic image below gives a summary of loading capacities for a standard 5950 × 3000 × 2800 mm unit:
Fig. 2: Visualization of the Allowable Vertical and Horizontal Load Limits Verified Through Structural Analysis.
The fire performance of building materials for modular integrated house solutions is determined by the standard GB 8624 Classification for Burning Behavior of Building Materials and Products. Structural sandwich panels incorporate cores made of non-combustible materials with an A1 fire rating. Fire classification is only concerned with the behavior of materials when exposed to fire and is not a complete fire resistance rating of the building.
| Load Category | Design Value | Reference Standard | Technical Definition |
| Dead Load (Gk) | 1.2 kN/m2 | ISO 2394 | The permanent weight of the steel frame, ALC panels, and internal finishes. |
| Live Load (Qk) | 2.5 kN/m2 | EN 1991-1-1 | Temporary loads including occupants, furniture, and movable equipment. |
| Snow Load (Sk) | 1.0 kPa | ASCE 7-22 | Accumulated weight of snow on the roof, calculated for 50-year return periods. |
| Wind Load (Wk) | 0.6 kPa | GB 50009 | Lateral and uplift forces exerted by wind speeds up to 120km/h. |
One of the common misunderstandings about the safety standards of prefab container houses is that they do not have the same level of comfort as traditional buildings. Nevertheless, current production of such houses is subjected to very rigorous testing of how they are environmentally resistant.
Apart from the outdoor water test, thermal and sound insulation are also essential aspects to ensure the indoor environment’s comfort. The housing components are chosen carefully, taking into account the impact of wind resistance. A rock wool panel with a thickness of 75 mm is capable of withstanding a wind pressure of 0.6 kPa without harm. Furthermore, noise tests showed a 14.9 dB reduction, thus lowering indoor noise to a comfortable level.
The wind load resistance of the structural frame and envelope is determined as per the provisions of GB 50009 – Load Code for the Design of Building Structures, and the verification of panel wind pressure is carried out based on the results corresponding to that structural frame. This makes certain that the specified wind pressure limit is in line with the requirements for structural design that have been established, rather than being just a lab result.
According to the Modular Building Institute, such energy-efficient insulation also has the potential to cut energy usage by as much as 20% when compared to traditional on-site construction.
| Feature | Test Parameter | Result |
| Waterproofing | 1.8 tons of water (30 mins) | No leakage |
| Wind Resistance | 75 mm Rock Wool Panel | Safe up to 0.6 kPa |
| Sound Insulation | Outdoor noise: 64.5 dB | 14.9 dB reduction |
| Air Quality | Formaldehyde & TVOC | Met GB 550162021 |
Table 1: The Key Environmental Performance Tests Conducted on a Standard Modular Container Unit.
We believe that the house defines the environment in which your health is maintained. With professional assistance, each unit within our Modular Integrated House Solutions is subjected to a series of tests to determine the air quality in accordance with the national standards, such as GB 55016-2021. Test samples taken from the apartments are checked not only for general air quality but also specifically for harmful substances such as Formaldehyde, Ammonia, Benzene, and TVOCs so that the safety of the occupants can be guaranteed.
Besides air quality, indoor illuminance is also measured so that the resulting space is not only adequately illuminated but also energy-efficient. Thus, by helping modular structural steel buildings to be more eco-friendly, efficient, and at the same time comply with safety regulations, we create living spaces for the long term. Quality indoor lighting and air are no longer a luxury; they are basic features of contemporary modular design.
Fig. 3: On-Site Air Quality and Illuminance Testing Conducted to Verify Compliance with Gb 55016-2021 And Gb 55015-2021.
| Feature | Standard/Limit | Performance Benchmark |
| Formaldehyde | GB 55016-2021 | Safe for occupancy |
| TVOC | GB 55016-2021 | Safe for occupancy |
| Indoor Illuminance | GB 55015-2021 | Energy-efficient & compliant |
| Sound Insulation | Typical Modular Expectation | 14.9 dB Reduction |
Table 2: The Measured Indoor Environmental Parameters and Their Compliance with National Health Standards.
The adaptability of high-performance, quickly assembled box units can be best appreciated through multi-unit stacking. For two-story models, in order to be safe, the building must comply with certain serviceability requirements for deflection and stress in its structure. According to the graph, the main beam vertical deflection max is only 14 mm, which is remarkably lower than the permitted 23 mm. This 14mm deflection is 40% below the safety threshold, ensuring that the second floor remains vibration-free even under heavy furniture loads
This level of structural stiffness is brought about by using high-grade materials, for instance, Q235 steel, which has a tensile strength of 428-450 MPa. These features make it possible for the support to have a maximum reaction of 25 kN vertically, thus, proving a firm base for the second floor. The stacked units, which are perfectly in line with national safety regulations, maintain structural stability if joint connection stiffness is thoroughly guaranteed.
Fig. 4: Beam Deflection and Reaction Force Data for a Multi-Story Modular House Stacked Configuration Under Serviceability Load Conditions.
Example Standards Summary:
| Parameter | Standard Reference |
| Structural Loads | GB 50009 (China) / Local Equivalent |
| Wind Pressure | GB 50009 Wind Load Provisions |
| Indoor Air Quality | GB 55016-2021 |
| Illuminance | GB 55015-2021 |
| Fire Classification | GB 8624 |
Case Study 1: Remote Workforce Housing, Australia
Location: Pilbara Region, Western Australia
Time: June 2023
The Problem: The client wanted a strong two-story residential complex that would be large enough to accommodate a mining crew in an area known for extreme environmental stress. They had to face the severe heat that goes beyond 40°C and the high-velocity wind gusts that occur quite frequently, any of which, if allowed, can lead to structurally unstable buildings. They were also told that conventional housing would be extremely slow to build. On the other hand, the typical modular units generally do not help with the specific requirements of the wind load and thermal comfort that are essential for keeping the workers at a mining site for a long time.
The Solution: I was in charge of the engineering team that installed several stacked high-performance, fast-assembled box units. We used 75 mm rock wool panels to resist a wind load of 0.65 kPa. The panels were the main element of the wind load resistance system. I was directly involved in the reinforcement of the joint connection stiffness to keep the horizontal drift at 16 mm, which is still significantly below the 18 mm limit. To be able to endure the monsoon rains, we put a dual-layer roofing system, which was able to pass our 1.8-ton water spray test. Even during the most severe weather conditions, the units were cool and kept their structural integrity, as stated by Mark Henderson.
Testimonial: “While planning a remote location in Western Australia, our main worry was whether a modular construction could really be resistant enough to the Pilbara’s wind loads. I was in contact with ZN House through the process, and you could see their great level of technical skills from the very first day. They went beyond just offering us a product. They gave us a structural analysis, supported by MIDAS/Gen software, that showed these units were able to take vertical loads of 1.2 kPa and the horizontal stress of our area. The two-story layout they designed has totally changed our team’s safety and comfort.”
— Mark Henderson, Project Manager at Rio Tinto
Case Study 2: Emergency Medical Clinic, Southeast Asia
Location: Jakarta, Indonesia
Time: November 2022
The Problem: After a massive flood, the local healthcare system was completely overwhelmed, and there was an urgent need for an additional clinical area. The new space had to be ready for use within a few weeks. Besides that, it was very important to provide a sterile and safe environment for the patients. The combination of high humidity and flood damage left the building very vulnerable to the development of mold and poor indoor air quality, while the constant showers made the building additionally susceptible to water leakage.
The Solution: I spearheaded the implementation of several Modular Integrated House Solutions using sustainable modular steel structures at a breakneck pace. As a foremost priority for patient well-being, we performed thorough air quality tests that confirmed the facilities were Ammonia, Benzene, and free of TVOC and complied with the GB 55016-2021 standard requirements. Facing the threat of the heavy rains characteristic of Indonesia, we relied on our pressure-tested wall systems (230 kPa for 5 minutes, water pressure test) to guarantee an interior that is perfectly dry. Additionally, in doctors’ workspaces that are highly visible yet at very low energy cost, we have fulfilled the indoor illuminance requirements according to GB 55015-2021. Dr. Aminah commended the clinic for delivering an environmentally friendly, clinical-grade facility in the shortest possible time.
Testimonial: “During disaster relief efforts, generally, one has to compromise either on the speed or the quality of the assistance. Nevertheless, the modular solutions from ZN House showcased that it is possible to get both at the same time. The lead engineer from the ZN House came to oversee the installation of our clinic and ensure that every unit complied with the GB 55016-2021 air quality standards for TVOCs and formaldehyde. The units stayed totally dry even at the height of the monsoon, mainly due to their intensive 1.8-ton roof spray testing that was incredibly effective. It is quite unusual for a company to be so devoted to the health and safety of the people living in their homes.”
— Dr. Siti Aminah, Director at 3Star Health Relief Foundation
To learn more about Shipping Container House, visit our product page here.
The modular integrated house solutions have demonstrated that they are a safe, efficient, and environmentally friendly option for building when compared to traditional methods. Through rigorous material testing and structural analysis, these units are able to deliver safety and reliability for housing and commercial premises. Whether using a single unit or a double-story configuration, with all emphasis placed on quality, safety, and performance.
For those looking to implement high-performance modular units in their next project, ZN House offers expert guidance and industry-leading manufacturing standards. Our structural integrity tests were conducted in September 14, 2022 following the GB/T 50017-2017 standard by MCC Inspection and Certification Co., Ltd.
Are modular homes safe enough for extreme weather?
Yes, high-grade modular units are engineered to be highly resistant to even harsh weather conditions. For instance, they undergo tests to ensure that the roof can take a weight of 1.0 kPa and the walls can resist wind pressures of up to 0.6 kPa while using 75 mm rock wool panels. Also, their frame structures are tested for a water pressure of 230 kPa to ensure no water penetration during heavy storms. Sound insulation tested according to ASTM E90 or ISO 10140-2 protocols.
Do modular houses have poor air quality or toxic materials?
Modern modular construction is done in compliance with very tight safety regulations to ensure healthy air. Different pollutants, such as formaldehyde, benzene, and ammonia, are tested in the units to make sure they comply with the GB 55016-2021 national standard. This way, the indoor environment is safe for people to live in the long run.
Can you build multiple stories with modular box units?
Modular units can be stacked safely up to a height of two-story configurations. Structural analysis results reveal that these models are able to meet the safety requirements with a main beam vertical deflection of only 14 mm (which is significantly below the 23 mm limit) and a horizontal column drift of 16 mm (which is less than the 18 mm limit), if the joint connections are adequately stiffened.
Disclaimer
This content is for informational purposes only and does not represent a formal site-specific engineering guarantee. For project-specific questions, you may want to consult a qualified technical representative at ZN House.
SAFETY & COMPLIANCE NOTICE
Foundation & Soil Disclaimer: Structural performance depends on local soil conditions and foundation type. Always consult a local licensed engineer before installation.
Site-Specific Loads: Wind pressure resistance (e.g., 0.6 kPa) and seismic resilience are theoretical maximums. Site-specific engineering (PE stamp) is required for final permitting.
Watch the following video of a coffee house made from standard shipping container:
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