Nepal is globally known for its earthquake risk. Located where the Indian and Eurasian tectonic plates collide, Nepal has experienced some of the most devastating earthquakes in history, including the 2015 Gorkha earthquake. These earthquakes have exposed widespread weaknesses in the country's construction practices, from weak brick-stone structures to irregular building designs.

Recognizing these risks, the Government of Nepal recently revised its National Seismic Design Code (NBC 105:2020), which increased the standards for seismic safety in new buildings. But, while earthquake preparedness is given so much importance, another silent but equally dangerous risk is often overlooked. That is fire. 

Fire incidents occur with alarming frequency in Nepal, especially in dense urban settlements, industrial areas and rural areas where narrow streets, combustible materials and limited firefighting capabilities increase the risk. Unlike sudden and infrequent earthquakes, fires are recurring events that cause immediate destruction, long-term displacement, and economic loss.

From residential fires in major cities of the country including Kathmandu Valley to industrial fires in godowns and the recent events after the Gen-G movement, not only how weak our buildings are, but also how unprepared we are to assess and repair fire-damaged structures. 

One of the biggest challenges after a fire is knowing whether a damaged building is safe to re-enter. Families, business owners, local officials and even government offices are often left uncertain, delaying recovery and putting lives at risk.

In such cases, engineers rely on a systematic process called Rapid Visual Damage Assessment (RVDA), a first-line assessment method designed to provide a quick but structured decision about a building's condition. The RVDA process begins with ensuring the safety of the inspection team and the surrounding environment. Before entering, the inspector confirms that the fire is completely extinguished and that no smoky material or re-ignition hazard remains. 

Electricity, gas and fuel supplies should be cut off and protective equipment such as helmets, gloves and boots should be used. Entrances to buildings are carefully screened to avoid unstable debris, falling glass or cracked surfaces that could collapse without warning. Only after the site is secured can the inspector proceed with structural assessment. Once inside the

, engineers focus on mapping the entire pattern of the fire. Burn marks and melted or blistered finish provide valuable clues as to which part of the building experienced the most heat. In such cases, firefighting efforts can create additional damage, such as freezing water weakening the foundation or chemicals released from the foam affecting the rebar. 

These initial observations help determine the most important areas for detailed inspection. Evaluation of the structural component then begins. In the foundation, inspectors look for signs of subsidence, visible cracks in the plinth, or sagging caused by heat and water.

pillars and vertical or horizontal cracks in the wall are checked for visible iron rods within the concrete. Wood parts are evaluated by measuring the depth of the burn, which is directly related to their residual strength. Bending, shear cracking and slab punching are recorded in beams and slabs, while roofs and trusses are inspected for partial or complete collapse. 

connections and joints are equally important, as at beam–pillar junctions, weld cracks or bolt breakage can seriously affect structural stability. RVDA relies heavily on visual assessment and is often more detailed than the general public imagines. Inspectors carefully observe the color of the concrete, which is a reliable indicator of the temperature it has endured. As

, gray color of concrete indicates temperature around 300 degree Celsius while pink or red color indicates exposure above 600 degree Celsius. Similarly, white-brown or buff shade indicates that the concrete may have reached as high as 900-1000 degrees Celsius. Such differences are very important, because they help to determine whether the concrete has only lost surface strength or whether its structural core has also been damaged. 

cracks are evaluated not only by how wide they are, but also by the direction in which they are seen. Straight (vertical) cracks usually indicate stress or pressure damage, while horizontal or cutting cracks indicate the effects of excessive loads during a fire. A straight-edge or laser device is sometimes used to determine how much a beam or slab is bent, which makes it easier to compare with an initially straight condition.

When the concrete cracks and the rebar is exposed, inspectors check to see if it has oxidized, bent, or lost its adhesion to the concrete. Small details visible on the surface are also taken into account, such as small lines like cracks, rock outcroppings or concrete surface shine. All these give an indication of the degree to which the heat of the fire has weakened the concrete. These little signs that seem like normal from the outside of a

are actually very important. Based on these, an experienced inspector can quickly distinguish which parts of the building are slightly, moderately, or heavily damaged. When it reaches about 3-400 degrees Celsius, concrete starts to weaken gradually and above 5-600 degrees Celsius, its cement paste and aggregates start to decompose. 

Above 400 degrees Celsius, steel begins to lose its strength and above 600 degrees Celsius, its load bearing capacity drops dramatically. For all these reasons, a fire-damaged building may appear stable but may actually be very weak. 

Fire inspection also examines non-structural components and life-safety elements. Walls, stairs and evacuation routes are checked for obstructions or collapses. Important systems such as alarms, sprinklers and hydrants are commonly destroyed, electrical wires are melted and gas lines are damaged.

This reduces not only the immediate security of the building, but also its ability to withstand future threats. All results obtained from RVDA are recorded in a sequential manner. Inspectors also take scale photographs of damaged parts, measure the width and inclination of cracks, and map the damage on a floor plan. Based on these observations the building is tagged as safe (green), restricted (yellow) or unsafe (red). 

RVDA can not only confirm the structural capacity of a building, it provides the necessary first step for decision-making and guides the need for further testing. In addition to rapid assessment, field and laboratory tests are important to understand the residual strength of a fire-damaged building.

In those areas, simple nondestructive tests such as the Schmidt hammer rebound test and ultrasonic pulse velocity are widely used to estimate surface hardness and detect internal cracking. A ferro-scanner shows the thickness of the concrete around the steel and a carbonation test with a phenolphthalein solution shows chemical changes. A core sample is extracted and sent to a laboratory for more accurate evaluation. There a compressive strength test confirms the strength of the remaining concrete. 

Chemical analysis of chlorides and sulfates, use of microscopes, heart-bath diffraction and differential thermal analysis are used to understand the microstructure and mineral changes of concrete. Where repair is possible, modern retrofitting techniques offer a promising solution. One of the most effective materials is carbon fiber reinforced polymer, which can be wrapped around weak pillars, beams and slabs.

Carbon fiber is extremely strong, lightweight, corrosion resistant and easy to apply. Steel jacketing adds bulk to the structure but carbon fiber provides strength without adding extra weight. Combined with high-strength repair mortars, BERNA can restore or improve the original load-bearing capacity of a fire-damaged building. It is also particularly suitable for the current situation in Nepal, where a rapid, cost-effective solution is needed to rehabilitate a large number of vulnerable structures. 

Finally, fire is not a rare threat but a frequent and predictable threat in Nepal's cities and villages. The lesson we must learn from recent fires is that without systematic assessment and modern retrofitting, buildings remain unsafe, lives are at risk and economic recovery is delayed.