Restore or Replace? How Professionals Determine What Can Be Saved After a Building Fire
After a fire, property owners should inventory what was clearly undamaged and what only appeared to be undamaged. The cost for the repair and replacement of the latter is often frighteningly high, and it is not always obvious during a cursory inspection with a flashlight.
What fire does to the building
While property owners are often focused on the visible aftermath of a fire, specialists are concerned with its less obvious effects. For example, the combination of high temperatures and temperature gradients typical of a fire renders structural wood, brick, and concrete buildings unusable due to the formation of cracks invisible to the naked eye, increased porosity, torsion of frame structures, and the delamination of materials due to the differential expansion of different materials. All this can be checked by tapping and touching the walls and surfaces. However, many of these effects are not visible to the naked eye, so non-obvious tests are needed.
Structural wood: charring and pyrolysis
When the wood frame building was subjected to fire, a char layer was formed on the surface of the timber. Charred wood can actually be protective because it insulates the interior of the beam from further combustion. The question is how thick this layer is in relation to the cross-section of the beam.
The generally accepted rule of thumb is that if the char depth does not exceed ten percent of the beam diameter or width, the framing can be saved. Charring is removed, the wood is subjected to a bearing capacity test, and then the surface is profiled and sealed with a suitable encapsulation composition. The latter is a special sealant with a consistent molecular structure that traps the remaining gases from the fire inside the wood.
Meanwhile, wood can be subjected to pyrolysis, which is the decomposition of the material under the influence of high temperatures without burning. A beam subjected to prolonged heat without direct burning, for example, next to the flame, can have a pyrolysis front develop inside. Such a beam may well look completely healthy and be able to withstand the load, but the internal structure will no longer be able to withstand the stress. To check for pyrolysis, the beam must be probed, and not just looked at, which is why pyrolysis is a structural integrity issue even if the framing is not charred.
Thermal shock and the foundation you can’t see
During a fire, fire fighters may use large amounts of water, which leads to thermal shock of masonry and concrete. In other words, materials that have been heated to a high temperature are cooled down too quickly, leading to cracking. Sometimes these cracks are visible, but they are more often not obvious signs of potential structural problems. Thus, the thermal expansion and contraction of concrete can cause cracking in the foundation or partitions, leading to a loss of load-bearing capacity and requiring rebuilding.
For example, a chimney made of concrete can look healthy but be shattered on the inside and pose a serious risk if it continues to be used. The same goes for concrete blocks in the foundation walls and concrete slabs in the floor of the house. However, these problems can only be identified by a visual and instrumental inspection, and some tests are destructive. A sounding mallet can help identify hidden cracks, but such manipulations can spoil the surface of the partition or wall to such an extent that it becomes difficult to distinguish between cracks caused by fire and cracks caused by rapid cooling from water used by fire fighters.
Therefore, one of the tasks of specialists who study the consequences of a fire for the building’s structures is to examine not only the visible signs of destruction but also to consider the thermal effects: what materials were subjected to high temperatures, what materials lost strength due to thermal stress, and where cracking could have occurred.
The chemistry of time: why the clock is ticking
Soot is not just soot. Depending on the materials that were burned, soot has different effects on the materials of the building and its contents. Organic materials such as wood and paper produce dry soot, which is relatively easy to remove from surfaces, fabrics, and interiors. At the same time, synthetic polymers typical of modern furniture, building materials, and insulation produce a wet, sticky soot that adheres very tightly to surfaces. In addition, the incineration of plastics can produce hydrogen chloride gas, which combines with fire by-products to form hydrochloric acid gas, which in turn coats everything it touches. Burning electrical appliances can produce corrosive gases and acidic residues.
According to the IICRC standard for fire and smoke restoration S540, there are specific alkaline and enzymatic solutions for removing various types of soot. In addition to cleaning procedures, the chemical interaction of the cleaning fluid with the substrate is also important. Neutralization and removal of the consequences of a fire are an essential procedure because different types of fire affect interior materials and objects in different ways. If a kitchen fire occurs, protein soot will be found, which requires special care when removing. But if a fire breaks out in an electrical appliance, the consequences of the thermal and chemical action of the fire plume will have to be minimized.
Most often, the clock is ticking for property owners during the time between the fire and calling in experts. Property owners comparing options for the best fire damage restoration company in NYC should ask how the provider assesses structural, smoke, soot, water, and contents damage. If the fire is large and occurs in a multi-story building with many electrical appliances, the intervention of specialized restoration services in the first 24-48 hours is crucial. First, because the consequences of the corrosive and acidic effects of soot will be long-term if they are not dealt with in time. Second, because it is in these 48 hours that all of the chemical effects of the fire can be identified and the necessary measures selected to deal with them. For example, in accordance with the IICRC S540 standard, the selection of neutralizing fluids depends on the type of soot found.
The hidden water and the clock of mold
One thing that property owners often do not take into account when managing fire restoration on their own is mapping the distribution of moist areas. In other words, even if the building appears dry to the eye, water that has infiltrated into the walls, partitions, and subfloor may linger inside for a long time. This is where the clock of mold starts, since its development begins within 24-48 hours after a fire.
Infrared cameras and moisture meters are needed to combat this clock. The former allows for identifying problem spots and estimating the extent of the damage by analyzing temperature variations on the surface of the walls and ceiling. The latter determines the level of moisture in the walls and partitions in percentages. The failure to take these measures means that in a couple of months, the owner will have to deal with mold damage in the walls, which is much more expensive and time-consuming than preventing it.
HVAC: trapping or spreading contaminants
During a fire, the HVAC air ducts act as a distributing unit for fire products and, after the fire, as a distributing unit for the same products. Therefore, when restoring the air ducts, it is necessary to take into account not only the materials with which they are made but also the methods of cleaning and their feasibility. For example, flexible plastic or metal ducts typical of residential buildings usually have a rough surface on the inside, which means that they have areas where soot and fire particles adhere. Such ducts cannot be cleaned effectively, which means that their removal is necessary.
Meanwhile, metal ducts can be cleaned by mechanical means several times, and their thermal resistance and stiffness can be restored by specially selected chemical solutions. In other words, the decision to save or remove the ducts is made taking into account the technology of restoration. Metal ducts are definitely not removed by default as flex ducts are.
The question of the contents of the building beyond the air ducts is also relevant, since there is a good chance that the air conditioner has spread particles of soot and smoke throughout the building, including those not affected by the fire. It is necessary to study these materials in detail and, if necessary, remove them, even if they appeared to be undamaged.
Drywall versus plaster: two different stories
In the case of modern constructions using gypsum plasterboard, the story usually ends with its complete removal. The reason is that its porous structure allows the absorption of both moisture and the products of combustion, which subsequently translates into a long-term emission of odor from the walls. Moreover, the release of harmful gases from the paper web is also possible. Even if the drywall was not damaged, its removal is more cost-effective compared to its cleaning.
Meanwhile, historic buildings with a plaster-lath system may allow the problem to be solved without losing a unique material. In principle, plaster is similar in structure to gypsum plasterboard, but it lacks paper, and its porosity is significantly lower. Therefore, if the plaster is not crumbling, and the lath is not charred, it is possible to clean and profile such a finish. This is an option worth considering when restoring old buildings, since the cost and time of removing and re-profiling the lath is much higher than the benefit.
However, this does not mean that plaster is being saved in all cases: the tapping method will show if the bond between the lath and the plaster has failed, which means that it is no longer possible to save. There may be localized areas of delamination, which will be revealed by the absence of sound when tapped on the surface. The same goes for cracks, which are also hidden behind the plaster.
Why painting over the smoke will not help
It is a frequent problem in fire insurance and restoration claims that the client or even a general contractor repaints the drywall after a fire using standard latex interior paint. Latex paints provide a quick solution to the problem of smoke odors and staining, but they are ineffective because they do not trap the scent and smoke of the fire. As a result, if the drywall was treated with only a basic cleaning, the odor will return within a few weeks, and the wall stains will soon begin to reappear. No matter how many times the walls are painted, standard latex paint will not stop the migration of the fire’s scent and soot through the wall’s surface.
Painting over is a viable option if the right materials are selected. In order to exclude the possibility of the smell and the visible signs of the fire from appearing on the painted walls, it is necessary to apply a shellac or oil primer after the chemical cleaning of the walls. The shellac primer seals the wood, preventing the smell and soot from getting out. Such primers are different from the traditional ones available in the hardware store: they must be selected with the help of a specialist and are used after a thorough chemical cleaning of the surface.
The contents decision: restore or replace?
The assessment of the contents in the context of restoration and insurance costs is a purely fiscal one. The cost of restoring an object using the available technologies is being compared with its market value. The replacement of the artifact is indicated if restoring it is not economically justified. For example, with items worth around a hundred dollars, there is no point in removing the soot, while with a thousand-dollar piece of furniture, this procedure may be fully justified.
The decision to remove or save depends on the nature of the damage: ultrasonic cleaning of jewelry or hard-to-clean objects with an immersion water jet in an ultrasonic cleaner may be cost-effective. At the same time, electronics subjected to the action of fire gases and heat can only be replaced because saving them does not eliminate the consequences of the fire on their performance. Clothing and upholstered furniture are somewhat in between: their salvage can be justified for sentimental reasons and high value. However, even the most thorough cleaning will not eliminate the possibility of odor from the fire, so such items continue to be a potential source of problems in the future.
The forensic approach to evaluating fire damage is not a theoretical exercise but rather a practical consideration of how to avoid unnecessary costs. The damage that may seem more severe may actually be easily restored. On the contrary, the damage that seems minor may be hidden, but it will cause serious expenses in the future. All of this must be taken into account no later than the first 48 hours after the fire in order to have a realistic idea of future costs.
