Single-Family to Multifamily Home Conversions: The Hidden Monsters

As communities age and populations grow, community requirements for residential structures change. Many communities in the United States feature large old homes that have evolved from being a single-family home into a multifamily dwelling. These structures pose many hazards because of their unique and unpredictable nature. These base structures can often be an old colonial Queen Anne, a New Englander, or a traditional farmhouse. Many of these homes have been retrofitted and heavily modified. This air of mystery in their construction can be a major barrier in making fireground decisions.

Often, these structures go overlooked. They can be numerous and unnoticed in a residential response district. Because of the commonality of the structure, fire companies drive by them without a thought as to the concealed underlying structure. These structures have become our “hidden monsters” and must be given the respect they deserve. They offer many challenges that include identifying the location of units, building layout, legacy-turned-modern construction, multiple living spaces, and obscure utilities.

Identifying Multifamily Homes

One of the first barriers to fighting fires in a converted single-family home is identifying that multiple living spaces are present and then identifying the number of units. When a first-due fire company is faced with this challenge, the 360° size-up is key; it will allow the company to size up the building as well as estimate the number of units.

One way to identify the number of units is to count the number of electric meters on the sides of the building. Often, the number of electric meters directly correlates to the number of units within the dwelling. This “trick of the trade” is a good rule of thumb, but it’s not always accurate. A first-arriving officer/company must also remember that some larger converted homes might have one communal meter for shared spaces and exterior lighting. Separate meters may be allocated to utilities such as water heaters. Additionally, some renovators may choose to not individually charge electric because of the added cost to renovations.


Another item to watch for while conducting a 360° size-up is counting exterior entrances. Some smaller converted single-family to multifamily homes will have their entrances on the exterior of the building. Some second floor and above apartments will have exterior stairs and could have the interior stairs removed. A company could simply count the doors. The fire company must exercise a reasonable amount of suspicion because of the variability of interior located apartment entrances. A simple way for a renovator to split a dwelling is by floor, so many developers will have two units share the main entrance where the primary staircase is located.

A telltale sign of an apartment unit existing on a second or third floor is some variant of a fire escape. The fire escape could be a black steel metal escape, but often it will be made of wood and painted to match the exterior. These fire escape platforms are common in converted single-family to multifamily homes; this especially holds true in converted attic apartments where there is only a single set of accessing staircases.

During the 360° size-up, fire companies should always be aware of the possibility of illegal apartment spaces. In a converted single-family home, you may find illegal apartments in the basement. Look for signs of occupancy such as heavily used basement entrances, finished spaces, and out-of-place sleeping arrangements. Without proper situational awareness, you may overlook these spaces.

There are many different tricks and tips to conducting 360° size-ups on these heavily modified multifamily homes. It is imperative that first-arriving companies remain vigilant and attentive to details. When dealing with unpredictable multifamily structures, it is a tactical and strategic priority to identify the number of units within the structure. Often, these structures may go without a preplan and attention until an emergency arises in them. Use these tactics as pieces of the puzzle in completing your 360° size-up.

(1) From the A side of the structure, it is easy to assume that the residence is a single-family home. With a proper 360° size-up, you can identify the presence of a multifamily dwelling. (Photos by author.)

Building Layout

In heavily modified multifamily homes, the building layout can become quite cumbersome for a fire company to envision; this is especially true when operating in a low-visibility, immediately dangerous to life or health (IDLH) environment. The fire company must take some extra steps to maintain orientation. Unit or apartment layout in this style of structure can vary in size and shape, but it is generally small with a limited number of rooms. It can be very common to find the entry room as a kitchen space that stretches into a family space. Finding common trends in your response district can help you look for clues when operating inside the structure.

One of the most terrifying aspects to these buildings is how some builders may choose to cut up the living spaces. Hallways and stairwells to “nowhere” can be found in individual units. Some rooms may have a strange shape or hidden spaces. It can be difficult to identify these variables from the exterior of a structure. Use regular communication to incident command so everyone on the fireground will be aware of any deadly obscurities.

In addition, many of these structures will use every inch for livable space. Attics may be converted into a livable space and can pose many challenges. Attic apartments often have knee walls and difficult-to-use stairwells. Tight, small, or exterior staircases can make multiple company operations difficult and dangerous. Hoselines quickly steal real estate on staircases that may not be designed to handle the traffic load of aggressively operating firefighters. Officers and safety officers on the fireground should monitor egress points and staircases to ensure they do not become congested.

In the fight for more space, basements may also be converted into livable spaces. The dangers of basement fires only multiply when you compound a belowgrade fire with heavily divided living spaces. Just as in all basement fires, crews need to show a great deal of respect toward these highly hazardous fires. The added confusion of a renovated layout can lead to a difficult-to-find fire with few egresses for firefighter evacuation.

A hazard in any multifamily building is the possibility of “cage” storage in the basement or attic. It is common to find that units will be allotted an amount of storage within a defined area. A typical image for this layout is chicken wire fencing with a simple studded wall creating walk-in cages. These spaces become a complete hazard zone for a fire company with an extremely unpredictable fire load. In any given unit storage space, you can find anything imaginable. Some contents might be unpermitted items such as motorcycles and gas cans. Some residences will become creative in their pursuit of privacy by covering their wired walls with flammable materials like paper or sheets.

When you are deploying and stretching hoselines, challenging building layouts will continue to pose difficulties. It is uncommon to be able to access every apartment space from the front door of the structure. Fire companies may have to scout ahead and find the best entrance to make the attack. When encountering strange floor plans, fire companies cannot become “moths to the flame” and misuse precious time redeploying handlines a second or third time. Taking an extra minute to decide the best course for the attack can ultimately save time in getting water on the fire. When an interior attack is taking place on the second floor or above, consider dedicating a hoseline to protecting stairwell egresses.

Ultimately, firefighters operating on the fireground must remember the basics. Sticking to rudimentary skills such as a right- or left-handed searches, following hoselines, searching with a tether line, regular radio communications, and using thermal imaging cameras can help you stay oriented in such a confusing structure.

Luckily, these structures have a small to medium footprint, making exterior walls and windows easier to find for firefighter rescue or bailout. Firefighters should always question where their nearest egress is located.

Legacy-Turned-Modern Construction

Old homes that have been renovated can become quite unpredictable regarding the expected era of construction. Put simply, an older or a legacy home is where a firefighter can expect small rooms, slower-burning structural members, the possibility of a balloon-frame structure, organically manufactured contents, and a plethora of void spaces for the fire to hide. As an older single-family home is renovated into a multifamily home, new material and modern building concepts are introduced. The overall fire behavior drastically changes as rooms become bigger with open concepts, new materials are used as furnishings, and lightweight building methods are used.

There are many tricks to identifying older and balloon-frame homes, such as looking for stacked narrow windows, old stone or brick foundations, and the general age impression of the structure. Unfortunately, these tricks do not always hold true in a renovated structure. Adding larger windows and new siding and maintenance upkeep can mask the age of a structure. Knowing the first-due district can help prepare a fire company on what to expect while operating in older homes.

Once a company has begun to operate inside the structure, features within the home can give clues to the structure’s estimated age. Knob and tube wiring; old, braided wiring; lath and plaster; and exposed timbers are clues to help a fire company identify older structures. Additionally, when working in older residential districts, assume a balloon frame is present until proven otherwise.

While operating inside these heavily modified structures, remember that the original structure was not engineered to support multiple occupancies. This means that the building will be more susceptible to structural compromises with the added weight within the structure. This can be especially true when dealing with attached barns or garages that have been renovated into new units. Companies will need to remain vigilant as fire, water weight, and other fireground operations damage the structural members.

Sometimes, the change from legacy to modern will not be in the original structure but rather within an addition. Many older homes that are not big enough to support more than one to two units will have additions built to supplement the desired living space. It can be an added technical challenge to fight a fire in a balloon-frame building while simultaneously fighting fire in modern lightweight construction in the addition.

Fire companies can often identify the location of additions from the exterior of the structure during a 360° size-up. In many cases, the addition will have a different ridge line level, a break in the siding, a different color or style of siding, and separate foundations. Where a change in the ridge line exists, it can be common to see the new and old roofs overlap. This newly formed void space is difficult to access from the inside of the structure and can act as a reservoir to carbon monoxide (CO) and other fire gases.

Firefighters should be aware of when construction type changes within the structure. It is imperative for any firefighter to be well-versed in the differences in fire behavior between modern and legacy structures.

Multiple Living Spaces

With multiple occupancies come multiple responsibilities for the firefighters on the fireground. It is a strategic priority to search for, remove, and deny entry to residents of the building. If a fire is perceived to be isolated to a single unit, additional fire companies must be sent to the above and adjacent units to check for extension. Fires in multifamily homes quickly become labor intensive when keeping the fire to the apartment of origin. When required, an incident commander should call for additional resources as soon as possible.

(2) From the B side of the structure, fire companies can identify three separate living spaces.

Just as in any multifamily structure, fire companies on scene must be on the lookout for obscure hazardous building contents. Because the occupying families are limited in available room, they are forced to store unpermitted items within their living space. Items like bicycles, motorcycles, snowblowers, lawn equipment, gasoline, propane cylinders, and other nontraditional items can all be tucked away inside the occupancy. In a converted structure, it is not unusual to find that occupants use hot plates and liquid propane burners to cook. Fire companies need to remain situationally aware and mitigate hazards as they are found.

Members of a fire company should be prepared to deal with a wide variety of demographics in these structures. Sometimes, the structure may be home to a large family, off-campus housing for a local school, or a family who speaks English as a second language. In many cultures, it is common for families to prefer to live as a multigenerational household. These examples showcase how a small footprint of a structure can easily become overoccupied.

Often, incidents will affect other units in the building. A fire company must understand its responsibility to ensure all units are safe from the hazards. Something as simple as a CO alarm activation can quickly become labor intensive because the other units in the building should also be monitored. Just as fire can travel through the various void spaces, so too can gases and smoke.


When plumbing and electricity need to be brought to places where they were originally not needed, the builders were forced to be creative in their renovations. Void spaces are created to run utilities, creating chaseways for the fire to run. When converting a new apartment, bathrooms and kitchens are placed in awkward-fitting rooms, forcing the renovator to use spaces wisely. What was once a closet may be transformed into a restroom and an old bedroom may now be a kitchen.

Just as in some older homes, the dwelling will have been retrofitted for heat as technology becomes available. Sometimes, this means that there will be multiple furnaces, oil and gas tanks, and electrical panels. When dealing with CO and nonIDLH incidents, it can force a fire company to use problem-solving abilities to handle the incident. The original structure may have traditionally located utilities, while the new addition will have separate utility spaces.

Individual units will not always have separate utilities. It is common for a renovator to have the entire building share one heating or electrical source. Fire companies should be cautious when shutting down utilities, as doing so may affect multiple units.

The once single-family turned multifamily building poses many hazards and has become many departments’ hidden monster. It is vital that fire companies identify and discuss these structures. Sometimes, this can be addressed with something as simple as a coffee table discussion, incident visualization, reading an article, or listening to a story told by a senior firefighter. Learning your response district’s building construction is key to successful fireground operations. Before your next incident inside one of these structures, take the time to think and preplan as a crew.

WILLIAM THALHEIMER is a firefighter/AEMT with the Derry (NH) Fire Department. He has a degree in fire science, is an Everyone Goes Home advocate with the National Fallen Firefighters Foundation, and is a New Hampshire state fire instructor.

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