What Is a Demising Wall?

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  • Written By: Mary McMahon
  • Edited By: Nancy Fann-Im
  • Last Modified Date: 28 January 2020
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A demising wall is a wall that separates spaces belonging to different tenants, as well as separating private tenant areas from common areas. Such walls may be treated separately in the building code to address concerns about energy efficiency, noise pollution, and tenant safety. A simple example of a demising wall can be found in an apartment complex, where the shared wall between two apartments represents a separation between areas that belong to separate tenants.

In some regions, the building code may require insulation in a demising wall, for a number of reasons. Insulation can keep down noise and minimize complaints about noise from shared walls. In addition, it can increase energy efficiency. Each tenant can control the temperature and other conditions in his own space, without worrying about paying for conditioning in the neighboring space. This can also be important when a demising wall separates an unusually hot or cold area from another region, like a shared wall between a commercial kitchen and a private residence.

Such walls may also need a fire rating to prevent fires from spreading between tenant areas. Walls and doors with fire resistance are an important part of construction to control fires in the event they break out. A demising wall with a high rating between two spaces can limit liability issues; if one tenant's carelessness causes a fire, for example, the neighboring tenant's space will be safe behind a fire wall.


Within a building, there may be rules about what tenants can do with the walls they share with other tenants and common areas. Typically they cannot move the walls, as they represent the outer boundaries of their space. They may also be barred from installing certain kinds of items on or near the wall, as a courtesy to fellow tenants. The lease agreement will provide information about any restrictions on property use so tenants know what is allowable.

In a building inspection, the inspector can evaluate the demising walls in a building to make sure they meet code requirements. Sometimes internal rearrangement may create a new separating wall where one was not present before. In this situation, it is important to check the code requirements before finishing the wall, in case it it necessary to take any special measures to meet the code. If it does not conform, the inspector may cite the structure's owner, and he will have to fix it before the building will be approved for use.


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Post 5

My condominium town house has wood-framed demising walls where it abuts neighbors on either side. The walls between living areas are framed in 2-by-4s and originally had no insulation. The walls between bedrooms have staggered studs with insulation woven between them (leaving big spaces around each stud); unfortunately, these walls were only a little better than the empty ones.

When I first moved in, I could hear complete conversations through all of these walls. Over the years, I've gone around making holes and filling the walls in with tightly packed cellulose and fiberglass insulation, topping off each space with bags of cement mortar mix to pack down the loose fill. It's important that such insulation be packed tightly to increase

the amount of friction; loose, fluffy insulation lets a lot of sound right through it.

I always filled these holes with generous amounts of joint filler and even added an extra layer of drywall to some places. Now, I can only hear really loud noises, like a baby that sleeps (and cries) right up against the wall, and even then, it's muffled and vague.

Post 4

@shell4life – You are fortunate to live in a place where the builder gave forethought to the quality of the demising wall. I would imagine that since you have an effective one, you probably have certain rules to abide by to protect it.

I have a great demising wall, and part of the lease I signed has restrictions about what I can and cannot put on it. I cannot mount a television screen, computer monitor, or anything else that might produce sound or warmth to the demising wall.

I can hang artwork or photos on it, but I can't put anything electrical on it. Even my space heater has to be a certain distance from it.

Post 3

I have never lived in an apartment, but I have visited my fair share of hotels. There are demising walls between the rooms to help reduce sound.

I remember the first time I opened up the door in the middle of the room that led to the neighboring room. I was surprised to find another door on the other side. That's a lot of wood that sound and temperature have to pass through, so both are significantly blocked.

Some hotel demising walls are thicker than others, though. It seems that in cheaper hotels, you can hear everything that's going on next door, while in luxury hotels, you barely hear even loud noises.

Post 2

Fire walls are amazingly effective. When my neighbor's apartment burned all over, I didn't have any damage to the side of mine that shares a wall with hers.

My smoke alarm did go off, but this is a good thing. If there is a fire anywhere in the building, it's best to be alert to it, even if the fire wall does offer protection.

She was at work at the time of the fire, but when she came home, she saw that the place was beyond repair. She quickly checked on me, and she was amazed that I had no damage whatsoever from the fire.

Post 1

The demising wall in my apartment complex definitely mutes sound. Even when my neighbors are arguing loudly, all I can hear is their highly muffled voices.

I would hate to live in a building with an extremely thin demising wall. My cousin does, and she can hear her neighbor's television blaring loudly. He is nearly deaf, so he has to crank up the volume, and since he usually watches TV late at night, my cousin has trouble falling asleep.

Just the background noise of my sound machine is enough to drown out my neighbors' voices. I turn it on to hear the soothing sound of ocean waves, and I can no longer hear anything through the demising wall.

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