Life cannot bear the weight! Can the load-bearing wall be repaired after it is demolished?

When renovating or remodeling a house, many people will have this question, that is, "Can this wall be knocked down?"

Sometimes removing a wall won’t have any impact, but if you remove a critical load-bearing wall, it could cause problems for the home.

There are countless cases of casualties and property losses caused by improper wall demolition:

In 2015, a bathing center in Tianjin privately dismantled and modified the load-bearing walls, causing the roof to collapse, resulting in serious consequences such as 6 deaths and 6 injuries.

In August 2020, the load-bearing walls of a warehouse of a company in Harbin were demolished continuously, causing partial collapse of the building, ultimately resulting in 9 deaths and 1 injury.

In July 2021, the auxiliary building of Four Seasons Kaiyuan Hotel in Wujiang District, Suzhou City collapsed due to illegal decoration, resulting in 17 deaths and 5 injuries.

The overall collapse scene of the Four Seasons Open Source Hotel

1. What is a load-bearing wall?

Load-bearing walls refer to walls that support the weight of upper floors and play a vital role in transferring building loads.

In the indoor space, the weight of the floor and the live load on the floor are all transferred to the load-bearing walls and structural beams through the floor, and then to the lower load-bearing walls or structural columns through the load-bearing walls and beams, and then to the foundation, forming the structural skeleton of the entire house.

If a building is compared to a human body, then the load-bearing wall is the backbone of the body. If it is removed, the body will not be able to stand upright well.

The same is true for load-bearing walls. Even if a small part of the load-bearing wall is removed, the load-bearing path of the original building will be changed, so the load-bearing wall must not be removed during renovation!

First of all, we must be clear that load-bearing walls must not be moved. Those walls that do not support the weight of the upper floors only serve to separate spaces, so the removal of such non-load-bearing walls will not have any impact on the house.

Not all walls are load-bearing walls. So how do we distinguish between load-bearing walls and non-load-bearing walls?

2. Simply distinguish between load-bearing walls and non-load-bearing walls

1. Look at the various walls in the structural form

(1) Masonry buildings

Masonry buildings mainly use mixed mortar to build walls with solid clay bricks. These walls serve as load-bearing walls to support the weight, while the roof is generally formed by prestressed concrete porous panels. This is the old brick-concrete structure.

Simply put, the walls of brick-concrete structures are generally load-bearing walls and cannot be demolished during renovation.

These walls not only bear vertical loads, but also resist horizontal loads (such as wind loads, earthquakes, etc.).

If these walls are knocked down during renovation, it will cause safety hazards to the structure and make it more likely to collapse under the action of an earthquake.

With the advancement of modern construction technology, more and more new materials are being used, and their solidity and stability are much stronger than brick-concrete. Reinforced concrete structures are divided into different structural forms according to the structural form and load-bearing components.

(2) Framework structure

The frame structure is mainly made of reinforced concrete or building materials, with beams and columns forming a geometric support plane.

Such a structure is conducive to dispersing the force to the whole building, forming a stable force-bearing structure. The frame structure has the advantages of flexible spatial layout, being conducive to arranging building structures that require a larger space, and being easy to construct.

As shown in the figure is a schematic diagram of a frame structure, in which beams and columns play the main load-bearing role. The walls inside a house with a frame structure are generally not load-bearing walls. They are built with porous blocks and play the role of dividing space. However, the filling walls are built after the frame structure and do not bear load.

If you see pillars protruding from the corners or walls of a room, the building is most likely a frame structure, and the walls inside can be reasonably demolished during renovation.

(3) Shear wall structure

Shear wall structure is a structure that uses reinforced concrete wall panels to replace beams and columns in frame structures to disperse and effectively control the vertical and horizontal bearing capacities.

This structure is commonly used in modern urban high-rise residential buildings. This type of structure has strong lateral stiffness, which will resist horizontal seismic effects well under earthquake action, so it is also called "seismic wall".

The load-bearing walls in this structure must not be destroyed (such as the black solid wall in the picture), but there are also non-load-bearing walls in the shear wall structure. These filler walls can be appropriately demolished during decoration (such as the gray diagonal wall in the picture).

2. Look at the drawings and find the markings

The most intuitive and reliable way to judge the load-bearing walls is to look at the original floor plan provided by the developer. Generally, in the floor plan, the load-bearing walls will be marked with black solid lines, while other walls will be marked with dotted lines.

It is not recommended to demolish the load-bearing walls and shear walls in the normal drawings. In the above-mentioned various structural drawings, if you see a wall marked in black, you must not knock it down easily.

However, in actual design cases, there have been cases where the walls marked with dotted lines turned out to be load-bearing walls when knocked down, so it is recommended that walls thicker than 200mm be designed with caution.

3. Look at the thickness and listen to the sound

In the absence of drawings, you can also make a preliminary judgment by looking at the wall material and thickness, and listening to the sound after knocking.

Generally, walls made of standard bricks are load-bearing walls. If they are made of aerated bricks, they are most likely non-load-bearing walls.

When you knock on the wall normally, if the sound is crisp and the echo is loud, then the wall is generally not a load-bearing wall. Knocking on a load-bearing wall often makes no sound or a very small sound. In addition, the thickness of a load-bearing wall is much greater than that of a non-load-bearing wall. According to relevant specifications, the thickness of a load-bearing wall cannot be less than 200mm, while other non-load-bearing walls may only be around 100mm.

4. Look at the junction of the beam and the wall

Generally speaking, if the method of oblique brick arrangement is used at the junction of beam and wall, then the wall is mostly a non-load-bearing wall, while the wall closely connected with beam may be a load-bearing wall.

5. Look at the location and make careful judgments

Finally, non-load-bearing walls are usually found in bathrooms, storage rooms, kitchens and corridors, while exterior walls and walls shared with neighbors are generally load-bearing walls.

3. What happens if a load-bearing wall is accidentally removed?

If a load-bearing wall is accidentally removed, the following problems may occur:

First of all, the load-bearing walls inside a building are used to support the floor slabs of the upper building. If they are altered, it will lead to insufficient support for the upper floor slabs, and the floor slabs will be prone to cracks. These cracks will gradually expand over time and eventually cause the floor slabs to collapse.

Secondly, for the floors that have not collapsed, since the load-bearing walls have been removed, their support for the upper floors is insufficient, the reliability, stability and earthquake resistance of the building will be reduced, the service life of the building will be greatly shortened, and when natural disasters such as earthquakes occur, the possibility of building collapse will increase.

In addition, the removal of load-bearing walls will change the force transmission path of the entire building, and the damage to the structure is irreversible. Even if the shear wall is removed, it will not affect the bearing capacity of the structure in a short period of time, but it may cause excessively wide cracks and excessive deformations, which will have an adverse effect on the structure. The appearance of cracks will affect the durability of the structure.

It should be noted that for some high-intensity fortification areas, the removal of shear walls will result in the loss of lateral force resisting components. When an earthquake occurs, the weak parts may be damaged and the bearing capacity may be lost. In severe cases, the structure may collapse. Even if the structure does not collapse, the damage to the components will be aggravated, and the economic losses caused will be immeasurable.

4. For the load-bearing walls that have been demolished
How to take remedial measures to minimize the impact?

1. Rebuilding

If only a small area is demolished, the demolished part can be filled in with cement or other materials of the same grade as the load-bearing wall.

2. Reinforcement

If you have already opened a doorway on the entire wall and do not want to rebuild it, you will need to obtain the consent of the housing management department and go to a regular building materials store to buy standard channel steel to reinforce the load-bearing wall.

3. Professional reinforcement

Some construction companies have set up professional load-bearing wall reinforcement operations. If you knock down a lot of load-bearing walls before you realize the importance of load-bearing walls, and large areas of load-bearing walls are difficult to repair, then you need to report to the property and housing management departments in a timely manner, and after obtaining consent, contact a regular reinforcement company to rescue the load-bearing walls.

However, no matter how it is reinforced, once the load-bearing wall is demolished, the damage caused to the building is irreversible. Therefore, during the renovation process, you must not demolish the wall at will. Randomly "drilling holes" is likely to affect the entire building. Moreover, after demolishing and modifying the load-bearing wall, it is not only dangerous, but you will also face a series of repair and fine troubles later.

In fact, in addition to demolishing load-bearing walls, there are many other random modifications to the house without professional analysis, which can cause damage or collapse of the house. For example: digging out half of a column, breaking a beam, making a hole in a beam, erecting a new column in the middle of a floor, digging a basement next to or directly below the building, adding floors, etc.

Professionals may break out in a cold sweat when hearing about these practices, but ignorance is bliss. There are always some people who think that once they buy a house, it is theirs and they can do whatever they want with it, not realizing that their "silly actions" may put the residents of the entire building in danger.

The saying “a thousand-mile dam can be breached by a single ant hole” means that a tiny ant nest can destroy the dam’s overall structure, causing it to burst. Randomly demolishing load-bearing walls and modifying structures at will may very likely become the original ant hole.

References:

[1] Li Xinya. On the types of house structures and the hazards of illegal renovation [J]. Shanxi Architecture, 2016, 42(01): 57-58. DOI: 10.13719/j.cnki.cn14-1279/tu.2016.01.031.

[2] Cui Mu. Analysis of the harm of irregular decoration to house structure and its countermeasures[J]. Heilongjiang Science and Technology Information, 2014(02):181.

[3] Yang Yunfang, Lou Hongqi, He Liping, Tong Xiaohang. The impact of irregular decoration on building structure[J]. Journal of Zhejiang Forestry College, 2003(01):73-76.

Author: Guo Yu College of Civil Engineering, Zhejiang University of Technology

Du Tianyu School of Civil Engineering, Nanjing University of Technology

Review expert: Chen Fengwei, School of Civil Engineering, Zhejiang University of Technology

Image source: Baidu, Zhihu, gifer, etc.