So you want to knock out a wall in your house or unit?

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So you want to knock out a wall in your house or unit?  Don’t get the sledgehammer out just yet…

Many unit blocks and townhouse developments built in years gone by were constructed before it became customary for architects to take shadow lines, perspective and sunlight aspect into consideration.  (Or, perhaps more typically, they were designed by developers who were more interested in cheap construction, rather than pursuing more ideal design layouts!)  For this reason, units can often suffer from dark and gloomy interiors – not due to lack of external windows and light sources, but due to unfortunate room layouts and placement of interior walls.

Another factor to consider is contemporary design: Right up until the early 1990’s, it was the fashion to divide a residence into small compartments, with walls separating kitchen and dining areas from the main living areas. These days, open plan layouts are much preferred in new buildings, with kitchen and dining areas blending seamlessly into living areas, giving an impression of a larger, brighter, more open space.

Not surprisingly, many people own or are purchasing units in these older blocks, and are now looking to either open up existing door openings or remove entire partition walls, in order to achieve a more contemporary (and functional) open plan layout.

As such, we here at Partridge typically get one to two enquiries every week to help unit owners (and house owners) remove internal walls and improve both the functionality and the value of their home.  So we thought it might be helpful to pen a few thoughts and tips on the issues surrounding knocking out a wall in your residence…

Due to Strata regulations, it is not permissible for an owner to remove any section of wall without permission from the Body Corporate of their Strata Plan. There are a number of reasons for this, and a number of steps that must be followed before the work can be undertaken.

Any internal wall in a residence, be it of brickwork, timber stud framing, or concrete construction, may be “loadbearing” or “non-loadbearing”.  A loadbearing wall is so called because the structure above the wall (typically the roof, walls, and floors of any neighbours above you) is actually resting on your wall, with all the weight distributed down through the wall to the floor below.  In this case, simply removing the wall would be akin to removing the support for the floors, ceilings and roof above, and could lead to a catastrophic collapse, particularly if, say, the wall was on a lower floor of a multi-storey block. The very best scenario would be that many of the walls above, and perhaps floors, would suffer severe cracking.

In some cases the wall may be non-loadbearing. In these instances, the floor or ceiling / roof structure above the wall would originally have been designed to span across the wall without actually being supported by it, and it may be feasible to remove the wall without having to install any new structural elements to support the remaining structure above.

Smaller unit blocks such as the classic “three storey walk-ups” from the 1970’s and 1980’s, typically featured brick walls and either concrete slabs or timber joists for the floors – in which case, the walls were generally loadbearing.  Larger, more recently constructed high-rise buildings (typically those higher than five storeys) were built as concrete frames, featuring concrete columns and beams to support the slabs.  In these instances, the internal partition brick walls were more likely to be non-loadbearing.  However, these are just generalisations and must never be taken for granted.

For example, when non-loadbearing partition brick walls are infilled in a concrete-framed multi-storey apartment block, the brickwork is usually built leaving a small gap between the top brick course and the underside of the slab above. When the render is applied to the wall, it sometimes partly fills this gap, inadvertently forming a load transfer between the wall and the slab above. As the slab above deflects over time (which all slabs will do!) more load can be transferred to the “non-loadbearing” infill wall through this render. Then, when the wall is removed, the slab may suddenly deflect further, causing cracking to the walls above.

For this reason, it is essential that an experienced structural engineer firstly examine the wall to determine whether or not it is loadbearing. This may be ascertained in a number of ways, such as by examining the original structural drawings for the building, (if available), or by physically inspecting the interface between the wall and structure above.  If neither of these options are viable, an engineer may use his/her experience to analyse the overall structure and determine the likelihood of the wall being loadbearing.

Okay, so that’s the background and it outlines the homework that both the owner and the engineer have to do first.  What happens if the wall you want to remove is actually loadbearing?

The first step is for the engineer to determine the most suitable procedure for removing the wall, and how the structure above can be re-supported after demolition, in the most aesthetically pleasing manner and with the minimum cost to the client. This is generally achieved by the design and installation of a structural beam (or lintel) across the top of the new opening.

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The procedure for removing the wall may entail propping of the existing ceiling/floor, followed by “needling” of the wall with structural members.  This is done to ensure that the process of removing the brickwork prior to installing the new beam does not adversely affect the structure above. Once the brickwork has been removed, and with the structure now fully temporarily propped, re-supporting the wall and floor above is achieved by installing the structural beam to span across the top of the new opening, with the beam designed and detailed by the structural engineer.  (There are many ways in which this is achieved, all dependent on variables such as the span of the required opening, the existing wall layouts, the height of brickwork above the lintel to be retained, the number of storeys above the area in question, and so on.)  The lintel beam may be structural steel, timber, or precast concrete, whichever suits the individual situation the best.

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When considering the removal of a wall, many people worry about the wall’s job in holding up the vertical structure above it.  However, sometimes, walls also serve a horizontal purpose – they provide lateral support or bracing to the building, which is essential to resist wind and earthquake loads.  The engineer must therefore also ascertain if the removal of the wall(s) in question will in any way affect the overall structural stability of the building.  If this is the case, it is often necessary to install a steel portal frame – consisting of a beam and two columns at each end (picture a soccer goalpost frame).

However, each situation is entirely individual, and must be assessed on a case by case basis, depending both on the existing wall layout and the extent of wall removal the client wishes to undertake.  Also, please note that if a neighbour above or below you in your building removed a wall, it does not automatically follow that you’ll also be able to do the same.

The structural engineer will provide a solution to the client in the form of new structural member types and sizes, and s/he should also provide drawings or sketches of the details and a methodology or specification on how to carry out the works. The engineer should also provide a structural certificate to the client stating that the extent of wall indicated on the accompanying sketch may be removed, provided the building works are carried out in accordance with the sketches and the nominated Standards and Codes.

These sketches and certification may then be presented to the Body Corporate for approval. The sketches and notes may also be given to a builder who can carry out the works based on their contents.

We’ve focussed mostly on apartment buildings in the above paragraphs, but the principles and the steps are very similar for detached houses.

The key thing to note in all of this is to seek advice first.  Don’t pick up the hammer yourself and just assume that pesky wall can be removed, or that you can automatically widen the door opening into your dining room.  Drop us a line if you like – we’d be happy to help.

Cheers,

RO’R & AD

COMMENTS

Just say Your opinion.

  • Alex Braim

    3 years ago

    Good to know! I agree that “Many unit blocks and townhouse developments built in years gone by were constructed before it became customary for architects to take shadow lines, perspective and sunlight aspect into consideration”. I already subscribed to your blog.

    Reply
  • eMoov

    3 years ago

    Everything that have been said here is right. The last tips should always be remembered. You just can’t get up and slam that wall because it will never work. Ask some advice, assess and make sure that you are doing the right steps for your home improvement project.

    Reply
  • Eugene

    3 years ago

    Great article that helped me read through the strata law’s that apply to removing internal walls within a unit!!

    While researching the strata by-laws, I found it difficult to understand how an engineer would classify what is a “structural change” vs a “non-structural change” when reconfiguring a wall? Depending on how works are classified by the engineer would determine which section of the strata law that applies.

    Eg ambiguous scenario.

    Let’s say that there is an internal non-loadbearing wall that is 3 x 4m and has an existing servery window of 1 x 2 . A lintel beam is currently in use. If the proposed works was to expand the servery window to 2 x 3 without removing the existing wall and requiring a new longer lintel beam, would a structural engineer define this as a “structural change” or “non-structural change”?

    Thought the definitions might be based on Building ACT or codes but can’t see how this would be defined, so any pointers on where I could read about this would be appreciated!!

    Reply
    • AD

      3 years ago

      Hi Eugene – many thanks for the feedback and further enquiry. Generally speaking, in multi-storey or strata situations, the engineer’s main focus is “Will the removal of this wall impact the structure and the neighbour above?”. If, in your example, the servery wall is non-loadbearing (i.e. it doesn’t support the floor above), then simply increasing the size of the servery window would be a non-structural change. Yes, the servery window might now need a new or larger lintel above it, but that’s a simple internal matter of just holding up the brickwork above the window. The sizing, configuration, and fire-rating of the lintel has no impact or influence on the floor and neighbour above, so we would deem it a non-structural change. Hope that helps!

      Reply
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