Prefabrication and modular construction are both off-site construction methods that involve building components in a controlled factory environment, which are then transported to the construction site for assembly. They are becoming increasingly popular for homeowners looking to expand their living space.


What’s the difference between a prefab extension and a modular extension?

Prefabrication generally refers to the process of manufacturing building components –  such as walls, floors, and roof panels – in a factory and then transporting them to the construction site for installation. These components are typically pre-cut and pre-assembled, sometimes with windows, doors, insulation and other materials, ready for quick installation.

Modular construction, on the other hand, involves the assembly of entire building modules –  including walls, floors, ceilings –  and other components, in a factory. These modules are typically fully finished, with electrical, plumbing and other systems installed before they are transported to the construction site for assembly.


Do I need an architect for a prefab extension?

An architect can help you determine the best option to suit your needs and ensure that the construction method is right for your site and brief. Additionally, your architect can assist you in meeting the necessary regulatory requirements, such as building regulations and planning approval.


Are modular or prefab extensions cheaper than traditional extensions?

Modular and prefab extensions are often more cost-effective compared to traditional extensions because of the benefits of economies of scale, reduced labour and minimised material waste. Nevertheless, if your needs are specific and unique, there may come a point where the cost of prefabrication no longer provides the best value for you.


Advantages of prefab extensions


Quick Installation

One of the main benefits of prefab extensions is their quick installation. Traditional home extensions can take weeks or months to complete, causing disruption to daily life. In contrast, prefab extensions can be installed in a matter of days, minimising the inconvenience and disruption to homeowners. This is especially beneficial for those who need to expand their living space quickly, such as families with growing children or those who require additional space for work or hobbies.


Quality control

Prefabricated construction can provide a better quality of finish than traditional construction methods due to several factors. The controlled environment of a factory helps to protect building materials from external factors, while standardisation reduces the risk of defects and errors. Quality control is higher in prefab construction, with each component carefully inspected before assembly. Skilled labour and advancements in technology also contribute to the improved quality of prefab buildings.



Prefab extensions can be very environmentally friendly. The manufacturing process produces less waste than traditional on-site construction, and the materials used are often sustainable and recyclable. Additionally, prefab extensions are designed to be very energy-efficient, helping to reduce the overall carbon footprint of the property.


Disadvantages of modular extensions

While modular extensions offer many advantages, such as reduced construction time, improved quality control and reduced waste, there are also some disadvantages to consider. Here are some potential drawbacks of modular extensions:

  1. Limited design options: modular extensions are built using standardised components and modules, which may limit the range of design options available to homeowners. Customisation may be possible, but it may also add to the cost.
  2. Transportation challenges: modular extensions are built in a factory and then transported to the site for assembly. This can create logistical challenges, particularly if the site is difficult to access or if there are obstacles in the way.
  3. Site preparation:site preparation is critical for modular extensions, and any issues with the foundation or other aspects of the site can cause delays and additional costs.
  4. Upfront costs: modular extensions may require a higher upfront cost compared to traditional extensions. However, this cost may be offset by the savings in construction time and labour costs.


Consult a design professional first

No matter which construction method you choose, a home extension is a significant investment in your property and it’s important to make the right decision.

An architect can help you determine which construction method would be the most cost-effective for your site and design needs. They can assess your specific requirements and recommend whether a modular extension or traditional extension would be more suitable, taking into account factors such as site conditions, design aspirations, and budget constraints.


Finding the right architect for your house extension

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Emily  Design for Me

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