Prefabricated House

'Prefab' is a broad term in modern home building that manages to describe nothing specific while covering almost everything.
There are a number of different approaches that can fit under the 'prefab' banner, which is why it can be a little confusing.
So, we thought we'd break it down and look at what some of the terminology means, what the appeal is, what the limitations are, and also where we sit within this area.

What is a prefab home?
Prefabricated houses, often referred to as prefab homes, are so called because they are primarily manufactured in advance off site, then delivered and assembled on site.

Historically, prefabs have been much maligned in the UK, having been predominantly associated with low quality, high volume housing that replaced stock destroyed by bombs in the Second World War. But such prefabs were only intended to be temporary, which reflects the standard they were built to, even though some remain standing to this day.
Whilst there is still some stigma around the term, modern prefab homes are now more often associated with quality and efficiency.

'Prefabrication' can be roughly defined as 'made before'. Traditional house building methods have long had elements of prefab to them, with components like timber roof trusses being made off site. However, by using 'prefab' to allude to a more modern method of construction, many companies now describe the virtues of their different approaches with this blanket term.

The lack of clarity around 'prefab' and the assumption by many that it only refers to a modern, cost effective method is why it is used so widely, but any home can be considered prefab if some part of it is made before arriving at the site.
Three other terms might sound familiar - these are often seen as interchangeable with 'prefab'. We consider these subcategories of the prefabricated home with their own specific traits: modular, volumetric and kit homes.

What is a modular home?
A modular home is a type of prefab home built in large sections, such as wall and roof panels; a bit like a big Lego set. Most of us will have seen a picture like below, where an entire wall (often with windows already installed) is craned into place on site.

Baufritz, a leading German prefab company, is a modular builder that prefabricates entire wall sections in a factory and cranes them in to place on site. This often gives the appearance of a home that will only take days to assemble. However, once the building envelope is in place there is still months of work ahead for the fit out to be completed and, of course, as with all prefab homes, the foundations will need to have been completed already.
For more examples of modular homes, check out this Grand Designs article.

'Modular is not delivering, here's why' is an article on the state of construction and modular building that states "Construction has been struggling for years with productivity flatlining at a low level, poor build quality, high cost and uncontrollable time schedules.
Ideas of volumetric modular construction, proprietary kits of standardised parts, and buildings prefabricated off-site, have returned in various guises over the past hundred years yet not been able to change how we build, let alone revolutionised construction. One wonders why." Read on.

What is a volumetric home?
Volumetric is defined as 'the measurement of volume' and, in this case, is used to describe the volume of air in a room or section of a home.
Volumetric modular manufacturing involves the prefabrication of a number of larger, fully finished elements. Considered a type of modular home, the volumetric modular units are joined together on site to form complete buildings. These 'modules' can be pre-fitted in the factory with electrics, plumbing, heating, doors, window and internal finishes.

An approach that is typically used for larger developments, it has the highest degree of standardisation and allows for an extremely quick assembly time on site as so much is done in the factory.
An example of a volumetric house building company is nHouse, which offers various sizes and configurations of a standardised home product.
In our opinion, volumetric homes are less successful for individual customers. One-off volumetric homes still have the factory and production line and rely on standardisation and, added to this, it is not always that easy to find a site that will perfectly suit this type of standardised house.