So you are working on a new housing project and you are wondering whether you should build it entirely on-site or you should take advantage of some sort of prefabricated construction method.

As soon as you look into prefab construction technologies, you realize there are 3 ways you can go about it:

  • pre-cut material
  • element construction
  • factory-ready volumetric modules.

How can you determine which one is the best for your project?

This article is all about that...


eas logoThis article was written with the support of the European Union European Regional Development Fund, in the frame of the project "PuitAIT vol3 House Machine".

 

After the success of the House Price ToolCreatomus Solution created another tool, this time to help you determine which is the best technology to use on your residential development project.

The tool is named "Prefabtype" and it offers a simple and straight forward way to figure out which prefab technology is best suited for any residential development project.

TRY THE PREFABTYPE TOOL

The Problem

There is a lot of misinformation about wooden prefab construction technologies.
A simple search for "element house" returns a bunch of modular units or a number of projects which are purely theoretical (renders of houses which have never been built for real).

This is confusing.

If you are a real-estate developer (or an architect working with developers) you need to have a clear picture on:

  • which are the available options when it comes to wooden prefab construction;
  • what is reasonable to expect for each one of those options.

The Options

For the sake of clarity, let's quickly review the 4 construction options available to a developer when starting a new residential project with wooden houses.

katus.eu cratomus prefabtype onsite

1. On-site construction

This is the traditional "stick-building", where all the parts are measured and cut on-site.
It is not a prefabricated method and it is slowly but surely sunsetting, leaving space to faster and more convenient prefab technologies.

Pros:

  • no detailed engineering design necessary. One can go from architectural design to implementation quite quickly;
  • since everything is decided on-site, changes to the construction can be made at any time. This gives a lot of flexibility and it is very forgiving (makes up for poor planning);
  • it offers quite good freedom in terms of architectural choices.

Cons:

  • it requires very skilled labor on the site;
  • it takes a lot more time;
  • it generates a lot of waste;
  • the construction quality cannot be guaranteed;
  • the construction time is hard to forecast.

katus.eu creatomus prefabtype precut

2. Pre-cut material

Also know a "kit homes", pre-cut houses make up for a large part of the housing projects in the US.
All the wooden parts of the structure of the house are designed with great accuracy and cut in the factory.
The material is then shipped to the construction site where local labor will proceed to its assembly.

This method is pretty close to the stick-building but it has the following benefits:

  • it generates less waste;
  • it allows for better quality;
  • it is way faster;
  • it requires fewer trucks for transport;
  • it offers even more freedom in terms of architectural choices.

Cons (compared to element or volumetric modular construction):

  • it requires skilled labor on the site;
  • it requires more time;
  • the construction quality cannot be guaranteed.

katus.eu creatomus prefabtype elements

3. Elements

In this type of construction, the structural components of the building are prebuilt in the factory to a high degree of finish.
Components are ready to be installed and they are mostly ready for exterior and interior finish.

Houses built with this construction technology are also known as: panel homes or flat-pack homes. 

Components that are generally produced as elements are:

  • walls
  • roofs
  • floors
  • balconies & terraces

Depending on the type of exterior finish, the walls can be delivered almost completely finished by the outside.
The interior generally requires leaving some spaces open to perform the connection between elements on site.

Overall, element construction presents the following benefits compared to pre-cut and stick-built:

Pros:

  • fast assembly (about 5 days for a 2 floors detached house);
  • guaranteed high quality of the construction;
  • it requires less skilled labor on-site;
  • it generates nearly zero waste;
  • less possibility of mistakes and delays;
  • it still maintains freedom in terms of architectural choices.

Cons:

  • it requires careful planning;
  • it requires very detailed engineering design (more expensive and more time consuming);
  • it does not allow for on-site last-minute changes;
  • it requires more trucks for transport (but still less than with modules).

katus.eu creatomus prefabtype modules

4. Volumetric Modules

Volumetric modular construction is the last frontier of prefabrication.
In this type of construction, entire sections of the building are assembled and finished at the factory.

The degree of finish is over 90% (kitchens and bathrooms are also installed in the factory).

Residential developers are fascinated by modules because of the short installation time. However, the wise developer should take into account all the phases of the project and the degree of architectural freedom that the project requires.

In fact, while modules offer fast installation, they come with a series of strings attached...

Pros:

  • super fast assembly;
  • fast exterior and interior finish;
  • guaranteed high quality of the construction;
  • it requires less skilled labor on-site;
  • it generates nearly zero waste;
  • less possibility of mistakes and delays.

Cons:

  • architectural freedom is heavily restricted;
  • it requires careful and detailed planning;
  • all the interior details need to be figured out before contracting;
  • all the technical installations need to be figured out and designed before contracting;
  • it requires extensively detailed engineering design (more expensive and more time consuming);
  • design and contracting time is way longer than for elements or pre-cut;
  • it does not allow for any on-site changes;
  • it requires more and larger trucks for transport.

katus.eu creatomus prefabtype money

Time and Money

Looking at the pro and cons of these 4 types of technology, it appears evident that the time and money required for the implementation of a project depend on the particular nature of the project itself. In particular, they depend on the following factors:

  1. the type of units to be built (it affects the design and engineering solutions)
  2. the destination of use of the units (it affects materials and engineering solutions)
  3. the size of the units (i.e. footprint and number of floors)
  4. the number of identical units (it heavily affect engineering design and production efficiency/speed)
  5. the location of the construction site (it affects transport costs and time)

With all these variables at play, a residential developer might get pretty confused.
Even for the most experienced builders, the best choice of prefab technology for a complex project is not always obvious.

Here is where the Prefabtype tool comes to help...

The Solution

Creatomus Solutions developed a simple educational tool that takes as input the 5 variables listed above and returns a dynamic time chart showing the most time-convenient option.


katus.eu creatomus perfabprice 1This chart refers to a project with the following configuration:

  • Type: Pair House (2 dwelling units)
  • Number of identical houses: 1
  • Number of floors: 2
  • Footprint: 10m x 15m
  • Location: United Kingdom

With this simple tool, any residential developer can quickly describe his project and get a feeling for which is the best prefab technology to adopt.

IMPORTANT: time and money should never be the only indicator on which to base a decision.
Architectural freedom also plays an important role (because, in the end, houses have to be sold or rented out). So make sure you factor this in every time you are inclined to decide for modules.

Assumptions and Limitations

The tool works by modeling the building and the construction process with a series of empirical coefficients.
In the calculations, it is made the assumption that all the units to be built are identical. This allows for reducing design and production time.

In case your project is composed of units with different floor plans, you need to run the tool several times and consider each floor plan design separately.

A note of caution

As a rule of thumb, the more repetitive + large + architecturally simple the project is, the more it is suitable it is for building with modules.
As the project begins to lack of one of those characteristics, you should be very skeptical of choosing modules and you should consider defaulting to elements.

 

Try the Prefabtype Tool

 

Get the list of manufacturers

 


If you want more information on the process of building a prefab home or you have any other kind of question, feel free to reach out to us.

 

 

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