There is no doubt about it: a prefabricated house is better than a house built on-site.
That is a pretty bold statement... isn't it?
To understand why we need to have a look at the entire process of building a prefab house.
Either you are considering to build your own house or you are just curious, this article will guide you through the various stages of how prefab homes are built.
What are Prefab Homes?
Prefabricated homes are nothing more than houses that are pre-built in a factory.
Instead of being built on-site, the house is built in a controlled environment by highly skilled workers.
Unlike in the traditional building process, factory production requires a lot of preparation.
When a house has to be made in a factory, details are very important (we'll come to that in a moment).
Prefabrication can be done to different degrees, depending on how finished the house has to be when delivered on-site.
The two main types of prefabrication "options" are modules and elements (also known as panels).
Building with elements gives more architectural flexibility.
Building with modules saves considerable time on-site while limiting the size of rooms and the shape of the building.
The pro and cons of modular construction are explained in detail in the article "Modern Modular Homes: Dream or Reality".
To get a better overview on what a prefab house can offer, I recommend you have a look at our comprehensive HOW-TO guide.
Let's now go through the step-by-step process for building a prefab home from start to finish.
NOTE: prefab houses can be built out of concrete as well but here on katus.eu we focus only on wooden buildings.
This is how prefab homes are built...
Stage 1: the Idea
It all starts with an idea.
One day you realize you need a better space for your family and you start to think how this dream home would look like.
Focusing on the needs of your family and on your habits and routines, you can write down a list of the rooms you need.
Ater that, you can browse the internet to find some examples of houses looking similar to the one you would like to have.
Once you listed down the rooms on paper, you can estimate the approximate floor area of the house and get a rough budget.
You can do this by multiplying the square meter area by 1300-1500 EUR.
NOTE: this method is VERY rough as the final cost of the house will depend on the architecture, type of technical installation, interior finishes, location, ...
However, the number you get is representative of the minimum budget you need to complete the project successfully.
If you feel the house is too expensive, you have to cut on the floor area (shrink or remove rooms) until the budget becomes a number you are comfortable with.
Stage 2: Drafting an Architectural Design
Once you have your sketch, a bunch of sample photos, a rough idea on the budget, you can reach out to a local Architect and begin working on the project.
Involving a local Architect from an early stage is very important for three reasons:
- the Architect is familiar with local requirements and best practices (these may be different from Municipality to Municipality) and following his advice will save you tons of time and headaches;
- the Architect can suggest proper spacial solutions that will greatly improve the look and functionality of your house (yes, a DIY design is generally a bad idea);
- in any case, you will need an Architect to deal with paperwork and permits in the Municipality.
...so, based on the three points above, the sooner you get an Architect on board the better.
IMPORTANT: to get the most out of the prefabrication process, the work done by the Architect shall be limited to a preliminary design.
In fact, when building with prefabricated technologies, it is better to use the help of a Manufacturer to decide on construction details and some architectural solutions.
The initial work of the Architect should be limited to adjust your sketch in a form which is functional and suitable to be approved by the local Authorities.
Typically the output of this stage is a set of drawings including:
- floor plans;
- side views;
- relevant sections.
All drawings shall come with measures or be easily measurable on paper or digital format.
Stage 3: Drafting a Budget
Many think that a prefab home is delivered by the Manufacturer fully finished and ready for you to move in.
In reality, only a few Producers are able to offer this service while the vast majority of them will just supply you the house and get it installed on the foundations you provide.
This leaves a LOT of things for you to deal with.
Let's see them in detail...
- groundworks and foundations: this is generally out of the scope of the works for a Manufacturer and you have to take care of it before the house is delivered.
- connections: same as the point above. Connections to the networks (water, sewer, electricity, communications, ...) shall be planned and executed together the foundation works.
- house structure: comes from the Manufacturer, generally installed and finished outside.
- windows and doors: generally supplied and installed by the Manufacturer... but make sure you clarify this well in advance.
- roof cover: this depends on the type of roof you select.
Due to transport issues, stone tiled roofs are generally left out from the scope of works of Producers.
If this is the case, who is going to supply and install the tiles? ...who is going to supply and install the wooden battens for the roof tiles?
- technical installations: heating, electricity, ventilation, plumbing are the main installations in the house and, generally, they must be performed by authorized local Companies.
This means you have to get quotes for these installations and partner up with a number a Companies that will deliver the service when the house is up.
- interior finishes: once the technical installations are in place, the house is ready to be finished.
Do not think only about painting works... things like internal doors, stairs, floors, floor trims, window trims... they have to be supplied and installed by someone.
You shall define well in advance "who does what and for how much".
- construction site: last but not least... accessibility, security, safety are the most important things when it comes to the construction site.
The construction site has to be managed.
For the selection of the right Contractors for these jobs, see the Stage 5 below.
Stage 4: Choosing the Manufacturer
Choosing the right Manufacturer is usually a time-consuming operation.
At this stage, the buyer has a lot of open questions and he starts to interact with Manufacturers trying to get some answers.
He is presented with a lot of information and different options... resulting in what is known as "paralysis by analysis".
Afraid of making the wrong choice, the home-buyer postpones his decision resulting in an unnecessary loss of time (and money).
I cannot stress enough the importance of choosing a Manufacturer as soon as possible.
In the article "The 5 Benefits of Choosing a Manufacturer Early" we cover the reasons why choosing early is important and the related benefits.
Stage 5: Choosing other Contractors
The best course of action to build a house "by yourself" is to find a local General Contractor to take care of most of the works that are not performed by the Manufacturer (all the concrete works, roof cover, interior finishes).
When you engage a General Contractor you can be sure the possibility of mistakes in the works will be reduced to a minimum.
You also relieve a lot of pressure from the Manufacturer, resulting in an easier collaboration.
In fact, when a General Contractor is involved, the Manufacturer has one competent contact person on the construction site and the flow of information is fast, reliable and very efficient.
Keep in mind that - in construction - a good information flow is often what makes or breaks the project.
For technical installations is recommendable to negotiate with specialized companies and choose those who present good technical solutions at a competitive price.
This will keep costs to a minimum while raising the Quality to the best you can afford.
Stage 6: Engineering Design
Once all the involved parties have been contracted, it is time to start the engineering design for the production of the house.
This stage takes considerable time and it is one of the fundamental steps of how prefab homes are built.
Depending on the size of the house and the complexity of the architecture, the engineering design can take anywhere from 4 to 12 weeks.
During this phase, the house is broken down in its basic components... like in a 3D puzzle.
Each component is then designed carefully.
While designing the components of the house, designers shall take into account the layouts of electricity, ventilation and plumbing installations.
For this reason is important that agreements with all the companies involved are finalized before the engineering design begins.
At the end of this stage, the full set of drawings for production is ready.
Designers will also prepare an installation manual of on-site assembly, along with the "plan of loads to foundation".
Stage 7: Preparing the Site
The construction site shall be prepared while the engineering design is on-going.
Before the design is completely finished, the Manufacturer will send the plan of loads to the "plan of loads to foundation", so that the General Contractor will be able to execute the foundation works.
Needless to say, a good timing is very important in this stage.
When the foundation has been cast and its measures have been confirmed to the Manufacturer, production can begin.
If the final size/shape of the foundation differs (for any reason) from the design given by the Manufacturer, immediate action should be taken to rectify the mistake.
Either the General Contractor will modify the foundation or the Manufacturer shall modify the design before production.
Additional costs and damages for this kind of mistakes shall be charged to the General Contractor who executed the foundation works (make sure this is clear in your Contract).
At this stage, you shall also make sure that the access road to the construction site is free for the delivery trucks to reach the foundation slab (see more about this in Stage 9).
Stage 8: Production
The production is one of the shorter stages of the entire process (transport is the shortest).
Production of one custom-made single-family house takes less than one week.
In case of row-houses, one unit can be produced in just 2-3 days.
That is remarkably fast.
In order to make it happen with no hiccups, the engineering design must be flawless.
This is why so much care and time is used in the design stage.
The outstanding attention to details is one of the aspects that truly separates prefabricated house from on-site built structures.
Good design and skilled execution result in a superior quality of the components delivered to the construction site.
Stage 9: Transport
Once manufactured, the house is shipped to the construction site.
We covered details of shipping in the article "How Do They Ship a Prefabricated House?".
Stage 10: On-site Assembly
Finally, the house is assembled on-site.
The time necessary for assembly varies depending on the degree of manufacturing and on the size of the house.
A single-family modular home can be assembled in a couple of days while a similar house made with elements might take up to one week.
Manufacturers usually provide the service of on-site assembly and they require the buyer to provide accommodation for their Team (usually 4-5 workers for 1 house).
The buyer is also asked to provide the crane to unload and lift the elements in position and the scaffolding necessary to perform the assembly and exterior finishing works.
Crane and scaffolding are relatively easy to arrange.
If you opted for engaging a General Contractor, you should be already covered and you have nothing to worry about as they will take care of running all the operations on site.
Stage 11: Technical Installations
Once the structure of the house is up, the assembly Team of the Manufacturer will leave and the site will be left in the hands of the General Contractor who shall coordinate the works of the Companies executing the technical installations.
Typical installations include plumbing, electricity, ventilation, heating, communications.
It may take several weeks to get all those works finished and tested properly.
NOTE: the long time of execution of technical installations is the main reason why the assembly Team of the Manufacturer leaves without executing the interior finishes.
Stage 12: Interior Finishes
In the last stage, the General Contractor (or other appointed Company) will perform the Interior Finishing Works.
Depending on the size of the house and the level of the finishes, this stage can take anywhere between two weeks and a few months.
It is important that finishing works are executed with no rush and great care.
In fact, even if the structure of the house is perfect, poorly executed finishing works might result in cracks on the walls and other unpleasant surprises.
Stage 13: Handing Over the House
Once the Interior Finishing Works are completed, the General Contractor shall perform a final inspection together with the Owner and they should verify that everything has been built according to the plan and the expectations.
Any remark from the Owner about quality or quantity shall be noted in written form and signed by both parties for the records.
Actons to rectify eventual shortcomings or mistakes shall be taken under the Guarantee provided by the General Contractor.
Should any problem arise with the structure of the house, the Manufacturer shall be held responsible and the issue should be fixed under the Manufacturer's Guarantee.
The house is now ready for the owners to move in.
Besides the question of how prefab homes are built, one should ask why to buy a prefabricated house in the first place.
Simply put, prefabricated houses are better.
Yes, I am well aware that stating that all prefab houses are better than all on-site built house is a generalization and it cannot be universally true.
However, when building a house we always have some type of constraint and the statement above is generally true when taking those constraints into account.
In an ideal World, anyone would be able to build the house he wants with no particular challenge.
In the real World, building a home for your family is a serious undertaking that will put to the test your decision-making skills.
Constraints are what drives the decision-making process.
Constraints are what separates dreams from reality.
When building a house, constraints can be factors like:
Given two houses that shall be built with a given set of constraints, the prefab version will surely be the best option (also the fastest to build and the one delivering better quality).
- fixed design and budget: prefabricated elements can be used to build just about any architectural solution and their construction can be adapted to fit smaller budgets;
- lack of time and workforce: building with prefab components will be faster and it will require less manpower on-site;
- fixed materials and budget: factories buy bulk materials, generally resulting in cheaper prices of the finished prefab product.
NOTE: the only situation where building on-site might be a wise option is when one has a hard-to-reach location.
If delivery trucks cannot reach the building site, the cost of moving elements can become very high.
In fact, one of the most common ways to move elements to impervious sites is by helicopter... and everyone knows how expensive this can be (thousands EUR per hour).
So, unless you are planning to build on the peak of a mountain, it is safe to assume that your best bet is to build a prefabricated house.
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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