Prefabricated Extensions: An Extension Expert’s Guide
In a way, prefabricated modules are actually a great choice when it comes to extensions. The advantage here is that, apart from being affordable options, they are quicker to build with little fuss. But the question is, do such building methods suit you and your ever-evolving lifestyle? We shall answer!
Gone are the days when questions were raised on the longevity of prefabricated constructions. Currently, the line is thinning, as prefabricated homes are being considered more as full-fledged house options than just temporary solutions.
Every year in the UK, approximately 15,000 homes are built as prefab homes. Though they represent a small portion of the total new build projects, predictions are that the number may rise to 50,000 in the coming decade.
Although the thought of a prefabricated home might still be a consideration among homeowners in the UK, one cannot deny the convenience of constructing prefabricated extensions. When it comes to building extensions, if one ponders between traditional methods against prefabricated extensions, arguably the latter can offer more the advantage.
What are Prefabricated Extensions?
Prefabricated extensions are essentially structures that are pre-built at an off-site facility in an environment controlled by high quality and precision.
They are designed, manufactured, and engineered as units before being transported on-site for assembly.
Why Considering Prefabricated Extensions is Advantageous?
When considering expanding your existing living space, prefabricated extensions can be more beneficial. When compared to traditional extensions, prefabricated home extensions can be built with faster timelines, are cost-effective, offer minimal disruption, and are sustainable as they are constructed on-site.
When considering a new build, traditional extensions offer longevity, structural strength, and quality, and hence outweigh prefabricated extensions in the long run. But if you are looking to expand your existing space, considering a prefabricated extension can benefit you more.
Relevance of Prefabricated Extensions
Arguably, if not for today, the relevance of prefabricated home extensions would have dated back to World War times where there was a dire need to construct homes at a faster pace.
Prefabricated homes were originally intended as interim solutions during World War 2 to quench the housing crisis post-war. The result was an astounding 500,000 prefabricated homes built within 5 years of the outlined plan.
In today’s context, the situation is ripe to consider prefab extensions. With the Labour’s ambitious plan to achieve 1.5 million homes, in 5 years since its announcement, prefab homes can be the saviour. For homeowners who are running hard on timelines and looking for cost-effective and sustainable means to expand their living space prefab extensions can be perfect.
How are Prefabricated Extensions Built?
Before building a prefab extension, various factors are assessed such as the complexity of the design, suitability of materials, and measurements that should precisely match the existing house dimensions, etc. These are done off-site during the initial design stage to avoid any backlash or errors during assembly and erection.
Most prefab extensions are designed such that they can be seamlessly installed at on-site foundations. These foundations are usually footings/joists made of concrete or timber and act as a structural base for the prefab structure being installed.
Below is a breakdown of the process –
1. Define Your Need
At first, you have to decide what will be the extension for. Is it for a kitchen, a home office, or an extra living space? The type of extension will determine the space and the layout, and thus the span of your prefab design.
2. Set the Budget
Determining the budget is crucial, as the choice of materials, type of design, type of installation, and area of the extension are all integral to the budget.
3. Hire a Professional
Prefab extensions can be delicate to build as you are assembling two different styles (attaching a prefab to a traditionally built house). An architect or a structural engineer are the best professionals who will be able to appropriately guide you and will also look after the necessary planning permissions and building regulations required for the project.
4. Designing the Extension
While aspects such as structural integrity and strength will be taken care of by a structural engineer, you can else focus on ensuring natural light flow, and flow & functionality between your living spaces and rooms, etc. You also have to be wary of the choice of materials and the type of finish you desire.
Because you are planning an extension, planning permission will be crucial when deciding materials.
5. Transitioning the Design
Plan the transition between the new prefab extension and your existing structure with a structural engineer to ensure a seamless and robust connection. This is a very important part of planning a prefab extension.
6. On-site Preparation
As your prefab units are being prepared at the factory facility, you need to prepare the ground on-site. Ensure the foundations (concrete or timber) are properly installed with the right number and orientation of flooring base and joists.
Make sure you check the on-site location for essential utilities such as electricity, water, and gas such that they are accessible to the extension.
7. Delivery and On-site Assembly
When transporting your prefab units to the on-site location, haulage is usually used for safe transportation. Haulage ensures that the structural integrity of the prefab is not disturbed even during tough paths or terrains.
Once the units are transported, they are then erected to be assembled on the foundations. While this happens, make sure the connection is a watertight and structurally sound one.
8. Finishing
Once the installation is done, complete all the necessary finishes such as decorating the interiors, flooring, and adding fixtures (plumbing and electrical). Before you wrap, check for final building regulation standards as they are a mandatory law for any renovation.
Things you Should Know when Planning a Prefabricated Extension
- Prefabricated extensions are characterised typically as pre-installed doors and windows. So, if you are planning one, make sure you check with your architect or builder.
- Some prefab projects come with internal finishing that includes wall plastering and flooring. If you otherwise desire to have your own style and choice, you can do so.
- Most prefabricated home extensions are bespoke and are designed according to the needs and aesthetic desires of the homeowner.
- Prefab extensions can conveniently accommodate matching claddings in brick slips or any other cladding that requires adherence to planning permission.
- They can also take up additional enhancements such as the addition of windows, doors, canopies, roof lights, decked areas, window glazing, and energy-efficient mechanisms.
How Long Does It Take to Build a Prefabricated Extension
It usually varies from project to project. To build units of prefab extensions for a single-storey house it may take as little as a few weeks. Whereas some prefabricated home extensions can be finished in a matter of 7-10 days, some require 4-6 weeks including planning, designing, erecting, and assembly.
The factors that are responsible for variations in timelines are design complexity, acquiring planning permission, the scale of the project, and where it is located.
Which is the Best Material for Prefabricated Extensions?
While there is nothing wrong with choosing the type of material, what you need to be conscious about is the budget.
- Timber: Timber is one of the most commonly considered materials for prefabricated home extensions as they are excellent insulators and can enhance the aesthetic appeal as well. While they are relatively quick and easy to construct, the exteriors of the timber frame can incorporate different types of materials which makes it a more convenient choice.
- Steel: Steel offers high durability and structural strength and is more suitable for wider spans. They are an automatic choice if the design warrants complexity and, hence are more flexible by nature.
- Structural Insulated Panels (SIPs): SIPs are lightweight panels and enable easy installation while also offer the benefit of durability. They are excellent energy-efficient options and reduce heat loss, this lowering energy consumption. Though they may have high upfront costs, they prove to be highly cost-effective in the long run.
What is the Cost to Build a Prefabricated Extension?
Though they are structures that have a defined process, there is no base price or a set cost for prefabricated extensions. The cost to build prefabricated home extensions usually depends on the type of material, choice of finish, and scale of the extension, to name a few.
On average, prefabricated extensions can cost you 25% less than your traditional house extensions. To give out an approximate cost, prefabricated home extensions may range from £1,200 to £1,900 per sq metre and are much more affordable than traditional extensions.
Total Cost for Basic to Premium Finishes
- Total cost for small-scale prefabricated extensions can cost between £20,000 to £35,000 for basic to premium quality finishes.
- Total cost for medium-scale prefabricated extensions can range between £30,000 to £45,000.
- Total cost for large prefab extensions can range between £40,000 to £60,000.
Conclusion
While prefabricated extensions have their own limitations in design, and transportation costs, and are relatively less durable when compared to traditional extensions, the fact they offer a quick resolution being cost-effective cannot be denied.
If maintained well, prefabricated home extensions can last up to 50 years or even more when built using high precision, skilled labour, with high-quality materials. So, it is important that these aspects should be given more cognisance for a long-lasting build at affordable costs.
At Extension Architecture, we have studiously bred and built extensions for more than 13 years. Our experience and expertise in extensions encompasses traditional, prefab, and modular extensions, and have successfully guided and executed many projects across London and beyond. Contact us for more details.
