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How Long Does A House Extension Take?

Building a house extension is an exciting time as you take on a project that can transform your home and improve your living space. When you’re visualising your extension, it’s common to wonder how long the entire project will take. The duration can vary significantly depending on several factors, including the size and scope of the project, the weather, and even the cooperation of your neighbours and local planning bodies. 

How Long Does A House Extension Take?

Posted on

November 16, 2023

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On average, a house extension project typically takes anywhere between 7 to 15 months, but it can sometimes extend beyond that. In this guide we’ll break down the factors that influence the amount of time a home extension takes, aiming to give you an idea of how long you can expect yours to take if you’ve got one in the pipeline.

What factors affect the timeline of extension construction? 

When it comes to home extensions, there are some factors that you need to consider before trying to establish how long the house extension will take. In most cases, the three factors you have to consider are: 

  • The size of the project
  • The complexity and exact scope of the project
  • The budget

These factors will determine how long the project will take, and are important to keep in mind when reading this guide. Now let’s take a look at the stages of a home extension project and how long each of these stages can last.  

Preparation and Initial Concepts: Between 2 – 4 Weeks 

Before you embark on your house extension journey, it’s crucial to do some preliminary preparations. First, determine your budget and list your priorities and what you need to achieve to get the end result you have in mind. Having a clear understanding of your goals will guide you through the entire process and will help you to communicate what you want to your contactors.

Once you’ve got your list, you can start approaching architects and designers. It’s a good idea to shop around and get multiple quotes before committing to one service provider. This stage entirely depends on how long it takes you to find your ideal provider that suits your needs 

Design: 2 – 5 weeks

After choosing someone to work with, it’s time to create the design for your extension. You may need to source the drawings of the home to give you an idea about electrics and plumbing. If you do have access to these drawings then the process can commence almost immediately. 

However, there are some cases where you may have to request the drawings from another party. If this is the case, then you’ll have to wait until you have them in front of you to start on the design of your home extension. 

Planning, Permissions and Paperwork: 8 – 10 weeks

The planning phase can often be the longest stint of a home extension and spans anywhere from 8 to 10 weeks, potentially longer with alterations. Although you may be very keen to dive into the project, you need to ensure that all the permissions and legalities are approved. This part of the planning phase should be navigated by your architect as they will know about the correct avenues to take. Delegating all the relevant applications to your architect, who are expert in streamlining submissions, will possibly speed up the process. 

Some projects may need what is known as a Party Wall Agreement. Typically, this is required for projects near shared boundaries or within 3 metres of a shared boundary. If your neighbours get consent to the agreement and get it over the line quickly, this can drastically speed up the process, but if they drag their feet with the process, they can hold up the whole project. 

Technical Design: 1 – 2 months

Assuming that your planning went smoothly and you obtained approval, the next step is the technical design phase. This is where you address the finer details of the construction, including building regulations and securing a structural engineer. These engineers are crucial as they ensure the entire structure remains stable.

The timing for this stage can vary significantly depending on the companies you work with, potentially leaving you waiting for up to 2 months. Use this time to research and compare different construction professionals to find the best service and price. You can also consider services that connect you with the top professionals in your area, making the selection process more straightforward.

Tender Process: 2 – 4 weeks

The tender process is essentially the stage where you hire a builder for your extension project. During the hiring process, you need to ensure that the builders and contractors you hire have the capacity to deliver the project exactly how you envisage it. It’s important to vet contractors before you make the decision to hire them. Try to get references for them and ask if you can visit any of the previous sites they’ve worked on, as this will give you a good idea about the quality of work they can deliver. 

how long do house extensions take: Building: 2 - 4 months

Building: 2 – 4 months

The duration of the actual construction phase depends on the size of your extension and the features you’re incorporating. For example, a design with a substantial amount of glazing may take longer to complete than a simpler design with plain walls. Additionally, the efficiency of the construction team you hire plays a significant role in how quickly your extension is built. 

Below we’ve broken down exactly what you can expect from the construction phase and the order in which builds are typically carried out assuming there are no delays, which there almost always are. 

Foundations and Initial Groundwork: 1 week

The foundation and initial groundwork phase is crucial to the stability and longevity of your house extension. During this week-long period, professionals excavate the designated area, lay the foundation, and undertake essential groundwork. This includes soil testing, ensuring proper drainage, and creating a solid base for the construction. The meticulous nature of these tasks, including curing time for the foundation, contributes to the duration.

Brickwork: 5 Days

Brickwork involves the construction of the structural walls of your extension. The duration of five days encompasses laying bricks, allowing for proper curing between layers, and ensuring structural integrity and accuracy. This meticulous process demands precision to create a robust and aesthetically pleasing framework for your extension.

Roofing: 3 days 

The roofing phase focuses on installing the primary structure that protects your extension from the elements. Over three days, roofing professionals secure the framework, ensuring it meets design specifications and complies with safety standards. The limited timeframe accounts for efficient teamwork and the use of prefabricated roofing components.

Roofing finishes: 4 Days

After the primary roofing structure is in place, an additional four days are dedicated to roofing finishes. This includes adding roofing materials such as tiles or shingles, addressing any necessary insulation, and ensuring proper weatherproofing. The meticulous approach to these finishing touches contributes to the overall durability and aesthetic appeal of your extension.

Window Installation and Glazing: 1 Day

The installation of windows and glazing is a pivotal step in creating a well-lit and visually appealing space. This one-day process involves precise measurements, fitting, and securing the windows. The limited duration reflects the efficiency of experienced professionals and the use of well-prepared openings in the construction.

Initial Electric and Plumbing Installation: 2 Days 

Ensuring that the electrical and plumbing infrastructure is laid out correctly is vital for the functionality of your extension. Over two days, professionals install the initial wiring, plumbing lines, and fixtures. This time frame allows for meticulous planning, accurate placement, and quality checks to meet safety standards.

Breakthrough to Main House: 2 days

The breakthrough phase involves connecting your extension to the main house structure. This two-day process ensures proper integration, aligning the extension seamlessly with the existing property. It involves precision cutting, structural reinforcement, and meticulous finishing to create a cohesive and integrated living space.

Plastering: 2 Days

Plastering adds the finishing touch to the interior surfaces of your extension. Over two days, professionals apply plaster to walls and ceilings, ensuring a smooth and polished appearance. The process includes drying time between layers, contributing to the overall aesthetic quality of the interior.

Secondary Plumbing and Electrics: 2 Days

The secondary plumbing and electrics phase focuses on refining and connecting the extended space to the main utilities. Over two days, professionals install additional plumbing fixtures, outlets, and wiring, ensuring seamless integration with the existing systems. This stage emphasises precision and compliance with safety standards.

Finishing Touches: 2 Days

The final two days are dedicated to the finishing touches that elevate your extension’s aesthetic appeal and functionality. This includes installing fixtures, adding final coatings, and addressing any remaining details. The careful attention to these finishing touches ensures that your extension is not only structurally sound but also visually pleasing and ready for occupancy.

What Can Cause Extension Delays? 

Although your contractors should do the best they can to ensure they stick to the project timelines, there are aspects out of their control which could cause delays to your home extension. These include:

  • Weather: Unpredictable weather conditions can impact construction schedules.
  • Illness: Health issues among key team members or professionals can lead to delays.
  • Legalities: Legal processes, such as planning permissions or Party Wall Agreements, may encounter unexpected hurdles.

Your Home Extension’s Timeline

While the timeline for a house extension can vary widely, the stages of preparation, design, planning, technical design, Party Wall agreements, the tender process, and the actual construction will collectively determine the overall duration of your project. 

To minimise delays, it’s essential to conduct thorough research and hire professionals who can work efficiently and meet deadlines. If you’re considering a house extension project, remember that each project is unique, and these time frames provide a general guide to help you plan your timeline effectively.