Typical Timeline for Extension & Renovation Project
/Part 1
Feasibility to Commencement Onsite
If you are thinking of kicking off an extension, renovating, or purchasing a home, it is important to understand the timeline to take you from the initial survey through to starting onsite.
Below, we will break down each key stage and how long it would take on average. We will also outline potential pitfalls and elements that could slow down the process. Understanding the timeline will help you plan the finances for the project and other elements such as moving out.
* A typical project often involves a large extension, a full loft conversion, and a complete house renovation, usually for a large semi-detached or detached property.
Feasibility through Design Development
The ideal way to begin any domestic renovation project is with a feasibility study. This typically involves a site survey followed by an initial design and project brief meeting. Before this meeting, please consider the following key aspects of your project
Scope of Works, for example: a single-storey extension and a loft conversion.
Budget: What is your available budget, and how do you plan to finance the project?
Timeline: Start by working backward from the desired completion date so you can start to enjoy your dream home.
Design Inspiration: Begin thinking about the style and appearance of the final design, and start collecting images from magazines and online sources.
What to look out for:
Does the company offer 3D design and computer-generated renders as standard?
Ensure the design and project build costs run in parallel. This approach allows you to either reduce the project scope or consider phasing the work.
Avg Time: 1 to 1.5months
Design Development and Planning
Following the feasibility report, the next phase is to fine-tune and develop the design so that the scheme is ready for planning submission. It’s important to finalise the overall size, key elements such as windows, doors, and external materials like cladding and tiles. At this stage, avoid focusing on internal finishes, as they won't impact the planning submission.
Once the design is finalised, the next step is to prepare the planning submission. This typically involves a set of planning drawings, a Design & Access Statement, and any additional requirements. The planning application is submitted through the Planning Portal. After a two-week validation period, the application usually takes an additional six weeks. During this time, your neighbours and other key stakeholders will be consulted, and the Planning Officer will often request a site visit.
What to look out for:
Always plan the best approach for the planning application, whether through a Homeowner Full Planning application or a Certificate of Lawfulness via Permitted Development. You may also consider the option of a split application, for example, doing part of the scheme under one type and another, such as a loft conversion, under the other.
Be sure to check for any additional requirements for your application, as there may be hidden costs, such as ecology surveys or flood risk assessments.
Avg Time: 2 to 3months*
*Please note, this timeline assumes the planning application is approved on the first submission. If unsuccessful, you may need to reapply for planning permission, which could take an additional 2 to 3 months, or appeal the decision, which could take 6 months or longer.
Post Planning
Planning permission is often not the only approval required when extending your home. In most cases, these steps are undertaken after planning approval is granted, but some can be initiated while your application is under review. Here are some additional permissions you may need:
A Party Wall Agreement is a legally binding document that outlines the rights and responsibilities of property owners when construction work affects shared walls, structures, or boundaries.
When building an extension, you may need to build over, or near, an existing drainage run that could be shared with your neighbours. If you are building over a drainage run, you will need to apply for a Build Over Agreement. If you are building within 3 meters of it but not directly over it, a Build Close To agreement is required. These applications are submitted to the local water authority.
If your planning application is successful, the planners may request additional information in the form of planning conditions. This is more common for larger properties, homes in special areas of interest such as conservation areas, or new-build projects. Planning conditions often require further details on external materials or ecological considerations. For larger schemes, it is advisable to check for any additional conditions in advance and allocate a higher budget for this stage of the planning process.
What to look out for:
It is often worthwhile to begin structural engineering at this stage, as key elements such as foundation design and beam locations can impact both Party Wall agreements and Build Over agreements.
Neighbours: It's often important to engage with your neighbours before submitting the initial planning application. This allows them to become familiar with the design before you begin the Party Wall process.
Avg Time: 1 month
Technical Design
This process typically begins with a technical meeting to review the engineering, services, and other key elements, along with specifications for windows, doors, and features such as bathrooms. A detailed set of technical drawings is then produced, which will be used for both the tender process and during construction on-site.
What to look out for:
It is often advisable to have pre-plans checked by Building Control to ensure that the drawing set complies with the latest building regulations and other requirements, such as thermal performance.
This is the time to engage with any third-party specialists, such as those for basement tanking or pile foundations. It is crucial to include the technical specifications in the drawing set for both Building Control approval and the upcoming tender process.
Avg Time: 1 to 2months*
* Please note, there may be an option to expedite the process by beginning some elements of this step alongside the previous phase: Post-Planning Permission.
Preparing for Tender
During the technical process, a detailed bill of quantities should be produced, including initial quotes and specifications. The take-off should cover all key elements of the build, such as:
Site Preparation & Overheads: This includes all non-construction elements, such as a site foreman, skip hire, scaffolding, and site protection.
Construction: This includes all structural elements, from the foundation to the roof structure.
Services: This includes all incoming and outgoing utilities, as well as internal systems such as drainage, water supply, power, lighting, AV, and other essential elements.
Building Envelope: This includes windows, doors, external walls, and roof cladding.
Room Logs: This covers the interior fit-out, including kitchens, bathrooms, decoration, and floor finishes. It also includes bespoke joinery, staircases, and fixtures such as doors.
Garden Logs: This includes all garden elements, such as patio finishes, fencing, grass, and planting.
The key areas where you have the most influence are the building envelope, room logs, and garden logs. For example, kitchen costs can vary significantly depending on the supplier, finishes, and appliances. It is advisable to obtain quotes and finalise specifications early in the process.
What to look out for:
Before the tender process, it is important to clearly define which items will be purchased by the homeowner versus the contractor. For example, will you be supplying the windows and doors? Will the kitchen be supplied by you, with the main contractor responsible for installation? Defining these details in advance helps avoid ambiguity and makes it easier to compare tenders from different contractors on a like-for-like basis.
It is crucial to obtain independent references for main contractors and, if possible, visit their completed projects or active sites. Additionally, research their financial history, insurance coverage, and whether they have a health and safety policy in place.
Understanding VAT as part of the project is essential. Are you exempt, or can you benefit from a reduced VAT rate due to the type of project (e.g. new build or conversion)? Certain eligible products may qualify for reduced or zero VAT rates. For larger projects, it may be advisable to seek advice from a VAT expert.
Avg Time: 2w/ks to 1 month
This is a good time to meet with the selected builders, show them the site, and allow them to assess the conditions. This will help them identify potential issues, such as access or parking constraints. It’s also an opportunity to get to know them, as you'll be working closely with them for up to 12 months or more, and they will be working in your home for the duration.
Tender and Pre Commencement
Once you're satisfied with the technical drawings and take-off, it's time to issue the documents, along with any other relevant information, such as engineering details, planning conditions, and essential elements such as Health and Safety pre-commencement documents, to your selected contractors.
A cover letter is typically included, outlining the scope of works and the timeline for when you'd like tenders returned, along with your preferred start date.
After receiving the tenders, they should be reviewed, and any questions should be sent back to the contractors. Once the prices are confirmed, a contractor is chosen. You'll then finalise any outstanding details, including questions and figures, before moving to the next stage.
This stage involves agreeing on the contractor, payment terms, and any initial deposit. A pre-commencement meeting is held with the contractor, followed by a final walkaround of the site. Contracts are signed, and payments are transferred as agreed.
What to look out for:
Before work begins, it is often necessary to obtain an asbestos survey, especially for properties built before 2000. This is a key health and safety requirement.
It is important to check with your home insurance provider to understand what coverage is included during renovation and construction work. Additional coverage or a policy adjustment may be required.
The type of construction contract is crucial. The best approach is often to use an off-the-shelf contract, such as a JCT Homeowner Contract, which provides protection for both parties.
It is important to plan the payment terms of the contract carefully. This includes determining the deposit amount and the retention held for snagging at the end of the project. Additionally, decide whether payments will be structured based on valuations or set stage payments.