House Extension Drawings and Plans: The Complete Guide

A house extension is the perfect way to increase the floor space of your home without resorting to the expensive and inconvenient option of moving houses. And with a range of styles and designs available that can be customised to your needs and tastes, it’s no wonder that house extensions have become the ideal solution to create beautiful, bespoke spaces in your home.

Good Design and Build helps you design and create the ultimate extensions that add space, value, and style to your home. The first step towards achieving this goal is to design and plan the ideal extension with the aid of detailed house extension diagrams that not only allow you to understand the feasibility of the project but also help bring your vision to reality.

House extensions are usually designed based on the area available on the property. As such, commonly found extensions in and around London include:

Built on the rear of a property, the versatility of rear extensions makes them a popular choice among homeowners. Rear extensions can be used to create kitchen extensions, guest rooms, playrooms, or office pods.

A combination of side and rear extensions that create an L-shaped structure, wrap around extensions add incredible width and depth to a property. As a result, these extensions are useful in creating multiple rooms, large kitchen diners, or even open floor plans.

These extensions utilise the area that runs along the side of a property, along with a portion of the rear. Side return extensions are ideal for creating beautiful indoor-outdoor connections that add an abundance of natural light and ventilation to a home.

Multi-storey extensions are a cost-effective solution by which you can add incredible floor space to a home. This is because these extensions essentially double the area of the extension without doubling the roofing and excavation costs. Double-storey extensions are perfect for creating additional bedrooms, bathrooms, or even high-ceilinged living spaces in a home.

Additionally, conversions and renovations of existing spaces within the house can also be designed and re-imagined using house extension drawings.

Good Design and Build help you select, design, draw, and construct the right extension that will be the perfect fit for your home.

Being the first step of conceptualising and initiating your extension, house extension drawings allow you to get an accurate and detailed picture of the extension you have in mind. This not only aids in the planning process and helps avoid critical structural and design errors, but also enables you to prepare a detailed budget and timeline based on the structural and technical requirements of the extension.

House extension drawings are also legally required for applications for planning permission or even lawful development certificates. This makes them a crucial factor in the success of the extension project.

Based on your requirements, and the requirements of the council, house extension drawings may be of the following types:

• Existing drawings

These drawings show the current house as is. The demarcated features help you to better understand how the different spaces relate to each other, allowing you to have a clearer idea of the changes required, or how the new extension will fit in.

• Floor plans

Floor plans show you the aerial view layout of the house. This basically includes the size, shape, and arrangement of the different rooms; and may also illustrate the placement of windows, doors, walls, and staircases as well as any fixed installations and appliances. This allows you to understand the suitability of the space and the manner in which you can move through the space.

• Elevations

An elevation drawing is a two-dimensional representation of one portion or façade of a building. It generally shows the exterior of a house with key features such as windows, doors, porches, steps, and decks. These drawings also show dimensions such as wall height in relation to the ground level.

• Structural drawings

These mostly consist of line work and are usually prepared by engineers. Structural drawings comprise of all the plans involved in the construction of a structure. This includes the framework, foundation and dimensions, wall sections, and load-bearing beams and columns. These drawings help establish the strength and stability of the proposed structure.

• Electrical/ Plumbing/ HVAC drawings

These technical drawings visually represent the various systems such as the electrical system, plumbing and drainage system, and heating, cooling, and ventilation systems. These vitally important details help in the installation process.

The time taken for a detailed drawing to be put together for a proposed extension may range from 3-6 weeks. However, this is dependent on a number of factors such as:

• The size/ complexity of the project
• The availability of the architect
• The availability of existing drawings

On average the cost of hiring an architect to prepare the requisite technical and structural drawings could range from £10,000 to £20,000. However, this varies depending on many factors including:

• The size/ complexity of the extension
• Location

• If the architect is charging a fixed fee, a by-the-hour rate, or a percentage of the project costs (for example 15% of the total construction costs)
• Whether the architect is hired only for the purpose of drawing plans for planning applications, or will they be involved in the project management as well
• The repute and experience of the architect or firm

Your planning application, be it for full planning permission or a lawful development certificate, must be submitted during the planning stage before any construction can begin. The extension drawings should be included with the planning application that is to be submitted to the local council.

Likewise, all technical and structural drawings must be submitted along with the building regulations approval application.

Unequivocally yes.

While you may be concerned about the cost of hiring experts, the decision to prepare extension drawings without professional help could prove to be much more costly. 

This is because an architect will drastically increase your chances of success by helping you to:

• Plan and design the ideal extension 
• Avoid common errors and design flaws
• Optimise the space to fit in your specific requirements or styles
• Choose the right design that is suitable for the space
• Understand and advise you on the feasibility of the plan by considering the area, cost and availability of building materials, environmental factors, and building guidelines

Quite simply, an experienced and expert team can help bring to reality your dream extension, but it all starts with the perfect plan.