How to Build a House Extension

Building a house extension is one of the most rewarding ways to add space, value, and functionality to your home. Whether you want to extend your kitchen, add a bedroom, or create a home office, understanding the process from start to finish is crucial. In this guide, we’ll walk you through each step of building a house extension, tailored for homeowners in Edinburgh and the Lothians.

1. Planning Your Extension

The first step in building a house extension is planning. This involves deciding what you want to achieve with the extra space and considering any local restrictions or requirements. Here are some key questions to ask yourself:

What will the extension be used for? (e.g., a bigger kitchen, additional bedroom, or home office)
How much space do you need, and where will it be added (side, rear, or above the garage)?
How much can you spend?

Once you have a clear vision, you’ll need to consider planning permissions. In Edinburgh and the Lothians, certain types of extensions, such as smaller single-storey ones, may not require planning permission, especially if they fall under permitted development rights. However, if your home is in a conservation area or listed, additional permissions will be needed. For specific tips on permits and approvals, check out our guide to planning permissions. To learn more, check out our blog post on house extension: where to start – click here.

2. Designing the Extension

Working with an experienced architect or designer is essential to bring your vision to life. During this stage, the focus will be on the layout, structural elements, and how the extension will blend with your existing home. Key considerations include:

Structural stability (especially for two-storey extensions)
Ensuring natural light flows into the space through options like skylights or large windows
Selecting materials that match or complement your existing home’s exterior

When it comes to cost, keeping the design simple (such as a rectangular shape with a flat roof) will generally be more budget-friendly.

3. Budgeting for the Extension

One of the most common questions we get is, “How much will my extension cost?” The total cost depends on factors such as the size, complexity, and materials used. On average, in Edinburgh and the Lothians, expect to pay per square metre for a standard single-storey extension, however there will be additional costs for planning permissions, architectural fees, and structural changes.

To save on costs, consider sourcing materials locally, or even tackling simpler jobs like painting yourself. However, leave more complex tasks such as electrics or plumbing to the professionals.

4. Managing the Build

Once the design and planning stages are complete, the building work can begin. This involves:

Preparing the site: Groundwork will be carried out, including excavating and laying foundations.
External Construction: The structure of the extension is built, including walls, windows, doors, and the roof.
Internal Construction: Once the structure is watertight, interior work begins, including installing electrics, plumbing, insulation, and plastering.

It’s important to maintain good communication with your builder during this stage. Consider splitting the project management between you and the contractor. For example, the builder could handle the main construction while you manage tradespeople for the finishing touches. If you plan to oversee the project, read our detailed guide on how to project manage a house extension. To learn more, check out our blog post on how to project manage a house extension – click here.

5. Finishing the Extension

As the build nears completion, attention will turn to the interior. At this stage, you’ll choose flooring, paint colours, and any other finishes. For the best results, make sure everything from plumbing to lighting is installed correctly to avoid any costly fixes down the line.

Lastly, your builder will conduct a final inspection to ensure everything meets building regulations. This ensures that the structure is safe, energy-efficient, and meets local legal standards.

Conclusion

Building a house extension can seem daunting, but by following a clear, structured approach, you’ll transform your home in a way that suits your needs. At Sawmill Contracts Ltd, we specialise in creating bespoke extensions in Edinburgh and the Lothians, helping homeowners enhance their living spaces while ensuring the build is smooth and stress-free.