How to Budget For Your House Build and Spot Hidden Costs

Buying a building plot is the first important step. You can get an idea of land costs with a bit of research. Local estate agents advertise land for sale and you can also search online using websites dedicated to self-build land listings. Remember to factor in legal fees and taxes.

If you’re building a bespoke home, a portion of your overall budget will need to cover hiring professionals like an architect, engineer and a quantity surveyor. However, if you choose to build a Coldwells Build Passivhaus, we offer all these services in-house, simplifying the process and potentially saving you time and money.

Factor in the cost of where you will live for the duration of the project. Can you stay on the site in a caravan, which you may have to buy, or will you need to rent somewhere to live?

If you're building a bespoke home, it's wise to set aside a contingency fund for unexpected expenses. A typical allowance is 15-20%, but consider your options carefully—what would you do if more funds were needed?

When building a Coldwells Build Passivhaus, a smaller contingency fund is usually sufficient. One of the advantages of choosing a pre-designed, prefabricated home is that many components have already been assembled in previous projects, making the costs and details much more predictable.

Once you know all of the above costs, subtract these from your overall budget – the total amount you can spend to build your home.

The location of your building plot can impact the overall project cost, especially if you're in remote areas like Scottish islands. In places like these, contractors may not be readily available, meaning they have to travel long distances to reach your site. This adds to the costs due to accommodation and travel and ferry expenses.

While it might be your dream location, if your budget doesn’t align with the realities of building there, you may need to reconsider your plans or look at increasing your budget.

Sloped sites are notorious budget busters, often demanding a split-level home, or extra digging, filling and levelling. It’s worth getting a topographical survey to make informed decisions on house position, access and the amount of groundworks required. If you’re building a Coldwells Build Passivhaus, this is included in our service.

The biggest cost uncertainties often lie beneath the surface of your plot. If you’re building a Coldwells Build Passivhaus, our service includes a complete site assessment, so you have a clear idea of the ground conditions. 

Extremely boggy or rocky ground could bump up costs. A boggy site could lead to drainage issues and may require deeper excavation and filling with imported hardcore. Larger rocks will need breaking up and any surplus removed from site. 

If you’ve found a site you want to buy, make sure to include a condition in your offer that lets you assess the ground conditions before finalising the purchase. This way, if the conditions are unsuitable for development, you'll have the option to withdraw from the purchase or renegotiate the price.

Make sure your plot has suitable vehicle and construction access. For example, a steep track could hinder the delivery of a Coldwells Build Passivhaus, as we use a large crane to lift and assemble prefabricated panels. Buying a cheap site that needs a long access road worth £40,000 can be a false economy. A level access road over a short distance is more economical. If you’re building a Coldwells Build Passivhaus, we’ll provide a quote for putting in access roads and clearing the site.

The availability of services like water, electricity and telecoms/broadband can affect the cost of developing a building plot. If your chosen site isn’t already hooked up to these services, it will cost extra to extend existing connections or install new ones. In rural areas, you might need to invest in a private septic tank or treatment plant if you can't connect to a mains sewerage system. If you’re building a Coldwells Build Passivhaus, we’ll obtain quotes from utility companies for service connections.

If you’ve bought an existing building, will it need to be demolished before your new home can be built? If so, this will need to be factored into the cost, along with skip hire and removing waste from site. If asbestos is present, a specialist contractor will be required to remove this safely. Similarly, if you're building on land previously used for agriculture or industry, there may be contaminated ground. This requires safely removing and disposing of the contaminated soil.

Building a bespoke home is complex. From hiring architects and contractors to design choices, material selections and layout decisions. For busy people, it’s a big commitment. 

A great way to streamline the process is to opt for a pre-designed prefabricated home like the Coldwells Build Passivhaus. Our ready-to-go homes are constructed off-site, saving you both time and money compared to custom builds. You’ll skip the added expenses of custom components while still living in the world’s best energy-efficient home.

You don't have to finish everything at once—consider phasing your project to spread out costs. For example, you could add the garage later or start with simple landscaping and add more features over time. You can also plan for future upgrades, like solar panels, by installing the necessary wiring now. This approach allows you to move into your home sooner, while making improvements gradually as your budget permits.

One area that is vital for keeping control of your costs is to stick to your design. Changing things on site can be expensive, especially if you have to keep altering completed work.

While it may cost around 4-8% more initially to build a Passivhaus, investing in a well-planned, extremely energy-efficient home will yield long-term savings on heating bills and maintenance expenses.