How do I calculate my home's rebuild cost?

Put very simply, your rebuild cost is the amount of money you’d need to rebuild your home from the ground up (including any driveways, boundary walls and outbuildings). This includes the cost of labour, materials, installations for water, gas and electricity, as well as planning and architects fees.

Providing an accurate rebuild estimate will make sure your home is properly insured. If the unthinkable happens, underinsurance could leave you liable for any difference in cost, so it’s always best to get an accurate assessment to cover your potential losses.

In most cases, the rebuild cost usually comes in below the market value of your home, because it doesn’t account for factors like land and location. However, if your home is listed or was built with unusual materials or features, this may not be the case.

If you have bought your home recently, the rebuild cost should appear on your mortgage valuation or deeds.

If not, there are two ways to calculate your rebuild cost: 

Use the Building Costs Information Service (BCIS) calculator for guidance

Hire a chartered surveyor to assess the property for you

You can find a chartered surveyor on the Royal Institution of Chartered Surveyors website.

The BCIS calculator sits on the Association of British Insurers (ABI) website - it’s a simple tool from a trusted body.

Simply enter your email address to get started, and make sure you have the external floor area of your property to hand.

The calculator takes into account clearing the rubble from an existing structure and is not applicable for houses containing hazardous materials, such as asbestos.

Follow these simple steps to help calculate the floor area of your home:

1. From the outside, measure the length and width of the ground floor of your property. Multiply these two figures together to give you the downstairs floor area.

2. If the upstairs of your home is the same size and shape as the downstairs, you can simply double the ground floor value.

3. If the upstairs space is different, you will need to measure it separately, before adding to the ground floor area measurement.

4. If your home has any more floors you can follow step 2 or step 3 again, depending on which one is relevant.

Once you have the total square footage of your home, you’ll be ready to use the BCIS calculator by following its instructions. BCIS also provide further instructions for measuring your home if you need any more help.

In England and Wales, flats or maisonettes are usually block insured under a single policy. It’s likely that you already pay for buildings insurance under a service charge, so always check your building documents before taking out any new policy.

In Scotland, it is more likely that you are expected to insure your own single flat for buildings cover.

In the event that you do need to insure a single flat or maisonette, you may want to hire a surveyor rather than rely on the calculator, as construction methods for flats vary.

You should review the rebuild cost of your home every time you renew your insurance policy, as the costs of materials and labour change over time.

Any building work you may have had done – including extensions or renovations – could also affect the rebuild cost of your home, so it’s vital you declare it.

If you're aware of your rebuild cost increasing, John Lewis Finance ask that you let us know within 30 days.

If the rebuild cost of your home increases and you don’t update the value of your home insurance, you could well find yourself underinsured with an insufficient amount to cover the rebuild cost.

Be sure to speak to your insurance provider before taking on any renovations that might impact the value of your home.

If you are covered by Specialist Home Insurance from John Lewis, and you have not recently had a full survey, we may decide to provide a desktop valuation at your underwriter's discretion to ensure you have the right cover. This is an independent survey of your property conducted remotely using ordinance survey data and various other tools.

A detailed report is then produced with recommendations for accurate rebuild figures based upon the property’s dimensions, age and construction materials.