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Calculating The Rebuild Cost Of Your Home

Estimated reading time: 6 minutes

The rebuild cost is the cost of rebuilding a home destroyed beyond repair.

The cost includes demolition, clearing the site, and the labour and materials needed to restore a home to its former glory.

The rebuild cost is not the same as a home’s market value – it’s usually lower because you already own the land the property is built on. However, the price can creep up if the property is not brick-built or has special architectural features.

Knowing your rebuild cost affects the price you pay for insurance cover.

If you substitute the market value, you will pay more than necessary for your cover, while guessing a lower value than the rebuild cost means you are underinsured.

Working Out Your Rebuild Cost

Depending on how your home is designed and built, there are two ways of working out your rebuild cost.

If the property is standard built – which means the walls are brick and the roof tiled – you can choose from:

  • Using the free online Building Cost Information Service’s home rebuilding cost calculator
  • Commissioning a chartered surveyor to deliver a cost report

If the property is of non-standard construction, is listed or has special architectural features, use a chartered surveyor to compile the figures.

Is your home listed?

Each UK country has an agency that monitors listed and historical buildings:

The relevant agency for the country where your building is listed should have the information online.

Be aware that the free online calculator is based on the cost of rebuilding an average home to its existing standard with modern materials. In contrast, listed buildings need to be replaced like-for-like. If a listed home must be rebuilt in its original style, the cost will be much higher than one returned by the calculator.

Do not rely on the calculator. Contact a chartered surveyor to work out a more accurate figure.

Finding a surveyor

To find a chartered surveyor, go to the Royal Institution of Chartered Surveyors website. Don’t leave the job to a builder or estate agent, as they are not qualified to calculate the rebuild cost.

When To Calculate The Rebuild Cost

If you are insuring a newly-built property, you may find the current rebuild cost is listed in the mortgage valuation.

Don’t use the mortgage rebuild value if the figure is more than a couple of months out-of-date, as the amount could have changed due to inflation.

But do check the rebuild cost is still valid every time you renew your home insurance.

Recalculate the rebuild cost if you carry out renovations or add an extension. Ensure you keep your insurer updated with any changes, so you are not under or overpaying your premium.

Need Help with your Finances?

How to use the rebuilding cost calculator

The Building Construction Information Service’s rebuild cost calculator is simple to use, but you will need to prep some data in advance.

Measuring house external floor areas

Working out the gross external floor area (GEFA) is the most challenging task for the calculator.

You need to measure the GEFA for each storey.

The best way to calculate GEFA is to go outside with a tape measure and take the length of the front and side walls of the ground floor. Measure in either feet or metres, but consistently use the same scale.

If your home has an integral garage, include this in the measurements.

For most homes, the ground floor GEFA is doubled or tripled to account for the second and third floors.

If the upper floors have different footprints from the ground floor, calculate the areas separately and add to the ground floor amount. Try to measure from the outside to account for the thickness of the walls.

GEFA includes:

  • Perimeter wall thickness and external projections
  • Areas occupied by internal walls and partitions
  • Columns, piers, chimney breasts, stairwells, roofs, lift wells and the like
  • Integral garages
  • Conservatories

GEFA excludes

  • Attached garages and canopies
  • Open vehicle parking areas, patios and terraces
  • Greenhouses, garden stores, external fuel stores and other outbuildings

Measuring flat internal floor areas

The rebuild cost of a flat is calculated differently from that of a house.

You need the Gross Internal Floor Area (GIFA) rather than the GEFA.

GIFA is the floor area of a flat measured to the internal face of the exterior walls. The measurement is different as the building owner will have the structure’s shell insured.

However, flats or maisonettes are usually insured together as a block to simplify the rebuilding task if there is a claim. The premium is part of the service charge.

Rebuild cost of outbuildings

For detached or attached garages, the rebuild cost is an allowance based on the number of car spaces you have.

The calculation also includes allowances for outbuildings, fences, gates, walls, patios and other hard landscaping.

Special features, like hot tubs or swimming pools, are calculated separately, usually by a chartered surveyor.

Other rebuild cost data

The remaining data for the rebuild cost calculator is easily collected:

  • Number of bedrooms and bathrooms
  • Number of garage parking spaces
  • Brick or stone wall construction
  • Roof type
  • If there is a cellar
  • Is the building listed or unusual?

Using the rebuild cost calculator

The calculator will return your home’s rebuild cost.

Homeowners can only use the calculator up to four times daily for free.

Home Insurance Rebuild Cost FAQ

How do I work out the rebuild cost for a loft conversion?

A two-storey home with a loft conversion is entered as a three-storey property for the calculator. Work out the internal floor area and then add a 30-centimetre or 12-inch allowance for the wall thickness for each side.

How do I work out the rebuild cost of a cellar?

A cellar is not included when counting storeys or measuring floor area.

My home is in bad repair, does that affect the rebuild cost?

Not necessarily. A home in a poor state still needs rebuilding to current regulations and with the latest materials, so is unlikely to cost less to reconstruct than any other similar home.

Can I use the internal floor area from an EPC instead of the GEFA?

The data is not interchangeable, but you can take the Energy Performance Certificate (EPC) data and add a 10 to 20 per cent allowance. The GEFA depends on the size of the house, so a tall narrow house would be nearer 20 per cent than 10 per cent.

How is VAT worked out for rebuilding costs?

A rebuilt home is a new build for VAT purposes. The materials are zero-rated, but professional fees are subject to VAT. The calculator accounts for VAT on fees.

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