How To Calculate Your Home’s Rebuild Costs

With home insurance, you are protecting the building against damage but also in the event that something disastrous happens and you need to rebuild the home in its entirety. Therefore, calculating the exact rebuild cost is essential using Rebuilding Cost Calculator.

Making sure you have the right level of protection for your home is essential. The Society of Chartered Surveyors Ireland’s Rebuild Calculator is a handy tool that can help you calculate the rebuild cost of your home, giving you peace of mind.

This calculator is intended as a guide only to give you an indication of the rebuilding cost of your house. To be totally confident that your home is adequately insured, an independent surveyor, can calculate the exact rebuilding cost of your home. Rebuild costs should also factor in the costs of professional services, if for example, you needed to avail of a solicitor or architect.

Why is the rebuild estimate so important?

An inaccurate estimate could mean you pay more for your buildings insurance than necessary, while an accurate rebuild cost means your buildings insurance provider will be able to cover all of the costs should your home need to be rebuilt from the ground up. 

You’ll avoid having to cover a shortfall in the estimate and the risk of invalidating your insurance if the rebuild costs exceeds your insurer’s criteria. 

It’s important to remember that if the actual cost is higher than the figure you gave in the quote, your insurer won’t be liable for the remaining difference, but you may be when you make a claim. 

Why is the rebuild cost different from the market value of my home?

The key difference between the rebuild cost of your home and its market value is the rebuild amount is not influenced by geographical factors related to your property. Factors such as market supply and demand, school catchment area etc don’t influence the cost of rebuild but will impact the market value of your home.

How Do You Calculate Your Home’s Rebuild Cost?

How you should find out your home’s rebuild cost depends on whether you own:

  • a standard brick-built house
  • a home constructed from non-standard materials
  • a listed building
  • a flat

How to calculate the rebuild cost of a house

If you live in a house constructed from standard materials, such as bricks, there are two ways to calculate its rebuild cost:

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

How to use the Building Cost Information Service (BCIS)

You can use the RICS’s Building Cost Information Service (BCIS) to calculate the cost of rebuilding your house for insurance purposes.

To use the calculator you need to register with an email address and accept the terms and conditions of use. 

Once registered, you will be able to use the calculator 4 times in any 12-month period. 

You’ll need to input the following information:

  • whether the property is a house, bungalow, or flat
  • its style (i.e. detached, terrace etc)
  • the number of storeys
  • the postcode of the property
  • the year it was built
  • the external floor area (in metres squared or feet squared)
  • the number of bedrooms and bathrooms the property has
  • whether it has garage space or a cellar
  • the wall type and roof type
  • whether it’s a listed or unusual property

The calculator will then give you a rebuild figure for rebuilding your home to its existing design in modern materials, using modern techniques.

The figure given will cover rebuilding the structure of the property including the foundations, walls, roof, floors, doors and windows, built-in fittings (i.e. kitchen and bathroom), plus installation for heating, hot and cold water, gas, electricity, lighting and ventilation.

However, it won’t include things like loose fittings and furnishing such as carpets and cookers.

How to calculate the floor area

It’s easiest to measure your home’s area from the outside. 

Measure the length and width of the ground floor walls, then multiply these two figures together.

If the upstairs is an identical size to the downstairs, simply double the ground floor area. If it’s different, or you have more storeys, calculate each floor separately and add it to the ground floor result. 

How to calculate the rebuild cost of a home constructed from non-standard materials

Most homes are built with brick or stone walls with a roof made of slate or tile.

A non-standard construction is basically anything that falls outside of this definition. The construction might include:

  • glass, plastic or fibreglass
  • concrete, metal, wood or flint stone walls
  • asphalt or shingle
  • steel or timber frames
  • corrugated iron walls or frames
  • thatched properties
  • flat roofs 
  • prefabricated concrete houses 
  • wattle and daub

If your home is made of non-standard materials, its rebuild cost may be higher than its market value. 

If you live in a home made of non-standard materials, you should contact a chartered surveyor and get a survey done to calculate rebuilding costs.

How to calculate the rebuild cost of a listed building

To find out if you live in a listed building you should visit the relevant website for your country and conduct a search.

If you live in a listed building or one with special architectural features, you should contact a chartered surveyor to get a survey done to calculate rebuilding costs.

How to find a chartered surveyor

You will need to hire a chartered surveyor if:

  • your house is built from non-standard materials
  • you live in a listed building
  • you want more details than provided on a basic BCIS calculation

You should visit the RICS website to find a chartered surveyor. You can search for a surveyor near you by entering your town or postcode.

The surveyor will carry out detailed measurements of your home and then prepare a professional Rebuilding Cost Assessment. This will cost about £250.

How to calculate the rebuild cost of a flat

Most flats are leasehold. If you own a leasehold flat in a block of flats, the buildings insurance will normally be the responsibility of the freeholder or their managing agent.

However, leaseholders pay for buildings insurance via service charges. 

If you own a share of the freehold of your block, you and the other leaseholder are jointly responsible for the buildings insurance. In this situation you’d normally take out one buildings insurance policy for the entire block, and share the cost.

It’s best to speak to a surveyor or insurance broker for advice about this.

Do I Need To Update My Home’s Rebuild Cost?

With most insurers, you won’t be required to update the rebuild of your property at renewal. 

Some insurers will ‘index link’ their buildings insurance policies, meaning they will automatically increase the rebuild cost of your property in line with inflation.  This should prevent you from being under-insured

If you make any improvements or renovations to your home – e.g. an extension, a loft conversion or a new kitchen – you should re-calculate your home’s rebuild cost to make sure you are fully covered.


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