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Technical Overview

Introduction

The BCIS Residential Rebuilding Cost Calculator service calculates the rebuilding cost of a residential property given minimal details of the property and is based on the BCIS Rebuilding Cost Models accepted as standard by surveyors and loss adjusters.

The BCIS models cover a wide range of houses (including bungalows), houses converted into flats and purpose built flats, but not all domestic property is covered. Exceptions and exclusions are described below, along with some information on the approach.

Detailed guidance is published by BCIS on the basis on which the reinstatement cost should be calculated. For example, costs include demolition of any remaining structure and rebuilding in accordance with current building control legislation. An allowance is made for professional fees. VAT is included on professional fees but not on the rebuilding work. For further details, please refer to the BCIS Guide to House Rebuilding Costs and the BCIS Guide to the Rebuilding Cost of Flats.

Using the BCIS Residential Rebuilding Cost Calculator will provide a reinstatement cost consistent with (although not as accurate as) an assessment made by a surveyor using the BCIS Rebuild Online service.

Listed or Unusual Properties

Listed buildings and properties that have special or unusual features are not covered by the service. Some listed buildings can require very expensive specialist crafts to reinstate them while other examples may cost little more than an equivalent modern house to rebuild. It is essential that professional advice be sought in these cases.

Buildings within a conservation area will normally be covered by the models, although any special or unusual features that would need to be recreated cannot be assessed. Professional advice should be sought if there are doubts. Buildings with special or unusual features, including architect designed houses, are not covered by the BCIS models.

Houses

Houses may be detached, semi-detached or terraced (end of terrace is treated as semi-detached). Bungalows, two, three and some four storey houses are covered. Styles of houses have changed over the years and BCIS has identified five age bands:

1720-1839
1840-1919
1920-1945
1946-1979
1980 to date

The approximate age passed to the service will be used to select the appropriate set of models. Table 1 shows the coverage for age and type but the principle exclusions are as follows:

Bungalows: No models for bungalows prior to 1840.

Four Storey Houses: Only available for 1720-1839.

Flats

BCIS recommends that flats are insured as a block rather than individual flats being insured separately. It is acknowledged that this is not always possible and so the service will calculate the rebuilding cost based on individual flats. If the block is to be insured then professional advice should be sought.

Houses Converted into Flats: Models are available for two and three storey houses built between 1840 and 1945 which have subsequently been converted into flats.

Table 2 shows the coverage for conversion flats.

Purpose Built Flats: Models are available for low and medium rise (two, three or four storey) blocks of flats built since 1945. Table 3 shows the coverage for purpose built flats.

Size

The main factor affecting rebuilding cost is the size of the property and the BCIS models use floor area to measure size. The service will accept three alternative measures of size: floor area; number of rooms and number of bedrooms. Further definitions of these measures are available in each case.

Area is by far the best measure of size and BCIS recommends that a reinstatement cost is calculated based on floor area whenever possible. Where the floor area is not available, the service will estimate the floor area from either the number of rooms or the number of bedrooms, taking into account the age, type and location of the property. This is achieved using a combination of BCIS research over the last 30 years and data from over 100,000 surveyor’s reports where the surveyor has visited the property.

The area of properties with the same number of rooms (or bedrooms) clearly varies. The expected area is used for the point estimate of reinstatement cost, while the 90% range is used when calculating the minimum and maximum costs.

Quality

Quality is another major factor in the cost of rebuilding houses and flats. The BCIS models have three levels of quality: basic, good and excellent. On average, surveyors class approximately 5% of properties as basic and 5% as excellent, although the proportion varies with type, age and size of property. The estimated rebuilding cost is based on the BCIS good quality dwelling, while the minimum and maximum costs are based on basic and excellent respectively.

Construction

The BCIS models are all based on ‘traditional’ construction of brick walls and tile or slate roofs but adjustments are available for stone external walls and thatch or flat roofs. The cost of stone in particular, and thatch to a lesser extent, can vary significantly depending on the type of material and construction. The selection of these forms of construction will therefore influence the range as well as the rebuilding cost.

Timber framed houses with brick cladding and pitched roofs have become more popular since 1980. The cost of constructing a single timber framed house in this style is similar to the cost of brick/block construction and the models therefore apply.

Timber framed buildings that are also clad in timber are not covered by the models.

Cement rendered block-work is a common form of external wall construction, especially in Scotland. The cost of construction is similar enough to brick wall construction for the models to be applicable.

Features

Many features will affect the rebuilding cost. The service currently allows adjustment for the number of bathrooms and a cellar.

If the number of bathrooms is supplied, then the estimate will be adjusted accordingly, otherwise the number of bathrooms in the modelled property is used, but an allowance is made to increase the possible range of costs.

The service is able to add the cost of a cellar to the reinstatement cost assessment if the existence of a cellar is passed to the service, otherwise it is assumed that the property does not have a cellar.

Garages

Integral garages within a house are included in the cost of rebuilding the house (and the floor area or number of rooms should reflect this). The cost of rebuilding attached or detached garages must be added to the assessment. The number of garage spaces (ie a single garage counts as one, while a double garage counts as two) can be passed to the calculator. If the number of garage spaces is provided then the reinstatement cost of the garage(s) will be included in the calculation.

Other External Works

It is possible that garden buildings and features may cost a significant amount to reinstate should they be damaged. Apart from garages, no allowance is made for other external works such as sheds, greenhouses, walls, driveways, decking, extended drainage runs, etc.

Demolition & Professional Fees

The rebuilding estimates include an allowance for the cost of demolition and removal of debris, support and weatherproofing needed to adjoining structures and architect’s and surveyor’s fees.

Current Prices

BCIS models are completely re-priced each year. Between annual updates the costs are adjusted using the ABI/BCIS House Rebuilding Cost Index. Costs are therefore always calculated at either the current month or last month’s levels and this is stated in the report.

Location

BCIS calculates location indices based on administrative areas. Indices are available for most district authorities in the UK, but in the few cases where insufficient data is available, the adjustment for the next level up (typically, county in England) is used.

Table 1 - House Coverage

Period	Type	Bungalow	Two Storey	Three Storey	Four Storey
1980 to date	Detached	✓	✓	✓	X
1980 to date	Semi-detached	✓	✓	✓	X
1980 to date	Terraced	✓	✓	✓	X
1946 - 1979	Detached	✓	✓	✓	X
1946 - 1979	Semi-detached	✓	✓	✓	X
1946 - 1979	Terraced	✓	✓	✓	X
1920 - 1945	Detached	✓	✓	✓	X
1920 - 1945	Semi-detached	✓	✓	✓	X
1920 - 1945	Terraced	✓	✓	✓	X
1840 - 1919	Detached	✓	✓	✓	X
1840 - 1919	Semi-detached	✓	✓	✓	X
1840 - 1919	Terraced	✓	✓	✓	X
1720 - 1839	Detached	X	✓	✓	✓
1720 - 1839	Semi-detached	X	✓	✓	✓
1720 - 1839	Terraced	X	✓	✓	✓

 

Table 2 - Converted Flat Model Coverage

Period	Type	Two Storey	Three Storey
1920 - 1945	Detached	✓	✓
1920 - 1945	Semi-detached	✓	✓
1920 - 1945	Terraced	✓	✓
1840 - 1919	Detached	✓	✓
1840 - 1919	Semi-detached	✓	✓
1840 - 1919	Terraced	✓	✓

 

Table 3 - Converted Flat Model Coverage

Period	Two Storey	Three Storey	Four Storey
1945 to date	✓	✓	✓

 

Input Parameters

1. LoginID*
2. Password*
3. Postcode*
4. Building Type*†  
5. Wall Type*
6. Roof Type
7. Building Age*
8. Number of Floors
9. Number of Flats on same floor (for flats only)
10. Area (GEFA for houses; GIFA for flats)
11. Number of Rooms (alternative to floor area)
12. Number of Bedrooms (required if Floor Area and Number of Rooms are missing)
13. Number of Garage Spaces
14. Number of Bathrooms
15. Special Features

* Mandatory inputs

† The building type consists of the house style or flat type and number of storeys.
Output Parameters

Four output parameters are returned: Expected Total, Minimum Total, Maximum Total, and Report.