Over-crowding is an indicator of housing deprivation and living in such conditions is associated with adverse personal and health effects. Brogan Taylor explains how the ONS is seeking to fill an evidence gap in this important policy area by combining new sources of data with other information about people and houses to provide new measures of living conditions.
How big is your house? It seems an obvious question, but maybe it’s not that straight forward. Here at the ONS we’ve been exploring the use of administrative data on housing and, in particular, floor space by property type.
Analysis of data from the Valuation Office Agency (VOA) has found that the median floor space for houses in England and Wales was 99 square meters (sqm) – that’s about nine typical parking spaces.
Meanwhile, the median floor space for flats was 43sqm – just under the size of four car parking spaces.
Our analysis found that floor space generally follows the expected distribution by property type, for example detached properties are larger than those belonging to a terrace.
When comparing property types, it’s important to note that the VOA has two distinct ways of measuring floor space depending on property type. VOA property types are different to accommodation types collected in the Census of England and Wales, and today we also published research on this topic (see our publication for more information).
Houses, bungalows and chalet style properties are measured using Reduced Covered Area which records the whole dwelling area within the external walls, excluding areas such conservatories, porches and attached garages.
Flats and maisonettes, however, are measured using Effective Floor Area (EFA). This means only the habitable area of the rooms within a dwelling are measured to the internal face of the walls of those rooms, therefore excluding areas like hallways, landings and passages and bathrooms.
The region with the widest range between the largest and smallest median floor spaces is London, with Bromley having a median floorspace of 97sqm and the City of London having a median value of 47sqm.
London Boroughs also tend to have smaller median floor space compared to those in other regions. The smallest median property size for a local authority outside of London is Brighton and Hove and measures 78sqm. In London 45% of the boroughs had a median property size smaller than 78sqm.
Meanwhile, domestic properties in Eden in the North West have the biggest median floor space at 110sqm closely followed by Ceredigion with 109sqm.
Why are we doing this?
Our job at the ONS is to provide clear and timely insight, targeted on the issues at hand. So when census users told us they wanted more detailed categories of property (accommodation) we drew upon improved access to datasets, including those held by other government departments, to see if we can fill an important evidence gap.
We are testing to see if the existing VOA property type data helps answer this need as part of our ambition to produce census-type statistics in new ways.
In the past information about floor space has typically been produced through surveys such as the English Housing Survey. However, due to sample size, analysis of floor space for sub-regional geographies has not been possible.
VOA data, on the other hand, is not based on a sample and therefore offers the opportunity for additional insight into floor space as it can provide information down to small geographies.
But it comes with its own unique challenges, for example, the use of different measures by VOA highlights a key challenge when repurposing administrative data. The data was not initially collected for the means we are using it for and subsequently is not a tailored form of data collection, like is found in surveys and censuses.
As a result of this, we must consider a range of factors when using the data and interpreting the analysis.
Why is this important?
Following the 2011 Census, the ONS used the Bedroom Standard to produce estimates of overcrowding and underoccupancy in England. The Bedroom Standard assigns the number of bedrooms theoretically required by the residents at an address and compares it with the actual bedrooms available, as recorded in the 2011 Census, to provide an indicator factor.
However, this method of deriving an indicator of overcrowding has limitations. When properties that have the same numbers of bedrooms and occupancy are compared, they may have different space available despite the apparent similarity.
VOA data could be used in the future to develop a new approach to understanding living conditions in England and Wales. This could include providing alternative overcrowding measures that focus on living space available (per person) instead of just looking at number of rooms/bedrooms.
Additionally, analysis of VOA floor space data enables housing policymakers to better understand the characteristics of the dwelling stock in their areas, and therefore better meet the future housing needs of residents. Also published today is research comparing census accommodation type with VOA property type which demonstrated the potential of using VOA data to provide more detailed categories of property type. For example, new analysis could include being able to distinguish between bungalows, houses and different types of terraced houses.
We will continue research into understanding how VOA data could be used to enhance 2021 Census outputs and produce admin-based housing characteristics.
We intend to publish additional research outputs later in 2020 including:
- Feasibility research into edit and imputation of admin-based statistics for number of rooms in Census 2021 for England and Wales
- Overcrowding measures, e.g. occupancy rating
- Other housing characteristics such as energy performance and central heating