Scottish House Condition Survey: Methodology Notes 2022

2 Definitions of Categories in the Key Findings Report

2.1 Dwelling Types

The SHCS uses the following definitions of dwelling types:

• Detached house: a house that is free standing with no party walls
• Semi-detached house: a house that is only attached to one other dwelling, commercial premises etc. The two properties taken together should be detached from any other properties.
• Terraced house: a house forming part of a row of three or more dwellings, commercial premises etc.
• Tenement flat: a dwelling within a common block of two or more floors (commonly up to five storeys but may be higher in certain circumstances) where some or all the flats have a shared or common vertical access. The selected dwelling need not share the access, but may be situated within the block with shared/common access (own door flat).
• 4-in-a-block: each flat in a block has its own independent access. Flats on the upper level have an internal or external stair.

Tower/slab: flats in a high rise (ten or more storeys) or flats where the common circulation is predominantly horizontal (maisonette, balcony, or gallery access)

Flat from a conversion: flats resulting from the conversion of a house only. A flat converted from a non-residential building (e.g., a warehouse) is classified according to the above flat types​​​​.

2.2 Household Types

The SHCS uses the following classification of household types:

• Families: households which contain at least one child aged under 16. Resident adults may be of any age
• Older households: small households made up of one or two residents, at least one of which is aged 65 or older
• Other households: these are all other households with adult residents (of any age) and no children

The pensionable age threshold used for SHCS key findings reports from 2015 onwards is 65 years for both men and women. Previous publications used 65 for men and 60 for women. Therefore, the categories ‘Older households’ and ‘Other households’ used from 2015 are not fully comparable with previous years.

2.3 Urban Rural Classifications

The urban/rural classification in SHCS key findings reports is the Scottish Government’s 2-fold and 6-fold urban rural classification. Dwellings in settlements with over 3,000 people are considered urban by this definition. For 2021 onwards, the 2020 urban rural classification is used for reporting, calibration weighting and in fuel poverty calculations to identify households in remote rural, remote small town and island (RRRSTI) areas for which uplifts to the UK Minimum Income Standard are applicable.

The Scottish Government published the 2016 urban rural classification in 2017. However, to remain consistent with the classification underpinning survey weight derivations, the 2013/14 urban rural classification (2011 data zone edition) is used for reporting 2016 to 2019 data. Prior to 2016, 2001 data zones are used.

2.4 Gas Grid Coverage Derivation

Determining whether a dwelling is within the coverage of the gas grid is primarily based on its proximity to gas distribution pipes. A dwelling is “on the gas grid” if it is within 63 metres of a low, medium, or intermediate pressure pipe, the usual maximum distance for a standard domestic connection. This methodology was used for deriving gas grid coverage for the 2013 to 2019 SHCS key findings reports.

Figure 2.1: Gas grid derivation using GIS mapping

Figure 2.1 shows how this is derived using GIS mapping. From the dwelling location information of surveyed properties, a 63-metre buffer is drawn. Where this buffer intersects a gas distribution pipe, the dwelling is said to be on the gas grid. In the example in Figure 2.1, dwelling A is on the gas grid, while dwelling B is not.

The gas grid information used for this mapping is provided by SGN.  It includes both the national gas network and the Scottish Independent Undertakings (SIUs), where gas is provided in areas remote from the national gas grid. It does not however include information on pipes owned and operated by Independent Gas Transporters (IGTs). Therefore, dwellings classified as off the gas grid by this method may be within 63 metres of an IGT operated gas distribution pipe and potentially have a connection to the gas grid. This methodology may therefore slightly undercount dwellings within the range of the gas grid.

The SHCS collects information on whether a dwelling has a mains gas connection. So, to account for the potential undercount of dwellings on the gas grid, from 2021 we have introduced an improvement to the gas grid coverage derivation whereby a dwelling categorised as being off the gas grid by the method described above but recorded as having a mains gas connection in the SHCS is re-categorised as being on the gas grid.

2.5 Reasons Why Home Heating is Difficult

Question HT14 in the Scottish Household Survey asks: “Which of these things, if any, make it difficult to heat your home”. There are 19 response categories and respondents can choose any combination of reasons why heating their home is difficult. Response categories are grouped for reporting in the energy perceptions section of the key findings reports from the SHCS.

“Poor or inadequate heating” corresponds to the response categories:

• No central heating
• Not enough heaters/radiators
• Position of heaters/radiators
• Poor system/need new system
• Radiators not big enough
• Heating not working
• Dislike storage heaters
• Inadequate heating
• Heating in part of house
• Can’t afford to replace system

“Hard to control heating” corresponds to the response categories:

• Difficult to control/regulate
• Hard to control heat

2.6 Hard to Treat Cavity Walls

Key findings reports from the SHCS use the Energy Company Obligation (ECO) definition of hard-to-treat cavity walls (HTTCs) to provide a breakdown of the remaining insulation potential of cavity wall dwellings in the Scottish housing stock.

Under this definition a cavity wall is considered hard-to-treat if:

• The building has three or more storeys. Dwelling spaces in lofts are not counted as storeys
• The building is severely exposed to wind-driven rain. The SHCS is not able to collect this information, which will lead to an underestimation of HTTCs
• Walls at risk of water penetration, i.e., walls requiring urgent repair to the wall finish and walls with penetrating damp
• Non-traditional building types, e.g., timber frame, metal-frame, and prefabricated concrete
• Partially filled, narrow or uneven cavities as well as cavities with failed cavity wall insulation. The SHCS is not able to capture this information. As a result, HTTCs may be underestimated

Note that the presence of a conservatory alone does not cause a dwelling to be considered hard-to-treat under the ECO definition of HTTCs.

2.7 Disrepair

Key findings reports from the SHCS use different categories of disrepair to describe the state of disrepair of a dwelling.

A range of elements - both internal and external - are assessed for the extent of disrepair, the urgency of disrepair (relating to external and common elements only), and in some cases the residual life of the element.

In a small number of instances, surveyors may not be able to assess the state of repair of certain elements of a property. This results in a disrepair status of ‘unobtainable’ for the full property since we are unable to say for certain whether disrepair exists. This usually affects a small number of the properties surveyed. Tables and figures relating to disrepair describe where these properties have been counted for clarity in reporting.

​​​​​​​2.7.1 Critical Elements

The critical elements are those whose condition is central to a dwelling being wind and weatherproof, structurally stable and safeguarded against further rapid deterioration. They are as follows:

• Roof covering
• Roof structure
• Chimney stacks
• Flashings
• Roof gutters and downpipes
• External walls - finish
• External walls - structure
• Access decks and balustrades (common areas - flats only)
• Foundations
• Damp-proof course
• External doors and windows (dwelling only)
• Doors, screens, windows, and roof lights (common areas - flats only)
• Internal walls/partitions[7]
• Floor structure
• Floor finish
• Dry/wet rot

Disrepair to critical elements is recorded where there is any disrepair, no matter how small, to the critical elements of the dwelling.

​​​​​​​2.7.2 Urgent Disrepair

Urgent disrepair is recorded where the SHCS surveyor deems that a dwelling has any disrepair which, if not rectified, would cause the fabric of the building to deteriorate further and/or place the health and safety of the occupier at risk.

Urgency of disrepair is only assessed for external and common elements. Internal room floor structures and finishes as well as internal walls/partitions and the presence of dry/wet rot are the only critical elements for which urgency is not applicable.

The presence of urgent disrepair to critical elements was first reported in the 2019 SHCS key findings report, for 2018 onwards.

​​​​​​​2.7.3 Extensive Disrepair

Extent of disrepair is usually measured on a 5 or 10-point scale.

The 5-point scale is as follows: 0 (no disrepair); 1 (small repairs up to 5%); 2 (minor repairs 5% to less than 25%); 3 (medium repairs 25% to less than 60%); and 4 (renew 60% to 100%).

The 10-point scale is as follows: 0 (no disrepair); 55 (less than 5%); 1 (5 to 15%); 2 (15 to 25%); 3 (25 to 35%); 4 (35 to 45%); 5 (45 to 55%); 6 (55 to 65%); 7 (65 to 75%); 8 (75 to 85%); 9 (85 to 95%); and 10 (95% or more).

Extensive disrepair is calculated to identify those dwellings where any disrepair present is of a relatively greater severity. It is recorded where:

• any building element has an overall disrepair score exceeding 20% by area; or
• any building element assessed has a score of 'medium' or 'renew' on the 5-point repair scale (equivalent to an area of around 25% or more of the element); or
• dry/wet rot is recorded in two or more rooms.

The average extent of disrepair is calculated from the 5 and 10-point scales by taking the mid-point of the relevant band for the element. So, for example, a chimney stack assessed as band 4 on the 10-point scale would contribute 40% toward the average value. Similarly, a bathroom wash hand basin assessed as medium on the 5-point scale would contribute 42.5% to the average value. The presence of dry/wet rot contributes 50% to the average value. Thus, measures of average extent should be considered approximate.

​​​​​​​2.8 Damp, Mould, and Condensation

Penetrating damp is usually the result of a defect in the building fabric, such as damage to the walls or roof, water ingress due to damaged seals on doors or windows or damp because of leaking plumbing.

Rising damp is the result of defective or missing damp proof coursing, leading to water leaching into the building fabric.

Condensation is the build-up of moisture inside a dwelling, which may be the result of insufficient or ineffective ventilation.

Mould is generally caused by cold bridging causing condensation as mould needs clean water to grow. Mould growth can occur intermittently and may have been removed (cleaned) at the time of surveyors visit.

​​​​​​​2.9 Bedroom Standard

The bedroom standard is defined in the Housing (Overcrowding) Bill 2003 based on the number of bedrooms in a dwelling and the people in a household who can share a bedroom.

Each of the following groups or individuals requires a separate bedroom:

• any couple;
• a person aged 21 years or more;
• two people of the same sex[8] aged between 10 and 20;
• two children (whether of the same sex or not) under 10 years;
• two people of the same sex where one person is aged between 10 years and 20 years and the other is aged less than 10 years; and
• any further person who cannot be paired appropriately.

This definition is distinct from the rules introduced by the UK Government in April 2013 for the size of accommodation that Housing Benefit will cover for working age tenants renting in the social sector, known as the ‘spare room subsidy’[9]. Applying the rules of the spare room subsidy requires information not collected in the SHCS. Statistics in this report relate to the bedroom standard only.

​​​​​​​2.10 Tolerable Standard

The Tolerable Standard is a minimum standard for habitability introduced in the 1969 Housing (Scotland) Act, and updated by the 1987, 2001 and 2006 Acts and 2019 Order.

A dwelling meets the tolerable standard if it:

• is structurally stable
• is substantially free from rising or penetrating damp
• has satisfactory provision for lighting, ventilation and heating
• has an adequate piped supply of wholesome water available within the house
• has a sink provided with a satisfactory supply of both hot and cold water within the house
• has a water closet or waterless closet available for the exclusive use of the occupants of the house and suitably located within the house
• has a fixed bath or shower and a wash-hand basin, each provided with a satisfactory supply of both hot and cold water and suitably located within the house
• has an effective system for the drainage and disposal of foul and surface water
• has satisfactory facilities for the cooking of food within the house
• has satisfactory access to all external doors and outbuildings
• has electrical installations[10] that are adequate and safe to use
• has satisfactory thermal insulation
• has satisfactory equipment for detecting fire and giving warning in the event of fire or suspected fire and
• has satisfactory equipment for giving warning if carbon monoxide is present in a concentration that is hazardous to health.

The criteria on electrical installations and thermal insulation were added by the Housing (Scotland) Act 2006. These requirements came into force in April 2009 and were first reported in the 2010 SHCS key findings report. The change in definition caused the fail rate for the tolerable standard to increase from 0.7% in 2009 to 3.9% in 2010.

The criteria on fire and carbon monoxide alarms were added by the Housing (Scotland) Act 1987 (Tolerable Standard) (Extension of Criterion) Order 2019. The Scottish Government has published guidance on these changes. These new standards came into to come into force on 1 February 2022 and are reported for the first time in the 2022 SHCS key findings report (this edition). These changes to the tolerable standard caused the failure rate to increase from 2% in 2019 to 29% in 2022. Without these changes the failure rate in 2022 would have been 2%.

In general, fewer dwellings fail the tolerable standard based on the presence of rising or penetrating damp than experience this issue overall. This reflects the fact that low levels of penetrating damp would not give grounds for action under the tolerable standard. A dwelling will normally be below tolerable standard if a surveyor finds persistent visible penetrating damp that covers an area greater than approximately:

• 10% of the overall wall space in one habitable room; or
• 10% of the ceiling in one habitable room; or
• 20% of the overall wall space or ceiling in one or more other spaces in the dwelling.

​​​​​​​2.11 Scottish Housing Quality Standard (SHQS)

The SHQS was announced by the Minister for Communities in February 2004. A target was agreed that all social landlords must ensure that all their dwellings pass the SHQS by 2015. Private owners and private landlords are currently under no obligation to bring their properties up to a standard which meets the SHQS. However, the SHCS collects the same data for all dwellings to allow comparison across the housing stock.

The SHQS is an aggregation of the results from 55 different elements grouped into 5 higher-level criteria, which in turn provide a single pass/fail classification for all dwellings. The 5 higher-level criteria specify that the dwelling must be:

• above the statutory tolerable standard;
• free from serious disrepair;
• energy efficient;
• with modern facilities and services; and
• healthy, safe, and secure.

A full list of assessed elements is available on the Scottish Government website. Only one element of the SHQS is not assessed using SHCS data: no information is collected on external noise insulation (element 43).

The data is assessed against the SHQS as it stood in the year the data relates to. So, for example, in 2019 dwellings were assessed against elements 31 to 35 (covering cavity wall insulation, loft insulation, water tank and pipe insulation, central heating and energy efficiency ratings based on NHER or SAP) in the energy efficiency criterion.

However, from 1 January 2021 these were superseded by the Energy Efficiency Standard for Social Housing (EESSH). Similarly, from 1 February 2022, elements 11 and 44 were replaced by elements 11A and 11B to cover changes to the tolerable standard relating to smoke, heat and carbon monoxide alarms. These changes to the SHQS are reflected, for the first time, in the failure rates presented the 2022 SHCS key findings report (this edition). Therefore, estimates of SHQS failure rates for 2022 onwards are not directly comparable to previous years.  

Figures on SHQS failure rates for 2014 onwards are not entirely comparable to previous years published in key findings reports from the SHCS. Because of missing tenure information, a small number of dwellings (see the subsection on missing tenure information for more detail) are excluded from tenure breakdowns in figures relating to years prior to 2014. In addition, small changes to data processing relating to failure thresholds for the energy efficiency criterion[11], as well as other minor data processing corrections were introduced in 2014. Although the effect of these corrections on the overall failure rates in the social sector was neutral, some discontinuities with previous years cannot be ruled out, especially when considering more detailed breakdowns.