Scottish Government

Volume 4
Chapter 5 Rising Damp & Penetrating Damp

5.1. A house meets the tolerable standard if the house is substantially free from rising damp or penetrating damp.

Introduction

5.2. Dampness has historically been a significant housing problem in Scotland and remains a real issue for some households. People should not need to live in houses with levels of rising or penetrating dampness that materially affect their health or comfort or cause further physical damage to the property.

5.3. Assessors will have to exercise judgement in deciding whether a house is 'substantially' free from damp or not. Each case will be different. In this chapter we highlight issues to consider and offer a method for assessing houses against this element of the tolerable standard.

Legislation

5.4. The tolerable standard was first defined in the Housing (Scotland) Act 1969 and has always included the requirement for a house to be substantially free from rising and penetrating damp. The Housing (Scotland) Act 2006 does not change this.

Definitions

5.5. Rising damp: is the vertical movement of moisture from the ground into the fabric of a building. This can affect any part of the building in contact with the ground, the most obvious being walls and floors. Rising damp will not normally rise higher than around 1.2m above ground level.

5.6. With the exception of some older houses, most houses these days will have been constructed with a damp proof course ( DPC) to prevent rising damp from occurring. This is a moisture resistant barrier inserted between the foundations of the house and the walls, such as slate, bitumen or plastic sheeting. Owners of houses constructed without a DPC sometimes arrange for silicone to be injected into the lower part of the walls to prevent rising damp.

5.7. Even where a house has a damp proof course, rising damp can still occur. If the DPC is damaged or 'bridged', moisture can travel unhindered into the building's fabric. 'Bridging' of the damp proof course is where the ground level becomes higher than the DPC, allowing damp to travel from the ground into the fabric of the building.

5.8. Rising damp will only affect the ground floor of a building. This means that in tenement blocks, for example, only the ground floor flats will be affected by rising damp. So any dampness found above the ground floor is likely to have another cause. Equally, it is possible that dampness at ground floor level may be caused by something other than rising damp and assessors should always try to identify its source.

5.9. Penetrating damp: is moisture which enters a house from outside because of a defect in part of its structure. There may be defects in the roof, the exterior walls, or rainwater gutters and down-pipes. The source of persistent penetrating damp can be difficult to identify because there may be no consistent pattern to the signs. For example, damp patches may appear in more than one room, and be located in different parts of the room.

Making the assessment

5.10. The flow-chart below will help guide an assessor through the process:

Dampness Indicators

5.11. There are a number of indicators of the possible presence of rising or penetrating dampness. The most common include discolouration and staining on walls, and deteriorated plasterwork. We have produced tables at the end of this chapter which summarise visible indicators that an assessor may find when looking at a house under this part of the tolerable standard. The tables describe patterns of dampness for the main building elements, and will help assessors identify dampness and distinguish between rising and penetrating dampness.

Dampness and Condensation

5.12. The tolerable standard does not extend to condensation. Condensation is a serious problem which is closely associated with, and sometimes confused with, rising and penetrating dampness. Condensation is often caused by inadequate heating, ventilation and thermal insulation as well as the way a household manages its heating and ventilation. Overcrowding can be a further factor. Where an assessor sees evidence of condensation he/she should pay particular attention to the chapters of guidance covering heating, ventilation and insulation .

5.13. Condensation is caused by warm moist air coming into contact with a colder surface. The colder surface causes the amount of moisture the air can hold to be reduced, and as a result the moisture "condenses" out onto the wall. The water that forms as a result of the process is pure water, and this allows the growth of mould, which requires pure water to grow in.

5.14. Sometimes mould growth will be associated with walls affected by rising or penetrating damp. This is because the rising or penetrating damp affected wall is more difficult to heat, and therefore generally at a lower temperature, thus creating a cool surface on which condensation can occur.

5.15. It is unusual to find fungal growth associated with rising damp, and even less so with penetrating damp, as the wall has to be very damp to support the growth of fungus. Assessors should be clear on the difference between mould and fungus and the type of problem they indicate. The presence of mould growth is not an indicator of rising or penetrating damp, and should not be used as such.

5.16. One of the most obvious signs of rising damp is the presence of a "tide mark", and, as for penetrating damp, the discolouration of the decorative surface affected. It is sometimes not easy to distinguish between rising and penetrating damp and condensation.

5.17. An important part of identifying possible dampness is to find out the cause. If an assessor concludes that the problem is due to condensation, then the house does not fail the tolerable standard under the dampness element. The tables at the end of this chapter summarise a range of common causes of rising and penetrating dampness and may help with this judgement. Condensation may well be a real problem for the occupant, and its exclusion from this element of the tolerable standard is not a reflection of its seriousness or the impact it can have on occupants' lives.

When is a house below tolerable standard?

5.18. To meet the tolerable standard a house must be "substantially free" from rising or penetrating damp. The nature of rising and penetrating damp problems can make this a difficult decision for an assessor. We intend this guidance as a framework to help ensure consistency and we do not expect assessors to use it in a prescriptive way. It does not describe every possible scenario. Assessors should use it alongside their professional experience to make an informed judgement on a case-by-case basis. The key consideration for assessors should always be whether the problem is persistent and whether the scale of the problem is such that it represents an unhealthy or uncomfortable living environment for occupants. A house with persistent dampness that produces an unhealthy living environment will always be below tolerable standard.

5.19. In cases of rising damp, the presence of visible indicators of damp (see tables at the end of this chapter) inside a house usually mean that the problem is of a persistent nature. It will not improve without action, and could over time affect the structural stability of the house. The presence of visible indicators of rising damp will normally mean that the house is below tolerable standard.

5.20. Assessing penetrating damp can be more complex. The patterns of dampness can be more variable. The severity of a problem can vary over time and factors such as the weather - for example periods of prolonged rainfall or extended dry periods - can affect how patterns of dampness develop over time.

5.21. We set out below a basic framework to aid assessors. Assessors should use it to complement rather than replace their professional judgement and should take account of all relevant factors. This is likely to involve considering whether the dampness is likely to materially affect occupants' health or comfort or cause further physical damage to the property. Where feasible, assessors may want to visit the house on more than one occasion to check if the problem is persistent or to track the development of the dampness. Assessors may also involve others with relevant professional expertise to help with this judgement. The Scottish Office produced a summary of the research evidence on the relationship between poor housing and ill health - available here ¹³. Assessors may find this useful.

5.22. A house will normally be below tolerable standard if an assessor finds persistent visible penetrating damp which covers an area greater than approximately:

• 10% of the overall wallspace ¹⁴ in one apartment in the house;

or

• 10% of the ceiling in one apartment in the house;

or

• 20% of overall wallspace or ceiling in one or more other spaces ¹⁵ in the house.

5.23. An 'apartment' is any room in the house not used solely as a kitchen, store or utility. A 'room' is any enclosed part of the house not used solely as a bathroom, shower room, washroom, toilet, stair or circulation area.

5.24. Assessors should base their judgement on the scale of penetrating dampness, not the seriousness of the problem that created it. In particular, an assessor should not base a decision on how easy it is to repair the defect that caused the damp. Assessors should not conclude that dampness caused by a relatively minor problem is not below tolerable standard. Minor defects that can lead to persistent penetrating damp problems include faulty window frames, missing or damaged roof tiles, or an upstairs neighbour's faulty plumbing.

Indicators of rising damp

5.25. The tables below give examples of features of a house that can be affected by rising damp and describes how this may appear to an assessor. This will help an assessor to identify that the house is affected by damp and to distinguish what type of damp it is.

Causes of Rising Damp

5.26. The next table describes the main causes of a house being affected by rising damp and explains how an assessor can identify defects in the damp proof course ( DPC). Assessors should note that the absence of a DPC does not in itself mean the house is below tolerable standard. In all cases this must be accompanied by the visible indicators of rising damp inside the house.

Indicators of Penetrating Damp

5.27. The following table summarises the main areas of a house that may be affected by penetrating damp and describes how this may appear to an assessor. This will help an assessor to identify that the house is affected by damp and to distinguish what type of damp it is.

Causes of Penetrating Damp

5.28. The tables below describe some of main causes of a house being affected by penetrating damp and explain what defects an assessor should look for that may indicate water penetration.