Damp and Condensation test

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Damp and Condensation Case studies

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Damp and Condensation Case studies

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This case study explores how failure to address a simple and very obvious problem can quickly result in exacerbated issues for residents. The problem reported by the occupant was a damp patch and black mould in a bedroom.

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In this example we will be looking at a ground floor, purpose built flat within a 1970s three storey building.

Access to the flat is through a communal external pathway, entrance and then hallway. The construction is traditional with a pitched roof and concrete roof tiles. The walls are cavity construction with outer faces of clay brickwork. We can also see PVC-u double glazed casement windows.

Property Description

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Surface water from the guttering has clearly been discharging over the face of external wall causing visible green staining over the clay brickwork. The amount of staining would indicate that the rainwater goods have been missing for some time. In addition, the missing section of downpipe is laying in the grass at the base of the wall.

Property Description

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Further Evidence

Dislodged rainwater goods lying on the ground adjacent to the bottom of the downpipe.

Closer view of the missing sections of rainwater goods.

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Has the dampness resulted in a possible ‘cooling down’ of the external wall which could have caused condensation problems within the dwellings? (Formation of condensation and the development of mould over the inside face of the external or party walls)

What issues could occur from the missing downpipe?

Has the water from the downpipe and guttering (which after all is designed to deflect water away from the building) caused an advanced weathering of the external face of the clay brickwork and/or the mortar joints?

Has there been any penetrating dampness through the external walls into the dwellings (either the front wall or possibly the party walls between adjacent dwellings, as this is clearly at a ‘junction’ in the building (evident from the differential roof level)?

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Trail of evidence to be followed:

Internal

External

Inspection of the clay brickwork and surrounding mortar joints assessing their condition. In this instance apart from the green staining the clay brickwork and the mortar joints can be seen to be in a reasonable condition. No remedial works being required to the brickwork or mortar joints. Cosmetic cleaning of the green staining could be undertaken.

Inspection of the affected room(s) – in this case the room affected was a bedroom. The surveyor observed and recorded the extent of the moisture damage and mold growth. (Note it is good practice when recording the issue to use a moisture meter and / or thermal camera). In this instance no moisture damage was observed in the ceiling or wall plaster. Some black mould was evident in the external corner near floor level – literally inside the wall where on the outside it was green stained brickwork.

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Further Evidence

Closer view of the mould. Note that the mould is affecting the surface decoration and not the plaster wall.

Low level black mould over the external and party walls.

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Using a Damp meter

By using the the moisture meter in pin mode, the surveyor determined that the inside of the brickwork itself was not wet, indicating that water penetration was not occurring from the damaged downpipe. Wet moisture readings would have expected to have been recorded throughout the height of the wall.While the water from the broken down pipe was making the outside brickwork wet it was not moving across to the inner skin. It was, however, making the inner skin colder where adjacent to the wet outer skin. Moisture on the wall plaster was caused by the cooling down of the internal surface of the wall below what is known as ‘dew point’. The result is condensation on the cold wall surface.

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Using a Damp meter

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Further Evidence

At risk reading circa 600mm from floor level

Low level wall reading, pin mode, near floor level

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Use of the moisture meter, psychrometric mode (Relative Humidity / surface temperature), records ‘Risk of condensation’ at low level and ‘At Risk of condensation’ at high level.

Further Evidence

At risk of condensation high level

Psychometric mode Risk of condensation low level

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Use of a thermal imaging camera also clearly indicates a much colder surfaces in the external corner of the room at floor level, where the mould was observed. Had the wall itself been wet this thermal pattern would have been different.

Further Evidence

Thermal imaging camera - typical triangular cold area is the external corner floor level, same area as the black mould.

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Why is there a condensation issue and not a penetrating damp issue in this case?

The external wall is built in cavity construction meaning there are two separated skins of brickwork/blockwork. There is no evidence of retrospective cavity wall insulation here. Cavity wall insulation will ‘fill the cavity’ and if the outside skin gets wet, water is much more likely to ‘wick’ across the cavity via the insulation (which is why it is so essential to keep filled cavity walls walls well maintained). Since the cavity is clear, this allows any moisture to safely drain away at the bottom and into the ground. The thermal performance of the external wall and connecting party wall is being reduced due to the external brickwork being damp leading to the ‘cooling down’ effect. This then causes the internal walls to also cool and hence condensation on the cool internal wall.

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Identify the appropriate remedial works.

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Summary of learning points

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Observing and recording the issues.

External and Internal inspection are needed, even if the symptoms are internal only.

Following identification of the defect(s) what are the exact nature of the issue(s) caused? In surveying parlance this is often referred to as ''Following the trail''.

Identification of the defects. In this case the issue can be seen from the communal pathway. Routine inspection by the landlord of the estate should have identified these issues. (In this case the property was in social housing control and the failure to correctly identify a very obvious, simple defect lead to criticism from the housing ombudsman).

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In this case study we look at how a simple plumbing fault can lead to much larger repairs. It illustrates the need to check that small repairs and installations are carried out correctly.

The landlord was alerted to the problem by the occupant when the kitchen ceiling partially collapsed. Prior to the collapse the tenant had observed moisture staining over the ceiling which was reported to the landlord. However, this was not addressed. We don’t know how the this defect was reported, what questions were asked of the tenant or if the leak was ever investigated. However, what we do know is that what ever action may have been taken it failed to address the underlying issue and part of the ceiling later went on to collapse. The partial collapse of the ceiling occurred whilst the tenant was present in the room, but fortunately the tenant was not injured. (Plasterboard is heavy and had the tenant been underneath at the time they might have suffered some injury. Also, though it was not the case in this example, the water could have got into the light fittings in the kitchen below).

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In this example we look at a late Victorian mid terraced house built on two floors and dating from around 1900.

The construction is traditional, comprising a pitched roof covered with natural slates over solid clay brickwork walls.

Property Description

On close inspection of the toilet, the surveyor observed a leak at a threaded joint, at the cold water supply into the w.c. cistern. It is quite common to see these joints with a plastic threaded tail and a metal nut connector - as seen in the image below:

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On further investigation a plumbing leak was identified in the first floor bathroom, which was located at the back of the property and immediately above the kitchen (this is an arrangement common in houses of this era where a former small back bedroom is converted into a bathroom). The leak in the bathroom was directly responsible for the partial collapse of the ceiling within the ground floor kitchen directly below.

The Housing defect

The probable cause of leak was cross threading of the joint and / or the fact that PTFE (Polytetrafluoroethylene) or Teflon tape was not used.The leak was relatively small but had been continuous – it had been going on for some time. It is worth noting through using an on-line drip calculator, the estimated volume of water being discharged per day onto the floor and the ceiling below, was approximately 1.4 litres. That's the same as 4 and a quarter cans of coke every day!

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Further Evidence

A volume of water equivalent to over 4 cans of Coke was leaking onto the floor.

Leak observed at joint position

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The leak has been dripping onto exposed butt jointed timber floor boarding. Typically, impervious floor coverings, such as sheet vinyl, are provided in bathrooms to provide protection to the floor in the event of splashes of water etc. In this instance if an impervious floor covering had been present this would have helped prevent escape of moisture into the kitchen below and the puddling of the water on the floor around the toilet might have alerted the property owners to the exact problem more readily.

Further Evidence

Exposed floor boarding below the leak is visibly wet

The escape of moisture through the floor boarding and into the kitchen below has resulted in a partial collapse of the ceiling. Moisture damage can also be seen around the edge of the collapsed ceiling.

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Further Evidence

Closer view of the collapsed ceiling area. Underside of the floor boarding is visibly wet.

View of the partially collapsed ceiling and surrounding moisture damage / staining.

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Summary of learning points

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Cost of repairing the leak on its own would have been relatively small but there was significant cost for the remedial repairs to the floor structure, ceiling and walls below.

Relatively small drip leaks can lead to a surprisingly large volume of moisture being discharged over a 24 hour period – don’t dismiss a small defect. Failure to act quickly can soon escalate.

Bathrooms / w.c’s floors should be covered with an impervious floor covering i.e. vinyl sheet material to help protect rooms below and make simple leaks like this more obvious.

It is important to gain as much information as possible when an issue is reported by the occupant. In this case it is likely that whoever was talking to the occupant failed to ask simple questions such as what the room above was used for etc. so failing to make an immediate connection to the leak in the bathroom causing the ceiling collapse.

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