The Case of the 'Uninhabitable Bedroom'
The property was a local authority second floor flat with concrete ceilings and 13" solid exterior walls and formed part of a large block. A severe flood in the flat above penetrated into the wall of the end of the main bedroom, and wallpaper peeled away. The local authority redecorated about three weeks later and the paper (vinyl) peeled off again.
After around 18 months with no further action, the tenant took the local authority to court and claimed the flat was unfit for habitation - and won his case. The local authority appealed and requested an investigation into dampness which was claimed to persist and caused the flat to be uninhabitable.
Only one wall was affected. Visually, wallpaper had peeled and slight black mould growth had developed on the underside of the paper showing that the wall was once clearly damp. Other than this, there was no other sign of damp or mould growth. At the time of the inspection the internal/external differential vapour pressure was less than 0.3kPa which indicated moisture production was being well balanced by ventilation.
The remaining wallpaper was well bonded to the wall which indicated the wall was, for practical purposes, 'dry'. Indeed, pulling the wallpaper caused the old underlying paint film to pull away. However high moisture meter readings were obtained through the paper but only on the upper half of the wall. (hygrometric data showed the wall surfaces were well above the dew point temperature and not affected by surface condensation at the time of the inspection).
A grid of moisture meter readings were plotted across wall together with a full moisture analysis of the substrate. The result showed only free moisture in the upper part of the wall, the highest levels being just beneath the heavy concrete ceiling. Further analysis showed these levels to be around 5% and less of the maximum moisture carrying capacity of the materials sampled.
The wall externally was protected by a stairwell, and had a very thick film of an oil-based paint applied over the external face.
The severe water leak some two years earlier had saturated the end wall causing the wallpaper adhesive to soften and the paper to peel away. This also occurred several weeks later when the wall was redecorated.
The current distribution of free moisture was residual from the flood above - it was related to the upper concrete ceiling (which acted as a reservoir). The wall had not fully dried out due to the vinyl paper and external painted finish retarding evaporation. But the levels of residual moisture were certainly now insufficient to cause softening of the wallpaper adhesive.
The very low levels of free moisture also caused the high moisture meter readings (electrical moisture meters are very sensitive to extremely low levels of free moisture). No surface mould had developed within the room, or indeed in the rest of the flat.
It was concluded that effectively the room was 'dry' and there were no organisms (mould) which would cause the room to be or remain a hazard to the health of the occupants. Indeed, there was no evidence, current or past, to show or even suggest that the conditions within the room had ever been a hazard to health (NB. high atmospheric moisture contents alone do not pose a health hazard!)
The local authority won their appeal.
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