Mould and ventilation management

Surveying mould

In a pre-purchase survey in the UK the inspection is essentially visual, with the aid of some basic tools and equipment, such as an electronic moisture meter. A surveyor is expected to note visible mould (it can also be smelt), and depending on the circumstances may recommend further investigation. The health risk of mould may need to be assessed and commented on. A surveyor who is not confident in making conclusions about the mould threat should recommend further investigations to identify risk and possibly how to deal with the mould.

Hidden mould presents problems that may not yet have been clarified or decided by legal case law. Surveyors need to be familiar with building types and know whether a particular building type or building with certain constructional detailing might be likely to contain mould or be susceptible to mould development. For example, a surveyor should note where a void is not ventilated and may be likely to harbour mould and other fungi. Non-surveyors are familiar with the smell of household mould. In Hacker v Thomas Deal & Co (see Case in point - Negligence in valuations and surveys) the judge made the point that even a surveyor with limited experience should be familiar with the distinctive smell of dry rot.

A surveyor's professional indemnity insurance cover needs to be scrutinised to see whether there is any exclusion of insurance cover for mould-related building problems. If there is no insurance cover, then a surveyor needs to incorporate a suitable clause in the survey report to protect his/her (and the client's) interests. But no number of limitation clauses will rid a property of mould or alleviate an occupier's health problems suffered because of mould.

Key pointers to reporting mould in pre-purchase surveys

Surveyors may need to report on:

  • mould actually seen, describing its extent and severity;
  • mould smells noted;
  • any information on mould offered by occupiers,
    building users or any other party;
  • any occupiers' or building users' obvious health symptoms likely to have developed from exposure to mould;
  • any industry or local knowledge regarding particular sites, buildings, construction techniques, or scenarios where mould is likely or known to be present or a past threat;
  • any dampness noted where mould could be a problem;
  • the potential or actual health risk of mould noted or suspected; and
  • further investigation of mould involving additional surveying equipment (e.g. to open up or inspect by borescope) or requiring additional expertise (e.g. mycologist or medical expert) should be advised depending on the nature of the mould development as found, suspected or referred to by any party or report, etc.

Where a surveyor might look for or find mould

Surface mould may be found:

  • on surfaces at cold bridges;
  • on ceilings subject to roof leaks;
  • on surfaces of unused or unheated rooms;
  • at a high or low level in a room corner – crescent shaped;
  • as dots of mould in a bathroom – e.g. along the line of the sealant;
  • around window panes near the frame and, when dirty, on the pane itself;
  • on roof timbers in the loft;
  • on clothing and bedding; and/or
  • on leather.

Hidden mould could be:

  • behind wall coverings;
  • behind cupboards;
  • under floors or carpets;
  • within ducts or hollow partitions;
  • behind bathroom panels; and/or
  • behind skirtings.

There are four levels of inspection of mould:

Level 1:

  • visual inspection; and
  • linkage of damp to mould.

Level 2:

  • visual inspection; and
  • use of moisture meters.

Level 3:

  • visual inspection;
  • use of moisture meters;
  • moisture meter with accessories (surface thermometer, air temp, relative humidity of air or void, dew point calculation);
  • borescope;
  • surface sampling;
  • opening up, e.g. covers, ducts, boards;
  • use of basic leak detection equipment, e.g. listening stick; and
  • thermal imaging.

Level 4 (usually a team inspection):

  • visual inspection;
  • use of moisture meters;
  • borescope;
  • surface sampling;
  • air sampling;
  • air monitoring;
  • surface data logging;
  • water sampling; and
  • collation/study of health records.

The team could include:

  • remediation coordinator/project manager;
  • professional damage management contractor;
  • tenant/occupier liaison;
  • services engineer;
  • architect/building surveyor;
  • mycologist/indoor air consultant;
  • building contractor/subcontractors; and
  • leak detection (contractor/supplier).

In pre-purchase property inspection, inspection of mould goes at least as far as level 2. Some of the techniques listed under level 3, such as borescope inspection, are more often used in a 'building survey'. However, survey methods under level 4, such as mould sampling, would normally be a specialist activity as part of 'further investigation' – advised in the pre-purchase report.