This survey was carried out because the client was baffled by the sudden appearance of the mould growth, shown below, in his bedroom.  He had recently had work done on the soffits adjacent to the mould growth but the tradesmen who did it denied any responsibility (nothing new there then!).  He had asked a contractor for an opinion and was told his only course of action was to install a positive pressure fan in the loft, at a cost of £750 plus VAT. 

There's nothing wrong with positive pressure fans of course, it's just that they're not always necessary....

Property   Mansfield, NG18

Instructions To inspect the property and report on areas of mould growth in the main bedroom and bathroom and also the entrance porch.

Background Black mould has begun to grow on the ceiling in the main bedroom. This has only occurred this autumn and winter and its start corresponds with work done earlier in the year to the roof and soffits. The mould growth in the bathroom and entrance porch will have occurred before, but is not as noticeable.

Disclosures I am not aware of any affiliation, financial or otherwise, with the client or the property.

Limitations Limited to observations regarding the mould growth.

Restrictions Nil

Date of Survey December 2005

Weather Fine, cold, clear.

Viewing Orientation All observations are made as if looking towards the house from the front.

Type of Property Detached and recently extended bungalow. Brick built under a tiled roof. The property has sealed unit double-glazing and gas fired central heating.

External Observations The property faces due north and the affected areas are on the north and east walls. On the northeasterly corner of the house recent repairs have been made to the roof and I am advised that repairs have also been made to the soffits in this area. There are no other relevant observations externally.

Internal Observations Severe mould growth (Aspergillus niger) is occurring in the main bedroom; mainly in the left hand corner at the junction of the walls and ceiling. This mould extends partially along the junction of the front wall and ceiling in a westerly direction.

The clothes inside a chest of drawers, which is also in this corner, are damp and there is further mould growth behind the bed position, which is against the east wall.

In the main bathroom, the mounting plate holding the extractor fan has mould growth, as does the lintol atop the entrance door in the porch.

In the loft, directly above the mould that is growing in the corner of the main bedroom and also, for a short distance along the wall, towards the west, the glass quilt insulation has been disturbed leaving the plasterboards above the bedroom unprotected. This probably occurred during the recent repairs to the roof.

Generally, in the loft itself, the insulation is inadequate, being too shallow and covered with debris, which is scattered liberally over it. This debris has been left by previous workmen and consists of electrical, plumbing and general building materials etc.

Discussion In all instances, the origin of the mould growth is undoubtedly condensation and any remedies attempted should proceed on this basis.

The affected areas of the property are on the north and east elevations, which are the coldest ones in the property. Although they all share this characteristic, their individual circumstances are different:

The problem in the bedroom is due to a lack of insulation in the left hand corner of the loft and along a section of the front wall. This is most probably a result of the roofing repair tradesman inadvertently moving the loft insulation and not replacing it. Correcting this should cure the problem.

The bathroom fan has been replaced at some time in the past with a smaller fan than was originally there. In order to accommodate the reduced size, a plywood plate has been constructed in which to mount it (fan). This plate is effectively at the same temperature as the outside and consequently condensation is occurring on it each time the bathroom is used.

The condensation and mould growth on the lintol over the front door is occurring because of a design fault created by the use of a single lintol that spans both external walls of the building; from outside to inside. The outside face of the lintol will easily transmit cold through to the inside of the building, where condensation will then occur. This is known as a ‘cold bridge’.

The loft insulation generally is below par and should be increased in line with current standards. Special care should be taken over the corner of the bedroom, both to ensure coverage of the living areas and also to retain ventilation from the soffit vents.

Conclusions Replace the bathroom fan with a Ventaxia Centrif 250HP, or similar. This fan should be controlled via a humidistat that is set to operate when the Relative Humidity exceeds 65%.

Replace the insulation over the affected corner of the main bedroom by installing quilt insulation to a depth of 200mm. In addition this depth of insulation should be installed over the entire loft area. Of primary concern, along with coverage of the living areas, is the preservation of ventilation via the eaves and soffit vents. This ventilation must not be blocked under any circumstances or condensation will occur in the loft space. I would recommend that specialists in this field carry out the installation.

The lintol over the front door needs to be covered with insulating materials as follows:

Fix 25mm x 50mm tanalised battens to the inside vertical and horizontal faces. Place 25mm ‘Kingspan’ insulation between the battens and then board over the whole with foil-backed plasterboards. Skim with Carlite board finish.

The above measures should provide a long-term resolution for all the problems presently being encountered. If they re-occur, please contact me again so that further measures may be considered.

I trust the above is satisfactory for your purposes but if you require further clarification please do not hesitate to contact me.

Surveyor Patrick F Doyle CSRT M. Inst. R.T.S.

Qualifications Certificated Surveyor in Remedial Treatments issued by the BWPDA.

Date of Report December 2005

Signed Surveyor

The above findings are based partly on the interpretation of results from a standard non-destructive inspection; this, by necessity, has limitations. If you require confirmatory/definitive diagnosis of my findings then this can be undertaken by the use of destructive methods of investigation: these will involve some damage and costs.