Cavity Wall Insulation can create a serious Damp Problem


damp causes Property Remedial Articles - Olympic Construction

Olympic Construction are full members of the PCA (Property Care Association) and our surveyor holds the industry recognised CSRT qualification (Certificated Surveyor In Remedial Treatment). So when undertaking any survey on your property you can be assured we will undertake a professional trustworthy survey and investigation, delivering peace of mind and correct diagnosis of any dampness related problems within the property.



j2Due to funding from the government, there has been a substantial rise in the number of properties which have cavity wall insulation installed. When taking into account the points within the’ CIGA (Cavity Insulation Agency) Property assessor’s guide’ it soon becomes apparent a large number of the properties where cavity wall insulation has been installed, were not correctly inspected or not suitable for cavity wall insulation to have been installed.

Unfortunately, homeowners are unlikely to be unaware the cavity wall insulation has not been installed correctly until a problem has developed, because until then there are no obvious signs of the defects, or incorrect installation. They will not know if it is over-packed, under filled, has slumped, were areas have been missed and sub-floor ventilation having been blocked or obstructed.

As part of our pre-purchase damp and timber survey service, undertaken by Olympic Construction our surveyors are qualified to recognise were cavity wall insulation has been installed, but more importantly where this has been incorrectly installed and were it is causing or likely to result in a potential problem within the property, in relation to dampness, timber decay and structural issues. Cavity wall insulation installed incorrectly can lead to expensive problems, resulting in damp penetration and fungal decay.

Why is this important

Properties constructed of cavity walls started around 1920 and two decades later it became standard industry practice. Cavity wall insulation can lead to an array of problems when incorrectly installed or installed into an unsuitable property, resulting in penetrating dampness leading to crumbling salt contaminated plaster and later to more serious structural and timber decay such as wet / dry rot and insect attack to structural timbers.

j3Increasingly, heavy wind driven rain has resulted in an increase in reports of damp issues in properties at 1st floor level and above. An increasing cause of damp penetration at these levels are defects being highlighted by the bridging of the cavity by the cavity wall insulation. Moisture penetrates into the cavities more noticeably on weather prevailing walls, resulting in the insulation material becoming saturated, this will inevitably result with dampness showing on the internal walls. Not all properties are suitable for Cavity wall insulation and extraction may be necessary for a number of reasons, which are clearly indicated within the CIGA Property assessor’s guide’ and should have been considered on the original survey undertaken, unfortunately this is very rarely undertaken correctly, if at all, as it would prevent a cavity wall insulation sale and loss of commission.



Photograph showing sealed subfloor ventilation by cavity wall installation contractors, resulting in dry rot affecting the ground floor timbers, due to the lack of ventilation.


Endoscope photograph showing miss/ slumped cavity wall insulation within the wall cavity.


Below are just some of the reasons a property would be unsuitable for cavity wall insulation to be installed

  • The property being exposed to wind driven rain, which can penetrate the outer leaf of brickwork causing rain water to enter the cavity
  • Porous brickwork or mortar
  • Defective external render
  • The cavity being less then 50mm in width.
  • Cold bridging which will result in condensation, to the internal elevations.
  • Any area pf the external brickwork being above 12m meters from the external ground level.
  • Any area of the external brickwork being single leaf.
  • The upper wall cavity not being sealed correctly.
  • Defective Wall ties or structural defects.
  • Dirty cavities from debris falling down the cavity during its construction or dust settlement over a period of time.
  • Defective rainwater or plumbing systems.
  • Poor installation practices such as neglecting to take account of cavity wall and sub-floor vents, designed to help the building breathe and stay dry, presenting a high risk of fungal decay to the installed timbers.
  • Cavity liners and barriers not having been installed.


None structural related problems

Issues related to cavity wall insulation can also affect a property, where no defects exist within the building or the new insulation, where owners find new problems with dampness in the form of mould developing. In these instances, it is normally found the insulation has stopped/restricted both warm moisture loaded air escaping from the property, due to the lack of adequate ventilation being installed so introducing air exchange through controlled ventilation, the wet air having nowhere to go, subsequently the humidity levels rise and mould growth becomes a new problem.

Should you have concerns if your cavity wall insulation has been installed correctly or have suddenly developed dampness related problems of staining, plaster disruption or mould, then feel free to contact us and we can arrange for one of our qualified surveyors to undertake a survey of your property, to establish the reasons for the dampness.

We must stress not all dampness problems within a property are related to the cavity wall insulation and it is not always a requirement to have the cavity wall insulation removed, but where this is a required, we are able to undertake these works and any associated remedial works found to be required.

These works don’t always have to incur a cost to the home owner, if the installer is registered with CIGA the works may be undertaken or be covered by the installer, if still trading, or under the CIGA guarantee where the contractor has ceased trading.

White Paper : Problems with Cavity Wall Insulation

Published by :Steven Hodgson :Chief Executive of The Property Care Association