Damp Report 23.11.13’08

image of the front of the Joint Position Statement RICS Historic England PCA (property care association) dated September 2022, featuring picture of drain


RICS (Royal Institute of Chartered Surveyors), Historic England (a public trust protecting sites of historic interest) and the Property Care Association (an association of mainly damp proofers) set out a Joint Position Statement (JPS), in September 2022 – see below.

There has long been disagreement about the causes of damp amongst surveyors. Historic England surveyors represent one extreme. They typically do not believe rising damp is a likely cause of internal dampness and rarely recommend altering walls to alleviate damp. By contrast PCA surveyors typically recommend rising damp treatment whenever they see dampness at the base of a wall and often recommend altering a building. RICS surveyors tend to be somewhere near the centre of these extremes. However, unlike Historic England and PCA surveyors, they rarely specialise in damp and often refer issues to PCA surveyors. We and most other independent surveyors are more closely aligned with Historic England’s position except that we are perhaps more pragmatic. For example, if a hole in the wall is the optimum way of solving internal dampness, then we will recommend it, but not otherwise.

JPS questions and answers

In addition to the content typically included in a professional and impartial survey report (e.g. client, surveyor and property details; limitations and exclusions), the report should include the following information:
1 A summary of the surveyor’s observations, including an Assessment of Significance.

Dampness from rain penetration and vapour

2 The importance of regular building maintenance and how a lack of even basic maintenance can lead to problems arising. This is especially important and relevant to roofs, gutters, hidden gutters, rainwater disposal and changes in external ground levels.

As is common with all buildings, gutters and other rainwater goods should be checked twice annually, ideally during or soon after a rainstorm, for evidence of overflow and rain not being dispersed properly from the property. You should also check that there is no flow of water flow during periods of absence for signs of a leak, for instance, by note the number on the mains water meter outside your house. Remove flaking paint, ensure gap-free render, use impermeable paint

3 An impartial diagnosis of the damp problem, which should be clearly explained and laid out systematically to communicate the relevant risks to the reader.

Dampness risk from exterior and interior sources

4 Where recommendations for the repair and recovery of moisture-affected structures are stated, the solutions should be clearly explained and prioritised as appropriate.

The solutions are explained in the Recommendations section. The primary recommendation is Insulate with plasterboard, ensure vapour barrier, monitor timber, check neighbour’s downpipe, improve ventilation

5 The client should be provided with alternative options for which each recommendation should include advantages and disadvantages and the relevant cost and time implications.

This question is primarily directed at PCA damp proofers, to encourage them to consider methods that address the source of water not just the symptoms, such as by hacking off plaster and replacing it with slurry. You can sometimes take this damp proofing approach with short-term success. However, water will eventually find its way through. Furthermore, treatment is disruptive resulting in high cost and a poor finish, with no worthwhile guarantee of success. It likely to lower the value of the property. In our opinion you are better off trying to stop the water at its source, as we recommend. ”

6 Where monitoring and staged interventions are appropriate or beneficial, the client should be informed of the reasons for these options, together with the likely cost and time implications of such recovery strategies.

Properties should be monitored for humidity and temperature using data loggers, see datalogger section of this report. The cost of data loggers is currently less than £20 for two, aim to keep the dew point, as shown on the app screen of each logger (bottom centre on the SensorBlue), within 3°C of the external temperature, especially at night (use ventilation and/or dehumidification to reduce the internal dew point – measure external conditions or refer to weather forecasts for night-time temperatures, such as BBC Weather – a short explanation is; that this will make sure the relative humidity of all surfaces will be below the mould point even if poorly insulated). We also suggest noting values monthly using a multi-functional radio wave and conductance damp meter costing about £24 to monitor and map damp patches on internal walls. This way you can monitoring the dry progress, which typically takes 1 month per 25mm thickness of walls and more if coated. This helps determine if the root cause has been fixed or there is an additional or new source of water, and therefore more actions are required. Ideally this should be started before or soon after starting our recommendations and for about a year, repeating monthly to check progress.

7 Where appropriate, clearly state whether the building concerned represents a financial risk to the buyer or lender and why.

8 Any conflicts of interest should be clearly stated.

There is no conflict of interest. We never profit from our recommendations.

As a background, although we charge a fee for undertaking damp surveys, profit is not our primary motivator. We are motivated to:

  • solve damp problems in properties,
  • encourage clients to spend money wisely for the protection of the property and, where possible to lower the environmental impact,
  • stop or at least play our part to reduce the over-diagnosis of rising damp and so called “damp proofing” treatment by replacing plaster with chemicals and slurry, rather than dealing with the root cause.
Good example in lower ground floor dig out
Questions and Answers
Q: We will be using the PIR on the wall. Would you recommend using it in the ceiling as well or can we use mineral wool insulation in that space?
A:I would advise against using PIR under the ceiling to avoid losing valuable ceiling height. The ceiling is internal, mineral wool will fit neatly between joists. You need a breathable zone at the top of the wall, say 100mm that can be covered by coving and I would use SpaceTherm see above.
Q: How big should the gap be left at the bottom with the PIR? Is it okay for us to cover this gap with a skirting board/something decorative?
A:Yes, the breathable zone at the base of the wall should be at least 100mm, (the larger the better, base it on the size of the skirting and SpaceTherm cost and available sizes) that can be covered by skirting with non-oil based paint to allow it to breath, I would use SpaceTherm as insulation see above. I would allow a very small gap at the base of the wall say 1 – 2mm (it is possible that some water will appear here, so allow for replacement of the MDF skirting. I suggest MDF as timber is more likely to warp with vapour, but wood could also be used. However, given the benching, you could probably do away with the SpaceTherm at the base of the wall, and instead of classic weep holes, you could allow water to weep through under the base of the PIR. I imagine there would be natural gaps above the rough contours of the benching bricks that would create gaps of 1 – 2mm. Potentially water could weep through to the benching, and safely evaporate away, off it. I doubt there would be much more than say a teaspoon a day in rainy season, and only in one or two zones, but it is hard to be sure until the PIR is in place.
Q: Would you recommend using a vapour barrier with the PIR?
A:I see no need so long at the foil is used, beside we wan to encourage evaporation at the top of the PIR.
Q: How do you suggest we set up necessary timber studwork to protect it against damp?
A:Insta-Stik foam adhesive is a fast-curing polyurethane foam adhesive that is suitable for bonding PIR insulation to a variety of substrates, including brick, concrete, and wood. However, it’s important to follow the manufacturer’s guidelines for using the adhesive to ensure that it is applied correctly and safely. Additionally, it’s recommended to use mechanical fixings in conjunction with the adhesive to provide additional support and stability to the insulation, this could include supporting from below with the SpaceTherm.
Q: Is it enough to have a continuous extractor fan in both the utility and bathroom space?
A:This should be sufficient, provided that you diligently monitor the humidity levels and use a dehumidifier to remove vapour, when humid. If you expect to generate vapour in the other rooms you could add vents there across the ceiling, for example adding a wet room, such as hot-bath or sauna, drying clothes without a dehumidifier or adding a gym etc. again you can use a dehumidifier here too. NB vents are for CO2 and VOCs as well as vapour removal, but keeping doors open when occupied is normally sufficient.
Q: Would you say Vent-Axia or Brookvent continuous extractor fan is better?
A:While I have no personal preference, Vent-Axia is a more established and widely recognized brand.
Q: Would you recommend any specific types of materials for the waterproofing and rendering of external brickwork?
A:Acrylic caulk for small render cracks and a cement based mortar for large cracks or the fillet of cement.
Q: Do you think we should add any additional air bricks? And/or put in modern vents/ducts?
A:See 2 above. You need air-bricks in voids, such as if you plan to keep voids under the kitchen extension. As a general rule a) Air-vents create heat loss. They are a safety mechanism should there be water such as from a leak. Therefore, using a hygrometer to monitor and adjust air flow in winter can significantly reduce heat loss. However, it’s crucial to check subfloor humidity weekly. b) You should have airflow from front to rear, or left to right, but extending or blocking the flow by making the basement into a useable space, as you are doing, you are effectively stopping the airflow. You can overcome this with mechanical fans, such as online extractor fans, and if required ducting to create airflow (with a grill to stop mice).
Ask A.I. about your report, in the “Type your message” you could ask:

What does the damp report say are the main causes of damp and main actions to stop damp?

¿Qué dice el informe de humedad sobre las principales causas de la humedad y las principales acciones para detenerla?
नमी की रिपोर्ट के अनुसार नमी के मुख्य कारण और नमी को रोकने के लिए मुख्य कार्य क्या हैं?
Que dit le rapport sur l’humidité concernant les principales causes de l’humidité et les principales actions pour l’arrêter?
Was sagt der Feuchtigkeitsbericht über die Hauptursachen von Feuchtigkeit und die Hauptmaßnahmen zur Bekämpfung von Feuchtigkeit?
Что говорится в отчете о влажности о основных причинах влажности и основных действиях по ее устранению?
Cosa dice il rapporto sull’umidità riguardo le principali cause dell’umidità e le principali azioni per fermarla?

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