Data loggers
In conclusion from the data loggers
- During the period under investigation, the surface relative humidity on the damp wall (green line) is high, peaking at 100%RH and risking condensation on the coldest surfaces. Relative humidity is above the mould risk of 85%RH for long periods.
- The surface relative humidity is calculated considering the temperature difference between the data logger and cold surface at the time of the survey – this is an approximation and illustrative. You can check the difference more accurately with a laser thermometer on a cold night to update the interface tab in the spreadsheet.
- For each -1°C, the relative humidity will be about 5%RH higher. The effect increases as the temperature difference between inside and outside increases such as when it’s cold.
- The grey line in the graph is called the dew point differential. It tells me that excess vapour is evaporating off the damp wall rather than within the kitchen as a whole, except brief periods. The most significant increases line up with warmer temperature and vice versa which tells me that evaporation from the wall is causing the increased vapour.
- There has been improvement in surface relative humidity since the survey, bringing internal dew points down inline with external dew points, suggesting better use of ventilation, perhaps from the bathroom, with door closed.
- Overall, there are clear signs of excess vapour, causing mould and condensation. Data loggers will be useful for ongoing monitoring following the implementation of my recommended actions. Working from home increases vapour from cooking, boiling the kettle and more respiration. The energy crisis has resulted in people turning down the heat in unoccupied rooms and closing vents and windows, drying clothes internally. The risk of condensation can be reduced with a 20L+ dehumidifier.
See https://damp.ai/glossary/monitor-humidity-with-data-loggers/ on how to use the data logger app.
Evidence & Illustrations
Considerable mould is growing on the cold wall behind the kitchen units.
Mould growth occurs where relative humidity exceeds 85% RH for more than six hours. Excessive humidity is usually due to insufficient ventilation, poor air circulation, and cold surfaces. Relative humidity measures the amount of vapour in the air relative to the air’s capacity to hold vapour. It is influenced by vapour pressure and temperature. As the temperature rises, the air can hold more vapour. Conversely, as the temperature drops, the air’s capacity to hold vapour decreases until it reaches the dew point at 100% RH, resulting in the formation of dew or condensation. Mould growth is inhibited by nitrates found in groundwater.
Vapour and a cold wall are the cause of mould and condensation. See data logger in the section above. To some degree it is unclear whether the issue is vapour from rainwater and heat loss from cold damp external walls or internal vapour, probably from the bathroom. Both will have an effect and both should be dealt with.
The presence of mould at the base of a wall rules out rising damp as the root cause and points towards condensation from unvented excess vapour.
Calcium sulphate salts are frequently found as white powder or crystals on internal walls. These salts are harmless, come from building materials, typically resulting from the constant fluctuations between evaporation and condensation.
The metal imbedded in the corner for plasterer’s beading causes heat loss, increasing the risk of condensation.
The wall was damp, as indicated by a Dr Moisture radio frequency damp meter. The meter measured 85%, signifying saturated pores deep within the wall. Readings below 30% are typically dry. These meters assess the extent of damp and are used to trace it to the source. The are inexpensive and worth purchasing to know you dampness is drying out.
There are three risks sees in this image:
- The front wall is next to a blocked drain, which could result in water entering the sub-floor void. I don’t think this is the cause, but you should either open up the gulley and make sure water is flowing away, or add a horizontal section of pipe to drain the water 2M or so away from the wall.
- The air brick, while useful for removing vapour should moisture enter the sub-floor, also causes heat loss, inreasing the risk of condensation.
- Your wall is covered whereas your neighbours wall is not. There is a risk of water penetrating through the uncovered brickwork, becoming trapped in the covered brickwork. Which can cause ingress, though there were no tell-tale brown stains, a sign of water penetrating through. But it can just cause heat loss increasing the risk of internal condensation.
I believe the issue here is heat loss increasing the risk of internal dampness from condensation. It is almost certainly residual damp from previous occupants as it can taken many months, often a year to dry out.
Other matters
Keep an eye on your heating system pressure. 1.1bar could be a sign of a heating system leak.
To keep the property dry | |
|---|---|
| Repaint external wall | |
| Wire brush the paint on the external walls back to brick, as much as possible at least to remove the surface salts. Then use a paint that is as impermeable, ideally the same as the existing paint, or more impermeable, such as Zinsser or Dulux external masonry paint. | £500 |
| Use a dehumidifier | |
| Maintain relative humidity, especially at night when it’s cold outside, with a dehumidifier such as PureMate 20L/Day Portable & Compact Dehumidifier with 6.5 Litre (£179.99 Refrigerant), Duux Bora Smart Dehumidifier (DXDH02UK £300 Refrigerant) or Meaco DD8L Zambezi (£260 Desiccant – best for colder environments) – Which! Best buys. There are plenty of alternatives available. I choose daily and tank capacity, low noise, whether it has a pipe out and easy of programmable functions over other considerations such as weight and aesthetics. The technology is old and easy to manufacture. So if these brands are not available, you are sure to find another alternative. Evaluate based on daily capacity (20L minimum) and whether it has a continuous pipe out (use this to drip into a sink when away in winter). | £180 |
| Use fan to expedite drying | |
| Direct a fan onto the leak to speed up the drying process. | |
| remove mould | |
| Consider sanding down mould where dry, and removing it with either bleach or anti-mould foam. I personally use HG Mould Remover Foam Spray, but imagine there is no major difference between brands. | £100 |
| Target insulation | |
| As a minimum I would insulate the kitchen walls and cold water and waste pipes. It is better to use vapour active insulation, such as Woodfibre on the walls and normal pipe insulation. | £1,000 |
| Clear gulley | |
| The front gulley should be cleared, although it is a freeholder responsibility and costs shared with the upstairs flat, it is so easy (and rewarding) to do it yourself, you might as well try. If it can’t be cleared, then consider bypassing it with a 2M downpipe connector. | £100 |
| Remedial actions – estimate of costs | £1,880 |
Actions if all else fails | |
|---|---|
| Consider installing a bathroom extractor fan with 30 minute overrun after lights are switched off. | |
| Consider installing a continuous flow bathroom extractor fan such as Brookvent Airstream DMEV 100 HT (Continuous Running Extractor Fan with Humidistat Timer) – I have installed one in a rental property I own myself, that was bought cheaply because of mould. Although important to have an isolator, it can be sited in a way that doesn’t tempt tenants to use it. Ideally the vent should be located away from the door, closer to the shower. I would also install a bathroom spring to encourage tenants to keep the door closed. Ideally the ducting should be rigid, for reduced air resistance, and insulated to reduce risk of condensation in pipe. | £500 |
| TIP: anti-condensation paint. Consider painting anti-condensation (e.g. DryZone by Safeguard on Amazon 5L £53.70) or anti-mould paint onto walls vulnerable to condensation or mould (top coat only). | £30 |
| Optimal actions – estimate of costs | £530 |
I conclude that there was penetrating damp through micro cracks in external paint, made worse by a cold wall worsened by a lack of airflow.
Blockage in the front right hand gully risks localised penetrating damp at the base of the front wall.
. By taking a root cause approach, rather than a focus on blocking the symptoms of damp the savings are likely to be around £5,000. This contrasts with typical damp proofing contractor recommendations such as chemical treatment for rising damp and untargeted ventilation, such as PIV systems.
Flood risk: No risk See Flood Risk (note most flood risk is not from groundwater).
Sub-soil rocks: Rocks with essentially no groundwater See British Geological Survey.
Therefore risk of Rising Dampremote possibility, see explanation by Dr Robyn Pender of Historic England.
I confirm that I inspected the property on 231017SH1000. I conclude that There was penetrating damp through micro cracks in external paint, made worse by a cold wall worsened by a lack of airflow. All buildings can be exposed to unvented vapour and external dampness to some degree. You will mitigate the risk of damp if you follow all our recommendations. This report is intended to be read in full including supplementary links in this report. Observations and opinions must not be taken in isolation. Given the right weather conditions almost any house can be affected by rain. Like any building, you need to be aware of the risks of damp arising in the future and should plan a programme of monitoring, prevention and maintenance accordingly. Damp Surveys Ltd reports are designed to provide you with an informed, independent expert opinion as to the cause of dampness in the property, together with any recommendations for further investigation or remedial work. We do not warrant any findings in this report unless we enter into a separate warranty agreement with you.
The survey was conducted during daylight hours. Damp will be more noticeable at night and when the weather is colder and more humid. Gutters are more likely to fail when full of leaves and during periods of prolonged rain and adverse wind. We make best endeavours but cannot guarantee being able to identify all forms of damp, rot and insect infestation affecting the property.
We carried out a careful and thorough inspection of as much of the property as was accessible. However, when a full inspection is not possible, we make a professional judgement regarding the likelihood of a defect being present. In certain circumstances, this may lead to a recommendation for further action to open up an area for additional investigation. We were unable to inspect the entire roof, all the guttering, and some of the drains. Similarly, inspection of woodwork or other parts of the structure that were covered, unexposed, poorly lit or inaccessible such as in the loft, cellar, or sub-floor void was not possible, and therefore we are unable to assert that such parts of the property are free from defect. There were no obvious signs of damp resulting from these limitations
Negligence claims must be made within 90 days of the damp survey site visit. Clients must make best endeavours to monitor humidity and temperature on a damp wall and the closest source of humidity, by purchasing and placing two data loggers for example the Smart Hygrometer measuring humidity on the wall and nearest source of vapour, before and after following our recommendations. These data loggers have sufficient memory capacity to store 90 days of data.
This report is for the sole use of the client (named on the invoice, but omitted here for anonymity) for whom the survey was undertaken and can only be relied upon for 90 days from the survey date. Unless expressly stated otherwise in this report, nothing in this report confers or is intended to confer any rights on any third party pursuant to the Contracts (Rights of Third Parties) Act 1999.
Simon Hichens
Site visit 231017SH1000
Simon Hichens BSc Chemistry RICS Qualified Expert Witness (Chartered Surveyors)
PCA Certificated Surveyor of Dampness & Timber in Buildings (Property Care Association)
Damp Surveys Ltd, 119 Longton Ave London SE26 6RF Reg. 10977488 (England & Wales)
Founder of damp.aï & Member of the Society for the Protection of Ancient Buildings (SPAB)
Our damp surveys are designed to provide a holistic diagnosis that identifies and deals with causes rather than a focus on symptoms. Symptoms will disappear over time, once damp is stopped at source. We look for risks of dampness, but unless moisture is present, we can’t guarantee to identify all risks of future moisture. Our reports:
- identify root cause(s) of major unwanted dampness within the property,
- identify major symptoms of unwanted dampness,
- identify major structural damage caused by dampness,
- recommend actions and estimated costs to stop damp at source and mitigate its effects,
- recognise that treating damp is often a staged approach, treating obvious causes first.
Understanding damp
For survey purposes, damp is defined as unwanted water. Water brings life. We need it. Unfortunately, fungus and insects also thrive in water. While a damp wall can cause decorative spoiling, it is not moisture, but the life it brings that causes the greatest concern in the home environment. FACT: vapour causes 85% of residential damp problems.
Independence and Methodology
Our only income is through damp survey fees. We are independent of contractors and never profit from remedial work. We do not receive or pay any fees or other inducements. Our motivation is peace of mind and practical, durable solutions. We use an array of equipment to identify the root cause of damp within walls. Our damp surveys follow guidance from RICS, Historic England and PCA joint position statement and support RICS’s highest standard, level 3 “Home Survey Standard” (HSS).
During the survey we assess likelihood of rising damp*, mainswater leak, penetrating damp, condensation, timber rot and woodworm. We profile the damp patches and consider the likely sources of dampness and test ventilation against building regulations requirements. We consider changes to the property and factors just before the first sighting of damp.
- Weather: dry overcast
- :Rear of the property has mould issues, primarily in the kitchen under the sink and behind the dishwasher. Lack of airflow and electrical underfloor heating likely contributes to the problem.
- :conversion into flats, underfloor heating to rear, rear platform, exterior paintwork, front render
- :owner occupied
- :mould
- :Excessive mould growth under the kitchen sink and behind the dishwasher due to high relative humidity and lack of airflow, worsened by penetrating damp.
- :damp to front wall
- :heat loss from poor insulation
- :There is no reason to be concerned about the sub-floor ventilation.
- :The sub-floor had normal levels of relative humidity.
- :ground floor flat
- :a terraced
- :Victorian
- :solid wall made of two brick widths (225mm)
- :The paintwork is disrupted to the rear
- :Internal dampness lined up with damage to external paintwork
- :The drains are of no special concern.
- :No suspicion of a mains water leak
- :There are no obvious signs of a significant mains or wastewater leak.
- :The floor is of no special concern.
- :There was no loft.
- :There are no suspicions of significant timber decay.
- :I understand that some damp issues were picked up when you bought.
- :There is no mechanical bathroom vent.
W.H.O. indoor air quality guidelines
“Management of moisture requires proper control of temperature and ventilation to avoid excess humidity, condensation on surfaces and excess moisture in materials. Ventilation should be distributed effectively throughout spaces, and stagnant air zones should be avoided.”
FACT: Houses contain 30 – 40 litres of water as vapour typically. Each day, each occupant adds on average about 1.5 litres as follows:
- Each shower results in 1/2L condensing (each additional shower in a series won’t add as much as the first, so long as the door is kept closed)
- Vapour from drying clothes releases about ½ litre per day if dried indoors
- Respiration releases about ¾ litre per day (of which ¼ l at night)
- Cooking produces about ¼ litre per day per person
- Unvented vapour can cause condensation, mould and allergenic dust mites. The simple rule for keeping your property dry and mould free is;
- Vent out as much vapour as produced, each and every day!
- Central heating and double-glazing reduce background ventilation. To overcome this you should use mechanical extractors. Where properties are rented, consider using monitoring devices (such as a Govee WIFI hygrometer) and if necessary, install continuous flow extractors, but beware there can be a thermal cost caused by continuous heat lost.
FACTS about Condensation and Mould
- FACT: warm air holds more water vapour than cold air. The warmer it is, the more air’s capacity to hold water vapour. Conversely the colder it is, the less capacity, until air cannot hold any more vapour. We call that the dew point or 100%RH. As soon air reaches capacity, condensation will form on the coldest surfaces.
- FACT: Mould and dust mites
- FACT: Mould only grows when air is humid for long periods. In the occupied home environment, it is 6 hours over 85% RH. For properties that are unoccupied for long periods, it is 75% RH for many days of consistent and high humidity. Avoid allowing the surface relative humidity of cold walls to exceed 85% RH by ventilating, dehumidifying, insulating, and ensuring airflow, particularly in cold corners, base of walls and ceilings, eaves, and cold window and door reveals.
- FACT: Dust mites are microscopic insects that can cause allergies. They grow in similar conditions to mould. So ventilate more to avoid allergies.
- FACT: Health concerns: There are no health and safety issues from damp noted. It is in the occupier’s interests to keep a property properly ventilated or dehumidified and temperatures above the dew and mould points throughout the property, thereby reducing the health risk associated with dust mites, bacteria, protozoans, as well as decorative spoiling caused by mould.
TIPS To Stay Condensation and Mould Free
- TIP: Reduce the production of vapour at source:
- TIP: Keep bathroom extractor fans running, or window open for at least 30 minutes.
- TIP: Keep bathroom doors closed at all times, and bathroom windows open safely.
- TIP: When filling the bath, run the cold water first then add the hot.
- TIP: Dry clothes outside, in a dryer, in a closed room with a dehumidifier or window open, never on radiators or heated rail without a door closed and a means of removing the vapour.
- TIP: Cook with tops on pots and pans, avoiding excessive boiling.
- TIP: Keep the kitchen door closed and extractor fan on where possible.
- TIP:Mechanical vents are best, but if you only have passive vents, such as a whole in the wall or chimney, then vents open with space for air to move, insulate where possible.
- TIP: Keep trickle vents open or alternatively, open windows on safety locks.
- TIP: Stop mould forming:
* Maintain external wall temperatures above 12°C, with low background heating.
* Declutter leaving space for warm air to circulate around cold surfaces.
* Where possible, avoid placing wardrobes and furniture against external walls.
* Avoid overfilling wardrobes and cupboards as it restricts air circulation.
* Use dehumidifiers or small wardrobe dehumidifying bags and replace regularly.
* Wipe mould and condensation off walls and clothes as soon as it appears. - TIP: Monitor relative humidity
* We recommend monitoring temperature and relative humidity with a data logger to see what is happening.
RICS, PCA, HISTORIC ENGLAND JPS REPORT
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.
Mould on rear wall, high damp meter readings through out rear wall and to the front
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. Repair external paintwork, open gulley to front
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.
Cracked paint causing rainwater to moisten walls, causing heat loss, localised vapour resulting in high relative humidity and therefore a risk of mould.
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 Repair paintwork, dry wall out, insulate wall, unblock front gulley
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. ” No alternatives required or appropriate.
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. Monitor visually and with a radio damp meter and data loggers, see recommendations.
7 Where appropriate, clearly state whether the building concerned represents a financial risk to the buyer or lender and why.
The property is not the subject of a sale. In our opinion, there is no material financial risk once you have followed our recommendations.
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.
| Question and Answers |
|---|
| Q: You asked me about removing the decking, or moving it back from the wall. |
| A:While it would be better without decking as rain water is less likely to bounce high onto the wall, it is not the decking that is the issue, but the wall covering. Also decking impedes the flow of sub-floor air, which is not a problem as you have normal levels of sub-floor relative humidity. |
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?
潮湿报告说什么是潮湿的主要原因和防止潮湿的主要措施？
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?