Data loggers
In conclusion from the data loggers – I note the 2nd logger may be by the WC next to the utility room.
- During the period under investigation the surface relative humidity on the damp wall (green line) is high, peaking at 100%RH i.e. the point where condensation starts forming on the coldest surfaces. Relative humidity is above the mould risk of 85%RH.
- 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. The unvented kitchen would have been the most useful room to monitor. I suspect that vapour is coming from the kitchen relative to the rest of the property, particularly 14th to 16th October, when I recall you mentioning family staying. The most significant increases line up with warmer temperature and vice versa which tells me that evaporation from the wall is increasing vapour i.e. drying out following periods of condensation. Increased vapour is not affected by external rain.
- The example property dew point is in fact from my house, where I run a dehumidifier to maintain a healthy environment and reduce the need for and cost of heating. For a large part of the tie your dew points are in line with mine and external dew points, which a well ventilated house should be recording.
- Overall, there clear signs of condensation being the root cause. Data loggers will be useful for ongoing monitoring following the implementation of my recommended actions. Working from home results in more cooking and more respiration. The energy crisis has resulted in people turning down the heat in unoccupied rooms and closing vents and windows. Risk of condensation can be reduced with a 20L+ dehumidifier.
Evidence & Illustrations
The utility room includes an internalised outbuilding. Outbuildings have thin poorly insulated walls, with considerable external surface area. The property has been insulated which is good. But judging by the data logs, the insulation has been poorly installed.
I am purposely showing you the Dr. Meter damp meter, as this meter is a very effective, non-disruptive, and inexpensive way for you to check whether dampness is drying out or, conversely, worsening after following my recommendations. The damp meter measured 100%. This 100% is the meter’s upper limit. It is relative to this limit and does not signify that the wall’s pores are fully saturated. Readings below 30% are considered dry for most materials. These meters assess the extent of dampness and are used to trace its source. Note that moisture is drawn downwards due to gravity. A wet wall is a poor insulator, increasing the risk of condensation. Therefore, dampness resulting from condensation is self-perpetuating and tends to accumulate at the base of the wall. This is often mistaken for rising damp. The higher parts of the wall will tend to dry out first.
Dry lining uses dot and dab adhesive to secure plasterboard to a wall. The issue is the adhesive causes heat loss increasing the risk of condensation.
There were no obvious cracks in the insulation. However, it is what is known as shallow-fit insulation, that is not insulated between the guttering and wall.
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 temperature rises, the air can hold more vapour. Conversely, as 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. A secondary cause of high relative humidity is a low temperature relative to the source of humidity.
Mould growth is inhibited by nitrates found in groundwater. The presence of mould at the bottom of a wall rules out rising damp as the root cause and points towards condensation from unvented excess vapour.
Other matters
To keep the property dry | |
|---|---|
| Reduce vapour from cooking | |
| Cook with tops on pots and pans to reduce the production of vapour from cooking by 80%. | |
| Target vapour from clothes drying | |
| Use a tumble dryer (like a heat pump), dry in a vented room with the door closed (possibly a bathroom with the extractor running or window open), or use a powerful dehumidifier. Don’t dry clothes in an unventilated room, such as the annex. | |
| Target vapour from bathroom | |
| TIP: Keep the bathroom door closed with the fan running or window open until the humidity from the shower has subsided – typically at least 30 mins after the last shower. | £500 |
| grout and sealant | |
| Remove grout around cracks and regrout. Seal with silicone between a bathroom and the wall or tiles. It is best to fill a bath with water and leave it there during the curing process. Using paint masking tape with a neat say 5mm gap either side. Squirt sealant, run finger along (in glove), have toilet paper at hand, within a few minutes, maybe 10 remove the making tape – look at YouTube videos online for top tips. | £100 |
| Seal gap at base of external wall | |
| Continue the fillet of cement based mortar along the line at the base of the rear of the building | £200 |
| Run a small line of external sealant in the gap between the roof level insulation covers. | £50 |
| Use a dehumidifier | |
| Maintain low relative humidity in the utility room, 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 |
| Remedial actions – estimate of costs | £1,030 |
Actions if all else fails | |
|---|---|
| Target vapour from cooking with an extractor fan | |
| Consider installing a kitchen extractor fan, ducted out. | £300 |
| Target insulation | |
| I would remove the plasterboard, which I think is dry-lined with either metal or dot and dab attachments causing the heat loss, replacing the dry-lining with insulation and plasterboard. Ideally, use wood fibre covered by plasterboard, as this is vapour permeable. If you want to avoid loss of thickness, consider using SpaceTherm (a brand of Aerogel), an expensive but very efficient insulation. I would include the rear wall in your insulation. | £1,000 |
| Consider replacing the bathroom extractor | |
| In my opinion, the optimal fans are ones that are targeted, with the fan located near the shower head (without being so close that water sprays onto it), removing vapour during and for at least 30 minutes after taking a shower or bath (which typically produces slightly less vapour). Ideally the fan should be separately wired up with an overrun. Installing the overrun can account for a majority of the cost. Consider installing a continuous flow extractor fan such as Brookvent Airstream DMEV 100 HT (Continuous Running Extractor Fan with Humidistat Timer). Note a continuous flow fan will expel warm air, thereby increasing heating cost by about £120 p.a. but this may be a small price to pay. You can use an isolator to manually turn off the fan when the property is sufficiently ventilated, but the risk is it is left off. | £300 |
| Optimal actions – estimate of costs | £1,600 |
I conclude that the primary root cause appears to condensation, made worse by either dot and dab adhesive, or a metal frame about a metre up increasing heat loss..
Other causes of dampness include an unventilated kitchen and drying clothes in the utility area. There is also a brown stain originating from a crack in the bath seal.
. 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 . I conclude that The primary root cause appears to condensation, made worse by either dot and dab adhesive, or a metal frame about a metre up increasing heat loss.. 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
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: Mild and rainy
- Property: Victorian terraced house
- Background: The owners bought recently, surveyor suggested there was rising damp
- Changes: The key changes that contribute to the damp issues include open plan kitchen, internalised out building to the toilet and probably utility room. There is poor insulation in the extended area and lack of ventilation in the kitchen.
- Occupancy: family of three, but had numerous visitors recently
- Notes: None.
- Primary damp concern: The main damp issue seems to stem from condensation, particularly around a suspected metal frame about a metre up from the floor.
- Other damp concerns: There are a few stains from leaks, nothing major or concerning.
- Compounding: heat loss from poor insulation
- Concern: You bought the property recently after being told by a surveyor and then a damp proofing contractor that you had rising damp.
- Sub-floor humidity: The sub-floor had normal levels of relative humidity.
- Exterior comment: There were no major concerns seen externally that would account for internal issues.
- Penetrating damp assessment: The exterior appeared to be OK from a damp perspective. There are no obvious signs of significant penetrating damp.
- Drains: The drains are of no special concern.
- Leak signs: No suspicion of a mains water leak
- Leak assessment: There are no obvious signs of a significant mains or wastewater leak.
- Loft: The loft has been converted.
- Timber assessment: There are no suspicions of significant timber decay.
- Last dry: It is difficult to know when dampness started, but judging by the work it started before you bought the property.
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.
Primary dampness was to outbuilding which is subject to vapour from the unventilated kitchen.
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. I would replace the dry lining with insulation.
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.
The risks will be minimised by following my recommendations to the letter.
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 Install a kitchen extractor fan and or use a dehumidifier and cook with tops on pots and pans.
5 The client should be provided with alternative options for which each 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.
Relevant examples of properties with similar damp issues: electric-sockets
[mwai_chatbot_v2 id=”default”]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?