Data loggers
In conclusion from the data loggers
- During the period under investigation, the surface relative humidity on the damp wall was below the dew point, where condensation begins. However, as it is October when day time temperatures are similar outside to inside, the calculation of surface relative humiditybecomes less precise then they would be when it is cold such as at night.
- The surface relative humidity is calculated considering the temperature difference between the data logger and the 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.
- The grey line in the graph is dubbed the dew point differential. It suggests to me that excess vapour is emanating from the bathroom; I suspect that drying clothes indoors and respiration from a lovely, but large dog are causing the background excess humidity.
- Overall, there are no clear indicators that condensation is taking place during this period; likewise, there are no clear spikes resulting from rainwater.
Evidence & Illustrations
Protimeter damp meters can be used in one of two modes, 1) in conductance mode measuring ionic conductance between two points. Below 20 – 30 WME is considered dry depending on the material.
The second mode is radio waves set to a suitable frequency, where below between 200REL and 300REL is considered dry. At worst the wall is marginally damp.
What does dampness at the base of a wall mean? It could be any one of 4 sources; groundwater that causes rising damp, penetrating damp from rainwater, a mains or waste water leak or condensation, the most common for of damp. All sources of damp will tend to cause high damp meter readings at the base of a wall because gravity draws water down and the base of walls are generally colder, often 5°C colder than higher up the same wall.
It is not without irony that damp proofers have caused some of the internal damp with their “French drain”. You could argue that the fact that you are not seeing damp inside, proves that slurry works. But that misses the point, as the slurry is blocking damp, rather than addressing the root cause. If the roof cause is not dealt with, there is a risk of rot to sub-floor timber and the wall will eventually show signs of salt damage.
Other matters
As part of my damp survey, I have reviewed the RICS survey and quote for remedial work from a contractor. I saw nothing to come close to justifying their recommendations, in particular rising damp treatment which has already been implemented despite the lack of groundwater the root cause of rising damp. I hope the evidence in this report highlights the need for surveyors to be financially independent from the recommendations they are reporting on. RICS surveyors should to recommend advice be taken from a fully independent surveyor, who never benefits from the recommendations made. I will be writing to the companies and organisations involved, asking them to review their reports in the light of my findings. I will name and shame them, unless they have persuasive evidence to support their claims.
To keep the property dry | |
|---|---|
| Insulate pipes | |
| Insulate around all pipes entering and exiting walls, including the ones in the bedroom and kitchen. The pipe insulation should go deep into the wall up to the brick, i.e. through the plaster. You could paint an anti-absorption cream such as by damp proofers (Dryzone Damp Proofing Cream £20 on Amazon), the cream works albeit used for rising damp when there is none (the slurry is the issue not especially the anti-absorption cream). Furthermore I would build, or buy ready made, a box to seal around the pipes. I would stuff in insulation such as wood fibres. If you do it yourself it should cost no more than £50, probably half a day plus materials for a general builder, say £200. | £200 |
| Clear gutter | |
| The front gutter 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. Use a long pole say 5M and gutter clearer, with adapter. I would take a photo afterwards and during a rainstorm, to make sure all is clear and running freely. If you do it yourself it should cost no more than £5, probably a few hours for a general builder, say £50. | £100 |
| Clear gulley | |
| Like the gutters, the front and rear galleys 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. I removed lots of shingles, but with a plumber snake and hose pipe you will be able to remove the remainder fairly easily, but it takes time. If you do it yourself it should cost no more than £50, probably a few hours a day for roofer or a general builder, say £100. | £100 |
| Monitor vapour with data loggers | |
| Monitor relative humidity and temperature against the wall or ceiling to observe the effects of improvements, such as ORIA Wireless Thermometer Hygrometer (20m (2 Packs)) – already in place. In addition monitor improvements on the damp wall a pencil line and damp meter such as dr.wood moisture meter, logging improvements each month. Monitor relative humidity and temperature against the wall or ceiling to observe the effects of improvements, such as ORIA Wireless Thermometer Hygrometer (20m (2 Packs)) – already in place. In addition monitor improvements on the damp wall with a pencil line and damp meter such as dr.wood moisture meter, logging improvements each month. | |
| 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. | |
| 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. | |
| Ask the neighbours to keep airflow behind their fridge. Monitor dampness with a damp meter. | |
| Monitor sub-floor humidity | |
| Use a hygrometer probe under floor. A probe can be pushed through cracks in floorboards or by discretely drilling out a hole. The sub-floor relative humidity will fluctuate. It was normal during the survey. In the unlikely event that it rises, remaining above 85%RH for an extended period then 1) check for leaks, see damp.ai. and if the leaks come from neighbours or outside property, then consider installing a fan into the sub-floor to blow air out. Increasing ventilation is tricky as there is limited accessibility. A company called ELTA made a Sub-Floor Ventilation Fan, which many clients with similar issues have installed with success, but ELTA have been closed down. This site seems to offer the same unit: https://www.builders-superstore.co.uk/product/ventilation-fan-sub-floor-mains-powered/ | £5 |
| Remedial actions – estimate of costs | £405 |
Actions if all else fails | |
|---|---|
| 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 |
| Optimal actions – estimate of costs | £180 |
I conclude that there was poor ventilation in wet areas like the bathroom and kitchen, combined with the presence of a large dog, causing condensation issues. blockage in the front gully, potential for penetrating damp at the front of the property but no signs of water ac.
Condensation was forming around pipes connected to the subfloor void and behind the fridge, causing a small area of dampness. The front gully is blocked, and there are also some risks of penetrating damp at the front, although no signs of water actually penetrating were found. The damp meter reading was marginally high on the front wall close to the party wall side. No major issues with the property. Use a dehumidifier, particularly during this time if selling the property, and consider it as a long-term solution in any future property.
I repaired the bathroom ventilation during the survey. The kitchen vent was less effective than it should be, I improved it. I helped the neighbours improve ventilation behind their fridge.. By taking a root cause approach, rather than a focus on blocking the symptoms of damp the savings are likely to be around £20,000. 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 There was poor ventilation in wet areas like the bathroom and kitchen, combined with the presence of a large dog, causing condensation issues. Blockage in the front gully, potential for penetrating damp at the front of the property but no signs of water actually penetrating through to the front wall. Condensation on cold pipes connected to the subfloor void and a small damp area behind the neighbour’s fridge.. 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: Overcast with intermittent rain during the day.
- Property: The property is a ground floor flat in a Victorian terraced house.
- Background: The owners bought to the property a few years ago. Their surveyor found some damp around pipes in the bedroom. The property is subject to an offer. The buyers are concerned about a quote for work from a contractor, following their survey which highlighted some damp.
- Damp treatment: Despite the low risk of rising damp, there has been an attempt at chemical treatment against rising damp. Rising damp treatment is normally a sign of insufficient ventilation. The walls have been drilled into by about 200mm and injected with damp proofing chemicals. In theory the chemicals are absorbed into the brick pores reducing the bricks ability to absorb moisture. Walls are replaced with damp proofers slurry. This can cause problems with absorption imbalance, resulting in increased condensation on other walls or vapour becoming absorbed and trapped behind the slurry. There was evidence of surface condensation in areas probably not treated with replacement plaster but no evidence of trapped vapour. The solution is through ventilation and humidity control.
- Changes: Conversion into flats, central heating, past damp proofing treatment reducing the buffering effect of absorbent walls, double glazing, central heating, modern life styles, increased occupancy due to Covid and large dog.
- Occupancy: Two owners with large dog
- Primary damp concern: The main issue is condensation, not rising damp.
- Other damp concerns: There is an easy to rectify, freeholder responsibility penetrating damp to the front, caused by a drain blocked by shingles from past damp proofing treatment, namely the so called “French drain”.
- Compounding: heat loss from pipework running into sub-floor void
- Concern: Your buyer’s RICS homebuyers identified a potential damp issue.
- Sub-floor humidity: The sub-floor relative humidity was normal.
- Exterior comment: Gutter blocked, signs of damp around front. Blocked gulley.
- Penetrating damp assessment: There is a risk of penetrating damp. So far there are no signs internally, but these identified issues should be rectified.
- Drains: The front and rear drains were blocked.
- Leak signs: No signs of a mains or waste water leak.
- Leak assessment: A mains or waste water leak is unlikely.
- Timber assessment: There were no signs of significant timber damage.
- Last dry: Not known, but has become worse since Covid and cost of energy crisis, both increasing the risk of damp from condensation, through increased occupancy and advice to reduce energy consumption
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.
Poor ventilation, blocked gutter, blocked gulley.
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. The front and rear patios have been raised sightly over time, there are no signs this is causing internal damp.
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.
Condensation from uninsulated cold pipes passing into the cold sub-floor and external walls meeting high humidity from poor ventilation, now repaired.
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 Maintain dew point of internal vapour within 3°C of external temperature and insulated cold water pipes including the plaster around pipes in the bedroom and kitchen.
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.
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.
The property is 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.
In this section I try to highlight typical issues with building work and surveying from a damp perspective. I mean this as a conversation opener. I estimate £500 Million to £1 Billion saving to the UK economy if a few relatively easy poor workmanship or misunderstandings could be remedied.
Fans of shame
The bathroom extractor fan back flow shutter was blocked. The kitchen extractor had blown off and therefore most air is recirculated. I fixed both.
I mean no harm, we can all make mistakes (including myself – I shame myself with a property I surveyed with extensive damp issues, 4 years after my homebuyer’s damp survey). I give persons to be named sufficient time for a right of reply before naming them. We should talk openly, not behind closed doors, to learn from each other. I have repeatedly tried to bring examples of poor surveys to the attention of the PCA and contacts at RICS with no apparent improvement. If anything the level of incorrect and inappropriate recommendations are increasing.
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?