Data loggers
In conclusion from the data loggers
- During the period under investigation the surface relative humidity on the damp wall (green line) is not above the mould risk of 85%RH, nor is there condensation taking place.
- However, 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 dew points fluctuate with vapour quantity and therefore are a good indication of ventilation. It is a sign of insufficient ventilation when internal dew points are significantly above external dew points.
- The example property’s 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. The difference between your dew points and the example property are narrowing suggesting ventilation improvement and or drying.
- Overall, there signs of condensation being a compounding factor from heat lost to damp external bricks, but not the root cause – see later in this report.
See https://damp.ai/glossary/monitor-humidity-with-data-loggers/ on how to use the data logger app. To work out the external dew point, you can install a logger outside and look at the dew points indicated on the logger app (for example SensorBlue), or as a rough guide if you pick up the Met Weather, look up your area, then take the external temperature and external relative humidity then take off 1° for each 5% below 100%RH to estimate the dew point. So for instance if the external temperature is 14°C and humidity 80%, as a rough calculation, the external dew pointis about 14-(100-80)/5 = 10°C.
Evidence & Illustrations
The wall was damp, as indicated by a Protimeter radio frequency damp meter. The meter measured 999REL, signifying saturated pores deep within the wall. Readings below 300REL are dry. These meters assess the extent of damp and are used to trace it to the source.
Moss grows where an external wall is wet for longer than it would normally be from rain.
I tried to unblock the down-pipe during the survey, but it will take more time with a plumber’s snake or similar to unblock the pipe.
Most mould germinates and grows 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. Brown mould grows at slightly lower but consistent and longer-term relative humidity around 80%RH. From experience it is typically found in properties left unoccupied for long periods. There was no ongoing localised source of vapour. The back of the cupboard is dry. I suspect the cause was something wet being left in the cupboard. This is the explanation, the solution is to remove the contents wash it thoroughly. Wash cupboard and any other signs of mould with anti-mould spray or bleach, which is the active ingredient.
Cook with tops on pots and pans and use a dehumidifier when drying clothes internally or when relative humidity is high, or the dew point is higher than the outside dew point, see your data loggers.
This section of wall is vulnerable to condensation such as from drying clothes as the wall is below the living room floor and therefore subject to sub-floor temperatures, which are likely to be close to external temperatures.
This is fine so long at the exterior coating is in good order, kept impermeable, but inevitable cracks and gaps need to be checked and filled and or painted over with an impermeable paint to ensure water can enter.
Typically the cause of high damp meter readings, which there were in the rear bedroom, is not ingress or rainwater passing through onto the inside wall, but heat loss leading to condensationfrom excess internal humidity. All of which is fine until you come to sell your property and contracts identifies damp with a damp meter and recommends unnecessary and expensive damp proofing treatment.
To keep the property dry | |
|---|---|
| unblock down-pipe | |
| I tried to free cement and other builder’s material blocking the down-pipe. I suggest using an old metal hanger straightened or buying a plumber snake, pushing the detritus up. See. Above link for further recommendations. | £10 |
| fill render crack | |
| Check and repair any cracks in the exterior walls to prevent water ingress. Address external render cracks by raking out, that is slightly enlarging and removing loose material and filling with an acrylic based caulk for small gaps and cement based mortar for larger gaps over 3mm. | £100 |
| 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. | £20 |
| external coatings | |
| Fill external coating cracks with external acrylic caulk and over paint with the original coating or if unknown an impermeable paint, such as Zinsser or Dulux impermeable masonry paint. | £350 |
| door seal | |
| Heavy rain can splash through the seal around the door causing localised damp around the doorway. Run your finger around the door seal to check for gaps, debris and damage. Test for integrity by spraying water around the base of the door. You may have to replace the seal if water is getting through. | |
| 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. | |
| Target vapour from cooking with an extractor fan | |
| Cook with tops on pots and pans. | |
| Remedial actions – estimate of costs | £480 |
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 dampness at the rear is due to a blocked down-pipe, resulting from roofers allowing rubble to fall into the down-pipe and block it at the bottom. there is also condensation..
The overflow pipe issue is due to the blockage caused by the builders.
. 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 231025SH0800. I conclude that Dampness at the rear is due to a blocked down-pipe, resulting from roofers allowing rubble to fall into the down-pipe and block it at the bottom. There is also condensation.. 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 231025SH0800
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: Light drizzle with some sun, mainly cloudy.
- :Victorian mid-terrace house.
- :The property is undergoing a sale. The buyer’s surveyor noted dampness in the front and rear reception rooms and concerns in the extension of the rear open-plan living room kitchen.
- :The property has been coated externally, damp-proofed, and has a large open-plan kitchen with an extension for modern living.
- :A young family occupies the property.
- :Mould has been noted in an internal cupboard, currently being addressed with a small dehumidifier.
- :Dampness near the radiator in the ground floor rear reception living room.
- :Mould in the kitchen.
- :Poor ventilation from the kitchen extractor fan and indoor clothes drying.
- :Sufficient airbricks present.
- :The sub-floor had normal levels of relative humidity.
- :house
- :a terraced
- :Edwardian
- :9-inch walls.
- :There was a blocked down pipe behind the rear living room wall, a crack in the render at the rear, and a possible leak through the rear bedroom doors.
- :Internal dampness lined up with external issues, therefore we conclude that penetrating damp, or heat loss caused by rainwater is a factor in the internal dampness.
- :The drains are of no special concern.
- :Aside from the blocked down-pipe, the drains seem to be in reasonable order.
- :No signs of a mains water leak.
- :Suspended timber floor.
- :No specific concerns regarding the loft.
- :There are no suspicions of significant timber decay.
- :Previous issues at the front of the property and the roof were addressed a few years ago; ironically, solving the roof problem has led to a blocked down-pipe.
- :Keep the bathroom door closed and ventilated until humidity has dropped. Cook with tops on pots and pans as much as possible. Use a dehumidifier to reduce excess internal vapour such as from drying clothes internally.
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.
Dampness primarily at the base of walls due to rainwater goods.
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. Check water flow during rain; ground levels appear to be satisfactory.
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.
Faulty rainwater goods causing penetrating damp, render cracks and internal condensation; no major risks identified.
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 Unblock the down-pipe, potentially using a plumber’s snake to remove stones from the bottom, as attempted during the survey but requires more time. Further recommendations listed in remedial section of this report.
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.
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?