Open – Print or Save PDF – Refresh
Data loggers
This graph comes from your data loggers. I chose this comparison as it was the most illustrative.
In conclusion from the data loggers
- During the period under investigation the surface relative humidity on the damp floor (green line) is high, peaking around 95%RH and probably condensing on the coldest surfaces. Relative humidity is above the mould risk of 85%RH and at risk of condensation.
- 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 floor rather than kitchen, except for 26 September. Cooking with tops on pots and pans would be beneficial.
- It is interesting that there is no increase in dew point in the living relative to the kitchen or outside despite some heavy rain around 26 – 27 September, this suggests that penetrating damp is not a root cause, at least not directly.
- 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. The difference between your dew points and the example property are narrowing suggesting ventilation improvement and or drying.
Overall, there clear signs of condensation on a cold impermeable surface, 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 can be reduced with a 20L+ dehumidifier.
Evidence & Illustrations
Remedial actions necessary to keep the property dry | |
|---|---|
Dry carpet and floor thoroughly | |
| I think you need a dehumidifier, see later. Also, consider getting a fan; it need not be large, and you don’t need one with a heater. Aim the fan at the damp, mouldy carpet and wet floor to speed up the drying process. Use a damp meter to determine if the carpet and floor are dry. I would recommend a Dr.meter Wood Moisture Meter log (£22) for monitoring improvement in dampness. | £42 |
Target vapour from cooking | |
| Cook with tops on pots and pans to reduce the production of vapour from cooking by 80%. | |
Target vapour from bathroom | |
| Keep the bathroom door closed with the fan running or window open until the humidity from the bath or 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. | |
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 a pencil line and damp meter such as dr.wood moisture meter, logging improvements each month. | |
Treatment of Hygroscopic salts | |
| Like grease stains they are benign, cause no damage or mould, but are unsightly, especially in summer during a heat wave, and cause problems renting or selling a property (keep this report to show prospective buyers). The best solution is to cover the salts, with an impermeable blocking material, with a significant overlap of at least 300mm (to reduce the risk of enlarging the damp patch). Ideally treat each section of wall equally, so that it is homogenous and therefore absorbed or repels humidity in the same way. Hygroscopic salts can be just under the surface. The simplest, cheapest and in my opinion the best is using 2 coats of Zinsser BIN Cover Stain, a solvent-based, primer-sealer. For each patch, it takes about 1 hour and costs around £15 plus any labour if required, the great thing with Zinsser is it is easy strip off and reapply. For significant areas consider painting a coat of gloss paint sandwiched between two layers of Zinsser BIN Cover Stain, and ideally paint all sections of wall affected, as like icebergs, there can be more hidden just below the surface. Most homeowner would be able attempt this. It will take a general builder a few hours, and so should be considered as part of a larger project. For saturated walls and if it doesn’t work immediately, consider sandwiching a layer of an oil base paint between two layers of Zinsser BIN oil based primer, then you can complete with a standard emulsion. | £100 |
Treatment of leak | |
| The leak upstairs was not within the scope of my inspection. I am unaware if it was caused by waste or mains water. A very slight change on the mains water meter for both properties was noted, suggesting a minor drip, although this could originate from a shower head, cistern or a similar source. Regardless, the source of the leak upstairs needs addressing as it could be ongoing. The extent of fungal damage and whether there is adequate strength remaining in the timber joist(s) should be assessed, and potentially, a joist may need to be attached with nuts and bolts to fortify it. The strength of the joist can be tested by pressing a screwdriver into it. Should the screwdriver penetrate deeply into the timber, an estimation of the remaining structural integrity is advised by looking at the timber and zone of fungal attack. Generally, if 50% or more of the strength remains, it should suffice—unless the joist is situated under a corridor or is bearing a heavy load, such as a bathtub, without additional reinforcement. | |
Repair defective pointing | |
| Where pointing is defective use a pointing similar to the original, which may be a lime based mortar. Ideally it should not be an impermeable mortar, as high concentration of cement would make it. This because the point should be a sacrificial from a damp perspective, absorb more moisture than bricks, so that moisture is not trapped by the pointing. | £200 |
Cap the top of the left-hand wall | |
| Render capping or coping stones can be defect rain water off the top of a brick wall. | £100 |
Reduce absorption of rain on external walls | |
| To address damp issues on the front wall, consider using StormDry Masonry Waterproofing Cream by SafeGuard (Amazon £35/l) on porous bricks next, see illustration of the most likely points of ingress. A litre of StormDry covers 4-5 square meters; one coat should suffice. Test on a hidden brick first. If satisfied, apply the cream up to 1m above the damp area, covering whole bricks for neatness and even dispersal. Also, treat the last 3-5 brick courses from the ground up. While Safeguard is generally reliable, exercise caution; they have a commercial interest in promoting unnecessary rising damp treatments. Always follow the manufacturer’s guidance. | £200 |
Remedial actions – estimate of costs | £642 |
Optimal actions to help remain damp free (if all esle fails) | |
|---|---|
Use a dehumidifier | |
| Maintain relative humidity, especially at night when it’s cold outside or you are maintaining lower temperatures downstairs compared to upstairs a night is easiest done 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. | £180 |
Target insulation | |
| As a minimum I would insulate on the ground around the damp zone, with modern insulated underlay, and behind the radiator and the radiator pipes. You can expect energy savings of approximately 5% – 10% p.a. for the first £1,000 to £2,000 spent by being selective in your approach. This recommendation serves as a starting point for discussion. You should assess whether this approach aligns with your financial and practical needs. | £1,000 |
Consider installing kitchen ducting | |
| If this were my property, I would install rigid ducting from the current kitchen extractor fan to the outside (test airflow with a piece of A4 paper it should blow more or less horizontally out). | |
Consider installing a 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. | £500 |
Remedial actions – estimate of total costs | £1,680 |
I conclude that there was condensation acting like rising damp off the cold concrete floor in the living room.
There are a lot of damp issues at this property. However, condensation is the primary cause of damp in the wall of greatest concern. The profile is that of a leak in so far as water is rising off the floor. However, the root cause is condensation forming on the floor and possibly the radiator pipes. There are other signs of condensation around the property, including the light switch by the front door and areas around the kitchen. There are a number of sources of vapour, not least the unvented kitchen where the ducting from the kitchen does not extract out. There are also areas of penetrating damp either side of the front bay. The property has been damp-proofed in the past. This has masked some of the issues but not resolved the root causes. There are hygroscopic salts in the chimney breast. There is a leak from the flat above, which has resulted in timber rot.
By taking a root cause approach, rather than a focus on blocking the symptoms of damp the savings are likely to be around £26,000. 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, see explanation by Dr Robyn Pender of Historic England.
I confirm that I inspected the property on 22 September 2023. I conclude that there was condensation acting like rising damp off the cold concrete floor in the living room. 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 dataloggers for example the Smart Hygrometer measuring humidity on the wall and nearest source of vapour, before and after following our recommendations. These dataloggers 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 22 September 2023
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.
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.
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.
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 (the ceond in aseries won’t add as much)
- 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 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 dehumidifer or window open, never on radiators or heated rail without a door closed and 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.
Relevant examples of properties with similar damp issues: electric-sockets
This Artificial Intelligence section of the report is being built using Chat GPT 4 by damp.ai which is in beta trial. Damp.aï is not yet content aware, so cut and paste anything that needs greater explanation. Chat GPT 4 is prone to error and “hallucinations”.
- Note Chat GPT4 retains your input text to enhance its performance and understanding.
- Since we can’t guarantee accuracy, we encourage you to prioritise simple, often free, damp solutions before considering more expensive alternatives.