Data loggers
In conclusion, from the data loggers
The dew points in your property are high, too high compared to external temperature, external dew points and average damp properties in London. It is possible that a small contribution comes from issues associated with the flood from next door, but a majority of excess vapour will come from the standard 4 contributors: drying clothes, showering, cooking and respiration. Each person contributing about 2 litres per day. The solution is targeted ventilation, such as overusing the kitchen extractor fan, keeping the bathroom door closed, with fan on, and using a dehumidifier constantly. Dehumidifier will reduce the need for heating, thereby saving money and CO2 production.
Background
Summary of Past Surveys and Damp Proofing Treatments
- Dampcoursing Limited (25th November 2009):
- Findings: Rising damp in various walls.
- Recommended Work: Physical and chemical DPC, waterproof replastering.
- Cost: An independent survey, a quote for work.
- R&D Management (London) Ltd (14th January 2014):
- Findings: High humidity, possible plumbing defects, and mould growth.
- Recommended Work: Install passifier units, bathroom extractor, investigate plumbing.
- Cost: Not specified in provided details.
- Peter Cox Ltd (14th December 2017):
- Findings: Rising dampness, condensation problems.
- Recommended Work: Install chemical DPC, Warmerwall paint, dry wall coating.
- Cost: £1,436.40 (DryWall and Damp Proof Course Installation).
- Peter Cox Ltd (20th January 2021):
- Findings: Condensation, mould growth, no rising damp.
- Recommended Work: Install wall-mounted PIV unit.
- Cost: £1,859.05 (Wall Mounted PIV Unit).
- Dampcoursing Limited (1st June 2021):
- Findings: Rising damp, condensation, defective sealant at kitchen sink.
- Recommended Work: Chemical DPC, replastering.
- Cost: £658.00 (Chemical DPC and replastering).
- In addition I understand there was a flood last summer from the neighbour’s side.
Evidence and illustrations
Note the mould growing on the slurry. Mould is inhibited by the hygroscopic salts found in rising damp. As previously stated the downsides of damp proofing treatment are, 1) rising damp, that is groundwater in contact with walls, is exceptionally rare, 2) impermeable slurry increases risk of mould and condensation, which is the primary cause of damp at the base of your walls.
There was a proposal to have Positive Input Ventilation “PIV” system. This is very expensive to install, maintain and run, with annual loss of heat, costing about £300 per year. They are untargeted and always on even when the external vapour pressure is higher than the internal average, such as when it is raining.
By contrast, a dehumidifier targets vapour. All the energy consumed stays in the property with about 50% bonus from entropy, like an air source heat pump. Therefore it is good for the indoor and outdoor environment and costs less, about £1 – 2 per day (arguably a similar cost but a dehumidifier adds heat, whereas PIV blows it out). The downside of a dehumidifier is it needs daily decanting. Like a PIV, a dehumidifier is not a substitute for use of a kitchen and bathroom extractor fan which target vapour production. It is best placed either where vapour is being generated e.g. respiration or drying clothes, or where mould is growing.
If going away I would leave the dehumidifier set to 70%RH dripping through a length of hose (normally sent with the unit when purchased), into a sink and leave some background heating.
To keep the property dry | |
|---|---|
| Ask tenants to remove vapour from cooking | |
| Cook with tops on pots and pans to reduce the production of vapour from cooking by 80% and use the kitchen extractor or fan whenever cooking. | |
| Ask tenants to remove vapour from bathroom | |
| Ask tenants to 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. Consider adding a spring to the bathroom door as an extra reminder. | |
| Ask tenants to remove vapour from clothes drying | |
| You have provided tenants with a means of drying clothes internally in the form of a powerful dehumidifier. | |
| 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 a dehumidifier based on daily and tank capacity, low noise, whether it has a pipe out, and ease 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 |
| remove mould | |
| Consider sanding down mould where dry, and removing it with either bleach or anti-mould foam. I personally use HG Mould Remover Foam Spray, but imagine there is no major difference between brands. | £100 |
| Check rainwater goods | |
| Check the flow of water from your neighbour rainwater goods onto your wall during a rainstorm. | £500 |
| Instruct a structural engineer | |
| This is presumably a freeholder responsibility | |
| 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. | |
| Remedial actions – estimate of costs | £780 |
Actions if all else fails | |
|---|---|
| Consider installing a continuous flow bathroom extractor fan | |
| Consider installing a continuous flow bathroom extractor fan such as Vent Axia or Brookvent Airstream DMEV 100 HT (Continuous Running Extractor Fan with Humidistat Timer) – I have installed one in a rental property I own myself, that was bought cheaply because of mould. Although important to have an isolator, it can be sited in a way that doesn’t tempt tenants to use it. Ideally the vent should be located away from the door, closer to the shower. I would also install a bathroom spring to encourage tenants to keep the door closed. Ideally the ducting should be rigid, for reduced air resistance, and insulated to reduce risk of condensation in pipe. | £400 |
| Consider updating your thermostat | |
| Consider installing a modern WIFI connected thermostat, with multiple heat settings, so as to ensure the wall temperature doesn’t drop below the dew point. | £400 |
| Consider insulating cold areas | |
| Consider installing thermal insulating plasterboard or thermal lining paper where mould is growing, especially around reveals, such as wallrock thermal liner or Sempatap thermal solid wall insulation to cold surfaces. Consider insulating to the side of and under the shoes prone to mould. This will reduce the risk of heat lost to the sub-floor and external wall. | £1,000 |
| Consider painting anti-mould paint onto walls vulnerable | |
| TIP: anti-condensation paint. Consider painting anti-condensation (e.g. DryZone by Safeguard on Amazon 5L £53.70) or anti-mould paint onto walls vulnerable to condensation or mould (top coat only). Bathroom would be a good example. | £300 |
| 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. | £200 |
| Block passive vents | |
| I would block up the passive vents with insulation, like expandable foam, making sure to follow instructions. You should open trickle vents were they are present, since you have the heat loss you might as well get some ventilation. | |
| Optimal actions – estimate of costs | £2,300 |
I conclude that there was no evidence of rising damp, which comes from groundwater in contact with walls. The risk of groundwater is very low. There were many signs of excess humidity causing condensation and mould.
Hygroscopic salts such as calcium nitrate cause deliquescence at 50%RH, that is a form of condensation. This is below the humidity that mould forms at, therefore mould is inhibited by calcium nitrate found in rising damp, besides groundwater is pumped out of the ground in cities like London.
I increased the bathroom extractor fan overrun to 30 minutes.. 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 Damp: remote possibility, see explanation by Dr Robyn Pender of Historic England.
I confirm that I inspected the property on 231117SH1030. I conclude that there was no evidence of rising damp, which comes from groundwater in contact with walls. the risk of groundwater is very low. there were many signs of excess humidity causing condensation and mould.. 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 231117SH1030
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.
- Rising damp concern: You were concerned about damp.
- Damp treatment: Despite the low risk of rising damp, disruption at the base of external walls suggests there has been an attempt at chemical treatment against rising damp. Internal plaster may have been 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.
- Weather: it rained during survey
- Property: lower ground floor flat in semi-detached Victorian building
- Background: We have had several rounds of Dampcoursing in different areas of the flat but it’s not making much of a difference. We believe there may be various issues going on- damp ingress, bad drainage from the property, condensation, rising damp, ? We are keen to fix this issue but need a solid action plan.
- Changes: conversion into flats, central heating, double glazing with no or insufficient trickle vents and lifestyle changes including more frequent showers and clothes washing, including greater occupancy during the Covid pandemic.
- Occupancy: young family
- Mould & notes: mould across property
- Primary damp concern: dampness and mould
- Compounding: poor insulation, including to the extension and past damp proofing treatment
- Airbricks: There is no reason to be concerned about the sub-floor ventilation.
- Sub-floor humidity: There were no concerns about humidity in the sub-floor void.
- Tenure: lower ground floor flat
- Attachment: a semi-detached
- Build: Victorian
- Walls: solid wall made of two brick widths (225mm)
- Exterior comment: There was a streak of dampness on the outside that appeared to be caused by rainwater overflowing from the neighbour rainwater goods – check during a rainstorm.
- Penetrating damp assessment: There is no significant discoloration on internal surfaces.
- 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.
- Floor: The suspended timber floor did not feel damaged.
- Loft: There was no loft.
- Timber assessment: There are no suspicions of significant timber decay.
- Last dry: I understand there were no damp issues when you lived in the property.
- Ventilation assessment: I improved the bathroom ventilation, the kitchen extractor fan is OK, but is it being used?
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.
