Background
The property recently had a quote from “The Leading Damp Proofing, Woodworm & Dry Rot Specialists. Established for over 40 years”, a PLC damp proofing contractor (“damp proofer”), as follows:
Damp-Proofing Treatment:
- To remove skirting boards and plaster: £980.00
- To provide a pressure injected chemical damp-proof course: £1,765.00
- To re-render and plaster the treated walls: £3,240.00
- Total (Excl VAT): £5,985.00
- VAT (20%): £1,197.00
- Total (Incl VAT): £7,182.00
Waterproof Tanking Treatment:
- To prepare masonry by removing plaster/paint: £2,265.00
- To apply waterproof tanking: £12,625.00
- To apply waterproof rendering system and plaster skim finish: £24,975.00
- Total (Excl VAT): £39,865.00
- VAT (20%): £7,973.00
- Total (Incl VAT): £47,838.00
Waterproof Floor Screed:
- To lay new waterproof floor screed: £8,700.00
- VAT (20%): £1,740.00
- Total (Incl VAT): £10,440.00
Grand Total for All Treatments (Incl VAT): £65,460.00
In addition there would be disruption, possibly necessitating moving or at least not working from home and redecoration.
[In my opinion, the damp proofers’ recommendations would have hidden the damp for a while, but not dealt with the root causes, including mould and condensation – they mention condensation, but don’t make any recommendations other than “provide ventilation”… Ironically the survey before this one had the same damp proofer tank their property after buying it, and ended-up in legal action.]
Interestingly the level of quote from this damp proofer is more or less the same as 3 damp surveys back (see previous reports), when the same damp proofer undertook a homebuyer damp survey. Again they were recommending the same unnecessary and evidenced damp proofing and tanking, but completely failed to spot the 14 actual root causes of damp.
Data loggers
In conclusion, from the data loggers
Your dew points are at the top end of my damp survey properties suggested poor ventilation – see the report and recommendations.
To keep the property dry | |
|---|---|
| Replace the bathroom ducting | |
| The duct is long reducing the airflow and also suspect there is a redundant fan blocking airflow. I would replace the ducting, making sure air can flow out of the bathroom. | £100 |
| replace the bathroom fan | |
| I would install a continuous flow bathroom extractor fan such as Vent Axia or Brookvent Airstream DMEV 100 HT (Continuous Running Extractor Fan with Humidistat Timer). Make sure there is an easy to reach isolator, so that you can turn the fan off if it ever makes too much noise such as at night, resetting it after. Ideally the vent should be located away from the door, closer to the shower. | |
| Target insulation | |
| I would insulate lower ground floor wall, such as with thermal insulating plaster board such as Celotex or Kingspan, PIR, especially to the second bedroom where there is mould growing around an out of use air vent. The cost will be in the order of £500 per square metre, make sure to use a foil tape to act as a vapour barrier. See survey https://dampsurveys.com/damp-report-23111308/ for more discussion. I would keep the existing render as it is offering an effective barrier against penetrating damp. I would look at the thickness of Thermal Insulation plasterboard, you may prefer Aerogel, such as SpaceTherm by Proctor, https://proctorgroup.com/products/SpaceTherm , which costs considerably more but is much thinner (also vapour permeable, less of benefit here). | £5,000 |
| Repair heating system leak | |
| Instruct a heating engineer or plumber to repair the heating radiator and then test the heating system for a leak. | |
| Adjust gutter | |
| Instruct a roofer and or general builder to adjust the gutters or replace them to stop the leak form the gutter and or down-pipe. Make sure that they test the flow of water and you see a picture or the test being performed. | £200 |
| Cover brick wall | |
| Cover exposed brick wall in front of bedroom, and ground level, with copping stones or other impermeable cover, which could include impermeable paint, see later. | |
| 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. | £100 |
| 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 |
| Repair paint | |
| Repair paint to the front retaining wall, using a wire brush and applying an impermeable paint, such as Zinsser or Dulux impermeable masonry paint. | |
| Remedial actions – estimate of costs | £5,680 |
Actions if all else fails | |
|---|---|
| I would tile the bathroom | |
| By tiling the wall next to the void, you can avoid ventilating the void, reducing the cost and heat loss. | |
| Ask local authority to check for cracks in drain | |
| I suspect that the front drain is repeatedly being blocked because of root damage within the drain. This could result in rain water saturating the soil near the property. | |
| Consider instructing general builder to duct out kitchen extractor fan (hole required to duct outside, which may require freeholder permission). | |
| The main issue to getting ducting out the extractor fan. Ideally it should be using rigid ducting (not flexible as the ridges create eddies slowing air speed), as short as possible with as few bends. In the meantime, cook with tops on pots and pans. | £200 |
| Optimal actions – estimate of costs | £200 |
I conclude that there is dampness and mould mainly caused by excess vapour from insufficient bathroom and kitchen extractor fan.
Mould only grows where there is excess humidity. It is inhibited by hygroscopic salts found in groundwater, the source of water rising damp.
. By taking a root cause approach, rather than a focus on blocking the symptoms of damp the savings are likely to be around £65,000. 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 231114SH1200. I conclude that there is dampness and mould mainly caused by excess vapour from insufficient bathroom and kitchen extractor fan.. 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 231114SH1200
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: The owners were concerned about rising damp; however, there are no signs nor is there a risk of rising damp.
- Damp treatment: There are signs of past damp proving treatment.
- Weather: Raining heavily.
- Property: Ground floor and lower ground floor Victorian end of terrace property.
- Background: The owners are considering a major upgrade to the lower ground floor and considering tanking the property once more.
- Changes: Conversion into flats, working from home, modern lifestyles, and making the basement into a habitable space.
- Occupancy: Couple who often work from home.
- Mould & notes: There are signs of mould.
- Primary damp concern: Penetrating damp.
- Other damp concerns: Mould.
- Compounding: A blocked rainwater goods causing increased heat loss to the front.
- Airbricks: Not relevant.
- Sub-floor humidity: Not relevant.
- Tenure: Flat.
- Attachment: End of terrace on corner.
- Build: Victorian.
- Walls: 9 inch.
- Exterior comment: There are signs of water overflowing the gutters; water was seen cascading down the front left-hand side during the survey.
- Penetrating damp assessment: Penetrating damp, especially to the right-hand side, the source of rainwater from the street drains.
- Drains: The street drains were blocked.
- Leak signs: Central heating leak and leak under the bathroom fixtures.
- Leak assessment: The main damp is not caused by condensation, made worse by penetrating damp and leaks.
- Floor: The lower ground floor has a solid floor.
- Loft: Not relevant.
- Timber assessment: There’s a marginal risk of rot to the small cellar area, check every 6 months.
- Last dry: I understand that you bought the property during Covid, there were no major damp issues found by your surveyor.
- Ventilation assessment: The bathroom ventilation is at best inadequate and possibly doesn’t work at all resulting from long muti-cornered and possibly blocked ducting. The kitchen extractor fan is not ducted out.
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.
