The property was surveyed by us in November 2020, focusing on penetrating damp high on the middle bedroom wall, an issue that has since been successfully resolved. The current problem, was previously concealed. Renovation work in the hallway, involving the removal of skirting, led to the discovery of wood rot extending below the concrete floor level.
In conclusion, from the data loggers
- I increased the flow rate and overrun on the bathroom extractor fan. It is difficult to tell if there are improvements as data does not extend back far before the damp survey.
- I would follow directions on reducing vapour levels so that the dew point, as shown on the logger app, is more less at or below external temperature.
Evidence & Illustrations
To keep the property dry
|Use absorption-reducing chemicals
|The primary recommendation is to verify for yourself the absence of any minor water losses, such as a leaking tap. I could not find an innocent drip anywhere. Should there indeed be no minor water losses, as suspected, the next step is to investigate and repair the leak. For instance, De-Yany Leak Detection Specialists at 17 Pevensey Avenue N11 2RB, email: LALeakdetection@gmail.com, tel: 07886 702094, have done a commendable job for a client previously. I have no connection with them. Be advised that this investigation could prove costly, and the risk of significant ongoing damage from a leak is relatively low if you follow my recommendations. For walls situated above a solid floor, where the water source cannot be eliminated, you should remove the skirting board at the base of the wall and trim the lowest 10 – 20mm of plaster away from the brick. Then, apply a ~10mm thick bead of a Silane/Siloxane thixotropic cream, such as DryZone by Safeguard, along the brickwork to minimise absorption; it may need reapplication after about 10 years. The skirting board can be replaced. Note, this measure does not replace other remedial actions. I do not recommend drilling holes and injecting chemicals or applying damp proofer’s slurry. These methods are not only expensive but could potentially damage the wall and require a party wall agreement.
|Support rotten timber
|I suspect that a piece of DPM (plastic damp proof membrane) could be slipped under the timber supporting the stairs. If it can be, then it should be. Otherwise, bolt or screw in supporting tanalised timber to support the rotten timber to a point above the damage. Alternatively, you could replace the piece of rotten timber. I would paint anti-fugal paint on the cut end of the timber and place it on a piece of plastic damp proof membrane, because of the ongoing risk of dampness from the likely leak.
|Repaint external wall
|Wire brush the paint on the external walls back to brick, as much as possible at least to remove the surface salts. Then use a paint that is as impermeable, ideally the same as the existing paint, or more impermeable, such as Zinsser or Dulux external masonry paint.
|Use a dehumidifier
|To manage relative humidity, especially when poorly ventilated, humid or cold, consider using a dehumidifier such as the 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 – optimal for colder environments) – all highly rated by Which!. There are numerous alternatives if these specific models are not available. When selecting a dehumidifier, prioritise factors like daily and tank capacity, low noise levels, the availability of a continuous drainage option, and ease of use for programming functions, over aesthetics and weight. The technology behind dehumidifiers is well-established and straightforward to produce, ensuring you can find a suitable alternative focusing on a minimum daily capacity of 20L and the presence of a continuous drainage feature.
|Use fan to expedite drying
|Direct a fan towards any damp areas to expedite the drying process.
|Target vapour from bathroom
|After showering, keep the bathroom door closed and the window open or fan running for at least 30 minutes to allow vapour to dissipate.
|Target vapour from cooking
|Always use tops on pots and pans to reduce vapour emission by 80% and where applicable use an externally ducted kitchen extractor fan.
|Target vapour from clothes drying
|Opt for a tumble dryer, dry laundry in a well-ventilated room with the door closed (such as a bathroom with the extractor fan on or window open), or employ a sufficiently high capacity dehumidifier. Avoid drying clothes in poorly ventilated areas and anywhere near cold walls.
|Mark improvements on damp walls with a pencil line or sticky note and use a moisture meter, such as the Dr. Meter Wood Moisture Meter 2 in 1 Pin & Pinless Multifunctional Water Detector £23.99 or similar damp meter, to log and monitor reduction to dampness in walls. By doing so, you will gain early confidence in these recommendations. Use devices like the ORIA Wireless Thermometer Hygrometer to monitor relative humidity and temperature near walls or ceilings, look to keep the dew point at or below the external temperature. The dew point is shown on the app (if not use https://mouldpoint.co.uk to calculate the dew point from humidity and temperature readings).
|Stay above the mould and dew points
|The dew point indicates when condensation begins, showing the air’s moisture content. To avoid condensation and mould, ensure proper ventilation and dehumidification keep the indoor dew point below the outdoor temperature. Use targeted extractor fans and strategically place dehumidifiers in areas prone to vapour production or dampness. Operating a dehumidifier in bedrooms before bedtime, by clothes drying during the day, and in kitchens overnight is highly effective. Always run at least one dehumidifier when leaving a property vacant, especially in winter. Place it on a sink to catch leaks, with the door open and the window closed, set to 70%RH. Doing this allows you to turn the heating down to its minimum to protect against frost, saving money while minimizing the risk of mould and condensation.
|Remedial actions – estimate of costs