Damp patches and mould on interior wall

This sounds like a classic case of condensation. Stop drying clothes inside the home. Ensure you open windows to air the building and close doors when showering. After showering, open the windows or ensure the fan is working and close the door to keep the moisture in. When cooking keep kids on pans and use the fan at all times. If your still struggling get a dehumidifier. Of course check the seals on the windows and the external pipe. But it sounds like too much humidity in the air. You could change the fans for humidity fans, it may help. Usually, it's clothes drying inside the home.

It sounds like you have penetrating damp issues, first the mortar and any damaged bricks need replacing,as well as ensuring all the windows are properly sealed, once these issues are dealt with, you can seal it, we use a product called Stormdry Masonry Cream, it's produced by Safeguard Europe, its possibly the best on the market, offering 25 year BBA approved guarantee. You did mention that your cavity is filled but have had this checked and told its OK, the problem with some cavity fillings is, once they're wet, they will remain wet and it will show as a damp area on the internal wall, this is why a lot of cavity insulations are being removed now. Hope this helps and good luck going forward. Dave. Viking Property Solutions including Dampfix.

Fit a p I v unit

I specialise in ventilation from single extractor fans to Whole House Heat Recovery Systems, so I hope this answer is helpful. Mould and condensation are almost always caused by excessive humidity BUT it must always be viewed in the context of a given wall temperature. Humidity alone is often very mis-leading. Humidity is often blamed on single specifics such as drying clothes indoors but this is just one element of a massive variety of sources. It can be as much, or more, about the number of people and pets, the heating regime, the fish tank (yes), the insulation, etc. What's more, a scientific paper put 40% down to the building itself. I can usually walk down a street and predict which properties will have bigger problems than others. Usually south facing walls are warmer and suffer less but this is not always the case. Your prevailing wind is a case in point. Again, as a general guide, but with exceptions, corners, low-level downstairs and high-level upstairs suggest insufficient air change. This usually but not always also means poor indoor air quality and a build-up of invisible pollutants in the house that are bad for you. Adjusting the heating regime can have a useful effect in reducing mould but does not improve air quality and can just move a mould problem from one wall to another. Window ‘reveals’ – the bits of wall nearest the window frames – are colder than other parts and so will suffer more. Ironically, just cracking open windows, if it does not create the necessary air change, can just make these areas even colder and....mouldier. Humidity sensitive fans in bathrooms and kitchens can only help but there are more effective solutions for the parts of the house you are describing. These are Air Input Systems – often known as PIV’s, Positive Input Ventilation Systems. As to cost, like most things, there is a range and it usually does not pay to buy the cheapest. Similarly, the most expensive units often have features that are 'nice to have' rather than essential. Installing a PIV doesn't cost much more than installing a couple of good Humidity fans ie hundreds but not thousands (there are plenty of poor extractors and it's not easy to tell the difference). Pound for pound PIV's usually give the best improvement, especially for bedrooms and living rooms. When considering a PIV, the key is in the assessment and installation, so choose someone that shows they understand the problem as much as the solution. Once installed, they take up to 6 weeks to get to full performance but you should see and feel major improvements within 48 hours. The other system not mentioned is Heat Recovery. These are the best you can get, but very expensive by comparison and likely to be total overkill.