We’re having a problem with damp appearing on the interior walls of our small office. The office is at the back of the house and when it gets cold outside, we start having damp marks appear on the walls of the office in the corner. Would this have to do with the exterior wall or insulation problems? What will we need to do to stop this from happening?
Damp or moisture on the face of your internal walls can be caused by several factors. It may be water ingress due to penetration; it may be rising damp, although the latter is incredibly rare and often misdiagnosed; or it could be condensation.
Your description, and the fact that this manifests when it’s cold, suggests that the damp your experiencing is condensation. Condensation forms when warm, moist air inside the office hits a cold surface, such as an inadequately insulated wall, and water droplets form. Over time, this can soak into the wall, leading to damp patches. Corners of rooms are particularly vulnerable because they tend to be colder due to reduced air circulation.
Yes, insulating your walls may be the solution but before you start spending money and applying for grants, I think you should consider a few things. Is there a bathroom with shower, kitchen or other room that may generate high levels of moisture linked directly to the room? If so, ensure that the door remains closed to prevent moisture travelling into the office or other rooms.
Often, we shower and leave the bathroom door open during or after, allowing moisture to migrate all over the house and affect fabric. Close all doors over a series of weeks and observe. Remember the room must be allowed to dry out first. If condensation continues, then you move to the next low-cost option.
Is there a vent in the room, like a hole in the wall? If yes, check that it is fully open to allow air flow. Often these are blocked or the shutter is closed. If no, consider installing a vent. It is important to note that often you will see a vent in the wall and there is black speckling (condensation) over it or around it. This is because a passive vent was simply not good enough to deal with the problem of moisture. Why? Well, that would take more investigation, but consider putting in a mechanical extract vent. When moisture builds up, this activates, pulling moisture out of the room. It’s money out but is a small disruption and may be the solution.
In either scenario above, its important to ensure the room is adequately heated. There are many solutions, but a suitable one is key. Before carrying out any works I suggest you contact a chartered building surveyor who specialises in thermal upgrades.
Brigid Browne is a chartered building surveyor and a member of the Society of Chartered Surveyors Ireland
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