Wet looking spots on walls when it rains – Should you worry?

Here in the UK we are no strangers to a bit of rain. We usually have a certain amount of bad weather all year round, but this can really turn up in the winter months.

One thing that can be particularly annoying, and even stressful about this type of weather, is recurring damp. This usually involves wet looking spots on walls, that always seem to appear when it starts to rain.

wet looking spots on walls

But should you worry about this type of damp? Are wet looking spots on walls a clear sign that something is wrong?

Isolated patches that appear exclusively in one area, usually mean you are suffering with penetrating damp. The fact that these wet spots only appear or get worse when it’s raining, would support this diagnosis even further.

Penetrating damp happens when a defect to the outside of your house, allows water to penetrate through to the inside. This passage of water obviously increases when it rains because more water enters the defect.

To solve this problem and to stop damp appearing and causing issues inside your property, you will need to do two things:

  1. Locate the defect on the outside of your property
  2. Fix the defect on the outside of your property

This really is the only way to solve penetrating damp issues. You need to stop the problem at its source. If you fail to fix the problem correctly, the issue will continue.

Locating the cause of wet looking spots on walls

There are two ways you can identify the cause of penetrating damp. The first is to carry out an outside inspection yourself. It may be, that you can easily locate the problem without any professional help.

Your second option is to hire a professional damp surveyor or a damp proofing company. Usually we would recommend a damp surveyor, as they tend to be independent and are not there to sell you solutions.

Even if you do end up hiring a surveyor to locate your problem, it would still make sense to try and locate the issue yourself first. After all, if you manage to find and fix it, you will save yourself the damp survey fee.

Common defects and what to look for

The first thing to do, is look at the areas where the wet spots are appearing inside. It is very likely that the moisture is penetrating from a similar location outside.

The water will either be penetrating through at the same point. Or it is possible, that the defect is a little further up the wall. In this case the water could be running down the inside of your cavity and bridging across lower down.

Bellow are some common defects to look for on external walls:

Another common cause of leaks is roof defects. If the problem is coming from your main roof, it should be more obvious. This is because the damp will usually be visible in the ceilings and walls of upstairs rooms.

However, you should also consider lower level roofs above bay windows, porches, and conservatories. Here, you should check for the following signs:

  • Slipped or broken tiles
  • Damaged pointing on ridge tiles
  • Problems with flashing

Finally, you should also look at the sealant around windows and doors. Look for obvious defects and signs of wear and tear.

Once you have identified an issue that is causing your problem, you now need to decide how you will fix it.

Will you DIY? Or will you hire a professional? This is completely dependant on your own level of confidence and experience.

There are quite a few jobs on this list that can easily be carried out by the homeowner. Such as, repointing, applying new masonry paint, or even replacing an old damaged brick.

On the other hand, bigger jobs like repairs to render and pebble dash and major roof repairs, will probably need the help of a professional.

What if you cannot find the defect?

In a lot of cases, finding the issue causing damp can be easy. As we have already mentioned, if any of the above defects are present, it may be obvious what is causing the problem.

However, this is not always the case. There are some instances, where the issues causing damp are not as clear cut.

If this is the case, then you should consider hiring a damp surveyor. This service will usually have a small fee attached to it. But in the long run, it will save you significant time and money.

If penetrating damp is left untreated it can cause more serious problems in the long run. This can include internal decorative issues. But it may also include more serious long term issues to structural elements of your property.

Damp also leads to mould, and once certain types of mould start to grow, they can spread quite quickly. This can have harmful effects on health due to breathing in mould spores.

For these reasons it is better to identify the problem sooner rather than later. Once you know what the issue is, you can take the appropriate action to repair the defect and stop the wet spots appearing on your internal walls.

To find a good surveyor we recommend using a comparison service. There are a few of these online and one we particularly like is called Bark.

The service compares quotes from local damp surveyors. This means you can get multiple quotes and save on the price.

What makes this even better, is the companies know they are competing for the quote, so they do tend to compete on price. This can mean significant savings on the price of surveys.

Finally, they all have company profiles. This means you can read about the company, as well as see all their past reviews.

The quotes are no obligation, so you are not forced to accept them, which makes this a great way to get a really good price on this type of job.

To get up to 5 local damp survey quotes click here


As you can see, wet looking spots on walls are usually a sign of penetrating damp. The good news is penetrating damp is often quite easy to identify.

Also, it is usually quite straight forward to fix. Many defects are jobs that can be done by the homeowner DIY, or even by a local handyman.

There are a few jobs that will need the help of a professional. But even if this is the case, it is worth paying for the professional help, as fixing it early will be far cheaper than leaving the problem to get worse.