Could the wet patches on our garage wall during sunny days be caused by a lack of insulation and condensation?
Asked by Freddie Alvarez 
6 months ago
Last Updated: June 20, 2024
Have you noticed those wet patches on the inside of our garage wall on sunny, warm days? Could it be because of poor insulation and condensation?
Is your home built on a concrete slab? If it is, it may be absorbing moisture from the slab.
It does have a concrete floor and it is connected to our home. But I’m not sure what ‘with your home on a slab’ means 🤔
‘on a slab’ means that it was built directly on a big flat piece of concrete. A home on a slab doesn’t have a crawl space under the first floor. My house is also on a slab. Knowing whether yours is or not can help me give you better advice. It seems like the moisture from your concrete floor is evaporating and causing condensation. How big of a problem this is depends on different factors like your location, flood zone status, yard drainage during rain, and the possibility of a leak under your slab. You can check for a leak by making sure no water is being used and then checking your meter. If the wheel is moving, you have a leak. Sorry for all the questions, but it’s hard to help without more information.
Ot it, thanks for the info. So the main part of the house has a crawl space. Before we moved in, the garage was connected to the house with a corridor shed and a galley kitchen. The garage, kitchen, and corridor shed are all on a slab. The wet spots on the wall are only on the top third of the north-facing wall. I live in Wales, UK, so it’s often rainy and damp here. I’m not in a flood zone and there are no drainage issues in the yard. I’m pretty sure there are no leaks under the garage concrete because there are no pipes or drains there.
Chances are you’re okay. It seems like the concrete is porous and retaining a bit of moisture. Using a fan might help. I recommend getting a hygrometer or another type of moisture meter because mold can start growing indoors if the humidity goes above 60%. You could also consider getting a dehumidifier or using some DampRid.
Thank you, I really value your advice.
If this happens when it’s not raining, it’s probably just a cool spot in your garage where excess moisture is condensing. In most cases, it’s not a big deal and will dry out once the sun comes out and it gets warmer. I had a similar issue with a shaded area in my garage that would stay damp while the rest of the wall dried out. When the tree branch providing the shade fell during a storm, the spot stopped forming. It sounds like you might have a similar situation.
It doesn’t happen after rain.
It’s only the front wall, facing north and mostly in the shade, except at the very end of the day.
I think it’s just condensation due to the wall being cooler, it shouldn’t be an issue as long as it can dry out. Which seems to be the case.
Alright, thanks. But if I want to eventually turn this into part of my house, like a room instead of a garage, how can I prevent this from happening?
Is this garage not insulated? If you decide to convert the garage into living space, make sure to insulate the walls, add vapor barriers, and condition the area just like the rest of your house. This will prevent condensation since that wall will no longer be a cold spot.
Thanks a lot, really appreciate it.
Completely lacking insulation.
Hey there! It’s great that you’re keeping an eye on things. This seems like just normal condensation, so no major worries. If it doesn’t dry up or start puddling, then we might have a bigger issue with water leakage. But for now, it sounds like everything will clear up as the temperatures warm up. This kind of thing is pretty common in snow belt regions, especially in early spring.