moisture in garage flooring when it rains


Old 09-09-16, 07:53 PM
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moisture in garage flooring when it rains

i have noticed wet spots in my garage floor which is concrete
specially when it rains heavy ( not always though )

can you suggest - what is the cause ? and how to cure it ??

remarks: noticed no leakage
i have brand new roof and is partially finished
one wall is fully insulated and drywall ( which is adjoining the house )
and ceiling has drywall too
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Old 09-09-16, 10:05 PM
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Where are the wet spots appearing.... in the middle.... around the outside ?
It's important that all the landscaping outside the house be sloped away from the house.
All leaders must be routed away from the building.

In times of high humidity.... moisture can condense on the cold concrete floor.
Old 09-10-16, 04:11 AM
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You also want to make sure the gutters are piped away from the house. My first thought was moisture migrating up thru the slab from below.
Old 09-10-16, 04:27 AM
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My equipment garage is in the basement so while it is not cool it is cooler than outside during the summer. If it's humid, like a rainy day, and I open the door wet spots of condensation soon appear. If I keep the door closed... no wet spots. The garage for our daily drive cars is totally above ground and gets hot and there is no problem in summer with condensation. Unfortunately both garages will get condensation in spring and fall whenever the garage and it's concrete floor is substantially cooler than outside when it's humid.

You could have water wicking up through the concrete. An easy test is when the floor is dry get a square of clear plastic sheeting. A plastic bag or rolled plastic sheet will work. Completely tape the edges down to the floor. Then keep an eye on the plastic for condensation to form underneath the plastic.

Then there is the obvious where water can be leaking in or brought in by your cars. Try to be in the garage during a heavy rain or immediately after and look for leaks. Water may be coming in under the walls or under the doors.
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