Wet spot (on garage floor)

[dmunson]

In my garage, at the front of the second bay after it rains I always see a small puddle under where my car rests. It's usually about this size. It dries in time but I have concerns. What can I do preemptively to stop water from bubbling up here? What i slikely causing it and how do I stop it.

The rest of the garage and house remains dry. The outside is to the left side of this picture.

Thanks

 

[bdbecker]

First of all, welcome to Garage Journal!

How well does your overhead door seal against the floor?

EDIT - I see you've been a member since 2023, I just saw that this was your first post when I said "Welcome".

 

[dmunson]

Hi. Thank you.
The overhead door seals beautifully. I replaced the doors within the year. The drive slopes away and the garage concrete is a small amount higher. the It's not ingress rain or flood but something that bubbles up. In the 5 years I have been there it has always had this wet spot. The first couple years I was thinking my Subaru had a problem but it's something else.
The wet spot never gets to the front edge where the house foundation should be under the garage door but this spot. And, just that spot. This kind of gives me hope it can be fixed without major work. But, I would like to get it done. And, I would like to understand what the mitigation is. Drill and knock out a small space to see what is under this and fill with something appropriate? Call a concrete guy. What is a concrete guy?

 

[dscheidt]

You have ground water coming through, probably via a defect in (or missing section of) the vapor barrier plastic under the concrete. The fix for that is cut out the concrete, repair the vapor barrier, and repour. I'd start by improving the drainage around the garage. Where do the gutter downspouts empty? get them as far away, and downhill, as possible. After that, you'd be looking at some sort of ground drain, details depend on your particular situation. Simplest case would be a swale or something to direct surface drainage around the building, more complex would be a set of drain tiles feeding a sump that's pumped away.

 

[rust in the eye]

I'd bet heavily this is coming from under the door, perhaps wind driven.

 

[moab11]

If you don't park in there for a few days, does the puddle continue or disappear? My car will often leave a puddle of water in my garage, condensate from the A/C

 

[bluedog225]

Yeah. Seems unlikely from the slab. I went out to the parking lot the other day and thought I had a leak. Mine was the only car with a puddle under it. Hot Texas day. Pretty sure some AC component had iced up and melted.

Could drill a 1/8” hole in slab just outside puddle zone and see if it fills with water from below.

 

[BillK]

In my garage, at the front of the second bay after it rains I always see a small puddle under where my car rests. It's usually about this size. It dries in time but I have concerns. What can I do preemptively to stop water from bubbling up here? What i slikely causing it and how do I stop it.

The rest of the garage and house remains dry. The outside is to the left side of this picture.

Thanks

Post some pictures of the outside of the garage. Do you have gutters ? Does the ground slope away from the garage all the way around ?

 

[BillK]

You have ground water coming through, probably via a defect in (or missing section of) the vapor barrier plastic under the concrete.

I always laugh when I read this. I bet there are hundreds of thousands of houses that were built without any type of vapor barrier and don't have issues. My house was built in 1978 and it certainly does not have a vapor barrier just like the other 1200 houses in my neighborhood. My detached garage also does not have it. Neither have a water problem.

I am not sure when or if they became a code requirement. And I really do not think that a vapor barrier is intended to keep large amounts of water out anyway.

 

[N_Jay]

Could never condensation, not groundwater.

 

[65ranchero]

Maybe pictures of the garage from different sides with gutter/down pipes locations

 

[dscheidt]

I always laugh when I read this. I bet there are hundreds of thousands of houses that were built without any type of vapor barrier and don't have issues. My house was built in 1978 and it certainly does not have a vapor barrier just like the other 1200 houses in my neighborhood. My detached garage also does not have it. Neither have a water problem.

I am not sure when or if they became a code requirement. And I really do not think that a vapor barrier is intended to keep large amounts of water out anyway.

Laugh all you want, but the plastic works. Most slabs don’t have problems because there is no bulk water in contact with them.


The entrance to my walk in basement is below my back porch, and is enclosed, though it is outside the building envelope. When we bought the house, it would flood. We had the stairs replaced with some drainage improvements, and did the slab there at the same time. yhis worked great for a couple years, and then the drain clogged. The crew who did the work were idiots and connected to an existing trap that could not be cleaned. We had to cut the slab and dig it up. As soon as the saw cut the plastic under the slab, water came through the cut. Water level was about three inches above the top of the slab, we had to pump it out to fix the drain, and then wait until the water level dropped. (We’re on clay and when it gets saturated, it takes forever to drain.) There’s a gap or something where the new plastic is taped to the old, and water will come up at the joint. If it weren’t under the porch, with a floor drain right there, I would probably fix it.

 

[Rc_Guy]

Could never condensation, not groundwater.

Huh?

 

[Chuckster in NJ]

Here is what you do: Place a piece of wood or cardboard sitting on wood or bricks under the car because this will eliminate any condensate confusion.…… If the cardboard is wet then it’s from the car.

BTW! Post up a picture of the wet area once you dry it off "IF" the slab isolation trick doesn’t work. There could be a crack or small hole in the concrete that is "venting" hydrostatic pressure.

 

[mikedodge]

Are you sure it's not coming from the car like condensation from AC or leak? Usually when it's from below the slab the slab discolors from having moisture in it and doesn't puddle like that. Does it show up if you don't park inside?

 

[dmunson]

Hi All.
It's a mid 60's house without vapor barrier. A poured concrete foundation not cinder block. I testify water does not come into the garage from outside through walls or front door or drip from car. The downspout on that side of the house is in great shape not dumping water down the foundation. It's diverted away. And, the wet spot happens when I park there or do not. It's done this the entire 5-6 years I've lived here every season and seems to just need rain or snow melt.
The ground slopes away from the house poorly. It will puddle but not be enough to flood the garage or house. From nearby down spout it transitions to a ~10ft gutter to the ground and then drain tile which then moves water to a cistern further away. I'm happy with water control. There is no water from anything nearby like condensate or leakage.
The watermarks on concrete have "sparkles". Efflorescence? Some sort of mineral salts left from water that seeps through then evaporating. It's slight and just where the water bubbles up.
More pictures? I tried to take a picture now but it's hard to catch the outline of the spot. It's not spalling or chipping but there is water marks.

 

[BillK]

The ground slopes away from the house poorly. It will puddle but not be enough to flood the garage or house.

But it is almost certainly finding its way under the slab. Fix the drainage so it no longer puddles and I bet your wet spot will be gone.

 

[kaehlin]

I'm betting on poor drainage or a leaking stormwater drain of some sort. Cutting out that section of slab will reveal the source, but may be messy and will likely reveal additional work to be done.

 

[jblnut]

It will puddle but not be enough to flood the garage or house.

If a puddle forms it is because the water cannot get away fast enough for some reason. Yours could be that the ground is very saturated and it cannot escape. Or. My guess is the puddle in the yard is sitting on a hard underground layer like clay or something quite compacted and the water is simply moving horizontally through the soil and finding the path of least resistance to be towards your garage. Water doesn’t flow up hill but it will wick uphill.

I’d agree with fix the puddle issues and see what happens.

A good floor sealer may prevent the water from coming in. It may cause other issues though. I have close to 2 acres of concrete here and none of it has a sealer of any kind nor does any of it wick water like that.

 

[Chuckster in NJ]

Hydrostatic pressure is excessive and must be relieved so I suggest installing a drainage system around the perimeter of the garage to relieve the pressure. Hydrostatic pressure can buckle foundations and wreak havoc on slabs.

 

[dmunson]

I'm betting on poor drainage or a leaking stormwater drain of some sort. Cutting out that section of slab will reveal the source, but may be messy and will likely reveal additional work to be done.

Yea. But it is a step to a resolution. The alternative in doing nothing in the face of a problem is unacceptable but I do not know if the problem is not really a problem. Today, I assume this gets worse in time and will not go away. On the other hand, I believe it has always (at least 10 years likely longer) done this.