Another slab/moisture dilemma

[wfopete]

I have a 10 year old 30x50 pole barn. The 6” slab floor was poured after the barn was built, so I guess it’s more of a floor than a slab since it doesn’t support the structure. My problem is I get occasional damp areas on the floor. The barn currently has no gutter system so rain water dumps out right next to the edge of the building.

I thought a solution would be to trench down a couple of feet around the perimeter of the slab and line it with black plastic to help ward off ground moisture. Then I wanted to pour a 10-foot apron around the building and finally add a 10-foot awning with gutters dumping into a French drain and away from the structure to keep water away from the slab. Would this likely solve my dampness condition?

Or is there a better solution?

 

[checkthisout]

I have a 10 year old 30x50 pole barn. The 6” slab floor was poured after the barn was built, so I guess it’s more of a floor than a slab since it doesn’t support the structure. My problem is I get occasional damp areas on the floor. The barn currently has no gutter system so rain water dumps out right next to the edge of the building.

I thought a solution would be to trench down a couple of feet around the perimeter of the slab and line it with black plastic to help ward off ground moisture. Then I wanted to pour a 10-foot apron around the building and finally add a 10-foot awning with gutters dumping into a French drain and away from the structure to keep water away from the slab. Would this likely solve my dampness condition?

Or is there a better solution?

Is the dampness from condensation forming on the surface or from water whicking up through the slab?

 

[wfopete]

That's the only explaination I can think of. Is there another reason besides a roof leak?

 

[Brad Beam]

My old garage did this after a period of cold days followed by warm high humidity days. Fixed it by keeping the garage a constant temp. Don't know if that is an option for you.

 

[checkthisout]

That's the only explaination I can think of. Is there another reason besides a roof leak?

Well ok, paint some sealer onto floor onto one of the spots that constantly gets wet.

If it gets wet on top of the sealer the problem is condensation. Whicking can be solved by merely throwing down and maintaining a nice coat of sealer.

Condensation will subside if you heat the space or if you place a vapor barrier to block to airflow into the building and such. You didn't say whether the space was insulated so we don't have enough information to offer fully-informed suggestions.

 

[Kevin54]

Moisture in or on the concrete can only be from a couple of things, minus the obvious as in a roof leak. Either it comes up from the bottom, or like checkthisout stated, from humidity. My son's garage floor will sweat like crazy on humid days and sometimes so bad if the humidity is real high like on warm foggy days, that he would have to squeegee the floor.
To wfopete, the first thing I would do is get the water away from the foundation perimeter. Will this cure it? No one can say for sure. Will it hurt? Absolutely not!!! You always want to move water away from any structure. Is your building on level ground or is it elevated with the perimeter ground sloping away? If you have any ground running towards your building, then you may want to excavate some. This would be cheaper than adding overhangs and a 10' slab around.
Can you post some pics up as to the lay of the land and the building?

 

[wfopete]

Ok here she is. Note the 12ft sliding door. It drops about 4-6 inches between the driveway apron and the slab of the pole barn. This creates a drain path for water to flow to the left side and down away from the barn. The soil is a clay & shale mix and does not absorb water easily, thus I will get standing water after a rain for days and the ground can remain soggy for weeks. This water has never been high enough to flood the slab & pretty much drains away from the building.

A 10ft concrete surrounding apron and overhangs with gutters will happen regardless of the drainage solution. Gives me a place to put stuff out of the rain/sun quickly.

 

[mustangmccance]

it looks like you have skylights in your building. is the rest of the garage insulated? if it is it is probably like my shop the cold air condenses on the skylights and it rains inside whenever I heat the shop.

 

[wfopete]

The ceiling can and does sweat under the right conditions, but I have had moisture on the floor regardless of the ceiling sweating. The building is not insulated but will be when upgrades are complete.

So what I am gathering here is that, if the damp spots are weather dependant it is likley not to be caused from water under the slab and likey to be caused from the temp/humidity of the surrounding air.

 

[glennm]

I have skylights like the building above and they will drip on occasion as well! Look at that first, they do tend to break down from UV and can leak from rain, snow and even condensation in the morning.

 

[AlphaGarage]

Haven't read the thread in detail, so please excuse if this is redundant. Has it been established 100% whether this is a result of hydrostatic pressure or not? If not, put down a piece of 3' x 3' clean plastic, tape the edges, come back in 30 - 40 hours and see if there's any moisture under the plastic. Or you can run a calcium chloride test, I'd post details, but need to head out now.

 

[krooser]

Controlling the moisture may include gutters, downspouts and grading around the building. Adding gravel around the building may help water to run drain away from the concrete.

 

[red]

You could also put in what is referred to as a "French drain" around the perimeter, but the question still remains about hydrostatic pressure. Do you have a high water table? Has a perc test for a septic ever been done? When building my house on one corner of the property I had a stream running about 4 feet underground, was totally amazed when we found it and really glad it wasn't anywhere near the house. Once you start to dig you will find out quickly if it's a high water table. The french drain will look like a moat!

 

[wfopete]

I'm planning to incorporate a French Drain (see my first post). I have a creek about 50 meters from the barn that runs away from the direction of the barn. The creek only runs during wet weather periods. When the barn was built I had 50% of the floor area filled with dirt, that was alot of dirt! So if there was a underground stream in the areas I would have seen it during excavating. At 4-6 feet from the rear of the barn the grade falls off about four feet.