garage drainage and basement. 2

[blatz]

We have lived in our Minneapolis house for two years, and it was built in 1977. The house is situated somewhat downhill in an area where the soil has a high clay content.

We notice that a section of basement cinderblock wall is frequently damp, and is beginning to degrade. The previous owners tried painting the block, and the block surface crumbled away.

What is particularly odd, and makes this mystery interesting, is the location of the wet spot.

The wet block forms a triangle that is about a foot wide at the top of the wall, and six feet wide at the bottom. Also, the wet spot is located in the middle of the shared wall with the attached garage. I believe this is an unusual place for ground water to pool.

We have noticed that water that gets into the garage, such as from melting snow carried into the garage on our two cars, does not drain out of the garage, but rather pools at about the spot above which is the water damaged basement wall.

There are also two hairline cracks in the slab that match up with larger cracks in the apron.

We are thinking that the pooling water could be primary factor, and we are thinking of pooring a slab on top of the existing slab so that the garage floor would drain properly. There is enough headroom clearance, and we were thinking of a slab that would be about 2" thick near the car doors, and 4 to 5" in the back.
Could pooling water in the garage be a likely cause of this water problem? And if so, does the slab on slab sound like an economical solution?

I am cutting an exploratory hole in the slab to check that there aren't other, less obvious problems. I also suspect that the home builder might have pushed a lot of sand against the garage foundation in that spot, and with the clay soil, water might be collecting there (sand would then be replaced with similar clay soil). Also, it could be possible that water is working beneath the slab through the cracks in the slab and apron (and possibly garage foundation), so we are going to replace the apron, and seal external cracks (epoxy ?) at that time.

Has anyone ran across a similar problem?
What other problems might be the cause?
Would the slab on slab be okay as I described?
I am also open to other solutions.

Your thoughts would be appreciated.

 

[jheidt2543]

I would offer the following suggestions:

1. Before cutting a hole in the slab etc., I would try the simple solution of patching the hairline cracks in the garage floor. The only material you may be able to get into a hairline crack is a two part epoxy. Epoxies can be hard to handle with short set times, but they are liquid enough to flow into the cracks. Mix the epoxy per directions and put it in an old ketchup squeeze bottle, the kind with the small tip, then squirt the epoxy into the cracks.

2. Check the mortar joints on the outside of the foundation/basement walls. I had a similar leak in my basement and it was due to a broken mortar joint next to a downspout. If you find such a problem, chip out all loose mortar, install a foam backer rod (Rod-o-Foam) that is 3/8" - 1/2" in diameter. Push it in far enough to leave an opening about the same depth as the joint is thick. Then caulk the joint with a grey colored latex caulk, like Tremco's NP1 "limestone".

3. Make sure all downspouts discharge well away from the foundation and the water flows away from the house. You should have at least a 2% slope away from the house for 6'-10' feet.

Good luck!

 

[Focht3]

The geometry of the dampness suggests a roof/top of wall leak; the water is spreading as it flows downward. I would expect a source of water at floor level to spread more or less uniformly up the wall.

Having said that, continue with your other avenues of investigation. Solving these kinds of problems can be very frustrating and time-consuming. And try to resolve the cause of those floor cracks -

Good luck!

 

[blatz]

Thank you jheidt2543 and Focht3.

Jheidt2543, I was already in process of cut a 2'x5' whole in the garage floor. So, now I can tell you what I found. This part of the foundation was backfilled with a whole lot of sand. The sand was damp, but not saturated. The foundation wall looks much better on this side than on inside of basement. Cost $180.

Focht3's observation suggests to me that water might be working its way inside the wall down from where the garage roof meets the house's exterior wall - potentially inadequate flashing issue. There is unfinished drywall on garage side, so for cost of two sheets of gypsum, I could look inside this wall - another inexpensive check.

I have found a low viscosity two part epoxy with 15 minute work-life I could use on the two hairline floor cracks.

Another interesting observation:
It appears that there is a chalky material about 1/2" thick between the garage foundation wall and the garage floor slab. Could this be sheetrock? and If so, why is it there?