Drainage Problem

[gchope2k6]

Hi all,

I have a drainage issue with my townhouse and I am in a dire need of a solution. There is an area in between my home and the next home that is pretty flat, about 30 feet long and 11 feet wide in between the houses. During the rains, most of the water pools next to my wall, so there is a slight slope towards my house. I attached pictures of the area from multiple angles.

The house does not have a basement and is slab-on-grade. The wall in question is the wall of the garage, and I can see efflorescence on the cinder block next to the wall on the inside. Somebody suggested a french drain dug 12 inches wide and 12 inches deep and only 12 inches from the foundation of the home, which would also be re-graded towards the french drain.

My concern is that 12 inches is too close from the house and that there is not enough slope in the area (which is pretty flat) to drain it to daylight. Do you think it is too close? What would the minimum slope be over 30 feet of french drain to make it work?

Any suggestions or alternative solutions will be greatly appreciated.

Thank you!

 

[cvg]

suggest you keep the drainage on the surface. maybe a curb and gutter along the edge of your wall would work better. A french drain wont work very well if you cant daylight it

 

[oldestguy]

This may best have some regrading done by an experienced landscaper. At the walls one might consider applying a waterproofing coating to the masonry there and the slab. There are paints that claim this feature.

I have discussed a treatment of soil areas to waterproof them ,but it may not fix the problem of water entering the walls from outside.

Do a search on this room forum for the key word "bentonite" and my handle as the writer. You will see several of my comments on this method.

 

[beej67]

If you want to properly fix the problem, then grade a slope away from your house at an inch per foot, for about ten feet, and then daylight that somewhere further downhill. Hard to know how to daylight it without more information.

Making sure your and your neighbor's gutters are both piped to the curb would help as well.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[gchope2k6]

Thank you guys for your answers. The problem is that there are only 10 feet between my house and the neighbor's house...

Some grading will definitely be done, but I am struggling with the decision if to put in the french drain or not, as most of the contractors are recommending it. It seems that it might be able to drain to the front of the house, but will be pretty shallow at only 12 inches deep. How close from the wall can it be installed? Is 12 inches too close if I decide to go with it? There is no basement, house is slab on grade.

 

[beej67]

Regrade it so there's a 10 inch deep swale centered five feet from each wall, that slopes up in a regular fashion to both walls, and then find some way to daylight the swale.

Also as mentioned prior, get the roof gutters into the road gutter directly.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[Twinkie]

Is the majority of this roof runoff?

If so, maybe try daylighting the roof leaders with some ADS flex pipe and see what that gets you before you pay for earthwork.

 

[beej67]

Also, don't go digging anywhere until you figure out what's underground. Particularly around the ominous green box.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[SuperSandman]

Do you need the grass? If you do not need the grass and the water is due to stormwater, pave the area and grade it towards that big garage door in the photo.

 

[brandonbw]

Can you take a picture straight up showing the above roofline?

Why is the french drain the contractors go to fix for all drainage problems??

B+W Engineering and Design | Los Angeles Civil Engineer and Structural Engineer

http://civilengineer.la

 

[cvg]

french drains are generally recommended for removing groundwater from saturated soil. where the water source is from rain or storm runoff, french drains are not effective. a french drain located just 12 inches from the house without a good outfall may actually increase the amount of subsurface moisture which would not be beneficial. providing better surface drainage is the best method for handling storm runoff and limiting the amount of infiltration. this can be done by many methods already suggested such as grading away from the house, concrete paving to limit water infiltration into the ground, placing some other type of impermeable material such as clay, extending roof drains so they do not discharge at the foundation. designing a functional underground piped storm drain is difficult if you do not have a good drainage outfall location or sufficient area for grading.

 

[civilman72]

Sue the developer.