Water Drainage Problems

[DYIM]

I would appreciate a little help.

I recently bought a 25 year old house that has a hill sloping 10 feet from the back side of the house. There is a parallel stone wall 10 feet from the back side of the house, 4 feet high, holding the sloping hill from the house.

Recently we had some heavy rains that ran water from the bottom of the stone wall to the house and down the foundation into a crack in the foundation into my basement.

I have dug a trench 1 foot from the stone wall, sloping parallel to the house and that seems to have temporarily solved the problem. My question is how to fix this problem permanently. I bought 100 ft of half perforated corregated pipe along with the fabric sleave to keep sediment out. The soil is clay so I was going to lay the pipe unperforated face down. Does the perforated side need to be down? Why? Since the pipe will be covered with the cloth sock, I was going to lay a little gravel on top and then cover with dirt. Any suggestions would be helpful.

Thanks,
Daniel

 

[Focht3]

Er, stop trenching!


It sounds like you are trenching parallel to the wall. If so, you are reducing the stability of the slope behind your house. This can have disastrous effects should inclement weather persist. The presence of the trench may also allow water to soften the toe of the slope - also very bad.

Check out this thread -
thread274-39678

Put the holes down - one row at the very bottom, or nearly so. And backfill the trench with sand, not gravel or crushed rock.

And do it quickly!

 

[DYIM]

Focht3,

Thanks for the advice. Please note that the trench is only 18 inches deep and is at the base of the wall, about 1 foot away. Your tread was an excellent source of advice. If you still don't recommend the drainage ditch what would you recommend.

Thanks again..

 

[Focht3]

Eighteen inches isn't too bad. How tall is the hill behind your home? How steep?

Since you're really intercepting surface water, it's preferable to construct a curb of some sort to redirect the water away from your home. If that's feasible from a site topography standpoint, of course.

Just be careful about trenching along the wall. You don't want to do anything that might cause the hill behind your home to end up in your den!

 

[Grouser]

The trench volume and pipe size should be based on the volume of water to be collected. What area of slope and rainfall intensity are being used? If the purpose of the trench/pipe combo is to intercept surface runoff, why does the trench need to be 18" deep. An earthen (clay) 'curb' between the trench and the house will help conduct water into the trench and will increase the factor of safety against retaining wall failure.

Re the slot locations: the slots should be down in this application to prevent buildup of water in trench and to assist in conveying it away. If in trench(soakage pit) slots should be up to force water level as high as possible (head increase) to assist in exfiltration.