French Drain

Bill

Here is my problem. I have seen many people install a drain using gravel and rock around a house but never really paid too much attention as to how its done. I just want to make sure that the mason that is subing from me is doing it correctly.

Basment walls are 8' tall and are 8" block and sit on a concrete slab.
The walls due to the ground compressing has caused the walls to buckle inward about 4' up. The mason stated he would remove the old 8" block and replace with 12" block. He has also contracted from me to waterproof the walls and run a drain around the walls which will empty into a 36" diameter by 8' deep well casing which will pump the water out and away. When he backfills how should the finished job look? Should the drain tile be at the footing or part way up the wall?

I am just concerned that how he installs the drain system that there will be no compression pushing against the walls again. My thought was to after waterproofing was to backfill with dirt 4' up and then install drain then slope dirt at a 45 degree angle away from the house and fill with gravel.

How would you do the drain and the backfill to prevent any future compression that would cause the walls to buckle?

__________________
Is it beer thirty yet
Virginia Department of Licensing
Virginia Plumbing Codes

WarnerConstInc.

Exterior drain tied into a sump pit inside house? Is that what you mean, or does it dump into a pit out side of basement then get pumped away? Either or you want to back fill with gravel up to a certain point and then sand and then top soil and I would kant it away from the house. I think that the tile should ble placed at the bottom of the footer so as to get all of the water drainage.

Just my 2cents. That is how new basements work. And how I have seen numerous other houses that have been jacked up and foundations replaced.

Jayrek

What kind of soil? In VA dont you have a lot of clay?

What slope, if any are you dealing with? Is it level, on a hill?

Do you get water in the basement?

Is it possible to get a little more info about your site?

Is he waterproofing on the inside or outside? Dont bother on the inside just becomes messy when the waterproofing peels.

Bill

Lots of red clay here.There is no grade away from the house so to speak. The drain will go into a pit outside the house to be pumped out away from the house. And yes, I will shy away from waterproofing the inside as this will only lock the water into the block walls. Also it is so DIY too!

__________________
Is it beer thirty yet
Virginia Department of Licensing
Virginia Plumbing Codes

neolitic

Tile goes below slab level, bedded
in stone.
Fill with stone or pea gravel at least
half way up the wall.

__________________
Put your location in your profile!
(Sorry....it seems there really are dumb questions)

Bill

OK, so fill the rest in with soil correct?

__________________
Is it beer thirty yet
Virginia Department of Licensing
Virginia Plumbing Codes

Jayrek

yeah, lots of stone and trap rock, but if you have clay a "french drain" will do you no good. All it is is a trench filled with trap rock to fill with water to leach off slowly.What your mason is describing is some kind of footing drain. If you have clay it will have to be moved mechanically, via pipes or pumps. Whatever he does make sure he does something to help prevent soil from getting into your trap rock, or you will be re-visiting in a few years. If you can keep the water away from the foundation altogether (couple feet or more) it will never get a chance to cause you a problem.If you are from rural VA some farmers have unique and interestingly easy ways of dealing with clay and water.

neolitic

I generally do as long as the operator isn't
a real cowboy.
The more stone, the less pressure on the
wall though, and the quicker the fill will
settle if it's lots of clods.
Depends on what you're worried about.

__________________
Put your location in your profile!
(Sorry....it seems there really are dumb questions)

ajbackhoe

Brace your walls when backfilling. The wrong kind of soil on backfill gives incredible pressure. Footing drains go at the base of the footing to deal with ground water. Down spout drains should not be tied into the footing drain and if to shallow can freeze when you need them most.

When backfilling make sure the foundation/block has cured properly.
If you don't have good soil buy some. Use the good soil/gravel within 4-6 feet of the foundation.

Oh and did i mention....BRACE the walls with spring braces untill your box is built. Cheap insurance....

__________________
A O Construction Inc.
Attleboro, MA 02703
Email: alan@aoconstruction.net
www.aoconstruction.net

genecarp

this is probably the reason the original 8" wall failed, improperly backfilled, or improperly built. walls dont just fail because of soil conditions, typically.

__________________

neolitic

Yes, braces!
We put up a vertical 2X flat to the wall,
kick that with one flat on the slab to
hold the bottom of the first one.
Then run a diagonal spring off the
horizontal one that braces the vertical
about 2/3 of the way up.

__________________
Put your location in your profile!
(Sorry....it seems there really are dumb questions)

Double-A

Understand that no matter what you do, bad soil is the enemy of drainage and clay is the worst. Water can only pass through it under certain conditions and those conditions are usually dry conditions or natural fracture or condition changes.

Your footing drain pipe should be on stone. I like to line the entire hole with fabric if possible and based on soil conditions. Proper grading, even just slightly can make a world of difference if your problem is just surface water making its way down.

I'm not a real excavation or foundation person like Nick and the others, they can advise you better, but I would not consider filling with soil at all. I'd prefer to stone up to or above finished grade if you're having water problems... The inward pressure can be from a number of things, not the least is expansive clay. Get your soil tested while the hole is exposed so you know.

If its expansive, you need to cut back from the foundation much further than just a trench large enough to allow the job to be done. If the soil is not highly expansive, the stone will transfer the force to the entire foundation wall, left, right, up and down, much more evenly than just soil will. Going to 12" block will help as well with stability. The only times I've run into block foundation failures has everything to do with improper drainage, undersized footings or improper back fill.

Sorry I couldn't be more help.

We have some folks with good experience on this subject and I'm sure they will weigh in soon.

__________________
"My clients’ wishes are the center of my attention." -- David Guido, a contractor in Woodstock, N.Y.
New York Times, July 20, 2006

genecarp

,
also allow enough time for walls to cure, prior to backfill, DONT RUSH THE BACKFILL!!!!!!!

__________________