HELP -need foundation drainage

[Gordon Gould]

My son wants to put in about 100 feet of drainage at the base of his concrete foundation on a 50 year old house. The footings are down 7 or 8 feet.
He thinks that if we rent a back hoe or small excavator we will be all set.
I told him I thought it would be very difficult trying to dig a ditch
along the foundation. We would end up with a huge hole and mountains of dirt and still not be at the footings.
BUT, I dont know a thing about ditch digging. My machinery experiance is pretty much limited to logging and road maintainance.
Are there techniques and equipment that allow one to do this or
should I try to convince him not to even try at the expence of being just a
pessimistic old man.

 

[Opti-Mist]

An experienced operator could dig a narrow, but wide enough, trench around the house with a standard backhoe of adequate reach. I would not consider this something for an inexperienced operator as it is far too easy to smash the house, causing more repair expense. Of course the usual precautions regarding water, gas and electric lines.

 

[KubotaSam]

My neighbor did exactly this a few years back. He borrowed a full size backhoe from his dad and dug around the perimeter of his house. He put the black drainage pipe is crushed stone, then backfilled. His water problem was gone. Go for it just go slow and careful.

 

[Dmace]

If you do rent, get a mini-excavator instead of a backhoe. With the backhoe you will be constantly moving and setting up plus the outriggers stick out so much it is very difficult to get close to the foundation. With a mini-excavator you can move as you go very easily without setting any outriggers, two pivot points to swing as opposed to one on a backhoe so you can get closer, and they typically have a much better reach and are more powerful per pound then a backhoe.

Keep the rpms low so the controls aren't too touchy and make sure you leave yourself plenty of time. My local Taylor Rental has a Yanmar Vio-27 with a trailer for a 3-day weekend (24 engine hours) for $300.

I used it to pull some stumps my tractor couldn't. It is so much faster and stonger, you can tell it was made for digging.


Click thumbnail for larger image

 

[Botabill]

Get a mini excavator with enough reach to go the depth you need. It'll out dig an excavator hands down. You also need to have someplace to drain the water to or you'll need to have a pump to take the water away from the foundation. Have fun.

 

[laen64]

Bota Bill means the Excavator will out dig the Back-Hoe. I"m with you as well. I learn so much, Thanks to all.

 

[Egon]

My son wants to put in about 100 feet of drainage at the base of his concrete foundation on a 50 year old house. The footings are down 7 or 8 feet.
He thinks that if we rent a back hoe or small excavator we will be all set.
I told him I thought it would be very difficult trying to dig a ditch
along the foundation. We would end up with a huge hole and mountains of dirt and still not be at the footings.

Why does the new drainage have to be at the base of the existing foundation. Could it not be back a few feet, maybe even a little deeper and still do the same/better job.

This may??? allow a bigger faster digging machine access to the area. You would not be in danger of affecting the load bearing area under the foundation. The larger machine has more reach so the spill pile can be farther away. It may also allow a trench to be dug which does not require shoring. Smaller machines may not have the reach for this.

When doing jobs of this sort where collateral damage could be significant it is sometimes best to have proficient personnel at the controls and perhaps even looking after the job.

Questions to ponder:
Have all utilities lines been located?
Will the trench impact neighbouring parties?
How will the new drainage be designed and where will it drain to?
What is the site location like and how much water will be expected to be drained?
How stable and uniform is the soil in the area in question?
How familiar are you with Trench Cave Ins? At eight feet a trench should be shored or dug in such a fashion so that shoring is not required. This may be the important question.

One more question: If the the water is drained and diverted will the foundation footings dry, shrink and cause settling problems?

 

[Gordon Gould]

Thanks for all the advise. We have used a mini excavator before on a wall
project. I had not thought about a way to get the water out of the hole.
Sounds like we should start the ditch where the pipe comes to day light.
Other than the risk of damaging the house or foundation I am starting to
feel better about doing it.

 

[Gordon Gould]

I just saw your reply, egon, after I posted my last one. All very good questions that only experience and knowledge can answer - which we dont have.
His problem arises from the fact that he lives on a terraced steep side hill.
I was wondering if a curtin drain away from the house would work.

 

[Botabill]

A word of caution on trenches. Don't go into one if it is over 4 feet deep. I've seen what looked like a solid trench just collapse for no reason. If a person was in the trench at the time it would have been fatal.

 

[Egon]

Gordon; My questions are very generic. Your situation should be evaluated on what you have in your location.

With a terraced hillside and obvious water problems make sure the trench will conform to the local codes of your area.

As stated starting from the daylight side is definitely advisable. You may also wish to consider a method where by very little open trench is left at the end of each day. That reduces the chances of sluffs and open trench that should be barricaded for legal reasons. Or the amount of shoring required. It also means you have to have all your elevations correct and you will have to able to set grades. [Since the advent of lasers this might be much easier than in past years of batter boards] The excavator must be able to dig to grade or you have to backfill with granular material to grade. You must also consider the type and depth of the granular material you will backfill with. Also consider what equipment will be used for backfill of granular material. Depending on trenching and spill piles it may also require reach.

Again this is all generic and your situation may be quite different.

With trenches always consider cave In's and legal liabilities.

 

[bearmtnmartin]

I do this job quite a bit. You need to figure out where the water is going to go for sure, and the best thing is to pipe it to a lower elevation somewhere. Rockpits have a nasty habit of being overwhelmed by heavy rain or high groundwater. An 8 foot cut is huge. You will have massive piles of spoil. If its 8 feet down(and you do need to go a little lower than where your lowest living space is) then you need a 1:1 slope, so you are 8 feet out at the top. Well, thats a spoil pile 8 feet high all the way around your house. Consider the ramifications of that before you start. A backhoe is the way to go if you have the room because you have way more reach and you can deal with the spoil easier. With a mini you might spend a lot of time working on your pile. When you have excavated the whole thing, (about 6 hours if you know what you are doing) you pressure wash the foundation and footing. Then seal up any cracks. I use roof tar. then foundation coat the whole thing and run your pipe. Perimeter goes along the footing and the rainwater goes on top. That way they are on something solid and they can't collapse or settle. Then a foot minimum of drainrock with filter cloth on top and you're done. I can do a small house with a labourer in a day. A big deep one is 2 days. If you screw around doing a wall at a time it will take forever.

 

[pat32rf]

You didn't mention what kind of soil you have. If it is heavy dry clay based then you can get away with a steeper sided hole, but remember, "If its deeper than it is wide, then its a trench, not a ditch". You are normally safe working in a ditch, but if its a trench that is deeper than waist height you are asking for trouble working down there without shoring. Its quicker to dig it wider than to cope with a cave-in.
If it is gravel type soil with good drainage, then you might get away with tar type waterproofing, cloth covered "big O" and crushed stone. If the soil is clay type where the water can't flow freely, then put one of the bubble type plastic coatings next to the wall so the water can drain down to the drain pipe.
If you have any stones over 6", make sure that they are well back from the wall when you backfill if you are in a heavy frost area.
And make sure that the squirrels and other critters can't use the discharge end of the drain to hibernate or store their food in. Have fun, I've done it with a mini and with a hoe, they both work if you have the space and the patience. Just do it once, right, the first time. You may also want to add foam insulation to the outside if you want a warmer basement. Its more efficient to insulate the outside than the inside in our climate. (If you insulate the inside, then the ground will freeze harder and is more likely to crack the foundation)

 

[Egon]

You didn't mention what kind of soil you have. If it is heavy dry clay based then you can get away with a steeper sided hole,

In the areas I am familiar with there are pretty clear and concise descriptions of the requirements a trench must conform to. Heavy dry clay will not alter those requirements. It goes "whoomp" when it falls in just like any other soil.

But I do believe Loess may stand on a vertical cut??

 

[pat32rf]

Egon- I'm thinking more of the last two feet of his excavation. Up here you cannot physically dig in the sand leaving a slope of greater(less??) than about 45deg (1:1) but you can "cheat" a bit if the soil has some clay (dirt) in it. As long as its nice and dry with no rain in sight I would dig the top 4-5 feet with 45deg sides, then go steeper for the next coupla feet while still staying wide enough to stand and work on the wall. The last foot of depth, where the tile and crushed stone would be I'd narrow down to about 1.5 feet...This way if something collapses the man in the trench will only find himself pinned by his legs BUT if the soil looks/seems unstable he shouldn't be down there anyway.

 

[Egon]

And if he's on his hands and knees leveling the fill or laying pipe where does the dirt land?

 

[Wis Bang]

Just after college I worked for a construction firm. One laborer had been buried two times and stated that he was too lucky to surrvive another. Your getting too deep not to consider some shoring. I think they rent 'hydraulic' shoring that is jacked in place and easy to move along...

The advise about backfilling as you go is what the 'pros' do...

 

[pat32rf]

He uses a shovel to do the leveling. It will fit into a space a lot narrower than his shoulders will. Like I said though, if there is ANY chance that the ground will shift, he shouldn't be there. This includes moving out of the hole if the machine is going to be moving in the area....

 

[2manyrocks]

I think there is a heavy safety thing called a trench box that can be lowered into the pit.

There is a lot of work involved in this project. If you push the dirt straight back into the trench to fill it, you can also crack your wall. It's not rocket science, but you've got to watch what you're doing every step.

 

[Egon]

He uses a shovel to do the leveling. It will fit into a space a lot narrower than his shoulders will. Like I said though, if there is ANY chance that the ground will shift, he shouldn't be there. This includes moving out of the hole if the machine is going to be moving in the area....

There are always innumerable reasons stated why a trench is safe. After it fails all these reasons don't mean nothing. And if the trench was not dug to meet the local specifications then things start to get real ugly for the fellow responsible.