HELP -need foundation drainage

[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.