# raising grade for walk out basement?



## paintr56 (Feb 4, 2005)

I have a five acre lot that is currently flat farm land. I would like to have a walk out basement that walks out to a pond is it feasable to pour the basement walls above grade then dig the pond using the dirt to raise the grade on three sides of the basement?


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## mdshunk (Mar 13, 2005)

Sure, it's done from time to time. You have some special considerations if you're in certan areas of the country with respect to freezing the footer in the walkout portion of the basement wall, but it's easily overcome. Be advised that you'll need a pretty dandy sized pond to get enough fill to slope the grade away from the house nicely without it looking like a big bubble that sprouted in the middle of the lot. A good excavator may be able to perceive some high spots on the lot he can shave off for some more cubic yards of fill material.


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## wasdifferent (Dec 18, 2004)

paintr56,
Oh yeah! A man who understands how important it is to get the grade right. I love it. You're gonna save yourself a lot of heartache. :Thumbs:


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## PipeGuy (Oct 8, 2004)

paintr56 said:


> is it feasable to pour the basement walls above grade then dig the pond using the dirt to raise the grade on three sides of the basement?


I live in a house in which the grade of the front yard is a full story higher than that of the back in order to accomodate a walk-out in the rear. As you move forward with your plans keep in mind that what you are proposing can make for a very awkward grading scheme as you transition from one elevation to the other, particularly if the entire back wall of the basement (or the walk-out side) is above grade. I've had to build some substantial retaining walls in order to terrace portions of the yard that were too steeply slope to otherwise be usable.


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## wasdifferent (Dec 18, 2004)

PipeGuy said:


> ...I've had to build some substantial retaining walls...


Pipe,
Don't you get tired of seeing everybody else's retaining walls flopped over and lying flat on the ground? I think that there is about a 90% failure rate on the retaining walls on residential jobs in my area. Sometimes, a couple of years after the owner selects the low bidder, I like to stop by, just to say "hi" and "Oh well, you could always use it as a sidewalk". :cheesygri


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## mdshunk (Mar 13, 2005)

mikesewell said:


> Pipe,
> Don't you get tired of seeing everybody else's retaining walls flopped over and lying flat on the ground? I think that there is about a 90% failure rate on the retaining walls on residential jobs in my area. Sometimes, a couple of years after the owner selects the low bidder, I like to stop by, just to say "hi" and "Oh well, you could always use it as a sidewalk". :cheesygri


My area has had such trouble with this, that you are required that all retaining walls over 4' be engineered. Of course, that doesn't necessarily mean that it'll be installed according to specs.


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## wasdifferent (Dec 18, 2004)

Some contractors seem to feel that the laws of physics can either be overcome by a spirit of optimism, or just be totally ignored. That's OK, contractors like this still play a valuable role in the industry. We use them for _Contrast._ :cheesygri


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## PipeGuy (Oct 8, 2004)

mikesewell said:


> Don't you get tired of seeing everybody else's retaining walls flopped over and lying flat on the ground?


A wall leaning forward of vertical is like nails on a blackboard - unfortunately my eye seems drawn to this phenomenon.
In the abscence of having worked around retaining wall construction it's hard to appreciate the forces at work on a wall. I think that's why many DIY walls wind up failing. Too little drainage, too little tie-back, too little wall mass and poor backfill will do it every time.

I used interlocking block for about 120 of wall ranging from 2 -6 high in multiple terraces and planters. Having built a number of timber retaining walls between 1980 and 1990, I decided never to use the stuff around MY house.


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## PipeGuy (Oct 8, 2004)

mikesewell said:


> I think that there is about a 90% failure rate on the retaining walls on residential jobs in my area.


Timber walls built buy guys who spend most of their time running zero-turn mowers or leaf blowers are the best. I've seen walls go up that were literally falling over before they were completed. Nothing like pinning some 6x's together and throwing some dirt behind them.

Around here there's been an explosion in the use of engineered block retaining walls. I mean massive structures that are being used to support 30 - 50 structural fills. The newest walls are incorporating a 'geo-grid' tie-back fabric in the backfill.
One wall that I watched go up about 10 years suffered a catastrophic failure last fall. With the area around the wall now fully developed, it's taken them about 3 months to demo the old wall and get it back up to about 40% of its roughly 45' height. Seems like there's a lot more stone backfill being used this time around.


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## wasdifferent (Dec 18, 2004)

PipeGuy said:


> ...The newest walls are incorporating a 'geo-grid' tie-back fabric in the backfill...


Here's some good stuff:
www.geogrid.com/slopes.html


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## paintr56 (Feb 4, 2005)

*How big of pond?*

Looking at about a three quarter acre pond running to about fifteen feet deep. Would this be big enough? I am having a real haard time visualizing how far out from the house I would have to take the dirt for it to look like the house was built on a high spot instead of a big bubble.

Jim Bunton


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## PipeGuy (Oct 8, 2004)

*How big a house?*

What's the proposed footprint of the house?

Depending on it's shape, the excavation for a pond with a 1/4 acre surface area sloped at 3:1 from the pond's edge down to a bottom 15' below grade is going to produce about 2500 cubic yards of dirt. That's about what it'll take just to fill a gently sloped front yard (no more than 5% gradient) for a house 60' across with a first floor that's 10 feet above the existing gound. A gently sloped front yard will be about 200' deep. You'll also need fill dirt to transition from front to back. The amount will depend on how much of the backyard you want 'at grade'


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## paintr56 (Feb 4, 2005)

PipeGuy said:


> What's the proposed footprint of the house?
> 
> Depending on it's shape, the excavation for a pond with a 1/4 acre surface area sloped at 3:1 from the pond's edge down to a bottom 15' below grade is going to produce about 2500 cubic yards of dirt. That's about what it'll take just to fill a gently sloped front yard (no more than 5% gradient) for a house 60' across with a first floor that's 10 feet above the existing gound. A gently sloped front yard will be about 200' deep. You'll also need fill dirt to transition from front to back. The amount will depend on how much of the backyard you want 'at grade'


Pipeguy Thank you for the reply.

The foot print is roughly 50' deep by 56' wide. This is the size of the plan we are currently looking at but no final decision has been made. We are still in the what is feasable stage.

When you talk of the dirt needed to grade the front yard I would guess you are talking about taking the grade down in three directions not just straight out the front. Let me know if I am right about that. 

Jim Bunton


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## PipeGuy (Oct 8, 2004)

paintr56 said:


> The foot print is roughly 50' deep by 56' wide. When you talk of the dirt needed to grade the front yard I would guess you are talking about taking the grade down in three directions not just straight out the front. Let me know if I am right about that.


NO, you are not right. I'm talking about only the dirt need to fill 60' wide, from 10 ' high at the front of the house to nothing at 200' away. 60' x avg 5' high x 200' = 60K cubic feet or about 2220 cubic yards. A width of 56' with a height sloping from 8' at the house to nothing at 160' away knocks it down to about 1330 cubic yards.

An uninformed guess about how much more dirt you might need to grade the side yards and backyard would be about 1/2 of what you need for the front. It's less because I presume you'll slope it from full height at the front of the house to nothing at the rear. You'll need substantially more, and some retaining walls, if you want to try and get usable space around the sides. Otherwise you're looking at about a 20% grade along the side yard from front to back. Might be tough to keep grass growing. 

Get with a local civil engineering firm and have them develop a site plan for you. They can accurately model cuts/fills and save you a lot of headache (and maybe a little money) in the long run.


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