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Discussion Starter · #1 ·
Hey there,

I have a renovation going on with a walkout basement. The owners want to backfill the whole basement walkout on the backside which is about 60-70 feet in length and 9 feet high. It will slope down on the sides with a staircase leaving the front with a walk out. We have had an engineer come give us some ideas and one is add a concrete wall along the back for the lateral pressure or a PWF system. Backfilling will be done with clay, bell posts, and additional soil at the top. Looking to see if anyone has any other ideas or has done a PWF system and how it ended up? Thanks in advance!
 

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I've done PWF in the past, I'm not a big fan unless you can be absolutely confident about the water control, and quality of backfill. I would never backfill a PWF with clay. Our engineers only ever spec aggregate.

Where are you located, and what backfill materials are available to you?
 

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I’m not understanding this

Is the basement existing, or are you building it?
 

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So ... they want to convert a walkout basement to a no-exit basement, completely underground? And I agree with NGC ... clay is the wrong material for backfill, unless they are using a bentonite membrane layer for waterproofing the below grade wall.
 

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Discussion Starter · #5 ·
I've done PWF in the past, I'm not a big fan unless you can be absolutely confident about the water control, and quality of backfill. I would never backfill a PWF with clay. Our engineers only ever spec aggregate.

Where are you located, and what backfill materials are available to you?
we’re in Alberta, and could also look into the aggregate. Is there another system you’d recommend other than pouring a concrete wall that’s similar to a PWF system?
 

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Discussion Starter · #6 ·
I’m not understanding this

Is the basement existing, or are you building it?
Basement is excising house is about 30 years old and has the landscaping in the back built out with retaining walls but it was over grown and looks somewhat like a dungeon now from the basement windows. On the garage side it is the same as if we were to fill in the back side so right now the house is about 3/4 walk out but now the whole back side will be filled and you can only walk out of the office on the basement at the front of the house
 

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Discussion Starter · #7 ·
So ... they want to convert a walkout basement to a no-exit basement, completely underground? And I agree with NGC ... clay is the wrong material for backfill, unless they are using a bentonite membrane layer for waterproofing the below grade wall.
The back is a walk out but they also have a man door at the front office on the basement so the back will be back filled but you are still able to exit on the front basement office.
 

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GC
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Basement is excising house is about 30 years old and has the landscaping in the back built out with retaining walls but it was over grown and looks somewhat like a dungeon now from the basement windows. On the garage side it is the same as if we were to fill in the back side so right now the house is about 3/4 walk out but now the whole back side will be filled and you can only walk out of the office on the basement at the front of the house
Sounds like the solution is to hire a landscaper.
 

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I don't know how that will hold up structurally, a typical foundation wall is reinforced by the slab at the bottom and the wood framing at the top.

An engineer can give you an idea as to how and reinforce the retrofit wall.
 

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Waterproof, drain tile, and backfill the first 2 feet away from the wall with pea rock to within foot of finished grade.

Clay is an expansive soil and can push on wall. Pea rock won't.

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