Question on retainer wall replacement and long standing grading problem

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Old 09-03-12, 04:46 PM
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Question on retainer wall replacement and long standing grading problem

Hi all,

I hope this is the right forum for my questions, as it involves a retainer wall. Apologies if not.

I am replacing an aging (read: rotting) wooden retainer wall with one constructed of 16" trapezoid retainer wall blocks:



The approach I've come up with is to partially entomb the existing wall (by partially, I mean I will rip down the top plank only) and this appears doable based on the distance I need to set the first row of retainer wall block forward of the line I want the top row to meet.

The biggest problem with this project is that grading on this side of the house has always been a shambles. The genius builder didn't bother excavating much on this side so there is sadly a slope TOWARDS the house (see below image.) Having said that I have never had a dampness or flooding problem in the basement (perimeter concrete foundation) and perhaps the steep slope in the perpendicular direction makes this a non issue (?)

Nevertheless, I had ideas about digging a trench for the first row that would be level all the way out 6-8' beyond the edge of the deck. This is proving to be a massive pain in the ass (thanks to a 45 degree slope making machine excavation impossible, and an ungodly amount of roots from neighboring trees making shoveling a real joy.) You can see my progress in the below image.

In the below image, you can also see a pier for the deck that is well above the elevation of the concrete foundation of the house. My plan is to leave this as-is with the retaining wall going right smack behind it (behind relative to the image below) and filling between the retainer wall and the pier with either dirt or gravel.

My basic questions are:

1) Is it of any importance for the first row of the retaining wall to be a single flat row? Or can I "step up" every ~6 or so feet away from the house to reduce the amount of trenching needed? (I'm already down about 3 feet on the far end, and would have to go another 18" or so to get it level all the way out)

2) Is it important to further excavate this entire area so there is a slope away from the foundation ALL the way up and down this side of the house? Presently there is only a slope away starting at about the staircase landing and down (to the right in the image below), above this (to the left in the image) it is sloping towards the house. One idea I had is to "box out" with more retaining wall about 6 feet further out than the deck piers, this would of course require much more excavation. Worth doing? If so, what should I do with that top-most deck pier which is much higher elevation than anything around it would become... leave it as an island? wrap it with retaining wall blocks?

3) Any issues with entombing the bottom half of the existing wooden retaining wall? I thought it would be best to do this to avoid an avalanche... the vertical 4x4 posts are set in concrete, but this could be pulled out with some effort I'd imagine.



Here is a video of the digging I've been doing (about 2.5 hours over the course of the day), so you can get an idea for what I'm talking about: digging - YouTube

Some appendix notes:
  • The height of the retainer wall as-planned would be just on 4ft
  • The reason the existing wooden wall is rotting is a bad drainage pipe behind it, which I have repaired. Even so, I do not find the wood particularly appealing which is largely the reason for going to concrete blocks.
 
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Old 09-04-12, 02:44 PM
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Can you post a few still photos of the yard? I don't understand the video.
 
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Old 09-04-12, 02:56 PM
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I will take a few pics tonight and post... in the video the trench you see being dug around half way through is for the first row of retaining wall blocks -- to replace the wooden retainer wall you can see at the left hand side of the video.

(Not sure how much clearer I can be with text)
 
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Old 09-04-12, 03:06 PM
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That's what I thought but it wasn't clear enough for me to comment on the job. Some pictures from the outside of the wall would help. That's some slope you have there. It would be a major project to correct that.
 
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Old 09-04-12, 05:43 PM
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Here are some more pics, sorry for the low res just shot with the phone:









 
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Old 09-04-12, 06:05 PM
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I see what you're trying to do now & instead of killing yourself, why don't you pay someone with a bobcat, for a few hours or rent one yourself. Doing all that by hand is way too much. If not, 3 or 4 day workers can do the same thing. That way, you can get the levels & the grading where you need them.
 
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Old 09-04-12, 06:18 PM
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It's a 45 degree slope (down the side of the house) so I just figured no machine could get in there. There's a deck on top of it too so headroom is an issue. Maybe I am wrong?

Have seriously considered a team of day laborers...

So let's say I have infinite shovel power... what is the ideal approach? Dig the WHOLE sector out so that the grade is away from the house all the way out ~6ft past the deck? (that's as far as I've dug the retaining wall trench out so far.) If so, how to deal with that high elevation deck pier? leave it as an island?

Or just finish the trench and lay down a retaining wall and call it "good"?
 
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Old 09-04-12, 07:01 PM
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If you go with the day workers, do everything you can with the slope. I used to work with some guys from Central America & they could dig like moles. You'll have to leave the pier as is. I don't any choice on that.
 
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Old 09-05-12, 02:17 PM
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While you're in there doing things right, why not just replace the entire "high-and-dry" column? When the wall is finished, just temporarily support the deck and replace the column with a longer one. And with a more substantial C.I.P. footing and anchored steel stand-off bracket this time.
 
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