[grlandscaping]

I just got a call sunday from a gentleman who's driveway is sinking and his tie wall is failing. The tie wall is about 9 feet high and supports the driveway, so the driveway needs to come out and a new segmental wall needs to be put in. This will be my first 'major' wall to build.

Everyone that builds rewalls, what was your first 'major' wall that you built and how'd it go? I'd love to see how it went and learn a tip or too. Let's hear your story.

[Bill Schwab]

Our first major wall was a 7 foot tall Sienna Stone sea wall with a set of steps down to a landing in the river.
The landing was infilled with Unilock Old Grenwich Cobble. We used strato grid 300, and back tied 12 feet into the bank. We had to sand bag and pump the river out of the void so we could create a dry area for the leveling pad. We took buckets and buckets of muck and crud out until we hit bedrock about 4 feet down, then poured a 6 bag concrete mix and placed a male groove in the finish to set the Sienna Stone.

The job went over budget, we broke even, and learned more than we made.

Sounds like if you got a wall near a driveway, the whole thing is going to have to be back tied with geo grid at ground level, then every 18" of course. The width of the grid? Look at the soils report and see what it shows you. Depending on weight, I would go with at least 6' wide grid, but some engineers want you to double or tripple that.

For the wall you describe, I would consdier Sienna Stone by Unilock, which can be pricey because you set them witha crane (480lbs ea) or Keystone Standard units, and geo grid. Standards weigh 120 lbs each and they make a tool that two of your guys can move the stone with to set it.

Have you prescreened your prospect as to possible costs, and so fourth? If you have to get an engineer invloved, he could charge $5,000.00 for a set of prints, just to prepare for permit submission. That does not even mean the permit will be issued without revisions, which, equates to money.

Just a little of what we have run into over the years, and I'm sure there are many insightful "tidbits" that can be offfered on this forum..

Good luck, let us all know what is progressing for you ok?

[grlandscaping]

Quite the project you had Bill.

This client is an engineer himself and is drawing up some of his own plans for this project. I'm going to check and make sure he is able to put his stamp on it or if i need to go to the civil engineer.

Here's a more detailed description of this project: This house has a 3 car garage on the south side of his home and the driveway runs along the south prop. line, which is about 25' from the face of the garage door. The exisiting wall starts at grade and follows the driveway as it goes towards the back yard. Once at the end of the driveway, the wall turns north to continue towards the home. This is the tallest section, 9'. If looking at this wall in plan view, it would look like a large J. So the "width" of the driveway is 25' and the 'lenght' is about 40'. The tie wall has pulled away from the home, about 1'. The driveway itself has settled about 6-8" and it is like a speed bump going into the garage. The driveway would be torn up approx. 45' back from the wall. Geogrid will definatly need to be used on this project. Soils are clay.

The main rewall systems in this area is Anchor and Versa-lok. You can get keystone if you want, but it isn't worth the cost. Also, i don't really care for their block, haven't been impressed with them at all.

I'll keep you posted on how its going, I'm gonna start putting some preliminary numbers together

[diginahole]

For certain in Ontario and I would suspect other markets as well, Risi Systems has engineers on staff to provide stamped drawings for Unilock retaining walls at little or no cost. Check with your Unilock dealer.

[scl]

Diggin got there before me. Contact your block supplier as most times they will engineer for a couple bucks a foot. 9' high, I like the Sienna stone too, cause of the long lines, but its about $25 a square foot at cost.
Our first big project was 600 ft., but not over 5' high. Had to jack hammer down in bedrock to install steps and some base. PITA. Didn't make much, but learned oodles.
At 9' high look to use larger blocks to minimize your install time and create larger lines. Small block like Pisa 2 lose their character in that quantity IMO.
And just a thought on working for an engineer/homeowner. Be ready for 1000 questions and 2000 opinions. I put in a patio for one this summer, and the guy was pretty cool, though he did just what I said. When I came back after 2 weeks to resand he said that all his neighbors loved it, but he stole some of my thunder by telling them it was his design, which it was. I asked if they were impressed that I made it work regardless LOL. We both got a chuckle out of that one.

[Paul]

Vehicular load bearing walls are a bit more involved. Problems with this type of wall are lack of supporting soils, poor toe conditions, minimal buffer area, plus add in water infiltration and limited budget.

I would rather work in a river than do this kind of work People seem to think that it's just a driveway and don't think of the loads that it carries or stress that can be put on it.

Since your limited to V-lock walls, I would plan on excavating 9' back, I would use a bi-laterial geogrid, back filled with angular 3/4" washed gravel. Use a hard PVC pipe for your drains add a clean out or two if you have room. I don't know the roof structure but check which way down spouts are running by the garage and pick them up with a separate PVC pipe. Don't plan on using your small plate compactor to compact the back fill, rent a large plate from the local rental yard. As you finish the wall look to see how the water is going to run off the drive, try to keep it away from the wall.

Lastly find out if you can put some type of guard rail up to protect yourself from having someone drive over the edge, or if you have room install a buffer area, 3' to 4' should be enough.

[jwholden]

GR,

I have no experience with walls this big, by want to throw my .02 in anyway.

Soils are clay.

Be careful, this is the worst type of soil to work with.

Your customer is an engineer and that's great. Is he a soils engineer? YOU are installing this project and YOU are responsible for it. If he wants to save a few bucks by designing the job let him, with some shmoe he found on the corner.

[grlandscaping]

Yeah, the clays we haver around here stink.

There's 2 downspouts that come down onto the driveway in the section that would affect the wall. What I'm thinking is to run these downspouts where they are now, but have the driveway more-or-less be concaved so that i can put a grated drain the lenght of the driveway to catch the downspouts and any rain that would fall. Run the drain out past the base of the face. Or i could run drains from the downspouts directly out without having them run onto the driveway.

I like the idea of maybe bumping the end of the wall out for a 'buffer area'. I always backfill with 3/4 clear behind the wall, how about for the rest of the 8'? I'm thinking of importing road gravel or some other soil besides clay?

[Paul]

My feeling is to use angular 3/4" gravel thru out.

[Bill Schwab]

Paul has some great input here, The bilateral grid is best, and if you can. no doubt the 3/4 infill rather than clay will be best. I would probabaly go with a jumping jack style diesel or sheeps foot vibratory compactor, lots less labor to achieve that 90% the engineer is going to want.

I just met with one of the guys we use, and he said that if you can pour the leveling pad, rather than gravel, the toe issue Paul mentioned would probably go away. Basically, he said excavate an 18"x 36" trench,, and you can make a slip form for the bottom of whatever channeled wall you would use, the other way is to set a jig where the pins would go and drop them in, and let the cement harden. Use 4 pieces of #4 rebar, at the 6" and 12" from the bottom positons.

I told him you have a freeze issue, but, that think, that deep, should not have an issue.

Paul brought this one up as well when he mentioned cost. Concrete ads a certain Cha Ching to the bid I'm not sure your client would want to pay...

Anyhow, hope this helps!

[grlandscaping]

thanks for the input bill, it helps!!

I was thinking about the concrete footings also, but wondered how tough it would be especially on the part of the wall that goes from grade to 6'. How would the footing be set then?

[Bill Schwab]

Stepping the footing is not as bad as you may think. Get your bearings, and figure where the footing needs to be stepped. Then check the thickness of your retaining wall (Unilock has had a problem with Pisa being inconsistently sized for example)

You will need to make the step the distance needed for the course to line up. Just remember if your concrete is off, so will your wall.

[grlandscaping]

I have a friend working for a company putting in their largest wall yet. It is around 20' tall with a second tier on top of that one, exact dimensions, i don't recall. Their footing was a little off and now they are fighting the fact that they are leaning more back into the hill and the variences between blocks are resulting in slight gaps between layers.

On large scale walls, how do you account for the 1/8 or 1/16" difference between blocks, because it just compounds as you go up and there isn't anything you can do about that varience.

[Bill Schwab]

We would usually set the short blocks aside and keep the for the row with geo grid. Or, you can shim the back side. Unilock had as much as 1/2" of compression on thier pisa 2 walls, and they claimed it was from stacking the walls after they molded them. The more I thought about it, I never made sense out of that arguement. If the width shortened up, then why did the top and bottom stay flat and in shape?

Since all we install here are Keystone, we have not had a short block problem....That may vary however. Keystone uses individual manufacturers to make block. RCP has thier contract here, and they are pretty strict about quality control. The only issue we have had is a pallet or two a year has had stress cracks behind the face, so, we toss them aside, and get a return for credit.

They sell these walls based on thier stackability, and being uniformly manufactured. Short of throwing those pieces aside for returns, there is not much you can do... And, the manufactirers should take them back for credit without a problem.

[grlandscaping]

The one time i used keystone it was with the mini units. I won't go into all the details, but the funny part of the experience was when I had 2 pallets of the mini units made with a different mold than all the other pallets. When I called the supplier, they told me that it was impossible and there is only 1 type of mold. So i loaded up a couple of the different mold with the 'normal' molded block. The different one had the holes a different shape and size as compared to the normal one. I went to the supplier, went inside to tell them i was there, and while walking out they kept saying that it was impossible and they had called the parent company where they got the block. When we got to my truck and looked at it they said, "Hmmm.....you're right, they ARE different, ummm....hmmmm" It was a pretty funny moment because nothing like that had happen before and they weren't quite sure how it happened. So they took those pallets back and brought me new ones and it was better. Makes me happy for suppliers that are willing to help you out!