Lip on SRW Blocks Not Important?

Discussion in 'Hardscaping' started by JimLewis, Jan 25, 2012.

  1. JimLewis

    JimLewis LawnSite Fanatic
    Messages: 6,876

    So we're in the process of constructing an SRW right now. About 100' long. At the highest point, it's 4' tall, including the footing. But most of the wall is 3'6" or less. We're using Anchor Wall Blocks (as pictured below). These blocks have a lip on the back of them, like many SRW blocks do. And as we were constructing the wall, the workers noticed a fairly high percentage of blocks where that lip was broken off by more than 50%. So we started setting those aside and just kept using the good blocks.

    After a while, we ended up with almost a full pallet of these blocks without full lips on them. So we called our supplier to ask for replacements. And here's what surprised me. I guess I just never knew this before. I wanted to vet it with all to see if you concur with what they told me.

    What they said was that the lip on the back of these blocks is unnecessary in terms of structural integrity. They said that's just there for lining up the blocks, nothing more. They assured me that the SRW walls are still totally stable structurally just because of the batter and the weight of the blocks and the proper construction techniques (drainage, batter, footing, foundation, etc.) alone. The lip isn't part of the equation.

    That's something I never knew or hadn't ever heard before. Can any of you concur with that statement? Is that true? The lip isn't totally necessary for anything except just to align the blocks a step back for batter?

  2. KrayzKajun

    KrayzKajun LawnSite Fanatic
    Messages: 10,737

    Jim its kinda funny ypou brought this up. Me and a helper we talking about this at lunch today. I'm doing 5 small walls only 3blocks hight + cap around some landscape beds. In the past I have kept the lip on the first row for anchorage. The rest I usually knock the lip off so the next level can be set back a tad and all the blocks be same distance from face of the lower level. The lip gets in the way when doing curves. I asked my pavestone supplier and he told me the same thing you were told. Its mainly to help when doing straight walls without curves. I just use a roofing hammer and knock the lip off.
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  3. DVS Hardscaper

    DVS Hardscaper LawnSite Fanatic
    Messages: 6,623

    Whats to keep that block from shifting forward? The lip may help with creating the batter and the alignment, but doesn't it also help keep the block from sliding forward?

    I think your supplier Jim, was feeding you a load of crap. Their block busted apart and they know it.

    In terms of curves, when you wack the lip off, you then use a little block glue to hold the block in place since the lip is gone.
  4. STL Ponds and Waterfalls

    STL Ponds and Waterfalls LawnSite Bronze Member
    Messages: 1,174

    I don't think it's a huge issue. Look at when you use sawed natural stone that has no lip or pins etc. If your wall is being pushed forward with hydrostatic pressure or whatever, those lips aren't going to help from failing.

    The bummer is you guy's probably waisted a lot of time knocking the lips off for the base row and already had plenty to use.
  5. TomG

    TomG LawnSite Senior Member
    Messages: 674

    Jim your supplier is correct. The friction between the blocks is enough to keep them from sliding forward. I have heard that from multiple sources, one of them being Paver Pete. Say what you want about him... but he knows his shi*. If the block is going to slide do you really think 1" of concrete or plastic pins are going to stop it?? Even though they wont move if the lips are broken off, we always put a little glue.
  6. StBalor

    StBalor LawnSite Senior Member
    Messages: 798

    Very interesting. I always thought that lip had alot to do with the integrety of the wall. just next time it may be better spread those broken ones out and not have them all in 1 area.
  7. JimLewis

    JimLewis LawnSite Fanatic
    Messages: 6,876

    All right. So I had to dig a little more and find out whether this was really true or not. Like Andrew (DVS) I sort of felt like the supplier was giving me a load of crap and just trying to get out of warrantying their product. And also like Andrew, I wondered what would keep the block from sliding forward if it didn't have that lip. It just seems to make sense that the lip is there for more than just alignment purposes.

    So I called one of the best structural engineering firms in town and talked to the principal engineer and owner of the firm. This is the firm we hire when we have to install the big complicated engineered SRW system. And I posed this question to him. He's one of the best structural engineers in our area. Here's what he told me.

    Essentially, he told me that the supplier was correct. The lip there is only for alignment purposes. And it is not calculated into the equation for anything regarding structural stability. I posed the same question that Andrew asked above, "Ok. Then what is to keep the blocks from sliding forward then?" He said simply, "Gravity" He went on to explain that this is the difference between what we call a "gravity wall" vs. a "MSE wall". A gravity wall is constructed so that the force of the gravity of the blocks pushing down is stronger than the force of the hydrostatic pressure of from the soil pushing forward on the wall. He explained that the way a SRW gravity wall is installed, just the gravity and the batter on the wall make it strong enough to withstand the force pushing against the wall.

    He went on to say that even the systems (like Keystone) that have the pins inside the block - even those are not for structural integrity. Those are only for alignment and to assure proper batter. That's all. They are also there to make it easier to attach geogrid. But they aren't taken into the equation for structural integrity at all. Just there to help you align the blocks properly when stacking. That's it.

    So.....I guess you learn something new every day. I still find it hard to believe. But I gotta take his word for it. This is what he does. He's engineered more walls in this city than I've ever dreamed of installing and he's one of the best in the area. And he has no reason to lie to me. He's not at all connected with my manufacturer. So I gotta believe he knows what he's talking about - as hard as it is to believe.

    The other thing I learned new today was that all of the 3 different brands of "Cuban" cigars I just brought back from my trip to the Caribbean last week are all fakes. Piss me off! Oh, well. I am still going to smoke those suckers. They look hella real to me. Here I went to all that effort to hide them from customs and everything. And they're fake! Oh well..... I honestly wouldn't have known the difference anyway. So I guess I'll go have a drink, smoke my fake cuban and think about the new things I learned today.
  8. TomG

    TomG LawnSite Senior Member
    Messages: 674

    Yay! Jim thank you, I love it when people post actual facts. Not just "I think this" "I think that"

    I along with you found it hard to believe that the lip has nothing to do with the wall besides aligning when I found out.
  9. KrayzKajun

    KrayzKajun LawnSite Fanatic
    Messages: 10,737

    Jim thanks for getting us the truth!
  10. DVS Hardscaper

    DVS Hardscaper LawnSite Fanatic
    Messages: 6,623

    I can assure you, the lip **helps** hold the type of block in the picture in place. Keyword: HELPS. We just wrapped up a job last week where they had a 4" block wall that we removed. No drainage aggregate. No fabric, no nothin. If it wasn't for that lip....the block would have been on the ground!

    And......I have pictures of the wall before I took it down. took 3 of 'em!

    And yes, the pins do shear.

    LOL - I think we've seen quite a few posts of mere speculation from 'ol Tom :)

    Stop using that junk block and use a real block Cornerstone

    Last edited: Jan 25, 2012

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