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View Full Version : The wall that won't die


paul
04-01-2000, 03:51 AM
Just an up date on that wall on poor soil,<br>They sent us new enginerring drawings reducing wall height and upgrading base prep.<br>reduced wall by 1/2 down now to 1800 sq. ft. but back fill gravel and base gravel has grown to 300 tons plus grid material has grown to 5 times original bid. We rebid job and increased priceing, to cover extra labor and material by 20k. Looks like we still won't be doing job park district had stroke over cost is looking at haveing the GC build it (I told them good luck) <p>----------<br>paul<p>

kermit
04-01-2000, 11:02 PM
Paul,good to see that you won't drop your standards to get the job. I have found that most people don't understand the engineering behind retaining walls and are surprised by the costs. We build walls out of precast concrete as well as natural stone and people usually freak when I tell them what the price will be. When I deal with a landscape architect the client realises that the job is being done proffessionally and will cost real money. I don't close very many walls I bid on by myself but that's OK because at least I make money on the one's I get. <br>Most contractors I see around here that grossly underbid me do a lousy job. After one winter the wall is failing because there's no base and the backfill isn't draining properly,if there is any. What bothers me is that these guys never repair their work. Don't customers go after these contractors? Hell if I screwed up that bad I'd expect to get sued. Well I've seen a few companies come and go and I'm still here so I guess things do work out.

steveair
04-02-2000, 12:19 AM
About this base subject:<p>A few years ago I went to a seminar and one of the engineers from Anchor was there. What he told us was that the base had no importance as to the desing of the wall. I found this very hard to believe. Now, it was mainly local contractors there and most of them would never do jobs like the one you are doing, but it is very interesting how he said that. For smaller guys, who only do wall in the 4 to 8 ft range, maybe the base isn't all that important (not that I believe it)<p>As for the cost of doing the wall right, I think you hit the nail on the head with the fact you refuse to do a job that asks you to change your standards. <p>I have never done any wall over 4 ft (because that would require a engineer here in jersey, and I don't do jobs of that scale) and wouldn't want to attempt too either without a engineer. Nor do I even do a wall that is only 3 ft without some examining of the soil and area. <p>I see some real disasters coming in the next few years with a lot of retaining walls, on the small scale that it. I have seen so many guys build walls, say in the 6, 8 or even 14 ft range, with no desing work at all, and no idea that they aren't 'legally' even suppose to be building the wall. A lot of them don't even put gravel, drainage, none the less grid material. <p>Basically, retaining block walls have only been around for 5-8 years, at least the real fad to have them residentially started at about that. Already I see walls in people's front yard beginning to fail, and it really makes me laugh. You look at even little 3 ft walls, and they are beginning to push over. <p>It really makes me laugh to see this. I remember the other day, I drove by a site and this guy had built a wall using retaining wall block , and it was 4 ft tall. It sure looked great! Behind it...<br>Nothing. He built the whole wall on level ground and didn't back fill at ALL! I had trouble holding my laughter in. A few weeks later, I drove by and he got to backfilling it finally (his house was on the other side of it). Even funnier, he left about 3 blocks sticking up still. Probably thinks it will stop his kids from crawling over the wall or something. Instead, they'll have a 80 block fall on their head. <p>People have no idea how these walls work. They think because of the fact its solid concrete and weighs so much, that nothing can hurt it. The wall itself is just part of the system, not the whole. In fact, the wall is actually a small part of the 'whole' design. Still, nobody seems to realize this. <p>When you look in any wall block brochure, the word &quot;system&quot; is always there, somewhere. It seems that no one reads this. Stacking blocks on top of each other is not a System. Its just a wall. <p>I guess this is a problem that will always exist. One good way to look at it is to go around, look at walls, and count all the money you can make replacing them when they fail.<br>

paul
04-03-2000, 08:08 PM
OK just some notes on base for walls.<br>Base does have little to do with how long a wall will stay up to a point. Shear factor has alot to do with how long a wall stays up along with load factor. The lower the shear factor the deeper the wall must be buried (you can over come this some what by pitching the wall back more). Base is what keeps the wall level, for no movement you need to start the wall below the frost line, at which point you might as well pour concrete. The wall system really floats on the ground, by not being a soild unit it move up and down with the frost. The load the wall carries behind it is the hard part of the equation. Knowing how much stress is placed behind the wall and which forces are working on it make our job harder. Achiving good drainage, stable soils and good compaction behind the wall will make or break you. Don't be afraid to included geo-grid in small walls (4' or less) use enough washed gravel and pipe with a sock. Not many of you will run into a wall that needs to be built on peat, but if you do be prepared to walk away or spend the money on enginerring. If it is enginerred please follow his advice and maybe do some extra work (like dig out the soils deeper, bury extra block, or add geo-grid to the base to help support the wall) all so learn to key in your front fill and compact it in lifts of 2&quot;. If you need help please ask here don't want any one getting into trouble.<p>E-mail me at Palnelson@aol.com<br> <p>----------<br>paul<p>