My Dad wrote a book on how to design and build retaining walls back in the
1950's. It's long out of print, but the laws of physics haven't changed much.
I've seen plenty of "your" walls, and they were bowed and crumbling.
Cool. I took soils engineering in college. This was the book we used
http://tinyurl.com/de9h6 and Lambe was the professor. He was a bit of
a dick and a mediocre teacher but he knew his stuff. What did you
You've seen nothing of mine. I don't know why you have your knickers
in a twist. The manufacturers specifically state that for walls 3' or
under there is no tie back required for a gravity retaining wall. For
walls over 18" they instruct you to install drainage behind the wall
with graded fill. That's it. No engineering required.
But of course the manufacturers of interlocking block probably don't
know anything at all about soils and engineering. Maybe you'd like to
contact them and have them revise their installation manuals to please
You seem to be the one with knickers in a twist. BTW - drainage and anything
else about designing a retaining wall so that it will stay where it is put "is"
engineering. I guess that means you must have flunked the class.
Nope. Hated it, passed it. Only good thing about it was we got to go
on a trip to Vermont for our final presentation.
So the guy reading the installation manual is doing "engineering"?
Interesting. I always thought it was more complicated than that. Too
bad the backpedaling can't be converted into forward motion - you'd
really be flying!
You wrote this: "A good retaining wall that will hold up needs a bit of
engineering. It needs substantial anchoring back into the hillside and
proper drainage. Otherwise, tons of hydrostaic pressure can build up
behind it and push it over. It's not just a simple stack of blocks."
Your point was that engineering was needed, implying, obviously, that
the OP needed to have the 30" high retaining wall designed, which is
not the case. And, actually, it is as simple as stacking block in this
case. There is no anchoring required. Throwing in some perf pipe
doesn't need engineering.
The OP is not up on this stuff or else he wouldn't have posted. You're
just muddying the waters for him on what is a very simple installation
that can be easily accomplished by anyone that can read the
installation manual. It's labor intensive, but to save ten or fifteen
thousand I think the OP will find the energy somewhere.
I would rather he do it right and do it once, rather than listen to your bad
advice. There are plenty of "your" walls out there and they fail all the time.
Yes, anyone can ignore reality and just throw up a block wall. It won't last,
though, and you'll get to do it again. Some people approach a situtaion and say
"what is the least amount of effort I can put into this?" . That's you baby!
What assumptions you make. Simply incredible.
You obviously think you have a better way of doing things, so please
inform your reading audience what steps are necessary to insure the
correct design and construction of a 30" high retaining wall. If you'd
care to include any calculations and cost estimates based on your
location, that would be wonderful.
No clue how to design a wall, huh? Maybe you should have read your
Pop's book. If you have a copy lying around, why don't you break it
out and run some numbers for a 30" high wall.
If you don't want to do the math, pick up the phone and call an
engineer friend. Ask them what they'd do to design a 2 1/2 foot tall
wall. You'll probably have to repeat what you said after the laughter
Both will give you the same answer - you're making a big deal out of
nothing. Your intentions are no doubt good, but in this instance the
"engineer it" advice is not applicable.
Read the manufacturer's installation manual, follow the instructions.
It really is that simple.
The ng works better if the discussion centers on the technical issues &
avoids the personal insults.
Not every structure needs to engineered (that is, re-engineered) if the
process & details have been "pre-engineered". Think about it.
I merely responded in kind to someone who chose to make personal
insults directed at me. Meanwhile, the insulter gave poor advice that
will not ultimately be helpful to the original poster when he has to
rebuild his wall every 5 or 10 years. I pointed out right from the
beginning that there was more to building a GOOD wall than just
stacking some interlocking blocks. Rico duh jour didn't even think
drainage was worth mentioning. Maybe he lives in the desert and there
is little moisture and no freeze/thaw cycles to worry his pretty
"Engineered" doesn't always mean hiring an engineer, or even doing any
math, for that matter. I merely pointed out (correctly) that a good
retaining wall needs to have proper drainage, and be anchored and tied
Indeed? Allow me to refresh your selective memory:
Do you see anything in there that is insulting? Bad advice? Wrong?
So then you piped up with this tidbit, "My wall will outlast your wall
by many decades."
Besides being a huge assumption and wrong, that is insulting. A
correction was necessary.
Either your reading comprehension is compromised or you just don't pay
attention. The OP lives in Australia. How's that fit in with your
My original advice to the OP:
"Call a local masonry distributor and find out what sort of
interlocking block they carry and how much they get for it. Then go to
the manufacturer's web site and check it out in detail. For a low wall
like that, they'll probably just instruct you to bury the first course
of block to keep the wall from sliding. Then it's just stacking the
block and backfilling."
Note the word probably. The manufacturer's web site will have all of
the information the OP needs to build a 30" high wall.
Thanks for telling us that the engineering has already been done by the
manufacturer for low height/load walls. Let me rephrase what you
wrote, "Follow the manufacturer's instructions." That's obvious and
you could have just said that.
If you're not equipped to do the math, compute the loads and design the
solution, you have no business telling someone when engineering is
needed because you simply don't know.
I have no problem telling people that they haven't supplied enough
information and/or that the situation is more complex than their simple
question, if that's the case. The original post was clear, the
information adequate and the solution obvious. The OPs situation is
not complicated, he could do the work himself if he's in half way
decent shape, and the interlocking block manufacturer's installation
instructions will guide him through the process.
I also have no problem pointing out a blowhard who makes mountains out
of molehills. You, for instance.
If by "be anchored and tied properly" you mean to say that in order
to perform properly that at retaining wall has to be tied back to the
soil mass it is retaining; you are incorrect.
Short walls (& some tall walls, for that matter) do not need to be tied
to the retained soil mass.
<It's not a steep slope. It's less than a 2/12 pitch>
thats a excellent reason to just slope the ground1
I chalenge every one of you, tour your neighborhood! How many walls
look like they were just built? If they look that way they are likely
Most walls are bowed, sagging, cracking or just plain falling over:(
Pittsburgh where I live has tons of hills and grade changes.
Most of those stack the block companies state how easy it is to
now go check your neighborhood, then go build that wall! It doesnt
bother me at all!
ITS YOUR BACK AND YOUR WALLET:)
I do agree walls can look nice when they are in good shape!
The trouble is they dont stay that way long:(
incidently my most troublesome wall is sitting right over a sewer line,
so I cant build it a proper foundation. the wall cant be settling
though, since the house was built in 1950..
this wall is beginning to bow, and will be the next one to go. moved
here when I was 12 and projects were fun. tomorrow I turn 49:( I guess
its better than the alternative!!!:)
I DONT want to be rebuilding walls at 75, so a permanent fix is the
For normal ground water, there is no need for drain tile using
engineered blocks. There is plenty of space between each block for
seepage. Now if the upper level gets swamp like, that would be a
Read the manufacturer's directions. The blocks vary in what they can do
without engineering and the height begins below grade so if the block is 8
inch block and the first row goes underground, if they say you can build a
30 inch high wall without engineering they really mean the above grade
portion will be 22 inches.
The specifications are always very clear when it comes to the allowable
dimensions. Almost invariably they will call out the allowable height
above grade and then indicate how deep the wall must go below grade for
To give the OP something in his own neck of the woods:
If you've a strong back it shouldn't take long. I did one roughly these
dimensions in two days:
day1 -- prep, get in the first course & make sure it's level
day2 -- put up the wall
I don't remember the name of the system, but it's the stack kind with
the lip in back, and filled with rock after each course. It would have
taken about 1/2 the time had the company delivered the blocks where I
was going to use them, not 100' away :)
I don't know what all the commotion about failing due to pressure is
about -- these things have gaps between each brick, there's *never*
going to be much pressure.
I don't remember what it cost, but materials were substantially below
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