I mean, really ridiculous. It's insulting. Case in point:
They'll support 97,000 PSF?! Most interesting - particularly in light
of the fact that the IRC allows a prescriptive soil bearing capacity
of 12,000 PSF for crystalline bedrock.
Most likely they are attempting to make the potential buyer aware that the
pavers are stronger than the roofing components they are covering. Green
buildings are the future in certain cases.
Point in fact is, there's nothing wrong with this type of advertising;
engineers know that a roof is only as strong as its weakest link....... they
are simply stating htat this isn't it.
Roofing components...? They're designed to be driven on - used in
landscaping. Saw no mention of living roof ballast, thought they
would obviously be able to handle _foot_ traffic on a roof.
Point of fact - it's a bunch of crap. They're saying that _one_
square foot of their _plastic product_ would support 2/3s of an M1
Abrams battle tank. Puh-lease. The stuff would be dust.
It's a simple, straightforward lie in advertising. They're either
misrepresenting the load capacity intentionally or through ignorance.
Neither is acceptable.
There's a new trend to develop green roofs (covered with grass). Used on
some commercial buildings made to be walked on by the tenets, also used to
make a roof greener for a penthouse. That's where I've seen these types of
products used, but not to any real extent.
As far as the loading goes, did you see that its designed to use a base of
6-7 inches of stone aggregate, covered with a bed of gravel 2' thick, with
the hollows filled with pea gravel covered over with a 6" sand cover. The
plastic pavers are used as a stabilizer for the gravel.
There should no problem in carrying a load of 675 psi using the method
advertised on the website. I don't think you read through the entire
As far as what they advertise for loading, 674 psi is high, but not unheard
"> Roofing components...? They're designed to be driven on - used in
It's not a new trend. There have been roof gardens aand roof top
swimming pools for decades. What I love to do is visit these roof
gardens couple decades on.....It's not just the psi, it's also wheher or
not your substrate (elastomeric, whatever) is meant to be wet all the
time when you water mr. roof garden.When you are doing drainage into
aggregate like you suggest, it's not wicking into ground water, it's
wicking eventually onto your substrate. Essentially, then , what you
have to design is a swimming pool that is designed never to be kept
clean on top of a roof...And the best way to conquer such an issue is to
give that water somewhere to go and to do it without clogging it with
Forget left field, you've jumped the fence and are hanging out in the
bleachers. Typical undisturbed prescriptive lsoil bearing capacity
loads, according to the IRC, are in the range of a ton or two per SF.
In other words, their paving plastic grid, resting on gravel (assume
five tons PSF bearing capacity for gravel to show I'm not being
unreasonable), increases the bearing capacity by TEN times. That
sound right to you? If so, I sure hope you don't do your own
ot http://www.grassypavers.com/specs.htm and select the load data
While I'm not the sharpest tool in the shed, I do like to hear good
feed back on the products I sell. I am a dealer for the product and I
own the site http://www.grassypavers.com . I use data given to me for
the site. If it is incorrect I would like to update the info so it
correctly represents the product.
You guys obviously know your stuff in the load arena. I would love
some feedback on this load data from MPI. Is it crap? if so why? This
is where the facts come from we use on the site (actually from the 4
page brochure on the specs page). I will be glad to send samples out
to anyone that would be willing to conduct these tests to see how our
products hold up.
I would also be willing to take feedback and a real world writeup on
soil load capacities and what benefits any kind of pavers provide for
that soil base.
I want everyone to know about the product and I want that info to be
correct. Architects, Designers and End users a like should have
factual information in making decisions and choosing products.
So I hope ya'll don't still want to take out behind the shed. My goal
is to provide factual data for our products. They are a good solution
and are more durable than people think.
Please keep up the thread. I like a good debate.
Most of the responses you are reading here appear to be from kids who are
not associated with engineering nor with how engineered products are
marketed (note the off-topic preoccupation with the falsely-accused Duke
Lacrosse college kids).
Some are arguing that the underlying soil is not strong enough to support a
truck, which is of course ridiculous. The substrate conditions would be
engineered to take the assumed reactions necessary, while the manufacturers
product is design to provide a soil base and drainage stratum. It is assumed
that the underlying soils would be considered in any installation, and
improved if needed. This product's advantage is only in the addition of
adding grass to such areas; already deemed capable of withstanding the
loading of vehicular traffic.
Reviewing the test reports provided, it appears to me (my opinion) that the
testing performed by the University of Southern Mississippi is completely
within established guidelines and have sufficient credibility. The only
additional qualification I would ask to see is the signature of a licensed
professional, registered in the state where the tests were conducted or from
the state where the product is manufactured. I work in plan review for a
nationally recognized testing laboratory and review test reports similar to
this product, on a regular basis.
As always, the best results is the feedback from existing installations. If
you still have any concerns over the product's durability, I would recommend
contacting the manufacturer to see what problems and failures are occurring
in the field.
A lot of words that don't say very much, and what they do say is
Obviously the product is intended for creating a drivable green
surface. Thanks for clarifying that - the name grassy paver had
"It is assumed that the underlying soils..." That's your idea of
engineering? ASSuming bearing capacity and soil conditions?
An 18 wheeler typically weighs in at around 80,000 pounds maximum load
(federally mandated maximum).
An average semi tire has approximately 60 square inches of contact
area - that's ~7.5 SF of tire contact area per truck, or roughly
If that grassy paver stuff has a rating of TEN times the maximum load
allowed on federal highway - with the graded, layered and compacted
base - why the nifong do they use asphalt and concrete for roads?
Your grasp of the numbers is as faulty as the manufacturer's claims.
Move on - please. This is getting embarrassing.
I visited the website & emailed the guy (he posted below) about the
claims being made.
He sent me a link to some info from the mfr (he jut sells them)
looks like the mfr had some tests done on the plastic unit (filled &
un-filled) AND the mfr (or their agent) did some hand waving based on
the ASSTHO H-20 loading
And then extrapolated the results to some of insane psf number
the guy who signed the test report is some sort of clueless
Phd.......reporting numbers with 6 or 7 "significant" figures,
reporting psf's that no soil in the world could possibly support
Using the ASSTHIO loading & then extroplating to a generalized psf is
like calc'ing the stress under a woman's high heel & extrapolating to
a psf for floor loading!
120 pounds, assume .375" diameter heel tip, standing equally on both
540 psi translatesto >>>>>> 78,200 psf
makes as much sense as their test report & product claims
What they really have is a product that can take a higher "point
load" (actually a local small patch distributed load) than normal
(unconfined / un-reinfornced) soil.
With the plastic grid & grass roots, you wind up with a reinforced
soil that (IMO) is at best is a few times stronger (locally) than
regular soil MAYBE 20 or 30 psi
but it ain't asphalt or concrete!
hehheh You obviously don't wear heels.
You forgot to account for the sizable percentage of weight on the balls of
Why do I suddenly feel like Reese Witherspoon in Legally
I was considering the load case when "she's" rocking on her heels. :)
I didn't consider the dynamic effect of foot fall "impact" while
I think i also may have over estimated the heel tip diameter (I'm
wearing flats today & didn't measure or reseach tip dia)
in any case I'm sure you get my example........heel tips are hard
even oak floors so my number of ~540 psi is in the ball park
You have no idea what's in my closet.... :)
I knew you were kidding me.
& I just pulled the example out of the air..... I divided the weight
bu two but I also chose 120lbs (wishful thinking?) ...could have been
I refuse to go measure the heel tips...even too geeky for me.
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