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# Re: Weight of Soil

• To: seaint(--nospam--at)seaint.org
• Subject: Re: Weight of Soil
• From: Daryl Richardson <h.d.richardson(--nospam--at)shaw.ca>
• Date: Mon, 21 Jul 2003 22:12:44 -0600

```Jason,

100 pcf is plenty if it's dry but you might want to use 125 pcf if it's
totally soaked.  If you want, you can calculate this for a variety of dry soil
densities as follows:

Relative density of most soil solids = (+-)2.7  Some organic
soils may be lighter; but this may, in fact, only be because they have a higher
void ratio.  Besides, even if they are lighter it may be necessary to add stones
or other weight to keep the wind from overturning the pots.

Void ratio = e

Assumed weight of dry soil = 100 pcf

Dry weight = 2.7*62.4*(1-e) = 100 pcf

Weight of water = e*62.4

Don't forget to allow something for the "growth" above the soil.  Over
time this might get quite heavy.

Regards,

H. Daryl Richardson

Jason Kilgore wrote:

> I've got an existing structure where the architect wants to put 3' diam x
> 1'-6" high tree/bush pots on the roof.  He's talking about a 4x5 grid of
> these pots, with only about 12" between them.  It's acting like sort of a
> barrier.  Using 100 pcf, (wet potting soil, clay pot, decent bush) this
> works out to be over 1000 # / pot.  Spread out over 16 ft. sq., this is
>
> My question is what is a good conservative weight to use for these pots?  Is
> 100 pcf reasonable, or should I go higher?
>
> Another thing to consider is that this is publicly accessible space in an
> apartment building (not that anyone can come in off the street, but this is
> where the parties would be held).  I'm leaning toward just designing for 100
> psf live and ignoring the stupid plants.
>
> ----
> Jason Kilgore
> Leigh & O'Kane, L.L.C.
> jkilgore(--nospam--at)leok.com
> 816-444-3144
> 816-444-9655 (FAX)
>
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