On Apr 23, 1:01 pm, Goedjn wrote:
On 23 Apr 2007 11:56:43 -0700, wrote:



Hello, I live in Southern California (Ventura county to be more
accurate). I am building a deck on to my house and I have a couple of
questions that I hope someone can answer for me.

1. I will be sinking footers at least 24" into the ground with
brackets for 4x4's to be the pilons for the deck. My question is
this, what diameter do I need to use. I will get a bunch of the round
concrete forms, but will the 8" ones be sufficient or do I need 10" or
12". The deck will not be holding any massive weight (no spa or
anything like that just foot traffic).

2. I've made up plans for both attaching the deck to the house and
also free standing. What do I need to know in order to make the
decision between the two. I suppose it would be more sturdy if I
attach it, but it would be easier if I build a free standing. I'm all
for doing it the easier way, but I want to know what are the possible
pit falls of free standing vs. attached.

If anyone could answer these questions for me I would greatly
appreciate it.

-D o n

Someone else should check my figures for this, but:

If the deck is big enough for a person to get under it,
figure it will eventually have around 100psf combined load
on it. If it's a low-lying deck, figure 60 PSF.
(It doesn't matter what you EXPECT to put on it,
use the values for the most anyone reasonably MIGHT put
on it.)

Undisturbed soil will support anywhere from 0 to 4000 PSF.
SInce someone's managed to build a house there that's not
sinking, you're probably safe at figuring at least
1500 PSF. If you're on solid well-drained gravel,
double that.

An 8" pile has a cross-section of a bit over 50 sqin.
and if the ground is good for 1500PSF, that works out to
about 350 pounds per piling, which, for a low deck,
means each pile will hold up 8+ sqft of deck.
By contrast, a 12" pile will hold up nearly
20 sqft of deck.

How big is the deck, and how many pilings are you
planning to use?

The deck is an odd shape. It is about 32' long, 18' wide at one end
and 4' at the other. It also covers a sloped area. Close to the house
the deck is at 27"high at the edge of the deck it is 40" high. I'm
trying to cut down the 40" by terrising(sp?) the yard. The plan calls
for 27 posts in all. the plan i got from Lowes.com says it is 41psf
live load and 10 psf dead.