On Apr 19, 8:07*am, cj wrote:
greetings, i am building a deck that will be 17 feet wide by 9 foot
deep. i will use 4x4's dug three feet into the ground, with a bag a
cement in each hole. my question is how much support(4x4)will i need for
the 17 foot span? obviously one 4x4 on each end but will one 4x4
centered be enough or should i break the 17 into thirds? so 4 columns
instead of three?
cj

You've got your whole project bassackwards. Take a breath here and do
some logical planning.

1) You will have to have a building permit in most communities.
2) A permit requires a set of plans with specifications such as
dimensions and materials.
3) The plans must meet the city building codes.
4) Many box stores have free deck planning services. Take advantage of
it.
5) Once you have applied for and received your permit, all your
questions will probably have been answered.
6) If you need clarification of any details, the inspectors in the
office can be amazingly helpful...all you have to do is to ask and
then listen.

Common sense says that reinventing the wheel is the curse of the
ignorant. Find out where the knowledge and expertise is in your area
and go for it. Good luck.

Joe


Unless you have a degree in civil engineering and lots of construction
experience it makes no sense at all to wade into any large project. .