CONCRETE
FOOTINGS:
The building codes in your community will be very specific about
this deck component (usually). However, here are several rules of
thumb for planning purposes: If
possible, footings should be placed on undisturbed soil or rock.
The footings must extend below frost line in your area, which ranges
from 24 inches minimum to 48 inches maximum. You can find out the
frost line depth in your area by phoning the National Weather Service.
If this agency is not conveniently reachable, your local Building
Department will know the frost line depth.
Footings
usually are placed concrete in rectangular, square, or circular
shapes depending on the post connection. Most footings extend 2
to 6 73] inches above ground (grade) level; if posts will be embedded
into concrete, the posts must be treated for rot and insect resistance
(such as termites).
READY
THE SITE:
Clean away all trees, shrubs, grass, big rocks, and other debris
BEFORE you order material.
The
ground should slope away from the house slightly for adequate drainage.
If
a lot of soil must be moved to provide this slope, it is recommended
that you have the soil moved professionally. The cost may not be
as prohibitive as you might think. It's worth a check and three
bids.
STAKE
OUT THE DECK:
With wooden stakes and chalk line, square the deck to the house.
By doing this, you also have created the shape of the deck with
string.
Take
your time with this task. Getting it correct at this point can save
you plenty down the line. The stake-out will be used to determine
all other deck dimensions as you proceed.
STAKE
OUT THE FOOTINGS:
Using the stakes again, locate the footing positions. Most posts
are set back from the leading edge of the deck by 18 to 24 inches.
If
the footing location happens to coincide with an underground utility,
you may get the utility moved, or you will have to relocate the
deck.
The
size and number of footings are determined by the size of the deck
and its expected load. Generally, for most decks, footings are placed
on 5-foot centers, front, middle, and back. If there will be lots
and lots of weight on the deck, the footings can be 4 foot on-center
for support. Don't skimp. It's better to overdo it slightly than
underdo it.
When
you have determined position, stake the position so the stakes are
"on-center" within the footing area. An auger or clamshell type
posthole digger can be used to dig the footing holes.
However,
it is suggested that you contract this work-especially if there
are lots of holes for you to dig. If the footings are circular,
you can buy a forming material called Sona Tube. The tube is set
in the footing hole, concrete is placed in the tube, and the top
leveled. When the concrete has hardened, the tubes can be stripped
quickly and easily. If the foundation will be square, you will have
to form the top of the hole with 2X4s to create this configuration.
After the concrete has hardened in the form for at least 5 days,
the forms may be removed. Let the work set longer if possible.
