After the ledger board is
installed it is time to locate the footings using batter
boards, string and some math.
Start by making the batter boards. Simply take two
1x4 stakes about 30" long and attach them together using
another 20" long 1x4. You will generally need 2 batter
boards per corner.
Place the batter boards about 3' outside of your rough
footing marks by pounding them securely into the ground
using a sledge hammer. The batter boards support string
lines that are used to mark the exact footing locations.
On the ledger board make a mark representing the center
of each post. Attach a string on the mark using a nail
and tie the other end to the batter board opposite the
ledger board. The idea is to make a grid that represents
the center line of each post and the beams.
The string that marks the center of the beam should
be parallel with the ledger board and the strings that
mark the post center lines should be at 90 degrees to
the ledger. Use the 3-4-5 method for squaring the posts
strings to the ledger.
Once all the strings are in place measure diagonal
corners, if the measurements are the same then the string
grid is square. Once square you can mark the exact
center point of the footings using a plumb bob. Mark
wherever the strings intersect at the corners and
at any point needed along the length of the beam.
Digging and pouring the footings
Now that you have established exactly where the footings
go it is time to dig, form and pour concrete.
Depending where you live the code for frost protection
varies. Check with the building department for minimum
depth of footings for your area.
A small back-hoe is needed to excavate the soil so
we can lay out the footings. Your deck plans will specify
the dimensions of the footings. Form a pad at the bottom
of the excavated hole according to your deck plans.
Using a "sonnet tube" form the rest of the
footings. Using reinforcement bars to add strength
the remainder of the footings.
Before pouring you may need to have a building inspector
approve the forms. Once you have an approval go ahead
and order your concrete from the redi-mix plant. Be
prepared when the concrete truck comes. Pouring concrete
is a very time sensitive ordeal. Make sure you have
all the tools ready for the pour. Tools
screeds and be sure to have the post saddles ready
to be inserted into the concrete before it sets.
After a day or two the concrete will have set up enough
for the back hoe to come back and back fill the soil
around the footings and smooth out the site.
Everything done up to this point can be tricky for
those with little or no building skills. You may want
to hire a contractor to get you through to this stage
WIth the footings poured and back-filled you can move
on to the framing.
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