of Project Here
1.) Calculate how much you'll need and purchase some 10" concrete form tube.
Refer to these illustrations
for how to setup a batter board to level this type of foundation. However, the batter board in this
case will be used more for establishing the perimeter and making the foundation square not level. We
will use a water level to establish the height of each pier and to make them level. Call your electric
or gas company and find out who to call to have your property checked for underground utilities if
you don't know already.
2.) When setting up the string add 1" to the width and length so form tubes won't interfere
with the string. When setting the tubes, allow a 1/4" clearance
between tube and string. That 1/4" along with the 1/4" thickness of the tubing equals 1/2", that
plus the 1/2" on the other end will give you 1" Tomorrow when you cut the tube away from the
concrete, you'll have the dimensions you desire.
3.) Depending on the distance the floor joist will be spanning you may need an additional row of piers
down the center, maybe two. If wood beams are to be placed under the floor joists, piers will need to
be lowered to allow for the height of those beams. Wood beams can be inline with the joist so long as
proper joist connectors are used. Hopefully you have an engineered set of plans to follow. Follow the
links provided with this illustration
for some insight
Mark hole locations
4.) At each corner measure 5-1/2" from each string and drive a stake. Setup another string being sure
this string falls on the 5-1/2" measurement. This is the center of each row of piers. Measure and
drive stakes along this string where piers need to be placed. For a 2x8 floor systems using a triple
2x8 beam, every 5 to 6 feet apart. For 2x12 floor systems using a triple 2x12 beam, every 8 to 10
5.) Depending on your local building codes, dig each hole 10" in diameter and an equal
amount into undisturbed soil as the top of the tube is out of the soil up to 3' deep.
6.) Starting at the highest elevation determine how high you want your piers out of the ground.
Some areas require 18" minimum under joist and 12" minimum under any wood beams.
Drive a wood stake near the hole and put a mark at the desired height.
7.) Setup a water level and cut
three pieces of 1/2" rebar 4" longer than what the hole is deep plus the length that the tube extends
out of the ground, which would be level with the mark on the stake. For example if your hole is 24"
deep and the tube is 24" from the ground to the water level height you will cut each
bar 4'4" long.
8.) Drive each 1/2" rebar stake into the bottom of the hole 6" deep holding the bar plumb
and about 2" from the sides of the hole. Space remaining two bars evenly around hole.
Now the bars should be 2" below the mark on the wood stake.
9.) Cut nine pieces of 1/2" rebar 8" long. Fasten three pieces to the inside and near the top of the
three 1/2" rebar stakes with wire ties to form a triangle. Fasten another three pieces half way to
the ground and another as far into the hole as you can reach. It may be easier to install the bottom
Setting form Tubes
10.) Take a measurement from the ground to the top of your steel. Add 4" and cut a piece of form tube
that length. Set tubing over steel and adjust tube till plumb and there is a 1/4" clearance from
the string. The cage of rebar should be below the top of the tube.
11.) Drive two wood stakes and brace the tube from two directions so the top can't move. Fasten the
tube to the braces by screwing through the tubing near the top and into your bracing. Repeat for all
12.) Once all steel is in and forms are installed plumb and braced, use the water level and mark the
outside of each tube in two locations using the mark on the wood stake as your height gauge. Then
drive a screw through each mark on the tube. These screws will serve as the concrete height indicators
13.) This is a fairly slow process if done with a mixer and a shovel. If you can get a truck to deliver,
you can run several wheel borrows at a time and use several shovels plus pour most of the piers with
the trucks concrete chute. Fill each tube to the height of the screws.