Foundation footings like the photo below are extremely important. A footing course is the first most critical step in building a new home or commercial building. There is a safety hazard in this photo, can you point it out?
Footings must be poured on solid ground! No exceptions. Whether it's for a new home foundation or a frost wall. Unless the digging is awfully hard I always use a ditching bucket to dig my foundations and frost walls.
The photo below is the start of a footing course for a commercial building. New ICF home foundation footings on average would be 22" wide and 8" deep or whatever the plan calls for.
A commercial foundation footing course would be at least 36" wide and 12" deep. Commercial ICF buildings are built with 8" ICF walls and ICF homes are built with 6" ICF walls.
The thickness of the ICF wall and the height of the ICF wall determine the footing course dimensions. Just follow the structurally engineered foundation designs.
All ICF foundation footings are built with 10mm horizontal rebar, can be 3-4 runs of rebar depending on the size of the footing course. We install our vertical rebar while the cement is still wet which is 10mm for ICF homes and 15-20mm for commercial ICF buildings. Follow designs for size and spacing requirements.
When I prepare the site for a foundation I always think ahead to the point of the actual footing excavation or basement excavation. When I dig a basement or a trench for a footing like the photo above, I make sure my excavator is sitting level.
If your excavator is sitting level while you dig, then the trench will be level from side to side. It doesn't matter about the long way because you will maintain a grade using a laser level while you dig. You dig?
When I dig out for any type of foundation work I do it almost perfect because it makes a lot less work for the crews that are setting the footing forms.
If the ground work is level, so will the forms. If the forms are level, then it's just a matter of driving stakes in the ground and screwing the stakes to the form.
When you set the grade for the footing forms, use a laser level. Sometimes we have to pull the form up a bit to be on grade and sometimes we have to hit the top of the form to drop it a bit. When I say a bit...I mean a 1/16th to an 1/8th. Sometimes we have to pull a bit of dirt out from under the form to allow the form to drop enough.
I use a ditching bucket to dig with because tooth buckets leave behind too much loose material. The ditching bucket can remove an inch at a time if need be and the bottom of the trench remains solid.
As I'm digging the foundation or the trench for a frost wall, the crew pre builds the footing forms. To speed things up, the crew installs the foundation footing forms in the trench to keep up with the digger.
The footing forms are placed, squared and leveled. As you see in the photo above, cross braces are placed every 4 feet. It doesn't always happen but the stakes should be driven between the cross braces to better support the sides of the form.
Make sure the form is level and square before the pour. Place the horizontal rebar on the ground before you set the form, makes it a lot easier then trying to slide the rebar under the cross braces.
Cut all the vertical rebar and lay it close to the form! Mark the spacing on the form with a black marker so there's no measuring or guessing once you're ready to place the rebar.
If you're pouring a full ICF wall, you will cut the 20 foot length of rebar in half and stand the piece in the wet cement. Place the rebar in the center of the form.
Slump basically means how wet or dry the cement is when it comes off the chute of the truck. The higher the number the wetter the cement is. Concrete loses it's strength when/if you add too much water.
Inspectors at commercial jobs would reject the load if it wasn't the right slump. Some inspectors won't allow water to be added to the load at the site so make sure it's the right slump before it leaves the plant.
How big of a vibrator do you need? Ask your wife! :) The size of the vibrator depends on how big or deep the footing is. A pencil vibrator will work on a footing 22 inches wide and 8 inches deep. For wider and deeper commercial footings with lots of rebar you should use an electric vibrator such as the one below.
Electric Concrete Vibrators can be bought in different sizes and lengths. Pencil vibrators are usually one size depending on the brand you buy.
Vibrate the wet cement and screed it off level then check it with the laser. Footings must be level for a better quality ICF wall. If the footing is smooth and level it's just a matter of placing the ICF block on the footing, there shouldn't be any shimming or trimming of the panels to make level.
If you have any questions or need any help with decisions you need to make don't hesitate to ask.