Ok. You need to build a concrete slab for your shed or patio but you don’t even know where to start. Well, you’re in luck. By the time you finish this article, You’ll be a pad pouring pro!
Our example for this project will be a slab for a 10×10 slab.
Tools you will need: spade or small shovel; concrete finishing trowel; hammer; level; measuring tape; pencil; carpenters square; wheelbarrow; bucket.
Materials List: 5 12’ 2×4’s; 2 8’ 1×4’s; 2lbs 16d nails; 7 (94lb) bags Portland cement; 14 cubic ft sand; 21 cubic ft gravel (¾” or smaller)
Preparing The Ground
Get out your shovel, it’s time to go to work! I’m assuming you’ve already decided the perfect plot for your pad so we’re going to go right to the ground work. Using your shovel and a good sturdy back, remove any grass and loose dirt from the area where the slab will go. Try not to dig very deep. You just want to clear the surface.
Next, get a good straight 2×4 (it needs to be long enough that it would stretch all the way across the slab) and a 6’ level. If you don’t have a 6’ level you can use a shorter one, but; the longer the level, the more accurate it will be. Lay the 2×4 down on the cleared ground edge up and place the level on top.
Work the 2×4 and level around the surface area and remove the high sides of the ground until the entire area where the slab will be poured is level. With that done you’re ready to build your forms.
Building the Forms
You don’t have to build the forms in place since this is a small concrete slab.
Since this is a 10×10 slab, we are going to need 2 10’ 2×4’s and 2 12’ 2×4’s. These can be low grade lumber, but they have to be straight.
Cut the 2 10’ 2×4’s so that are exactly 10’ (many times 10’ 2×4’s will actually measure 10’ ¼” or something other than 10’). We will leave the 12’ 2×4’s to length.
Using the 10’ and the 12’ 2×4’s, Build a frame that has an inside dimension of 10’ by 10’ when you’re done you should have a form that looks like the one below.
Measure from inside corner to inside corner diagonally from both directions. Move one end of your form slightly until both measurements are the same. This will ensure that your concrete form is square.
Nail a 2×4 across one corner of your form once it is square to hold it in place until we set the form and secure it with pegs.
With our forms built and square; we are ready to place ‘em and set ‘em.
Setting your Concrete Forms
Carry your forms over to the area where your concrete slab will reside and set it in place. Remember that 6’ level we used earlier? Use it to check each side of the form to make sure it is level.
With the form level and square, Drive wooden pegs at about 3’ apart (it doesn’t have to be exact) around the outside perimeter of your forms. To make the pegs just rip a couple of 8’ 1×4’s and cut them into 2’ lengths. Cut one end of each peg so that it comes to a point. The top of the pegs should be driven down until thet are flush with your concrete form.
Nail through the peg into the slab form. This will secure the form and prevent the concrete from bulging.Be sure not to drive the nail all the way in. You will need to be able to pull these once your project is done. Also make sure the nail doesn’t stick through the inside of the form.
Finish Preparation
Dig a ditch, approx. 6” deep and 8” wide around the inside perimeter of your concrete form. This will be the foundation for your slab. We will be pouring a mono-slab which means we will pour the slab and the foundation together.
With your concrete form built and your foundation dug, Step back and admire your work. Take a short break and go drink a pepsi. When you come back, We’ll Start adding the concrete.
Adding the Concrete
See: How to Figure Concrete to learn how to calculate how much concrete you will need.
See: How to Mix Concrete to learn how to mix concrete and the proper ratios to use.
Mix 1 part cement 2 parts sand and 3 parts gravel in a wheel barrow using a spade shovel (example. 2 scoops of cement 4 scoops of sand and 6 scoops of gravel.) and add a little water with a hose. Stir the concrete mix and continue adding water just until it is pour-able but not so thin that it is soupy.
Pour the concrete mix into the form and repeat until the level of the concrete is about 2” from the top of the form.
Lay rebar around the inside perimeter of the form (about 2” from the edge of the form). Be sure to bend the rebar around the corners. Rebar should never end at a corner. Each Piece of rebar needs to overlap each other at least 16”.
Continue mixing and filling the form with concrete until it is flush with the top.
Finishing Your Concrete Slab
After filling your form with concrete, Get a good straight 12’ 2×4 and a helper to screed the top of the concrete. Do this by starting at one end of the form. Place the 2×4 so that it rests on each side of the form and begin working across the concrete form to the opposite end. Work the 2×4 in a sawing fashion. Use some of your mix to fill any low areas.
Now that you have a level flat surface. You can rent a float and float the surface of the concrete or you can use a finishing trowel to finish your concrete and give it that smooth professional look.
Removing the Forms
The forms need to stay in tact at least until the next day. You can remove them after about 24 hours. Remember the concrete is considered ‘green’ and is still weak so if the forms don’t come off easily, it’s best to leave them for a few days to allow the concrete to harden.
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