How to make Concrete Stairs

OK, so long project short; I demolished a sidewalk and lowered the area it was in by about a foot and a half or so.  Now I need a way to get into the side garage door.  A set of stairs was the only choice but what kind?  I could make wooden stairs easily, but would be remaking them years later or possibly have the issue of someone getting hurt when they finally gave way, also I didn't want any little critters living under the stairs as we live close to the great outdoors and critters abound.  I could do stacked stone, that was pretty permanent but very costly.  Concrete it is.

The first thing I must do is determine the size and shape of the stairs, the dimensions we need are called rise and run.  Rise is the height of the stairs and run is the length of the stairs.  If the stairs just open into a yard then run may be an open variable but in my case I was limited to about 43 inches (give or take) due to the fact the stairs ran into a shared alley between houses and I couldn't block traffic.  My rise was determined to be 25 inches from the door threshold to the ground.

After determining your rise and run for the stairs as a whole it is time to figure out the rise and run of each step.  Steps should be a minimum rise of 5 inches and minimum run of 9 inches.  These measurements may be different by code in your area and also note these are minimums as stairs with a rise of 7.5 inches and run of about 11 inches are a better more comfortable fit for higher traffic areas.  My stairs are for the once in a blue moon entry to the side of the garage, uncomfortable and small work just fine.  A simple determining factor for me was left over 5.5 inch plank lumber from a previous project, this would make a good stair height and would allow for five steps high.  At five steps high and nine inches deep per stair this would give an overall rise of 27.5 inches and a run of 45 inches.  A bit larger in both directions than optimal, but it will work.  The run is just two inches further than I wished, but not so much it would cause any serious issues and the extra 2.5 inches of height would be easily concealed by sinking the whole set slightly below ground.

Construction of the wooden form that would hold my concrete was a simple process of marrying two pieces of plywood with five pieces of said planking lumber for the steps. First I cut the two pieces of 3/4" plywood to the design of the steps and securely screwed the planking wood (also 3/4" thick) to the ~FRONT~ of what will be the stairs. Digging the area slowly where the stairs will go so that they sit level is important, do not over dig as loose soil does not make a good foundation for stairs.  After the stair form is in place I took the opportunity to stack the inside with loose pieces of concrete that I otherwise would have had to dispose of, after all a bag of concrete saved is a bag of concrete earned.  It is very important to not stack the loose concrete within about 4 inches of the outside of the form as this would weaken the overall block of concrete.  Before we start with concrete, it is very important to reinforce the form to hold the weight of the concrete with dirt and stakes.  If you fail to secure the form you could have a blow-out where the form fails under weight and concrete pours out.  Cleaning up after a blow-out is much more difficult than properly securing your form.  By digging a hole beneath where your form sits you will create a piling that when filled with concrete will help your stairs to not shift away from your house over time.

25 Bags of concrete
Now that we have a pourable form in place all we need is concrete, but how much?  Well, I hope your geometry is up to snuff if you did anything tricky, otherwise calculate the area of the side of the stairs and multiply that by the width.  The total will be the cubic inches of the stairs and each 80lb bag of concrete makes about 2/3 of a cubic foot of concrete or about 1140 cubic inches.  Divide your volume by 1140 and you have the number of bags of concrete you will need, my stairs require 25 bags.  Yes...holy crud...25 bags of back breaking concrete.  If your stairs take more than about 5 or 10 bags (depending on age, physical prowess and number of helpers) I can't tell you how much you should look at renting or buying a small cement mixer. Always buy a few more bags than you need as the last thing you want is an emergency trip to Lowes during your pour.  Concrete can not be poured in phases, it must be poured at once with wet concrete on wet concrete as it will not adhere properly to cured concrete.

Since my form was stacked with waste concrete I must mix my new concrete kind of soupy so it will fill the voids around all the pieces.  Now, a lot of concrete aficionados will complain that wet concrete does not cure as hard as thicker mixes, and this is true.  True, but not needed. These stairs are not "structural" they do not hold up part of the house and the soupy mix makes for an easier pour.  Soupy concrete fills the form, needs little leveling and smooths easily.  And as such, once you pour the form full, just smooth the tops of each stair with a trowel and then walk away.

You can remove the form the next day as the concrete will be setup by then.  Be careful if the concrete is still dark as it will be soft and prone to chipping if you are rough with it.  Once you have removed the wooden form take a rock, brick of similar rough item and rub it against the corners of the stairs to remove sharp edges.  Wait to use the stairs for a few days as the concrete turns white and rock hard.  You now have a set of stairs that will outlast the house.

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