Pouring concrete slab brings back memories of summers long ago. I first learned this manly art in middle school when my dad wanted to pave in an area around the front porch to make it more usable. It started out as a six by ten foot area bounded by an existing sidewalk, but soon expanded to include a sidewalk around the front and side of the house. A few summers later we paved one quarter of the back yard.
Don’t pull bushes with your car.
Before we could even start we needed to remove some bushes, and dad thought the quickest way to get this done without a lot of hacking and digging was to tie one end of a heavy rope around the bush, and the other end to the bumper on his old car. He put it in gear and slowly took out the slack and then gave it some gas. Nothing. He gunned it and promptly pulled one end of the bumper clean off the car. I heard some new swear words that day!
The hard part.
The worst part of pouring slab concrete is digging the hole. I can’t tell you how many times I’ve seen someone just stick some forms up and pour, and now they have a sidewalk that is 4 inches higher than the surrounding yard. It’s ugly, a trip hazard, and just plain lazy. Digging down 4 inches and hacking out any roots is a real pain in the ass, but the results are well worth it. Once you get this done it all gets easier.
Giving shape to your sidewalk or patio.
I’ve found the best materials for making forms are cheap 1x4x8s, or if you need fancy curves then quarter inch plywood in 4 inch wide strips. Next you need stakes to stake your forms into the ground. Cement is heavy and your forms need to be strong enough to not break free. If you are pouring steps that will have a lot of concrete in them, then you need to consider using 2×6 or 2×8 pieces of wood using 2x4s as your stakes. But if you are just doing simple flat work, then cutting some 1x2x8s with one end pointed will be just fine. Most of the time you will want to nail the forms to the stakes to keep things from moving around.
Make your forms with your pour in mind.
If you are mixing the cement yourself, then you may not want to attempt to pour a long sidewalk all at once. Especially not a large patio. We did a large patio, probably around 500 square feet in 6 foot by 6 foot sections. The reason for this is that you need time to work the cement you poured. If you are busy mixing and pouring a large section, the first part you poured may be harder to work and finish by the time you are doing mixing and pouring the whole section. If you are dead set on pouring large sections, then have a cement truck deliver and pour into your forms.
Calling in Reinforcements.
Do you really need rebar (reinforcement bars) or wire mesh? I would only use rebar if you are pouring slabs that will be bearing a lot of weight like cars, and then I’d make it six inches and not four. It cost more, but that’s just me. Most driveways and sidewalks are four inches. I would definitely always use concrete reinforcing wire for large slabs and driveways. Sidewalks are optional, but I’ve seen long sidewalks start to buckle and shift after just a few years. Reinforcing wire can help minimize that. Tip – don’t just pour cement on top of your rebar or wire. The reinforcement works better if it is elevated a little so that it is roughly in the middle of the slab.
The cement can stick to your forms and make it hard to remove them after the concrete has set. All you need to fix this is a can of cheap motor oil and a paint brush. Just before pouring the cement, lightly coat every part of the form with oil that will come into contact with concrete.
Baked from scratch.
If you are doing a tiny pour, then just a few bags of ready mix, some water, a wheelbarrow and a hoe is all you need to mix it up and pour. If you are doing a large batch of several cubic yards, you can often buy ready mix in a trailer ready to pour at hardware and tool rental stores. But if you are going to be hard core like my dad, then you can buy or rent a cement mixer and make your own.
When we did the huge patio in the back yard, my dad had dump trucks deliver a huge pile of sand and another huge pile of gravel right next to each other. Then he had a pallet full of bags of cement powder delivered to the house. Then he got seven galvanized buckets, probably around two gallons by capacity. The size of the bucket isn’t critical to the recipe. We followed the old 1-2-3 recipe. 1 bucket of Portland cement powder, 2 buckets of sand, 3 buckets of gravel and around one bucket of water. Add the water slowly until it’s the right consistency, keeping track of how much you used so that you put the exact amount in the next batch without trial and error. You don’t want it soupy or dry and clumpy, but just wet enough that you can work with it to move it around the form with a heavy rake or shovel. With my dad, mom, brother and little sister, we had an efficient assembly line operation going.
Tip – if you will be pouring on a slope then consider making your mix a little dryer so that it doesn’t all flow down to the low end of the form.
The fun part of concrete.
Finishing the surface of the newly poured slab is the fun and easy part, if you don’t wait too long to do it. Concrete starts to set and harden as soon as you pour it, depending on factors of how wet the mix is, and the outside temperature. For sidewalks and patios you will usually want a nice lightly textured surface that isn’t a slip hazard in wet weather.
The picture above shows how to “strike” concrete. On small sections of patios or a sidewalk, just cut a 2×4 a foot or so longer than the width of your form. Then one, or usually two people start and one end of the poured concreted and start making a sawing motion back and forth across the concrete as you work your way to the other end of the form. This helps settle and level the concrete and make a semi smooth surface to finish.
Next you lightly drag a shop broom across the cement to texture it. Hardware stores also sell special purpose texturing brooms extra wide and with longer handles to do larger sections. After surfacing the concrete you would then use one or more of these edging tools.
To put some nice edges around your sidewalk and also make some dividing edges in the sections.
Planning for Disaster.
Things don’t always go to plan. For instance a pop up storm may threaten to ruin your finish. Be sure to have some plastic sheets and brick to cover your cement in case of a storm. You can usually remove your forms after 24 hours, but it may take up to several days for your concrete to cure depending on your mixture, thickness and weather conditions.