Step 1: Planning and tools
Front walk site
Stick to sidewalk projects in flat or gently sloping areas. Adding steps is much more complicated.
If the thought of pouring concrete scares the bejeebers out of you, don't feel like the Lone Ranger. This story will teach you the basics so you'll be confident and ready to go when the concrete truck pulls up to the curb. And you'll save to cost of hiring concrete pros to boot.
You may need a building permit—check to be sure
At this site, we didn't need a building permit for a residential sidewalk on private property. But take five minutes and call your local building inspector to make sure that's true in your area. You'll save some embarrassment and possibly a fine.
A giant ready-mix truck driving up to your house can be intimidating. I always get butterflies when I hear the diesel roaring a half mile away. But being prepared with solid forms, good equipment, a couple of strong helpers and a well-planned wheelbarrow route will help calm the nerves. Once you dump the first few wheelbarrow loads and get the hang of moving the wet mud around, you'll feel in complete control.
You're going to need a couple of heavy-duty wheelbarrows, shovels, rakes and a variety of professional-grade concrete finishing tools. We describe the tools in detail below. The hand tools may be worth buying if you intend to pour more concrete down the road. For a modest price you can own a set of high-quality tools (minus the wheelbarrows) for life and not have to hassle with rentals. Take heed. Concrete is heavy and time is short. Once the ready-mix truck (the concrete is premixed and ready to pour) shows up, you and your helpers will be muscling around 200-lb. wheelbarrows over gravel. This work is intense—you won't be taking any coffee breaks for a while.
After pouring and screeding (Photo 11), you may see things slow down a bit, but they can get a little frantic again when the concrete begins to firm up. Follow the tips and advice in this article, get ahold of the right professional-grade tools, line up at least two reliable, beefy helpers and pick a good weather day, and you'll end up with a long-lasting, attractive sidewalk you'll be proud to carve your initials into.
Concrete might be the cheapest building material on the planet
It's hard to imagine a material that gives more bang for the buck than concrete. What other material yields a permanent, finished, durable, maintenance-free outside surface at a low cost and a day's work? Around these parts, many contractors won't put down a gravel base or even use steel reinforcing. Bonus: Your sidewalk will be stronger and last longer than many professionally poured sidewalks. In addition to the cost of concrete, suppliers usually add a ‘short load’ charge for small orders (generally under 3 yds.). This 4-ft. wide by 60-ft. long and 4-in.-thick walk required just over 4 yds of concrete.
Two Heavy-Duty Wheelbarrows Can Save the Day
Secure your tools a day ahead of time or at least contact the rental store to reserve them for the pour day to make sure they're at the site when the truck comes. Rent each of these tools:
- Contractor-grade wheelbarrows with leak-free tires. Even on small pours, you'll be in big trouble if your sole wheelbarrow gets a flat tire or a broken handle, so get two! It'll also speed up the pour. A full ready-mix truck at the curb with no way to unload it is expensive. Concrete is heavy. The neighbor's garden-grade petunia hauler will collapse under a load of concrete, and the hard, narrow tires make for tough wheeling in soft ground or gravel.
- Bull float with an extension handle (Photo 12).
- Concrete broom (Photo 16; use the handle from the bull float).
- A groover that cuts control joints 1 in. deep. If the rental store only has groovers for shallow cuts, use it to shape the joints and deepen them with the corner of a trowel or a stiff putty knife. Unless the grooves are at least one-fourth the thickness of the concrete, they're of little value.
- Two magnesium hand floats.
- Two edgers.
- Iron rake to move around wet concrete (Photo 10). In addition to the earth-moving equipment for the excavation work, you'll need:
- Hand maul for pounding in stakes.
- Bolt cutters (Photo 8) for cutting mesh.
- Sod cutter (Photo 2) if you have lots of grass to cut through.
- Screw gun for anchoring forms to stakes.
- Circular saw for cutting forms.
- Marking paint for outlining the walkway.
TIP: Fill a wheelbarrow with water, and brush and rinse off your tools every time you use them.
Step 2: Excavate the walk
Photo 1: Lay out the walk
Rip 12-in. hardboard siding to 6-in. widths, flex it to the desired shape of your sidewalk and stake it down. Use marking paint (upsidedown spray paint) to mark the ground next to the form. To outline the sidewalk for digging, mark the unformed side using a spacer block.
Photo 2: Dig out the sidewalk path
Slice off sod with a sod cutter (rents for $16 a day), then dig out the rest of the sidewalk path to a depth of 6 in. Dig out about 3 in. wider on both sides of the paint marks to leave room for forms. Set aside some topsoil to fill against the forms (see Photo 7) and sidewalk later.
Digging out the path is 80 percent of the job
Lay out the path with 6-in. ripped strips of hardboard siding tacked to temporary stakes (Photo 1). That'll not only give you the overall shape but also provide the forms to mark the outline for digging. You'll also find out if curves are too sharp for the bending qualities of the siding.
It took two of us a whole day to cut off the sod (Photo 2) and dig out the path to prepare the base for this sidewalk. Believe it or not, pouring and finishing the sidewalk was easier, faster and a lot more fun than excavating. Tree roots, stones and heavy clay made for tough digging. Renting a sod cutter to remove sod, and using axes for cutting out roots and pickaxes to loosen soil make the job a little less blister-producing.
Start thinking about drainage issues at this point. If water tends to collect in the yard in spots, you may want to elevate the walk in those areas, so don't dig as deeply there. Long, flat areas should have one side of the sidewalk lower so water can drain off the side.
In most cases, make the top of the finished walk even with the (freshly cut) top of the grass for easy mowing and a neat, clean appearance. The bottom of the trench will be about 6 in. below grade to allow for 4 in. of gravel below the 4-in. thick slab of concrete. If your sidewalk abuts another sidewalk or driveway, keep the top of the sidewalk at the same level or build in a 4- to 7-in. step at the transition. Don't make a step that's shorter than 4 in. You'll trip every dinner guest who comes over.
Tip: If you don't have a place to dump excess soil and sod, rent a trash container for a couple of days. We ordered a 10-yard unit for $225 that handled everything we dug out.
Step 3: Build the forms
Photo 3: Drive stakes every 3 feet
Pound in two stakes about 1 ft. from the ends of the form positions. Screw the forms to the inside of the stakes with a couple of 1-1/4 in. drywall screws. Bend the forms to make smooth curves, anchoring them with more stakes every 3 ft. Keep the tops of the forms about 1 in. above the cut grass height for easy mowing and a nice appearance.
Photo 4: Reinforce form joints
Cut 18-in. lengths of form material and screw them to the backside of the ends of the forms with 1-1/4 in. drywall screws. The splice will smooth out the curves at butt joints.
Photo 5: Space and form the second side
Space and level in the opposite form sides using a homemade gauge board-just a 1×4 that's a few inches longer than the width of the sidewalk. Screw short blocks onto the bottom spaced the same width as the sidewalk. Use this gauge board to position the forms and stakes to keep a consistent width the entire length of the sidewalk. Rest a 4-ft. level on top of the gauge board to keep forms level from side to side. For better drainage in long, level areas, drop this side about 1 in.
Photo 6: Pack the soil
Pack the underlying soil with a plate compactor (rental). It's important to uniformly pack the entire base (including the sides near the forms).
Photo 7: Spread gravel
Spread gravel 4 in. deep between the forms. Pack dirt against the outside and gravel against the inside of forms to add support when pouring and to achieve smooth curves. It's not necessary to compact the gravel.
Photo 8: Cut concrete mesh to fit
Cut off the stakes flush with the tops of the forms. Park a helper on the end of the reinforcing mesh for ballast and unroll the mesh, holding it down with your feet. Cut it to length with a pair of bolt cutters. Flip the mesh over and pull one end toward the other to back-bend it slightly to eliminate the natural curl. Cut the edges of the mesh at least 3 in. back from the forms.
Photo 9: Wrap mesh ends
Overlap mesh layers at least 6 in. and join them by either twisting cut ends around the next sheet or wrapping wires on each 6-in. square.
Use cheap hardboard siding to form even the tightest curves
Straight concrete forms are generally made with sturdy 2-by lumber, but curves call for a more flexible material. Concrete pros use 12-in. hardboard siding ripped down to 6-in. strips in 16-ft. lengths. Full-service lumberyards and home centers carry all this forming material as well as reinforcing mesh and expansion strips (Photos 1, 8 and 17) you'll need. Roughly measure the length of the walk and divide it by 16 to get the number of siding pieces needed. Hardboard siding's cheap, so buy an extra length to make sure you have enough. Also, pick up enough wood stakes to anchor each side of the form every 3 ft., a 1-lb. box of 1-1/4 in. drywall screws for anchoring the forms to the stakes and enough 6-in. (the size of the grid openings) steel reinforcing mesh to lay in the whole sidewalk trench.
Tip: Getting the long, flimsy strips of siding home from the lumberyard is tricky, even in a pickup truck. Buy a 16-ft. 2×4 to stiffen the stack of siding and wrap packaging tape around the whole works for the ride home. Don't forget to staple a red flag to the end of the load for safety. Later on, you'll use the 2×4 for making temporary forms called bulkheads (see Photo 17).
Keep your finished sidewalk dry—slope the forms
Photos 3, 4 and 5 show the details of how to install the forms. Our sidewalk path's consistent, natural slope away from the house toward the street provided good drainage. So we made the forms level from side to side (Photo 5). If your grade has dips or level sections, slope the sidewalk in those areas by dropping one side of the forms 1/4 in. for each foot of sidewalk width. A 4-ft. wide sidewalk should have one edge about 1 in. lower than the other in level areas to prevent ponding or ice accumulation during the winter.
For a long-lasting sidewalk, plan on a 4-in. base of gravel under 4 in. of concrete (Photo 7). If you live in a frost-free climate with a natural sand base with good drainage, you can pour right on top of the sand. But other soil types will expand and contract with weather conditions and can crack overlying concrete. Gravel protects concrete from these shifting conditions. Just about any gravel works well, but 3/4-in. crushed rock is easy to shovel and packs well so you can run heavy wheelbarrows on it without the wheels bogging down. Look for a supplier under “Sand and Gravel&rdquo in the Yellow Pages. Gravel is ordered by weight, not volume like concrete. Divide the gravel volume by 1.4 to calculate the tonnage to order (see “Order the Right Concrete Mix” for help).
Steel mesh and expansion strip prevent heaving, cracking and buckling
Mesh comes in 5-ft. wide, 25- or 50-ft. long rolls. Some lumberyards also carry 5 x 8-ft. flat sheets of mesh that are easier to handle but cost more per square foot. If a roll is a little too short for the job, finish up the rest with these sheets rather than buying a second roll.
CAUTION: DON'T LOSE AN EYE! Mesh is wound like a spring. After you cut a length, it can leap back at you with steel fangs. Wear safety glasses and make sure you and your partner understand that neither of you steps off an end without warning the other.
Expansion strips are asphalt-impregnated fiber strips that compress when concrete expands to prevent heaving, cracking and buckling. Pick up 4-ft. expansion strips (Photo 17) for each 30 ft. of sidewalk and for ends where the sidewalk abuts other unyielding masonry surfaces such as driveways, other sidewalks, house foundations and steps.
Order the Right Concrete Mix
Order the concrete a few days ahead. If rain threatens, you can usually cancel up to two hours before delivery. Although dispatchers are quite helpful, you should at least know the basics before you call:
- Calculate the right volume. Concrete is always ordered in cubic yards. First figure out the cubic footage, then convert to yards by dividing by 27. Here's how: Multiply the length of your sidewalk times the width times the depth (4 in. = . 33 ft.) and divide the total by 27. Using our sidewalk as an example: 60 ft. (long) x 4 ft. (wide) x .33 ft. (deep) = 79.2 cu. ft. ÷ 27 = 2.93 cu. yds. Concrete is cheap and nothing's worse than coming up short (except rain). A good rule of thumb is to order an extra 5 percent rounded up to the next 1/4 yd. to handle spillage and uneven bases.
- Order from the nearest supplier. Get fresh concrete mixed near the site, not mixed across town by some company with a lower price.
- Ask for 5 percent “air entrainment” in the mix. Suppliers add a chemical that traps microscopic air bubbles to help the concrete handle the expansion and shrinkage caused by climatic changes such as freezing.
- Get the right strength. Tell them you're pouring an exterior sidewalk and they'll recommend the correct “bag mix” (ratio of cement to gravel and sand). In cold climates, they'll probably suggest at least a 3,000-lb. mix. That means concrete that'll handle a 3,000-lb. load per square inch without failing.
- Have your checkbook ready. You'll have to pay on delivery after the concrete's unloaded.
The truck comes with the concrete premixed with the correct water content. But the driver may send a little concrete down the chute and ask if you'd like more water added. Unless the mix is too dry to get down the chute, forget it. The mix should be thick—not runny. Wetter mud may be easier to place (fill the forms), but the wetter the mix, the weaker the concrete.
Video: How to Pour a Concrete Slab
Step 4: Pour the concrete
Photo 10: Pour the concrete
Hold the mesh 2 in. above the gravel with small globs of concrete while pouring the sidewalk. Pour a few feet of concrete, heaping it slightly higher than the forms. Don't shovel concrete; pull it back or push it forward with a steel rake.
Photo 11: Level and flatten with a screed board
Level concrete as you pour with a screed board (a straight 2×4 about 1 ft. longer than the width of the sidewalk). Rest the screed board on the forms and use a sawing motion while pulling the board toward the end of the pour. Fill lower areas with fresh concrete and repeat screeding over the same area.
Photo 12: Flatten the surface with a bull float
Draw a bull float over the fresh concrete immediately after screeding to force down aggregate and raise cream (gravel-free concrete) near the surface for finishing. Work in the opposite direction of screeding and push the bull float away from you, slightly lifting the leading edge, then pull it back while lifting the back edge.
Watch the weather channel; dry, cool weather is the best for pouring
The quickest route to disaster is an unexpected rainstorm, either in the middle of your pour or during the finishing process. If there's a chance of rain on the pour day, cancel the order and set it up for a different day. During normal summer weather (60 to 80 degrees F), you'll need three to five hours to pour and finish. Don't order concrete for delivery too late in the day or you'll be finishing in the dark. To ensure a strong sidewalk, avoid very hot days and days that are followed by freezing nights.
Have three helpers ready to haul and level the concrete
Dump the concrete into the forms. Then screed (level the concrete even with the top of the forms; see Photo 11) every few feet of pouring. With three people, have one person screeding and directing wheelbarrow dumps while the other two haul concrete to keep the project moving along. The person who's screeding can usually also go back and do large sections of bull floating (Photo 12) over freshly screeded areas.
Tip: For smooth sides, tap the sides of the form every couple of feet with a hammer to work out air bubbles. Wear safety glasses; concrete will splash.
Use the bull float right after screeding (Photo 12) if there's no bleed water present. Bleed water is water that migrates to the surface from the fresh concrete in small pools. Look carefully; bleed water can be hard to spot. Don't work concrete with bleed water present; wait until it reabsorbs or evaporates. It'll seriously weaken the surface, which may flake off later. Wait until it disappears before using the bull float or hand float.
Working with Concrete Safely
Concrete is a fabulous, inexpensive paving material. But as any emergency room doctor can attest, its benign appearance belies a caustic, highly alkaline nature. Wet concrete on skin can cause everything from mild redness to third-degree, permanently disfiguring chemical burns. A few drops of concrete isn't dangerous, but avoid practices like working in concrete-sodden clothes, concrete-filled boots or gloves wet with concrete juice. It'll keep you out of the hospital waiting for skin grafts. Take these steps to protect you and your helpers.
- Wear eye protection. Sandy concrete splashes can wreak havoc with your eyes.
- Wear long pants and long sleeves to protect your skin. (We didn't only because it was very warm and humid. But we did rinse off any skin that got splashed.)
- Wear tall rubber boots if you have to wade in wet concrete.
- Wear gloves (rubber gloves are the safest bet).
- If your clothes get saturated with wet cement, remove them, thoroughly rinse your skin and change into clean clothes before going back to work.
Step 5: Finish the concrete
Photo 13: Smooth with a mag float
Wait until any bleed water disappears and hand float the surface with a magnesium float, starting at the beginning of the pour. Use sweeping motions, lifting the leading edge of the float slightly.
Photo 14: Round over edges
Round over the outside corners with an edging tool. Use a back-and-forth motion in a 1- to 2-ft. area, lifting the leading edge on each pass and working your way down the sidewalk edge.
Photo 15: Cut control joints
Cut in control joints every 5 to 6 ft. with a groover. Plan your cuts by measuring the length of the pour and evenly dividing it so all the segments are about the same length. During the first pass, use a straight board held perpendicular to the forms for guiding the groover.
Photo 16: Texture the surface
Gently rest the broom on the far side of the sidewalk and slowly pull it toward you and off the edge of the form. Work your way down to the end of the sidewalk, overlapping previous sweeps about 6 in. If clumps of concrete start gathering or you feel the texture is too rough, the concrete is still too wet to broom. Go over broomed areas with the mag float to smooth out marks, and try again in 15 minutes.
Photo 17: Add an expansion strip
Pull off the temporary bulkhead after brooming and lay in expansion strips before continuing the next section if you're pouring two separate segments. Keep the top of the strip even with the bottom of the rounded edge of the concrete. If you're doing the sidewalk in one pour, slip the expansion strip into the wet concrete every 30 ft. and use the edger to round concrete edges.
Photo 18: Mottling eventually disappears
The grayish-blue mottling on this concrete surface is caused by the plastic contacting the concrete unevenly, especially in direct sunlight. The mottling disappears eventually.
Here's what you need to know to shape and smooth fresh concrete
Start hand tooling (floating, edging and grooving) when you can't push your thumb into the surface more than 1/4 in. The series of step-by-step photos may give the impression that each tool is used only once for a specific task. While that's true of the bull float and broom (Photo 16), you'll need to switch between the hand tools throughout the finishing process as the concrete firms up. Use the mag (magnesium hand float; see Photo 13) to resmooth areas and to work out holes as they appear. You'll also use it to soften transitions between edges, corners and control joints after they're cut in, and to smooth ridges you produce with the groover and edger (‘Two Heavy Wheelbarrows Can Save the Day,’ p. 108). The first time is easy; light pressure will even out the surface. As the mud continues to set up, you'll have to work harder and harder to smooth out imperfections. Toward the end, you'll have to put both hands on the mag's handle and scrub to smooth problem areas.
Make the first pass with the edger and groover when the concrete is just beginning to firm up to form the rough shape. Use them to push the aggregate (gravel in the concrete mix) away from the rounded edges (Photo 14). The next pass gives a more finished shape as the concrete begins to harden. One last time polishes the final shape and smoothes out inconsistencies. Always work the concrete from where you poured first. Avoid overworking the concrete. Your goal is to create a flat, ridge-free surface for the broom finish. If you tool the surface too much, you'll weaken it.
Tip: If the concrete “gets away from you” (sets up faster than you can finish it), just concentrate on getting the hand floating, edging and brooming done and forget the control joints for now. You can always rent a diamond masonry saw and cut in the 1-in. deep control joints another day. Focus first on getting a good-looking surface.
If you can't pour it all at once, separate the pours with bulkheads
To make sure we had enough time to work the concrete, we had half the load of concrete delivered in the morning for the first 30 ft., and the other half in the afternoon. That way, we knew exactly how much to order for the second load. After the truck emptied, we installed a temporary bulkhead (Photo 17) while we finished the first half. With two helpers, don't be afraid to pour 30 ft. of sidewalk a day. After that, you'll know exactly what you can handle. A bulkhead is also a way to end a pour if you come up short on the order. You can throw in a bulkhead and order the rest later.
Tip: If you need a little stoop or pad somewhere out in the yard, having it formed up ahead of time gives you a place to put excess concrete to good use!
After finishing, cover the sidewalk with 4-mil plastic to get maximum strength
Although you can walk on concrete the day after finishing, it takes about a month for it to reach most of its full strength. Concrete needs water to cure (harden) properly. In order to have a strong sidewalk that won't scale, spall or crack, cover the sidewalk with plastic sheeting after brooming. (Cover the concrete once your fingertip no longer leaves an impression.) Anchor the sides of the plastic with boards, bricks or stones to keep it from blowing off. Leave the plastic on for a day, then keep the concrete wet for a few days by occasionally running a sprinkler or soaker hose to slow down the curing process. After removing the plastic, you may see grayish-blue mottling on the concrete surface (Photo 18) where the plastic contacted the concrete unevenly. These marks will eventually fade (ours took two months to disappear) and cause no lasting damage. To prevent them, pour on a cool, overcast day or plan your pour so it's finished late in the day. That way, the plastic won't have any direct sunlight baking the surface under it.
Resist the temptation to remove the forms; wait until the next day
The day after you pour, pull the forms by jamming the tip of a shovel into the stakes and prying against the ground to lift the whole works out of the ground. You'll crack sidewalk corners or edges if you pull the forms the same day as pouring.
Required Tools for this Project
Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.
- Circular saw
- Drill/driver - cordless
- Garden rake
- Utility knife
- Wheelbarrows (2 minimum)
Push broom, stiff bristled,
Required Materials for this Project
Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.
- 1 2-in.wide Wood stakes
- 1/1/4-in. screws
- Concrete mesh
- Expansion strip
- Hardboard siding
- Plastic sheeting
- Spray paint