Concrete
Outdoor & decks

Concrete slab or footings

PRO STEP
Bags or ready-mix yards, gravel base, rebar or mesh and forms for a slab, a pad or footings.
Sheet A-1 · Concrete

20′ × 12′ slab, 4″ thick

PRO STEP
Concrete
2.96
cu yd at 4″
Order
3.5
cu yd (+10%)
Slab
240
sq ft
Panels
6
joints every 6′ 8″
34–53 h of work
Prep over a weekend, pour in a morning with a crew, then a week before light use.
Draft
The rules behind this Sheet are waiting for a licensed pro’s sign-off.
Outdoor concrete in freezing winters
Where winters freeze, porches, steps and garage floors take 3500 psi air-entrained concrete, 5–7% air (IRC Table R402.2); order the same for driveways and patios. Bagged mixes usually aren’t air-entrained: seal them and keep de-icing salt off the first winter.
Pour day is a crew job
A truck brings 3.5 cu yd at once, and in warm weather you have an hour or two to place and finish it. Plan at least 3 people for the first yard and one more for each one after, or hire a finisher for pour day.
Call 811 first — it’s the law
Call 811 a few business days before digging (your state sets the wait). Free. Wait for the utility markings.
Usually no permit
Most places follow the IRC, which exempts sidewalks and driveways from a building permit (R105.2); a patio on the ground is treated the same almost everywhere. Zoning can still limit how much of the lot is paved, and setbacks apply.

Drawing

Plan + section
1
Control joint 1″ deep, ¼ of the slab, so it cracks along the line.
2
Isolation joint ½″ strip where it meets the house: they move apart freely.
3
Forms On edge, staked every 3 ft, tops at the finished height.
4
Slope ⅛–¼″ per foot away from the house.
5
Slab 4″ of concrete, mesh at mid-depth on chairs.
6
Base 4″ of crushed stone, compacted in layers.
Joints at the spacing this Sheet counts. The section is to its own scale.

What to buy

11 items
Save to your jobs to check things off in the store.
Lumber
Forms
2×4 × 10′
2 boards
Framing lumber, actually 1½″ × 3½″.
Forms
2×4 × 12′
2 boards
Framing lumber, actually 1½″ × 3½″.
Fasteners
Duplex (double-head) nails 16d
1 box
The second head stays proud so forms come apart easily.
Concrete & landscape
Concrete
Ready-mix concrete (delivered) · 4000 psi, 5–7% air
3.5 cu yd
Ordered by the cubic yard (by the cubic metre in Canada) from a local plant; the truck chutes it into the forms.
Base
Crushed stone base, bulk · ¾″ minus, with fines
4 cu yd delivered
Crushed stone with fines (¾″ minus), delivered in bulk from a landscape or stone yard. Compacts into a firm base.
Welded wire mesh, 5×10 ft sheet
6×6 W1.4×W1.4, 5×10 ft
6 sheets
6×6 W1.4×W1.4 (10-gauge) mesh: holds cracks tight in patios, walks and shed floors. Set it on chairs so it ends up inside the slab.
Rebar chairs or dobies
2″ chairs
28 chairs
Plastic chairs or small concrete blocks that hold mesh or rebar at the right height while you pour.
Rebar tie wire
16-gauge roll
1 roll
16-gauge annealed wire that ties bars where they cross and laps together.
Forms
Wood stakes · 18″
18 stakes
Hold form boards in place.
Expansion joint filler, 10 ft strips
½″ × 4″ strips
2 strips
½″ asphalt-impregnated fiber strip that separates a new slab from the house, steps and old walks so they can move apart.
Concrete cure-and-seal compound
1 gallon
Sprayed or rolled on right after finishing; it holds the water in so the concrete cures strong. About 200–300 sq ft per gallon.

Tools

You own 0 of 20 must-haves
Tap the ones you already own. That builds your Tool Shed as you go — no setup.

Must have

The job stalls without it.

Rent it

Costly to buy for one job. Rent it for a day.

Nice to have

Faster or cleaner, not required.

Order of work

34–53 h of work
01
Call 811 a few business days ahead and wait for the utility markings.
02
Lay out the slab with stakes and a string line, 20′ × 12′, and square it by measuring the diagonals. Plan the slope: ⅛–¼″ per foot away from the house.
Check first
Measure both diagonals: when they match, the corners are square.
03
Dig out 8″ (4″ of concrete on 4″ of gravel), plus 6″ past the edges for the forms. Strip sod and soft soil down to firm ground and tamp the bottom.
Check first
Soft spots dug out and refilled with gravel, not loose dirt.
04
Set the forms on the open sides: 2×4s on edge, stakes every 3 ft on the outside, tops at the finished height with the slope built in. Nail through the stakes with duplex nails, and fasten the expansion strip against the house.
Check first
Form tops at the finished height with the slope built in, checked with a level along every side.
05
Spread the gravel in 2″ layers and compact each one; finish it flat, 4″ below the form tops.
Check first
Plate compactor on hand (rent it): compact every 2″ layer.
06
Lay the mesh 2″ in from the edges, sheets lapped one full square plus 2″ and tied; set it on 2″ chairs about every 3 ft.
07
Pour: have the crew, wheelbarrows, a concrete rake and the screed ready before the truck comes. Start at the far corner and fill to just above the forms.
Check first
Helpers, wheelbarrows and tools ready before the first batch — and no extra water.
08
Strike it off with the screed, sawing it along the form tops, then float it once. Wait for the bleed water to soak back in before the next pass.
09
Edge the slab and tool the control joints 6′ 8″ apart at most (6 panels), 1″ deep with the groover; then broom it across the slope for grip.
Check first
Control joints 1″ deep and at most 6′ 8″ apart: mark them on the forms before the pour.
10
Cure: spray the cure-and-seal as soon as the sheen is gone. Keep it from freezing for 48 hours.
Wait 24–48 h — walk on it and strip the forms after 1–2 days
Foot traffic after 24–48 hours. Cold weather slows it down: give it the long end below 50°F, and keep it from freezing.
Wait 7–10 days — light use after a week (cars on a driveway after 7–10 days)
Patio furniture and grills after about a week; cars after 7–10 days. Keep heavy trucks off for the full 28 days.
Wait 4 weeks — full strength at 28 days
Concrete reaches its design strength at about 28 days; penetrating sealers go on after that.
11
Strip the forms after 1–2 days and backfill along the edges.

Mistakes that ruin the job

4 mistakes
1
Adding water to make it pour easier
Extra water makes weak, dusty concrete that cracks and scales. Use the water the bag or the plant says; rent a mixer instead.
2
Finishing over bleed water
Troweling the water back into the surface makes it flake off after the first winter. Wait until the sheen is gone.
3
Joints too far apart, or too shallow
Concrete shrinks and cracks: cut joints ¼ of the depth and about 8′ apart at most, so you decide where.
4
Pouring on soft, muddy or frozen ground
The slab settles and cracks where the ground gives. Firm, compacted base; never pour on frost.

Plan it

The load

To haul
120 lb
from the store to the room
Helpers
2
for some steps
Heaviest
Welded wire mesh, 5×10 ft sheet · 6 sheets · 63 lb
2×4 · 4 pcs · 50 lb
Bring a helper: pour day is a crew job
Plan at least 3 people for the first yard and one more for each one after, or hire a finisher for pour day.
Rent: Plate compactor

When you’ll finish

Pick when you can start and how many hours you have.
Hours you can work
Each weekday evening
0
h
Each weekend day
8
h
Saved for every Sheet. Waits run overnight and on days off; work only fills the hours you have.

DIY vs hiring it out

Estimate
Typical US store prices and labor rates, not a quote. A real price can differ a lot.

Do it yourself

Materials
$910–$1,250
Tools to buy
20 must-haves you don’t own
Rebar cutter-bender, Pump sprayer, Tape measure (25 ft), Mason's line + stakes, …
Rentals
1
About $40–$90 a day each
Your time
34–53 h
Total
$910–$1,250 + tools

Hire a pro

Materials + 15%
$1,050–$1,400
Pros mark up what they buy
Labor
19 h × $65–$95
$1,250–$1,800
Their time
19 hours
Permits
usually none
Total
$2,300–$3,200

Before you go

0 of 8 checked
The small stuff that causes a second trip to the store.

Rules used

6 rules · Draft
Every number on this Sheet comes from these rules. A licensed pro reviews each one before a Sheet is marked verified.

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Project
Concrete
Sheet
A-1
Date
Scale
Not to scale
DIY time
34–53 h
Rules
Draft — pending pro review
Other common sizes
10×10
10×20
20×20