Sonotube Sizes: Concrete Forming Tube Guide for GTA Footings & Posts
If you’re pouring deck footings, fence posts, lally columns, or a small porch, a concrete forming tube — what most people on a GTA job site call a “sonotube” — is the fastest way to get a clean, round footing in the ground. The two questions that trip people up are always the same: which diameter do I need, and how much concrete will it take to fill?
This guide covers the common tube sizes, what each one is normally used for, and the concrete volume per foot so you can order the right amount of mix the first time.
Common sonotube sizes and what they’re for
| Diameter | Typical use |
|---|---|
| 6” | Light fence posts, mailbox posts, small sign posts, deck stair landings. |
| 10” | Standard residential deck footings, pergola posts, smaller porch columns. |
| 12” | Heavier deck beams, two-storey decks, porch and carport columns. |
| 14” – 16” | Structural columns, heavy beam loads, engineered footings. |
| 18” – 24” | Large columns, commercial footings, sign bases, anything engineered for big point loads. |
The right size is driven by the load and your local building department — not by what looks about right. A single-storey deck and a deck carrying a hot tub are two very different footings. Always size to your permit drawings or your engineer’s spec.
How much concrete each tube holds
Concrete forming tubes are round, so the volume per foot is just the area of the circle times one foot of height. Here’s the math already done for the sizes we stock — in cubic feet per foot of depth, and in 80 lb bags of pre-mix (one 80 lb bag yields about 0.60 ft³).
| Diameter | Concrete per foot of depth | 80 lb bags per foot |
|---|---|---|
| 6” | 0.20 ft³ | about 1 bag per 3 ft |
| 10” | 0.55 ft³ | about 1 bag per foot |
| 12” | 0.79 ft³ | about 1.3 bags per foot |
| 14” | 1.07 ft³ | about 1.8 bags per foot |
| 16” | 1.40 ft³ | about 2.3 bags per foot |
| 18” | 1.77 ft³ | about 3 bags per foot |
| 24” | 3.14 ft³ | about 5.2 bags per foot |
Worked example: a 10” tube set 4 ft deep needs 0.55 × 4 = 2.2 ft³ of concrete — roughly four 80 lb bags per footing. Six of those footings on a deck is about 13 ft³, which is the point where ordering bulk mix instead of bags starts to make sense. For anything past a dozen footings, get a delivery quote and we’ll work out the volume with you.
Add about 10% for waste, over-dig, and the flared base if you belled the bottom of the hole. Running short mid-pour is the one mistake you can’t fix cleanly.
How deep do GTA footings go?
In the GTA, footings have to bear below the frost line so they don’t heave in winter — that’s about 4 ft (1.2 m) deep across most of the region. The exact depth required for your job is set by your local building department, so confirm before you dig. Cut the tube so it finishes a couple of inches above grade, brace it plumb, and backfill around it before you pour so it doesn’t shift.
A few field tips
- Keep them dry until you pour. Forming tubes are heavy paper. Store them off the ground and under cover — a soaked tube goes soft and loses its shape.
- Brace before you fill. A tube that isn’t braced plumb will lean the moment concrete hits it. Use 2×4 kickers off stakes.
- Pour in lifts and rod it. Fill in stages and rod or vibrate each lift so you don’t trap voids around your anchor bolts or post bases.
- Set your hardware while it’s wet. Drop in your post saddle, anchor bolt, or rebar cage as soon as the tube is full and screed flat.
- Strip the collar. Once it’s cured, the paper above grade peels off; the part below grade can stay.
Pair them with the right forming accessories
A footing pour is more than the tube. Most crews grab these at the same time:
- Rebar or a vertical bar to tie the footing to the column or beam above — see our rebar sizing guide for which size to use.
- Anchor bolts, post saddles, and J-bolts to land your hardware.
- Tie wire and chairs if you’re caging the footing.
All of it lives in our Forming & Accessories category alongside the tubes.
Buy sonotubes in Mississauga & Brampton
2AZ Group stocks 6”, 10”, 12”, 14”, 16”, 18” and 24” concrete forming tubes in 12 ft lengths at our Mississauga and Brampton yards. Contractor volume pricing, same or next-day GTA delivery — Mississauga, Brampton, Toronto, Vaughan, Oakville and across the Greater Toronto Area.
Browse forming tubes & accessories → Request a quote → Call: 647-926-2597 for current pricing.
Frequently asked questions
What sonotube size do I need for a deck footing?
Most GTA residential deck footings use a 10” or 12” forming tube, with the exact size set by the load and your local building department. Bigger beams, a second storey, or a hot tub usually push you to 12” or larger. Always confirm against your permit drawings.
How much concrete does a sonotube hold?
A 10” tube holds about 0.55 ft³ of concrete per foot of height (roughly one 80 lb bag per foot), a 12” holds about 0.79 ft³ per foot, and a 24” holds about 3.14 ft³ per foot. Multiply by your footing depth for the total, and add about 10% for waste.
How deep should a footing tube go in the GTA?
Footings must bear below the frost line, which is about 4 ft (1.2 m) deep across most of the GTA. Your local building department sets the required depth for your job, so confirm before you dig.
What sonotube sizes does 2AZ stock?
2AZ Group stocks 6”, 10”, 12”, 14”, 16”, 18” and 24” concrete forming tubes in 12 ft lengths at our Mississauga and Brampton yards, with same or next-day GTA delivery. Call 647-926-2597 for current pricing.