How Many Screw Piles Does a Deck Need?

The honest answer is that pile count comes out of the beam and joist design, not the deck’s square footage. But people asking this question want a number to plan around, so here are realistic ones — followed by what moves them.

Typical counts

Deck size	Typical piles
8 × 8	3–4
10 × 10	4–6
12 × 16	6–8
16 × 20	8–12
Wrap-around or multi-level	12+

Treat these as a planning range, not a specification. A 16 × 20 deck can legitimately need eight piles or fourteen depending on the three factors below.

What actually determines the number

Beam span. This is the big one. Piles support beams; beams support joists. The stronger the beam, the further apart the piles can sit. A deeper built-up beam might let you space piles ten feet apart where a shallower one needs six. Fewer, larger piles or more, smaller ones can both be correct — they are just different designs.

Load. Live load, dead load, and anything unusual sitting on the deck. A hot tub is the classic example: a filled tub with people in it is a very concentrated load, and it usually needs its own dedicated piles regardless of what the rest of the deck is doing.

Soil capacity. A pile in dense till carries more than the same pile in soft clay. This is why the capacity is verified by torque during installation rather than assumed from a table.

Common things that change the count

• Attached vs freestanding. A deck ledgered to the house carries differently from one standing on its own, which usually needs an extra line of support.
• Stairs. Landings and stair stringers frequently need their own piles. People forget these when estimating.
• Cantilever. Joists can overhang the beam, which lets you pull the pile line in from the deck edge. Used well it reduces pile count.
• Hot tubs, outdoor kitchens, planters. Any concentrated load needs designing for specifically.

Do bigger piles mean fewer piles?

Often, yes. A larger shaft with more helices carries more, so you can space them further apart. Whether that is cheaper depends on the numbers — fewer expensive piles versus more cheap ones lands differently on different jobs.

This is worth asking about rather than assuming. We will price both where it is a genuine choice.

What we need to give you a real number

Send whatever you have:

• Deck dimensions and rough height above grade
• Attached to the house, or freestanding
• Anything heavy going on it
• Beam and joist sizes if you have a plan
• Your address, so we know what ground we are dealing with

That is enough for a pile count and a price, usually within 48 hours. If you have a drawing, even a sketch on paper, that is better than a description.

One thing worth knowing before you call anyone

If a contractor quotes a pile count without asking about beam span, load or location, they are guessing. It might be a good guess — plenty of decks are routine — but it is still a guess, and you should know that is what you are buying.

---

Send us your dimensions for a pile count and a firm price, or see what screw piles cost in Calgary.