Deck Building Cheat Sheet
Span tables, footing and code rules for a safe DIY deck, sized to your dimensions.
Doing this on a real job? Build a deck: materials, tools and steps sized to your numbers.
Get the planCode basis: IRC 2021 R507 Check your local amendments. Last reviewed October 2026.
Your deck at a glance
- Joists
- 13 x 2x10
- at 16 in on center
- Beam
- 2 x 2x12
- 3 posts about 8'0" apart
- Posts and footings
- 4x4, 18 in dia
- 36 in deep, 21 bags of 80 lb concrete
- Ledger fasteners
- 1/2 in lags every 15 in or bolts every 29 in
- Guard
- Required: 36 in min, 4 in sphere
- Stairs
- 5 risers at 7.2 in, handrail required
Your 16 x 12 ft deck: 13 joists, 3 footings at 36 in. Save this deck plan to Blueprint for the materials list with quantities, a weekend-by-weekend schedule and the inspection checklist to tick off at the lumber yard and on inspection day. Full material pricing is in the deck calculator.
Build a 16' x 12' deck
A 192 sq ft attached deck with joists at 16" on center, 3 posts on concrete footings and a flashed ledger. Sized from your 16 by 12 ft footprint.
- Materials
- $2,189
- Time
- 2-3 weekends
- Level
- Advanced
- 1
Permit, 811 and layout
Attached decks need a permit almost everywhere. Call 811 before digging, then stake out the 16 x 12 ft footprint and square it with matching diagonals.
- Pull the permit and note the inspections
- Call 811 and wait for marks
- Stake and string the outline
- 2
Install the ledger
Remove siding where the ledger lands, flash behind and over it, and fasten it to the rim joist with 1/2" lag screws staggered every 15" (or through-bolts every 29") for a 12 ft joist span (IRC R507.9.1.3). Never nail a ledger.
- Flash before mounting
- Ledger 1" below door threshold plus decking
- Fasteners every 15" staggered
- 3
Dig and pour footings
Dig 3 footings at least 36" deep below your frost line, set tubes, and pour. Most inspectors check holes before the pour.
- Holes below frost depth
- Footing inspection if required
- Set post bases in wet concrete
- Deck area
- 192 sq ft
- Joists
- 13 at 16" o.c.
- Footings
- 3
- Est. cost
- $2,189
8 steps · 9 tools · 8 materials
5 more steps, the full tool list and a shopping list you can check off as you go.
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Deck joist span chart (Southern pine)
| Joist | 12" O.C. | 16" O.C. | 24" O.C. |
|---|---|---|---|
| 2x6 | 9'11" | 9'0" | 7'7" |
| 2x8 | 13'1" | 11'10" | 9'8" |
| 2x10 | 16'2" | 14'0" | 11'5" |
| 2x12 | 18'0" | 16'6" | 13'6" |
IRC 2021 Table R507.6: No. 2 grade, wet service, 40 psf live and 10 psf dead load. Cantilever up to 1/4 of the joist span. Change the species in the tool above. Highlighted: your joist.
Deck beam span table (max distance between posts)
| Beam | 6 ft joists | 8 ft joists | 10 ft joists | 12 ft joists | 14 ft joists |
|---|---|---|---|---|---|
| 2 x 2x6 | 6'10" | 5'11" | 5'4" | 4'10" | 4'6" |
| 2 x 2x8 | 8'8" | 7'6" | 6'9" | 6'2" | 5'9" |
| 2 x 2x10 | 10'4" | 9'0" | 8'0" | 7'4" | 6'9" |
| 2 x 2x12 | 12'2" | 10'7" | 9'5" | 8'7" | 8'0" |
| 3 x 2x6 | 8'2" | 7'5" | 6'8" | 6'1" | 5'8" |
| 3 x 2x8 | 10'10" | 9'6" | 8'6" | 7'9" | 7'2" |
| 3 x 2x10 | 13'0" | 11'3" | 10'0" | 9'2" | 8'6" |
| 3 x 2x12 | 15'3" | 13'3" | 11'10" | 10'9" | 10'0" |
IRC 2021 Table R507.5, southern pine. Longer joist spans and snow loads over 40 psf: the deck beam span calculator.
- 4x4: up to about 6 ft 9 in to 8 ft tall depending on species and the area it carries (IRC R507.4).
- 6x6: up to 14 ft tall, and the minimum wherever a beam is notched onto the post.
- Spacing: set by the beam table above, usually 6 to 8 ft; posts at the beam ends and every support point.
- Connections: a post cap or a notch with two 1/2 in through-bolts; never toe-nail a beam to a post.
Deck footing size and depth
| Area one post carries | Load (50 psf) | Round dia, 1,500 psf soil | Round dia, 2,000 psf soil |
|---|---|---|---|
| 20 sq ft | 1,000 lb | 12 in | 12 in |
| 40 sq ft | 2,000 lb | 16 in | 14 in |
| 60 sq ft | 3,000 lb | 20 in | 18 in |
| 80 sq ft | 4,000 lb | 24 in | 20 in |
| 100 sq ft | 5,000 lb | 26 in | 22 in |
Bottoms at least 12 in into undisturbed soil and below the frost line (about 12 to 18 in in the South, 42 to 48 in in northern states). Set post bases above the concrete; never bury wood posts in it. Size your exact footings with the deck footing size calculator and the concrete footing calculator.
Ledger fastening and lateral load
| Joist span | 1/2 in lag screws | 1/2 in through-bolts |
|---|---|---|
| Up to 6 ft | 30 in O.C. | 36 in O.C. |
| 6 to 8 ft | 23 in O.C. | 36 in O.C. |
| 8 to 10 ft | 18 in O.C. | 34 in O.C. |
| 10 to 12 ft | 15 in O.C. | 29 in O.C. |
| 12 to 14 ft | 13 in O.C. | 24 in O.C. |
| 14 to 16 ft | 11 in O.C. | 21 in O.C. |
| 16 to 18 ft | 10 in O.C. | 19 in O.C. |
- Ledger at least 2x8, on a solid 2x rim joist, staggered top and bottom, 2 in from the edges (IRC R507.9.1.3).
- Never attach to brick veneer, siding alone or a cantilevered floor; build freestanding instead.
- Lateral load: two hold-down devices of 1,500 lb within 24 in of each end of the deck, or four of 750 lb (IRC R507.9.2).
- Hardware in ACQ or CA treated lumber: hot-dip galvanized G185 or stainless steel, matched with the same coating on every nail and screw.
- Use same size as joists (typically 2×8 or 2×10)
- Install 1" below interior floor level
- Remove siding and flash properly
- Attach with 1/2" lag bolts or structural screws
- Spacing: by joist span, from the table above (lags 10 to 30 in O.C.)
- Use washers with all fasteners
- Install flashing to prevent water intrusion
- Never attach to brick veneer or siding only
Spacing
- Pressure treated: 1/8" gap (will shrink)
- Composite/PVC: Follow manufacturer specs
- Cedar/Redwood: 1/16-1/8" gap
- Use spacer for consistent gaps
Fastening
- Two fasteners per board at each joist
- 3/4" from edge minimum
- Stainless or coated deck screws
- Hidden fasteners for composite
- Pre-drill hardwoods to prevent splitting
Height: 36" minimum (measured from deck surface)
Post Spacing: 6 feet typical (manufacturer listing and common practice, not a code number)
Baluster Spacing: 4" maximum gap (sphere test)
Top Rail: 200 lb concentrated load at the top in any direction (code)
Required When: Deck is more than 30" above grade
Graspable Handrail: Required for stairs
Always verify with local building codes - requirements vary by jurisdiction
Riser Height: 7-3/4" maximum, 4" minimum
Tread Depth: 10" minimum (11" recommended)
Stringer Spacing: 16" O.C. maximum
Stair Width: 36" minimum
Landings: Required every 151" (12' 7") of vertical rise (IRC R311.7.3)
Handrails: Required if more than 3 risers
Uniformity: All risers must be within 3/8" of each other
Deck stair calculator
- Risers
- 5 at 7.2 in
- Treads
- 4 at 10 in
- Total run
- 40 in
- Stringer length
- 53.81 in (cut from a 2x12 x 8 ft)
- Handrail
- Required: 4 or more risers, 34 to 38 in above the nosings
Max riser 7-3/4 in, min tread 10 in, risers within 3/8 in of each other. Notches and stringer layout: the stair stringer calculator.
Deck details inspectors check
Pressure Treated
Economical, durable, requires maintenance, use .40 retention for ground contact
Cedar/Redwood
Natural beauty, rot-resistant, requires sealing, more expensive
Composite
Low maintenance, won't rot, higher initial cost, can fade
PVC
No maintenance, won't fade, most expensive, can get hot
Additional Information
This comprehensive deck building cheat sheet provides essential reference information for planning and constructing a residential deck. From joist spans and beam sizes to railing code requirements and stair specifications, this guide covers the structural and safety requirements for a deck that's safe, code-compliant, and built to last.
Building a deck is one of the most popular DIY projects, but it's also one where mistakes can have serious consequences. Undersized joists, improperly attached ledger boards, or inadequate footings can lead to structural failure - and deck collapses cause serious injuries every year. This reference provides the specifications and code requirements you need to build a safe deck.
Deck construction requires permits and inspections in most areas because it's structural work that must meet specific safety standards. This guide helps you understand these requirements so you can plan your project properly, communicate effectively with building inspectors, and build a deck that adds value to your home while providing years of safe enjoyment.
Having quick access to deck building specifications helps ensure your project is structurally sound, meets code requirements, and will pass inspection. This guide prevents costly mistakes and safety hazards.
- Size joists and beams correctly for your deck dimensions and loads
- Determine proper post sizes, spacing, and footing requirements
- Install ledger boards safely with proper flashing and fastening
- Meet railing height, baluster spacing, and strength requirements
- Build code-compliant stairs with proper rise, run, and handrails
- Select decking materials appropriate for your budget and maintenance preferences
How far can a 2x8 deck joist span?
How deep do deck footings need to be?
Do I need a permit for a deck?
When does a deck need a railing?
Can I attach a deck ledger to brick?
What spacing for composite decking?
How many footings for a 12x16 deck?
Freestanding or attached deck?
Next: price it in the deck calculator, keep it up with the deck refinishing guide, and fence the yard with the fence building cheat sheet.
Pouring footings or a pad? Cure times, mix ratios and bags per yard are on the concrete cheat sheet.
Permit check
Usually needs a permit
Attached decks and most decks over 30 inches off grade need a permit.
Inspections: Footings, then Framing, then Final
Job checklist
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