Building a Deck: DIY Guide
A ground-level deck is a manageable DIY build with basic carpentry skills. An elevated deck is a bigger job, with real safety and permit stakes.
Conditional — Part DIY, Part Pro
Ground-level decks (typically 30 inches or less off grade) are DIY-friendly — simpler footings, often no railing required. Elevated decks need deeper footings, structural railing, and in most places a permit and inspection — doable for an experienced DIYer, but the stakes for getting footing depth or ledger attachment wrong are real structural failure, not just a cosmetic issue.
Skill Level
Intermediate
Time Required
3–7 days for a ground-level deck; 1–2+ weeks for an elevated deck with railing and stairs
Physical Demands
Heavy lifting (lumber, concrete for footings), kneeling, some ladder/height work for elevated decks
What this costs
| Tool rental | Post hole digger or auger $40–$80/day |
| Your time | 3–7 days for a ground-level deck; 1–2+ weeks for an elevated deck with railing and stairs |
What moves the number
- Frost depth — Fairfax County's 24-inch footings against Anne Arundel County's 30 inches is a quarter more excavation and concrete per hole, multiplied across every post.
- Ledger versus freestanding — A freestanding deck adds a row of posts, footings and bracing — but it is the only option on a veneered wall, and removes the highest-consequence connection.
- Species and span — Redwood and western cedar span less than Southern pine at the same size, so the prettier board can force closer joist spacing or a deeper joist.
- The 30-inch line — Crossing 30 inches adds guards, guard-post anchors and usually stairs — and converts an otherwise exempt deck into a permitted one with three inspections.
Run your own numbers with the cost calculator.
Before you start
A deck is the most structural thing most homeowners will ever build. Above the framing it is carpentry you can learn in an afternoon; below it, everything is load path — decking to joists, to a beam or ledger, to posts, to footings, to soil that will not move. One weak link fails the whole surface with people standing on it.
Three decisions set the difficulty. Does the deck touch the house? The American Wood Council's prescriptive deck guide prohibits ledger attachment to exterior veneers — brick, masonry, stone — to hollow masonry, and to cantilevered floor overhangs or bay windows, and requires a freestanding deck instead. How high is it? The same guide requires a guard above 30 inches, and the model permit exemption reproduced by Grant County, Washington from the 2021 IRC covers a deck only if it is 200 square feet or less, no more than 30 inches above grade at any point, not attached to a dwelling, and not serving the exit door required by Section R311.4 — all four at once. And where are you? Fairfax County, Virginia requires footings to bear 24 inches below grade; Anne Arundel County, Maryland requires 30 inches for an attached deck. Both follow the same rule — footings bear on undisturbed soil at least 12 inches below the undisturbed ground surface or below the frost line, whichever is deeper, with the frost line set by the authority having jurisdiction. Get yours from your building department before you dig.
Code and permits
A deck is regulated structural work almost everywhere in the United States. The model code exempts only a narrow case, and the numbers that matter most — frost depth, footing size, stair geometry — are set locally even where the section numbers are identical. Confirm all four exemption conditions rather than just the size, and get your frost depth and assumed soil bearing capacity from your building department before you dig.
International Residential Code 2021, as reproduced by Grant County, Washington § R105.2, Building item 10 — A deck is exempt from a permit only if it does not exceed 200 square feet, is not more than 30 inches above grade at any point, is not attached to a dwelling, and does not serve the exit door required by Section R311.4. Exemption from permit requirements does not authorise work performed in violation of the code.
AWC DCA 6 (2015 IRC edition), citing IRC R507 § Footings; Ledger Attachment Requirements; Prohibited Ledger Attachments — Footings shall bear on undisturbed soil at least 12 inches below the undisturbed ground surface or below the frost line, whichever is deeper, with the frost line determined by the authority having jurisdiction. Ledgers shall be minimum 2x8 nominal pressure-preservative-treated No. 2 lumber, and attachment to exterior veneers, hollow masonry, cantilevered overhangs or bay windows is prohibited.
The two counties cited here disagree on footing depth and stair geometry while working from the same model code. Your building department decides which edition applies, what your frost depth is, what soil bearing you may assume, and whether a prescriptive guide such as DCA 6 is accepted in place of stamped plans.
Permit requirements for this project vary by state and municipality. Select your state above for specific guidance, or check with your local building department before starting work.
Stop and call a pro if…
These are hard stops, not cautions. If you hit one, the job is finished for you until a licensed trade or your building department signs off on it.
Your house wall is brick, stone or masonry veneer, or the deck would land on a cantilevered overhang or bay window
A veneer is cladding, not a structural wall. Lag screws into it hold long enough to pass a shove and not long enough to hold a party.
Who to call
A licensed deck contractor or structural engineer to design a freestanding deck, or your building department to confirm the non-ledger detail it accepts.
AWC DCA 6 (2015 IRC edition), citing IRC R507 § Prohibited Ledger Attachments — Attachments to exterior veneers (brick, masonry, stone), to hollow masonry, and to cantilevered floor overhangs or bay windows are prohibited; a non-ledger deck is required in those cases.
You cannot verify what the house band joist is made of, or it is thinner than 1 inch
Everything the ledger carries lands in that band joist. If it is an undersized rim, a truss end or an unknown engineered product, no prescriptive fastener table applies to it.
Who to call
A structural engineer, or your building department for a plan review.
AWC DCA 6 (2015 IRC edition), citing IRC R507 § Ledger Attachment Requirements — Band joists supporting a ledger must be at least 2-inch nominal solid-sawn lumber or a minimum 1-inch engineered rim board. Where the band board is thinner or cannot be verified, a non-ledger deck or a full plan submission is required.
Any part of the build brings a person, ladder, board or auger within 10 feet of an overhead power line
Contact does not require touching a conductor by hand — a lifted 2x12 or an aluminium ladder closes the gap for you, and the outcome is not survivable.
Who to call
Your utility, to de-energise, shield or relocate the service drop before work starts.
International Residential Code 2021, as applied by Anne Arundel County, Maryland § Deck Construction Guide — site safety — No person or object may get closer than 10 feet to high-voltage power lines during deck construction.
Safety Warnings
- • Call 811 before any digging — every time, even for a small footing
- • Wear safety glasses and gloves when working with pressure-treated lumber and concrete
- • Never work alone when setting posts or handling large framing members
- • Keep every person, ladder, board and tool at least 10 feet from high-voltage power lines
- • Do not stand on unbraced framing — temporary bracing stays until the frame is fully connected and square
Choosing your materials
| Option | Best for | Trade-off |
|---|---|---|
| Pressure-treated Southern pine | The default, and the species the prescriptive span tables are written around. | It moves as it dries. The American Wood Council calls for decking spaced approximately 1/8 inch apart, and Fairfax County notes wet lumber laid tight opens to roughly that gap on its own. |
| Naturally durable cedar or redwood | Decking and guards where appearance matters and you will maintain a finish. | Structurally weaker. A Southern pine 2x8 at 16-inch spacing spans 11 feet 10 inches in the American Wood Council's table; redwood and the western cedars span 10 feet 7 inches. |
| Composite or PVC decking | Low-maintenance surfaces over treated framing. | The board sets the joist spacing, not the code table — Fairfax County notes plastic composite spans are per the manufacturer and requires an evaluation report from an accredited agency such as ICC-ES. |
| Freestanding (non-ledger) framing | Veneered walls, cantilevered overhangs and unknown band joists. | More posts, footings and bracing. It costs more and it is the safer build. |
Tools & Materials
Tools
- Post hole digger or augerRent — $40–$80/day
- Circular sawBuy
- Drill/driver with deck screw bitBuy
- Level (4 ft) + string lineBuy
- Speed squareBuy
- Post levelBuy
- Tape measureYou likely own
Materials
- Decking boards (UC3B treated, or composite with an evaluation report)
- 6x6 posts and 2x8 minimum ledger (UC4A); joists and beams (UC3B)
- Concrete for footings, sized from your jurisdiction's footing table
- Joist hangers and structural fasteners rated for treated lumber
- Ledger flashing — copper, stainless, UV-resistant plastic or G-185 galvanised steel
- Hold-down tension devices for the lateral load connection
- Guard components, guard-post hold-down anchors and 2x12 stair stringers
Step-by-Step
- 1
Check permit requirements and call 811 before digging
1–2 weeks of lead time
Call 811 (free utility locate service) at least a few days before digging any footings, and confirm your permit requirement using the state-specific guidance below.
Settle the permit question first — a deck attached to the house fails the exemption immediately, whatever its size. While the building department is on the phone, ask for your local frost depth and the soil bearing capacity you may assume. The American Wood Council's tables assume 1,500 psf and require a soils investigation where the building official believes the soil is weaker; Anne Arundel County sizes footings from IRC Table R507.3.1 assuming 2,000 psf. Those assumptions are the footing size. Then call 811 and wait the full locate period.
Check your workYou have a written frost depth from your own jurisdiction, a permit in or a documented exemption, and locate marks on the ground. Anne Arundel County's inspection sequence — footings, framing, final — then dictates your build schedule: footings before concrete, framing before decking covers the connections.
⚠ Skipping the 811 call risks hitting a buried gas, electric, or water line — a serious safety hazard, not just a fine.
- 2
Lay out and dig footings
1–2 days · Post hole digger or auger, Level (4 ft) + string line, Tape measure
Mark post locations with string lines, then dig to your frost-line depth (varies by climate — check local code) and pour concrete footings.
Footing width comes from load, not post size: both county guides size footings from the tributary area each post carries, and Fairfax County's range runs from a 12-inch square or 14-inch round up to a 26-inch square or 29-inch round. One trap catches people building close to the house — Fairfax County requires that where a deck footing's edge is closer than 5 feet to an exterior house foundation wall it must bear at the same elevation as the existing house footing. If a permit applies, the footing inspection happens before any concrete.
Check your workEvery hole reaches undisturbed soil at or below your local frost depth, and diagonals match within a quarter inch.
⚠ Anne Arundel County requires that no person or object gets closer than 10 feet to high-voltage power lines.
- 3
Set posts and attach the ledger board (if attached to the house)
1 day · Drill/driver with deck screw bit, Post level, Level (4 ft) + string line
The ledger board connects the deck to your house framing and carries significant structural load — use proper flashing to prevent water damage behind it.
Posts first: the American Wood Council requires deck posts to be 6x6 nominal or larger, centred on their footings. A 4x4 is a guard post, not a deck post.
The ledger is where decks fail. The specification is a minimum nominal 2x8 pressure-preservative-treated No. 2 board on a band joist of at least 2-inch nominal solid-sawn lumber or a minimum 1-inch engineered rim board. Fastener spacing is a table row: for a 2-inch nominal band joist, ½-inch lag screws run from 30 inches on centre at a 6-foot joist span down to 10 inches at 16 to 18 feet, staggered, hot-dipped galvanised or stainless, with no more than a ½-inch gap between ledger and sheathing.
Then flash it: the siding comes off before the ledger goes on, with continuous corrosion-resistant flashing over it — metal of at least 0.019-inch nominal thickness, never aluminium against treated lumber. Fairfax County accepts copper (copper nails only), stainless steel, UV-resistant plastic or G-185 galvanised steel.
Check your workFastener spacing matches the table row for your actual joist span, flashing is continuous with no reverse laps, and the ledger is dead level.
⚠ A poorly attached ledger board is the single most common cause of deck collapse. Use structural lag screws or through-bolts, never just nails.
- 4
Install the lateral load connection
2–4 hours
Hold-down tension devices tie the deck framing back into the house floor framing so the deck cannot pull away from the ledger.
Bolting the ledger to the band joist resists gravity, not the horizontal force of people moving on the deck. The American Wood Council requires hold-down tension devices in not less than two locations within two feet of the deck edge, each rated at not less than 1,500 lb allowable stress design capacity, with the wall sheathed in minimum 3/8-inch wood structural panel; Anne Arundel County describes a four-device alternative at not less than 750 pounds each. Nothing looks wrong without these, and they cannot be retrofitted once decking is down.
Check your workDevice count, capacity and distance from the deck edge match what your building department accepts, with fasteners landing in framing rather than sheathing alone.
- 5
Frame the joists
1–2 days · Circular saw, Speed square, Drill/driver with deck screw bit
Set joists at your decking material's required spacing (typically 16" on-center, tighter for some composite boards).
Joist size comes off a species-specific span table. In the American Wood Council's — 40 psf live load, 10 psf dead load, No. 2 grade, wet service — a Southern pine 2x8 spans 13 feet 1 inch at 12-inch spacing, 11 feet 10 inches at 16 inches and 9 feet 8 inches at 24 inches, and a 2x10 reaches 14 feet 0 inches at 16 inches. Hangers are rated hardware: Fairfax County requires hanger depth of at least 60 percent of the joist depth, fully filled with the fasteners it was tested with.
Check your workEvery joist size and spacing traces to a published span-table row for your species, and the frame is square before decking goes on.
- 6
Install decking boards
1 day · Circular saw, Drill/driver with deck screw bit
Leave manufacturer-specified gaps between boards for drainage and material expansion.
The American Wood Council requires 2-inch nominal dimension lumber or span-rated decking, fixed to each joist with two 8d threaded nails or two #8 screws, spaced approximately 1/8 inch apart, with each segment bearing on a minimum of three joists — which quietly outlaws the short off-cut spanning two joists at the end of a row. For composites the manufacturer's instructions govern.
Check your workNo board bears on fewer than three joists, gaps are consistent, and every board has two fasteners at every joist.
- 7
Build railing (if elevated) and stairs
1–2 days · Circular saw, Speed square, Drill/driver with deck screw bit
Railing height and baluster spacing are code-regulated (typically 36" height, balusters spaced so a 4" sphere can't pass through) — this isn't just an aesthetic choice.
Guards are triggered above 30 inches, which Fairfax County measures at a point 36 inches out from the deck edge. The City of Spearfish, on the unamended 2021 IRC, gives the model figures: guardrails 36 inches high, openings that will not pass a 4-inch sphere, 4⅜ inches on stair guards, maximum riser 7¾ inches (R311.7.5.1), minimum tread 10 inches (R311.7.5.2), minimum stair width 36 inches and handrail 34 to 38 inches. Fairfax County, on the 2021 Virginia Residential Code, permits an 8¼-inch riser and 9-inch tread — same model code, different enforced numbers, so get yours locally before cutting a stringer.
Guard posts must be minimum 4x4 nominal on minimum 2x8 joists or rim joists, with hold-down anchors rated at not less than 1,800 pounds for a 36-inch guard, and Fairfax County prohibits notching the post. Common to both: 2x12 stringers, a handrail on any stair with four or more risers, a landing not less than 36 inches in the direction of travel, and no more than 3/8 inch variation between risers or treads.
Check your workGuard height, opening size and post anchorage match your jurisdiction's figures, and risers and treads vary by no more than 3/8 inch across the flight.
⚠ Do not notch guard posts for a flush face — the notch removes exactly the section that resists the load.
Common mistakes
Digging footings to a depth taken from a national frost-line map
Why it happens
The map is easy to find and the building department is shut on Saturday.
The fix
Get the number from your own jurisdiction, as the American Wood Council's rule directs. A footing poured too shallow in a frost region will heave, and the repair is to dig alongside, pour a correct footing and re-support the post.
Bolting the ledger through brick veneer or a bay window overhang
Why it happens
The wall looks solid and the lag screws bite into something. From outside, nothing distinguishes a veneer from a structural wall.
The fix
Those attachments are prohibited outright and a non-ledger deck is required. If a ledger is already on a veneer wall, add posts, beams and footings so the deck carries itself — do not add more bolts.
Spacing ledger fasteners by eye at 16 inches because that felt like framing
Why it happens
16 inches on centre is the number every carpenter has in their hands, and a ledger looks like framing.
The fix
Read the row for your actual joist span — 30 inches at a 6-foot span, 10 inches at 16 to 18 feet. Adding staggered fasteners to the correct spacing is a legitimate repair, but do it before decking covers the ledger.
After the job: care and maintenance
After the first season, then annually
Inspect the ledger flashing line and the band joist behind it for staining or softness — it shows as a stain long before it shows as movement.
Annually
Lean hard on every guard post and re-tighten the through-bolts. An anchor is rated at 1,800 pounds when torqued; a loose bolt is not.
Annually
Clear debris from between the decking boards and off the joist tops at the ledger. The 1/8-inch gap only drains if it is open.
Every 2–3 years
Re-finish the decking. Treated wood resists decay, not UV — the use category says nothing about weathering.
FAQ
Do I need a permit to build a deck?
Usually. The model exemption reproduced by Grant County, Washington from the 2021 IRC applies only when a deck meets four conditions at once — 200 square feet or less, no more than 30 inches above grade at any point, not attached to a dwelling, and not serving the required exit door. A deck attached to the house fails immediately regardless of size, and the same section states that being exempt from a permit does not authorise building in violation of the code.
How deep do deck footings have to be?
There is no national answer, and this is the number people most often get wrong. The American Wood Council's rule is that footings bear on undisturbed soil at least 12 inches below the undisturbed ground surface or below the frost line, whichever is deeper, with the frost line set by your authority having jurisdiction. Two counties cited here show the spread: Fairfax County, Virginia requires 24 inches, Anne Arundel County, Maryland requires 30 inches for an attached deck, and cold-climate jurisdictions go considerably deeper.
How high does deck railing have to be?
Under the unamended 2021 IRC, as set out in the City of Spearfish's deck handout, a guard is required on any deck more than 30 inches above grade and must be 36 inches high, with openings that will not pass a 4-inch sphere — 4⅜ inches on stair guards. What people miss is the post connection: guard-post hold-down anchors need a minimum allowable tension load of 1,800 pounds for a 36-inch guard, and Fairfax County prohibits notching the post. A tall guard on a notched, under-anchored post is weaker than no guard, because people lean on it.
What is the lateral load connection?
The pair of hold-down tension devices that tie the deck framing back into the house floor framing so the deck cannot pull away from the ledger. The American Wood Council requires not fewer than two within two feet of each deck edge, each rated at not less than 1,500 lb allowable stress design capacity; Anne Arundel County describes a four-device arrangement at 750 pounds each. It is required, invisible once decking is on, and cannot be retrofitted without pulling boards.
Does all treated lumber do the same job?
No, and the difference is printed on the end tag. The American Wood Protection Association's use categories put posts, structural posts and ledgers in ground contact at Use Category 4A or higher, deck boards, joists and beams above ground at UC3B, and a sill plate at UC2. A board treated for above-ground use, buried or sitting on soil, is being used outside what it was treated to survive.
Sources
Every figure, clearance and code section on this page traces to one of these. Manufacturer instructions govern their own product and override anything general said here.
- American Wood Council. Prescriptive Residential Wood Deck Construction Guide (DCA 6), based on the 2015 International Residential Code — accessed September 3, 2026.Footing depth, post and ledger sizing, lag-screw spacing, prohibited ledger attachments, hold-downs, joist spans, decking.
- Fairfax County, Virginia — Land Development Services. Typical Deck Details, Version 2021.0 (2021 Virginia Residential Code) — accessed September 3, 2026.24-inch footings, the 5-foot foundation rule, flashing materials, 1,800 lb guard anchors, amended stair geometry.
- City of Spearfish, South Dakota — Building Department. 2021 IRC Residential Building Code: Residential Decks handout — accessed September 3, 2026.Unamended model figures: 36-inch guard height, the 4-inch sphere, 7¾-inch riser (R311.7.5.1) and 10-inch tread (R311.7.5.2).
- Anne Arundel County, Maryland — Inspections and Permits. Deck Construction Guide, 2021 International Residential Code — accessed September 3, 2026.30-inch footings, IRC Table R507.3.1 sizing, the 750 lb hold-down alternative, the 10-foot power-line rule.
- Grant County, Washington. 2021 International Residential Code (IRC) Section R105 Permits — work exempt from permit — accessed September 3, 2026.The four conditions a deck must meet at once to be permit-exempt.
- American Wood Protection Association. Select the Right Preserved Wood for Your Project — AWPA Preserved Wood Use Categories (2021) — accessed September 3, 2026.UC4A ground contact for posts and ledgers, UC3B above ground for decking, joists and beams, read off the end tag.
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