Wood, aluminum, steel, glass or cable railings for decks, balconies, porches and stairs: posts, panels, hardware and the height rules.
Answers
Sheet
Sheet A-1 · Railings
24′ wood railing
DIY OK
Guard
36″
code: 36″
Posts
5
6′ on center
Balusters
52
3-1/2″ gaps
Length
24′
of railing
14–21 h of work
Two weekends.
Draft
The rules behind this Sheet are waiting for a licensed pro’s sign-off.
Guard: 36″ tall, openings under 4″
It’s 4′ down to the ground or floor, so this deck or porch needs a guard at least 36″ tall. No opening may let a 4″ ball through. The top must hold a 200 lb push at any point, the infill 50 lb on any square foot.
Permit: ask your town
Guards are part of a deck, porch or stair permit. Replacing a whole railing often needs a permit of its own — Christiansburg, VA asks for one to replace guardrails, New Prague, MN a re-deck permit for a new railing system — while small repairs usually don’t. Confirm with your building department.
Drawing
Elevation
1
4×4 post Two ½″ bolts through the rim, blocking behind.
2
2×6 cap Joints over a post.
3
Balusters 13 per opening, 3-1/2″ gaps.
4
Ball test A 4″ ball must not pass any opening.
5
Bottom rail No more than 3-1/2″ above the floor.
Guard 36″ tall, posts 6′ on center. The red circle is a 4″ ball: it must not fit through any opening.
What to buy
9 items
Save to your jobs to check things off in the store.
Lumber
Posts
Pressure-treated 4×4 post · 4×4 × 12′
2 lengths (5 posts)
Railing posts.
Rails
Pressure-treated 2×4 · treated 2×4 × 12′
4 boards
Treated against rot — for wood touching concrete or outdoors.
Cap
Pressure-treated 2×6 · treated 2×6 × 12′
2 boards
Treated against rot — for wood touching concrete or outdoors.
Balusters
Treated 2×2 balusters · 36″
52 balusters
Vertical guard pickets.
Blocking
Pressure-treated 2×10 · 2×10 × 8′ (or your joists’ size)
2 boards
Joists, beams and ledger, actually 1½″ × 9¼″.
Fasteners
Through-bolts ½″ for guard posts, with nuts and washers
½″ × 8″
10 sets
Through the post and the rim joist or stringer: two per post, washers on both sides. Hot-dip galvanized or stainless with treated wood.
Coated deck screws
2½″ coated
≈268 screws (3 boxes of 100)
Exterior-rated screws for treads and risers.
Hardware
Guard post hold-down (tension tie, about 1,800 lb)
5 ties
Ties the bottom of a guard post to blocking inside the frame. The deck guide’s detail uses one rated about 1,800 lb per post (such as a Simpson DTT2Z) with its own screws.
Paint
Exterior stain or sealer (deck and railing)
1 gallon
Semi-transparent or solid exterior stain. Rough treated wood drinks more than the can’s coverage.
Tools
You own 0 of 13 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.
Tape measure (25 ft)
The red boxes every 16″ on the blade are stud spacing.
Carpenter's pencil
Flat, doesn't roll away, marks rough lumber.
4-ft level
Plumb every post both ways
Cordless drill/driver
Drills holes, drives screws, mixes small batches.
Impact driver
Drives long framing and deck screws without stripping.
Miter saw
Square and angled cuts on rails, balusters and the cap
Speed square
Triangle square for marking square and angled cuts on lumber.
Sawhorses
Cutting support.
Auger bit set
½″ bit long enough to go through the post and the rim
Socket and ratchet set
Tightens the bolts, lags and anchors
Safety glasses
Every cut, every nail, every time.
Work gloves
Tack strip, block and lumber shred hands.
Hearing protection
Saws and nailers are loud enough to damage hearing.
Nice to have
Faster or cleaner, not required.
Post level
Shows plumb both ways at once while you fasten
Mason's line + stakes
Lines the posts up along the edge
Circular saw
Cuts posts to length
Clamps (2)
Hold rails level while you fasten them
Order of work
14–21 h of work
01
Check what the railing fastens to: the rim joist and the joists behind it must be solid, with no rot.
Check first
Probe the rim, joists or slab edge where each post goes: soft wood or cracked concrete there means repair first.
02
Mark the posts: each end and corner, then evenly between, 6′ on center (no more than 6′).
Check first
Posts at every end and corner, and no more than 6′ apart between them.
03
Add blocking behind each post, then bolt the posts: two ½″ through-bolts each plus a hold-down into the blocking. Plumb them both ways before the final tightening.
Check first
Blocking in place before the posts go on; 4×4s are never notched where they’re fastened.
04
Install the bottom rails (bottom edge no more than 3-1/2″ above the deck) and the top rails between the posts.
Check first
Bottom rail no higher than the Sheet says above the deck or the nosings.
05
Fasten the balusters with a spacer block cut to 3-1/2″: 13 per opening, so a 4″ ball can’t pass anywhere.
Check first
Spacer block cut to 3-1/2″ — every gap the same, and a test ball that doesn’t pass.
06
Screw the 2×6 cap on top of the posts and rails, joints centered on a post.
07
Stain or seal the wood once it’s dry (treated wood can take weeks — water should soak in, not bead).
Check first
Sprinkle test: water soaks in, not beads, before the finish goes on.
08
Test it: lean hard on every post and the top between posts — nothing should move — and try a 4″ ball in every opening.
Check first
Lean hard on every post and the middle of every top rail. Anything that moves gets fixed now, not after someone falls.
Mistakes that ruin the job
4 mistakes
1
Notching the posts
A notched 4×4 keeps half its wood right where the push is highest, and the IRC (R507.10.2) forbids notching a 4×4 guard post at the connection: bolt it whole to the rim.
2
Posts bolted to the rim alone
Without blocking or a hold-down, the rim twists and the post leans out under a push. Tie each post into the framing (R507.10.1).
3
Eyeballing the gaps
Gaps creep. Cut a spacer block to the gap and use it for every baluster: one opening a 4″ ball gets through fails the inspection.
4
A high bottom rail
More than 3-1/2″ under the bottom rail and a small child fits under it. Measure from the floor.
Plan it
The load
To haul
400 lb
from the store to the room
Helpers
0
a solo job
Heaviest
Treated 2×2 balusters · 52 pcs · 101 lb
Pressure-treated 4×4 post · 2 pcs · 84 lb
Pressure-treated 2×4 · 4 pcs · 72 lb
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.