What's included
- Guard posts attached with blocking and tension hardware rather than lag screws into a single rim board. The American Wood Council's deck guide calls for hold-downs rated at 1,800 pounds for a 36-inch guard.
- Infill options to suit the view and budget: aluminum balusters, composite rail systems, stainless cable on view lots, or glass panels where wind and cleaning allow.
- Stairs at least 36 inches wide, with risers no taller than 7¾ inches and treads at least 10 inches deep, and no more than 3/8 inch of variation within a flight.
- Stringers sized and spaced for the tread material — composite treads typically need closer stringer spacing than 2x wood treads.
- A graspable handrail on any stair with four or more risers, set 34 to 38 inches above the tread nosings.
- Stair bases on a concrete pad or footing so the bottom of the stair doesn't move separately from the deck as the ground freezes and thaws. Boise's code tables put the city in the severe weathering category for concrete, so exposed pads are poured with that exposure in mind.
- Post-cap, riser and tread lighting for safe footing at night, wired with the framing so no cables run across the deck surface later.
Materials we use
| Category | Options |
|---|---|
| Railing systems | Powder-coated aluminum post-and-baluster · Composite railing kits (Trex, TimberTech, Fiberon) · Stainless cable infill · Tempered glass panels |
| Stair components | Pressure-treated 2x12 stringers · Composite or wood treads and risers · Concrete pad or footing at the stair base · Graspable round or shaped handrail profiles |
| Post attachment | Tension-tie hold-downs with solid blocking · Through-bolts into blocked rim joists · Surface-mount aluminum posts with structural anchors |
| Stair and rail lighting | Low-voltage post-cap lights · Riser lights on each step · Recessed tread or landing lights · Under-rail strip lighting along the top rail |
How the work goes
Measure and test
We measure the total rise from deck surface to the landing below, check the deck's height above grade along every open edge, and push on existing posts. Total rise sets the number of risers; height above grade sets where guards are required.
Lay out the stair
The rise is divided into equal risers no taller than 7¾ inches, treads are set at 10 inches or deeper, and we choose a straight run, a turn at a landing or a wider stair. The code caps a single flight at 151 inches of rise between landings.
Choose the railing system
Aluminum keeps sight lines open and needs little care; composite matches composite decking; cable suits view lots but needs stout end posts to hold tension. We confirm the system is tested for the guard height and post spacing we're using.
Build posts and stairs
Guard posts are blocked and bolted into the frame before decking goes down. Stringers are cut, hung from the rim with hardware, and supported at the bottom on a pad or footing rather than on loose pavers or soil.
Install and test
Infill, top rails and handrails go on, then we push on every post and rail and check each riser with a tape. Steps that vary get fixed before we leave, not noted for later.
Treasure Valley conditions we design for
- Permit needed above
- 12 in
- Frost depth
- 24 in
- Ground snow load
- 20 psf
- Design wind
- 90 mph
- Nights ≤ 32°F / yr
- 108
- Annual precip
- 11.51 in
Sources: City of Boise — Residential Construction brochure; City of Boise — current codes & design criteria; NOAA NCEI U.S. Climate Normals 1991–2020, Boise Air Terminal (USW00024131)
Red flags to watch for in any quote
- Guard posts notched and lagged to the outside rim with no blocking behind them. It's the most common way railings work loose.
- Balusters spaced "about 4 inches" apart. The rule is that a 4-inch sphere can't pass, so the clear gap has to be under 4 inches.
- Riser heights that change from step to step. The code allows no more than 3/8 inch between the tallest and shortest riser in a flight, because uneven steps trip people.
- Stairs set on loose pavers or bare soil. The bottom moves with frost, the whole stair racks, and the top connection to the deck takes the strain.
- Cable rail run between posts designed for balusters. Cable tension pulls the end posts inward; they need heavier posts and bracing.
- No handrail on a four-step stair because it "looks cleaner." The code requires one on any flight with four or more risers, and it is the part people reach for when the treads are icy.
Budgeting? Our railings & stairs cost guide breaks down published Treasure Valley price ranges.
Frequently asked questions
- How high does a deck railing need to be in Idaho?
- Idaho's residential code, based on the 2018 IRC, requires guards where a deck surface is more than 30 inches above the grade below, measured within 36 inches of the edge. Required guards must be at least 36 inches tall above the deck, or 34 inches along the open side of a stair. Some owners choose 42 inches on a high deck for comfort. Height is measured to the grade below, so on a sloped lot a deck can need guards on one side and not another.
- How far apart can deck balusters be?
- Close enough that a 4-inch sphere can't pass through anywhere from the deck to the required guard height, so clear gaps sit a little under 4 inches. The triangle under a stair guard, formed by the tread, riser and bottom rail, may pass up to a 6-inch sphere. Horizontal infill such as cable has to meet the same 4-inch rule, so cable runs need tight spacing and real tension. Our deck railing options guide compares infill styles.
- What are the code rules for deck stairs?
- Risers no taller than 7¾ inches, treads at least 10 inches deep, and no more than 3/8 inch of variation between the largest and smallest riser or tread in a flight. Stairs need to be at least 36 inches wide, and a handrail is required on any flight with four or more risers, mounted 34 to 38 inches above the nosings.
- Which deck railing is best for a view?
- For views toward the Foothills or open space, cable and glass block the least. Thin aluminum balusters come next and need the least upkeep. Cable needs rigid end posts to hold its tension and periodic re-tightening; glass needs regular cleaning, shows water spots from sprinklers, and adds wind load. On a Foothills lot, ask about the fire performance of the railing system as well as the decking.
- Can you replace just the railing on my deck?
- Yes, if the framing the posts attach to is sound. Railing replacement often uncovers the real problem: posts lagged to a single rim board that has started to rot. We open the attachment, add blocking and hardware, then install the new system. If the rim or joist ends are soft, that deck repair comes first, because a new rail is only as strong as what it's bolted to.
- How much do railings and stairs add to the cost of a deck?
- On a raised deck they're often a large share of the total, because railing is priced by the linear foot and stairs by the step, and both need hardware and footings. The Boise deck cost guide breaks out components, and the deck cost calculator lists railing and stairs as items priced at the site visit. A low deck with one short stair spends far less on these than a second-story deck does.
- Do deck stairs need a footing at the bottom?
- They need a stable base that won't move. The American Wood Council's deck guide shows long stringers supported on posts and small concrete footings, and a stair resting on soil or loose pavers shifts as the ground freezes and thaws. With 108 freezing nights in an average Boise year, a concrete pad or footing keeps the bottom tread where it belongs.
- Does a low deck need a railing?
- Not always. The code requires guards only where the walking surface is more than 30 inches above the grade within 36 inches of its edge, so many ground-level decks don't need one. Stairs are different: any flight with four or more risers needs a handrail no matter how low the deck is. Some owners add a railing anyway near steps, along a drop to a patio, or where small children play.
Sources
- Idaho Residential Code (2020 Edition, 2018 IRC basis) — Chapter 3: guards R312, stairs R311.7 (UpCodes)
- American Wood Council — DCA 6 Prescriptive Residential Wood Deck Construction Guide
- Idaho Residential Code (2020 Edition, 2018 IRC basis) — Chapter 5: decks R507 (UpCodes)
- Trex — Railing systems
- TimberTech — Railing systems
- City of Boise — Residential construction permit guide (deck, patio cover, pergola rules)
- NOAA NCEI U.S. Climate Normals 1991–2020, Boise Air Terminal (USW00024131) — annual/seasonal
Last reviewed .