Deck railing options: which one fits a Boise deck?

How do the main railing types compare?

Railing is priced by the linear foot, and the spread between the cheapest and most expensive systems is wider than for decking. The table compares the five common types on the points that matter in the Treasure Valley.

What does code require for deck railings in Idaho?

Idaho builds to the 2018 International Residential Code with state amendments, and Boise applies the 2018 IRC to residential permits. The guard rules in Chapter 3 are what every railing has to meet, whatever it is made of.

• Guards are required on open sides of walking surfaces more than 30 inches above the floor or grade below.
• Deck guards must be at least 36 inches tall; guards along the open side of stairs at least 34 inches, measured from the nosing line.
• Openings must not let a 4-inch sphere pass. The open side of stairs allows a 4-3/8-inch sphere, and the triangle formed by the tread, riser and bottom rail must block a 6-inch sphere.
• Stairs with four or more risers need a handrail between 34 and 38 inches above the nosing.
• Guards and handrails are designed for a 200-pound concentrated load at the top.

Do not confuse the guard rule with the permit rule. A deck can need a Boise or Nampa permit at 13 inches high, since both cities draw the permit line at 12 inches, yet need no guard until it passes 30. Permit details are on the Boise deck permit page.

When aluminum or cable makes sense

Choose metal when you want low maintenance and an open view. Aluminum is the practical middle of the market; cable costs more and opens the view further.

• Views of the Foothills, Table Rock or the river corridor, where thick balusters would block the outlook.
• Owners who do not want to paint or stain railing again.
• Decks in the wildfire overlay, where noncombustible railing removes one fuel source at the deck edge.
• Composite decks where composite railing would add bulk and cost.

Cable has two cautions. Cables stretch and need periodic re-tensioning, more so with large seasonal temperature swings, and they must stay tight enough to block the 4-inch sphere between posts. Some parents also dislike horizontal infill because children can climb it; the IRC does not prohibit it, but it is worth thinking about.

When wood or composite railing makes sense

Wood railing is the cheapest way to meet code and suits a wood deck you already refinish. Composite railing suits a composite deck where you want the rail to match the boards.

Know the trade-offs. Wood railing is vertical and exposed on every side, so it weathers faster than the deck boards and is usually the first part to need refinishing. Composite railing avoids that but has thicker profiles than aluminum and sits near the top of Fixr's price table. A common compromise is a wood or composite top cap over aluminum balusters.

Glass railing: views at a price

Glass gives the most open view and a wind break, at the highest price in Fixr's table. Panels are tempered safety glass held in metal posts or base shoes. In Boise, dust, pollen and sprinkler overspray show on glass quickly, so plan on regular cleaning, and expect drifting snow to pile against solid panels.

How do Boise's wind, snow and sun affect railings?

The connection to the deck matters more than the infill. Boise's design wind speed is 90 mph, and Star lists 115 mph. A person leaning on a rail puts a large bending force on the base of each post, so posts need through-bolts and blocking or tested post-mount hardware rather than a few screws into a rim joist.

• Sun: on a 90-degree afternoon a black aluminum top rail can be too hot to rest a hand on. Bronze, white or a wood or composite cap stays more comfortable.
• Snow and ice: Boise averages 17.6 inches of snow a year. Glass and solid panels collect drifts; open balusters let snow fall through.
• Freeze-thaw: water that sits in wood post tops and rail joints freezes and opens them. Post caps and sloped rail tops shed it.
• Wildfire: TimberTech suggests noncombustible railing such as aluminum alongside its WUI-compliant decking in wildfire-exposed areas. Confirm overlay requirements with Boise Fire; our Foothills wildfire decking guide covers the rest of the deck.
• HOA review: many architectural committees approve railing style and color along with the deck. The HOA approval guide covers what to submit.

What drives railing cost on a quote

Length is only the start. Stair rail sections, corners, gates and the way posts are mounted add labor quickly. Ask each bidder to list linear footage of level rail and stair rail separately, post spacing and mounting method, the infill type and any lighting in posts or caps.

Railing and stairs are their own service: see deck railings and stairs. For how railing fits a whole budget, the Boise deck cost guide has the component table, and the deck cost calculator lists railing as priced at the site visit.