Does each level of a multi-level deck need a guard?

Only where that level's surface is more than 30 inches above the floor or grade below within 36 inches of its edge. A low lower level may not need one, while the upper level and any stair over that height will. Guards must be at least 36 inches high on the deck and 34 inches on stairs, with openings that won't pass a 4-inch sphere.

Do I need an engineer for a multi-level deck in Boise?

Boise's #406 checklist requires stamped calculations for any deck more than 6 feet above grade and for designs outside the IRC's prescriptive rules. Lots in the Hillside overlay need engineered footings. A modest two-level deck on a gentle slope, with each level under 6 feet, can often be built from the IRC tables without an engineer.

How many steps should there be between deck levels?

Enough to divide the height into equal risers of no more than 7-3/4 inches, with treads at least 10 inches deep. A single step between levels can be a tripping hazard if it's not obvious, so many designers use either two or more steps or a change in decking direction or color to mark the edge clearly.

Are multi-level decks more expensive than single-level decks?

Usually per square foot, because they add stairs, guards, extra beams and posts, and more footings at different heights. On a steep lot, though, a multi-level design can cost less than one very tall platform that needs taller posts, bracing and engineering. Our cost guides have sourced ranges, and height is one of the biggest variables.

Can a multi-level deck work on a small Boise lot?

Yes. Two small levels, a landing at the door and a slightly lower sitting area, can make a narrow yard feel larger than one platform would. Watch setbacks and easements, which limit how far the lower level can extend, and keep stairs compact. On flat lots, a single step down can define zones without adding height.

Multi-Level Deck Ideas for Boise Lots

Where do multi-level decks make sense?

A single deck off a main-floor door on a sloped lot either ends high in the air on the downhill side or needs a long stair down to the yard. Breaking it into two or three levels follows the grade instead. The Boise Foothills, Harris Ranch and Barber Valley, lots near Hill Road and Eagle's hillside subdivisions are where this comes up most, along with walkout basements anywhere in the valley.

Two-level composite deck stepping down a sloped backyard with a wide connecting stair — Illustration for ideas only — not a Valley Decks project photo.

Layout ideas that work

Upper dining, lower lounge

Put the dining table on the upper level just outside the kitchen door, where carrying plates is short, and drop a lounge or fire-table level a few steps down. The level change separates the two uses without walls.

Wide stairs as seating

A broad stair between levels, several treads wide, doubles as overflow seating. Keep risers within the code limit and add a handrail where the code requires one.

View platform

On Foothills lots, a small upper platform aimed at the view, with a glass or cable guard, keeps the sightline open while the larger level sits lower and closer to the yard.

Raised view deck with cable railing overlooking the Boise valley at dusk — Illustration for ideas only — not a Valley Decks project photo.

Use the space below

A second-story level creates a dry or partly dry area underneath. Under-deck drainage systems can turn it into usable patio space; in Boise's wildfire overlay, the space underneath may have to be enclosed or protected instead.

Which code rules shape a multi-level deck?

Multi-level decks have more edges and more stairs, so guard and stair rules come up at every level change. The 2018 IRC numbers, as adopted in Idaho:

Guard, stair and post limits that shape multi-level decks (2018 IRC; Boise #406 checklist)
Item	Limit	Source
Guards required	Where the surface is more than 30 in above the floor or grade below within 36 in of the edge	IRC R312.1.1
Guard height	36 in minimum on the deck; 34 in on stairs	IRC R312.1.2
Guard openings	Must not pass a 4-in sphere	IRC R312.1.3
Stair riser	7-3/4 in maximum	IRC R311.7.5.1
Stair tread	10 in minimum	IRC R311.7.5.2
Post height, 6×6	14 ft maximum to underside of beam	IRC Table R507.4
Stamped engineering	Decks more than 6 ft above grade	Boise #406 checklist

The guard rule is measured at each level: a lower level only 24 inches above grade doesn't need a guard, while the upper level does. Plan the drop between levels so stairs come out at even risers. Our deck railings and stairs service and railing options guide cover guard choices.

Do hillside lots need engineering?

Boise's Hillside Development Overlay applies where slope exceeds 15 percent, and the city's #406 checklist requires stamped engineering for footings and foundations in the overlay and a Hillside Questionnaire for every property in it. Slopes over 25 percent are restricted unless an engineer shows the site limitations can be overcome. In Eagle, homes in the Avimor and Valnova hillside developments require structural stamped plans because of topographic wind effects and special snow load areas.

Footings on a slope also need care: each one reaches the 24-inch frost depth at its own grade, and downhill footings sometimes need to be stepped or deeper to reach undisturbed soil. Our footing depth guide explains the sizing.

Neighbors, HOAs and permits

A raised level changes sightlines. HOA committees often look harder at second-story decks, so show the deck on elevations with neighboring windows and add privacy screens to the design rather than later. Every level above 12 inches is permit work in Boise; see the Boise deck permit guide. If you're in Eagle, the Eagle deck builder page covers local context.

Starting a multi-level design

Begin with a topographic sketch: door thresholds, grade at each corner, and where the view and sun are. Then decide uses before sizes. Custom deck building walks through our design process, or request an estimate for a site visit.

Frequently asked questions

Does each level of a multi-level deck need a guard?: Only where that level's surface is more than 30 inches above the floor or grade below within 36 inches of its edge. A low lower level may not need one, while the upper level and any stair over that height will. Guards must be at least 36 inches high on the deck and 34 inches on stairs, with openings that won't pass a 4-inch sphere.
Do I need an engineer for a multi-level deck in Boise?: Boise's #406 checklist requires stamped calculations for any deck more than 6 feet above grade and for designs outside the IRC's prescriptive rules. Lots in the Hillside overlay need engineered footings. A modest two-level deck on a gentle slope, with each level under 6 feet, can often be built from the IRC tables without an engineer.
How many steps should there be between deck levels?: Enough to divide the height into equal risers of no more than 7-3/4 inches, with treads at least 10 inches deep. A single step between levels can be a tripping hazard if it's not obvious, so many designers use either two or more steps or a change in decking direction or color to mark the edge clearly.
Are multi-level decks more expensive than single-level decks?: Usually per square foot, because they add stairs, guards, extra beams and posts, and more footings at different heights. On a steep lot, though, a multi-level design can cost less than one very tall platform that needs taller posts, bracing and engineering. Our cost guides have sourced ranges, and height is one of the biggest variables.
Can a multi-level deck work on a small Boise lot?: Yes. Two small levels, a landing at the door and a slightly lower sitting area, can make a narrow yard feel larger than one platform would. Watch setbacks and easements, which limit how far the lower level can extend, and keep stairs compact. On flat lots, a single step down can define zones without adding height.

Sources

Last reviewed October 15, 2026.

Multi-Level Deck Ideas for Sloped Boise Lots