New deck building in Pocatello

The part that matters is underground

Almost every conversation about a new deck starts with decking boards — cedar or composite, grey or brown, grooved or face-screwed. That is the fun decision and it is nearly irrelevant to whether the deck survives.

What determines that is the footings, and in Pocatello the number is 36 inches. That is the published design frost depth for this area, and every post footing has to bear below it. For comparison, Boise's figure is typically 24 inches and much of the country sits shallower still. A crew that has worked mostly in the Treasure Valley, or a builder following a set of plans downloaded from a national site, will underdig without ever realising it.

Here is what happens when they do. Soil holds water. Water expands roughly nine percent when it freezes. A footing bearing at 20 inches in ground that freezes to 36 gets lifted every winter and dropped every spring, and the movement is not uniform — the shaded north side of the house heaves differently from the sunny south side. Over a handful of seasons the frame racks out of square. Doors onto the deck start catching. Railings loosen. Stair stringers pull away at the top. The decking gets blamed and replaced, which fixes nothing because the problem is three feet down.

The dig is genuinely hard work in Bannock County's rocky soil, and it is the easiest thing to shave off a bid without the homeowner noticing. When you compare quotes, ask each builder to state footing depth and diameter in writing.

What a proper footing looks like

• Bearing below 36 inches, on undisturbed soil — not on backfill, and not on a few inches of gravel thrown in the bottom of the hole.
• Sized for the load it carries. A post supporting a corner of a small platform and a post carrying the middle of a beam on a two-storey walkout deck are not the same footing.
• Proper post-to-footing connection — a rated base that holds the post off standing water and resists uplift, not a post buried in the concrete.
• Inspected before the concrete goes in. This is the single most valuable inspection in the whole project, and it only happens if you pull a permit.

The ledger: where decks actually collapse

When a deck fails catastrophically — and they do, usually with people standing on them — it is almost always the ledger, the board that fastens the deck frame to the house.

The failure mode is simple. The ledger is attached with nails or undersized screws instead of through-bolts or structural fasteners. Or it is fastened through siding without proper flashing, so water gets in behind, the rim joist of the house rots quietly for a decade, and one summer afternoon the fasteners pull through soft wood.

Two things make this more relevant in Pocatello than in a lot of markets. Walkout basements are common here, which means a large share of local decks are elevated six to nine feet — high enough that a ledger failure is a serious injury rather than a scare. And freeze-thaw cycling drives water into any gap in flashing far more aggressively than a mild climate does.

What good practice looks like: correctly sized structural fasteners or through-bolts in a specified pattern, proper flashing over the top of the ledger and integrated with the house's weather barrier, and a gap that lets water drain rather than sit. Ask to see the flashing detail before it gets covered.

Framing for snow

Pocatello's design snow figure is 35 psf, with ground snow load in the area generally cited in the 35 to 40 psf range. Snow lands on a deck and stays — extended sub-freezing spells mean it does not clear between storms the way it does at lower elevation.

Practically, that pushes joist spacing tighter and beams heavier than a generic span table would suggest. Sixteen inches on centre is a common default; heavier snow assumptions or certain composite products can call for twelve. Composite decking in particular often requires tighter spacing than wood, and tighter again on stairs or on a diagonal layout — a detail that gets missed when someone frames for wood and then switches material mid-project.

If you are adding a roof, pergola or patio cover over the deck, this becomes a structural design question rather than a rule-of-thumb one. A covered structure holds snow load, and Pocatello's 115 mph design wind speed adds uplift. Covered decks here need engineered connections.

Ground level, raised, or multi-level

Ground-level platforms

Under 30 inches at all points, these are the simplest and cheapest builds, and often fall outside permit requirements. Fewer stairs, no guardrail requirement, less structure. If your yard grade allows it, this is the value option by a wide margin.

Raised and walkout decks

The common Pocatello situation. A walkout basement means a deck at main-floor level sitting six to nine feet up, which brings in guardrails, proper stair geometry, taller posts with lateral bracing, and a much more consequential ledger. Cost per square foot climbs meaningfully compared to a ground-level build, and the structural work stops being optional.

Multi-level

Stepping a deck down toward the yard looks good and solves awkward grade changes, but every level is its own frame with its own footings, plus a stair run between them. It is the most expensive configuration per square foot by some distance. Worth it on a sloped lot; rarely worth it on a flat one.

Decking material, briefly

Pressure-treated pine is the budget standard and performs acceptably here — the dry climate is kind to wood, decay pressure is low. It needs a finish schedule and it will check and grey under high-desert UV if neglected.

Cedar looks better, costs more, and weathers to grey handsomely if you let it. It is softer than PT and marks more easily.

Composite costs substantially more up front and eliminates the staining cycle entirely, which in a market where UV is the primary enemy is a stronger argument than it is elsewhere. It has its own considerations — surface heat, joist spacing, expansion. Covered in detail here.

The build sequence

1. Design and layout. Size, height, stair location, railing style, and how it relates to doors and grade.
2. Permit. Site plan and construction drawings with member sizes, spans and footing details. See the permits page.
3. Footing dig and inspection. Holes to depth, inspected before concrete.
4. Concrete and post bases.
5. Ledger and flashing. Integrated with the house weather barrier.
6. Frame. Beams, joists, blocking, lateral bracing.
7. Framing inspection.
8. Decking, stairs, railings.
9. Final inspection.

Common questions

How deep do deck footings need to be in Pocatello?

Design frost depth for this area is 36 inches, so footings must bear below that. This is materially deeper than Boise's typical 24 inches and it is the number to check on every bid you receive.

Can I attach a deck to a house with stucco or stone veneer?

Yes, but it needs care. The ledger must bear on and fasten to the structural rim of the house, not to the veneer, and the flashing detail through a veneer wall is more involved than through lap siding. Some builders will recommend a freestanding deck instead to avoid the detail entirely. That is a legitimate solution, though it brings its own footing considerations.

What size deck should I build?

A common guideline is keeping the deck under about 20 percent of the home's floor area, mostly so it stays proportionate. More practically: measure your patio furniture, add circulation space around it, and add a bit for the grill. Undersized decks are the most common regret, but so is paying for square footage that ends up empty.

Will a deck raise my property taxes?

A permitted deck is an improvement and can affect assessed value. The effect is usually modest relative to the project cost, but it is real, and it is one reason some people are tempted to skip the permit. That is a bad trade — unpermitted structural work surfaces during a home sale and can be expensive to resolve at the worst possible moment.