What's included
- Board selection by exposure: lighter capped composite or PVC for decks that take afternoon sun, darker tones only where shade covers the surface by mid-afternoon — the July normal high at the Boise airport is 92.7°F.
- Joist spacing taken from the manufacturer's installation guide rather than the 16-inch wood default. Idaho's residential code sends plastic composite decking back to the manufacturer's instructions, and diagonal or herringbone layouts need tighter spacing and extra blocking.
- End and side gaps set for the temperature on install day, so boards don't push against each other in August or open wide joints in January.
- Butyl tape on joist and beam tops to keep water out of fastener holes, because the treated frame under composite has to last as long as the boards on top.
- Picture-frame borders and matching fascia that hide cut board ends and the treated rim, with stair treads and risers from the same line.
- For lots in Boise's Foothills wildland-urban interface overlay, a check of which composite lines carry a current ignition-resistance listing before you pick a color, since some published listings have lapsed.
- Stairs detailed for composite: stringers spaced to the tighter limit most lines set for treads, and a contrasting or grooved nosing board so the edge of each step reads clearly at dusk.
Materials we use
| Category | Options |
|---|---|
| Capped composite | Trex (Enhance, Select and Transcend lines) · TimberTech Pro and Edge collections · Fiberon capped composite · Deckorators capped composite |
| PVC / cellular | TimberTech AZEK collections — no wood fiber, lightest boards, a good fit for damp shaded spots and hot tub surrounds · PVC fascia and riser boards to trim either board type |
| Framing under composite | Pressure-treated joists at the manufacturer's spacing · Butyl joist and beam tape · Hidden clip fasteners or color-matched face screws · Light-gauge steel framing for long, flat spans (by design) |
| Railing to pair | Composite railing from the same manufacturer · Powder-coated aluminum railing · Cable or glass infill for view lots |
How the work goes
Exposure and use check
We note which way the deck faces, how many hours of direct sun it gets in July, what sits beneath it, and whether a hot tub, grill or heavy planters will load it. Those answers narrow down the board line, the color and the framing before anyone looks at a brochure.
Sample boards in your light
You see samples outside at your house, laid on the ground or old deck in mid-afternoon. Surface heat, glare and how a gray or brown reads against your siding color are far easier to judge in real sun than under showroom lights.
Frame to the board's spec
Joists go in at the spacing the chosen line requires, with extra blocking at butt seams, borders and stairs. Joist tops get butyl tape, and the hidden clips and screws are the ones the manufacturer lists for that board, not a substitute from another brand.
Install with temperature-aware gaps
Composite and PVC grow and shrink with temperature, so end gaps follow the install guide's chart for the day's conditions. Hidden clips land on every joist; color-matched face screws go where clips can't, such as the outer edge of a picture frame or the front of a stair tread.
Finish and care briefing
Fascia, rails and stairs go on and every cut end is covered. We cover care before we leave: soap, water and a soft brush, a plastic shovel blade in winter, checking the manufacturer's guidance before any ice melt, and keeping rugs and planters from trapping moisture on the cap.
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
- Composite boards laid on an old frame built at 24-inch spacing. Most composite lines need closer joists; boards over spans that are too wide sag and bounce, and the manufacturer may not stand behind them.
- No mention of end gaps or install temperature. Boards butted tight on a cool October day can bow by August, and boards gapped on a hot July afternoon can show wide joints by January.
- Uncapped composite presented as "the same thing" as capped boards. The cap is what resists staining and fading in high-desert UV.
- A dark board recommended for a west-facing deck with no one mentioning surface heat or shade.
- A board described as "fireproof" or "WUI approved" with no current listing to show. Listings carry expiration dates; ask for the document and check the date.
- A scope that just says "composite" with no brand, line or color, or clips and screws borrowed from another brand. Entry and premium lines differ in cap, weight and warranty, and installing outside the manufacturer's instructions can complicate a claim later.
Budgeting? Our composite cost guide breaks down published Treasure Valley price ranges.
Frequently asked questions
- Is composite decking worth it in Boise?
- It is if you plan to stay in the house and don't want to stain. Wood in Boise's sun and dry air needs cleaning and refinishing every few years; capped composite needs washing. Composite costs more up front, so the payback comes from skipped maintenance and longer board life, not from a lower price. It also suits decks that take hard use from dogs and a grill. Our composite vs. wood decking comparison puts the trade-offs side by side.
- Does composite decking get hot in the summer?
- Yes, and in Boise it matters. The airport's July normal high is 92.7°F, and NOAA's 1991–2020 normals show about 55 days a year at 90°F or above and about 9 at 100°F or above. Dark, dense boards in direct afternoon sun run hottest. Lighter colors, some PVC lines and shade from a pergola or cover help. Our guide to decking for full sun compares options.
- How much does a composite deck cost per square foot?
- Installed cost per square foot depends on the board line, the deck's height, railing length, stairs and how many footings the frame needs. Published 2026 ranges and their sources are in the composite deck cost guide for Boise, and the calculator applies them to your size. A Valley Decks quote follows an on-site measure, not a per-foot guess.
- Trex or TimberTech — which should I choose?
- Both make capped composite in several price tiers, and TimberTech also sells AZEK PVC boards. For most Treasure Valley decks the deciding factors are how a color looks in your light, surface texture, heat in full sun, and which railing system you want to pair with it. Our Trex vs. TimberTech comparison lays out the lines; composite vs. PVC covers the material difference.
- What joist spacing does composite decking need?
- Whatever the board manufacturer's install guide says for that line and layout. Idaho's residential code sets 16 inches for 5/4 wood decking laid square, but sends plastic composite back to the manufacturer's instructions. Many lines allow 16 inches for straight runs and call for 12 inches on diagonals and stair treads. Stairs are where shortcuts show first: a tread spanning too far between stringers flexes underfoot. Check the guide for the exact board before framing.
- Is composite decking fire resistant?
- Not by default. The code only requires plastic composite decking to have a flame spread index of 200 or less. Some boards hold wildland-urban interface listings — a TimberTech Reserve grooved line is listed by California's State Fire Marshal through June 2027 — while older listings for some other products have expired. For Foothills lots, read our wildfire-resistant decking guide.
- Can composite decking be installed in cold weather?
- Yes. Cold doesn't stop the work, but it changes the gaps: boards are at their shortest in the cold, so end gaps follow the manufacturer's temperature chart, and stiff boards are cut more carefully. Boise's median first fall freeze is October 21; when footings are poured before the ground freezes, the decking can go on through early winter.
- How do you clean and maintain a composite deck?
- Wash it with soap, water and a soft brush a couple of times a year, rinse off pollen and cottonwood fluff, and move planters now and then so moisture doesn't mark the cap. In winter use a plastic shovel blade, not metal, and check the manufacturer's list before using ice melt. Our deck maintenance guide for the Boise climate has a full seasonal routine.
Sources
- NOAA NCEI 1991–2020 normals API — Boise days at or above 90°F and 100°F
- NOAA NCEI U.S. Climate Normals 1991–2020, Boise Air Terminal (USW00024131) — monthly
- Idaho Residential Code (2020 Edition, 2018 IRC basis) — Chapter 5: decks R507 (UpCodes)
- TimberTech Reserve (grooved) — California State Fire Marshal WUI listing, valid through 2027-06-30
- City of Boise — Wildland Urban Interface Overlay (IR1 / IR2)
- Trex — Decking product lines
- TimberTech — Decking (composite and AZEK PVC)
- City of Boise — 301 Current Codes and design criteria (2018 IRC; snow, wind, frost depth)
Last reviewed .