Planning estimate · Herriman, Utah
Composite deck cost calculator
Composite costs more to build and next to nothing to keep. This calculator prices the composite deck, prices the wood deck alongside it, and works out the year the two have cost the same.
What is behind the number
What decides the price of a composite deck
A complete capped composite deck in Utah runs roughly $65 to $95 a square foot installed. The spread is not mostly about the board: it is the guard, the stairs, the footings and the height. Two decks the same size with the same boards can sit at either end of that range.
There is one cost that belongs to composite specifically and it is under the surface. Composite boards are less stiff than wood, so the joists have to come in tighter, often to 12 inches on centre where boards run diagonally. That is about a third more lumber and hangers than the same deck in wood, and it is the line most quotes leave you to discover afterwards.
The rest of this page is the comparison people actually want. Building in wood is cheaper today and not free afterwards: cleaning, sanding and re-coating runs about $2 to $5 a square foot every time, every two to three years, in a climate with a lot of sun and very little humidity. So the calculator runs both decks and tells you the payback year rather than asserting one.
The composite line
Entry, capped mid-range, premium capped and PVC are a real ladder, and the difference is mostly the cap and the warranty rather than how it looks in the first year. The mid line is what the $65 to $95 range is built on.
Joist spacing
The framing cost that belongs to composite. Tighter spacing than wood, and tighter again for a diagonal layout. It is invisible once the boards are down, which is exactly why it should be visible in the estimate.
Height, and therefore the guard
Above 30 inches to the lowest grade you need Herriman’s permit at $432.39 and a guard around every open edge. On a composite deck that is often the largest single line after the deck itself.
Guard material
A composite deck with a wood guard reintroduces the sanding and sealing you bought composite to avoid. Composite and powder-coated metal do not, and cable and glass are three times the cost per foot of either.
Fascia and trim
Wrapping the rim and stair stringers in composite so no pressure-treated pine shows is almost always worth it and almost always missing from the first quote. It is the detail that makes a composite deck look finished.
What you would have built instead
The comparison deck is priced with the same footings, the same ledger and the same stairs, so the difference you see is the surface and its guard, not two unrelated jobs.
What pushes it higher
- Crossing 30 inches, which adds the permit and a guard around the whole open edge.
- A diagonal board layout, which brings the joists to 12 inches on centre.
- PVC or a premium capped line rather than a mid-range board.
- Cable or glass guard rather than composite.
- Under-deck drainage, which only makes sense on a tall deck.
- A hot tub, which changes the framing beneath it.
What brings it down
- Keeping the walking surface at 30 inches or less above the lowest grade.
- A straight board run rather than diagonal or picture-framed.
- An entry composite line, if you can live with more fade.
- A composite guard rather than cable or glass.
- Sizing the deck to the furniture rather than to the wall.
- Leaving drainage out, though lighting is far cheaper now than later.
Turn the estimate into a real number
Send a couple of photos, rough dimensions, and the height down to the lowest corner. You will get a straight answer about the permit, the guard and what the ground is likely to want, before anyone talks about boards.
What people ask about this
How much does a composite deck cost in Utah?
Roughly $65 to $95 a square foot installed for a complete capped composite deck, which on a 300 square foot deck comes to about $19,500 to $28,500. Where a specific deck lands inside that depends far more on height, guard and stairs than on which brand of board goes down.
Does composite really need no maintenance?
It needs no sealing, no staining and no sanding, which is the maintenance people mean. It still wants sweeping and an occasional wash with soap and water, and capped boards can still stain if something is left on them for a season. What it does not want is a weekend every second spring.
Does composite get hot?
Yes, noticeably, in full Utah summer sun. Darker boards more than lighter ones, and composite more than PVC, which has no wood flour in it and runs cooler. If the deck faces west with no shade, it is worth choosing a lighter board or planning shade into the design.
Why does the frame cost more under composite?
Because composite is less stiff than wood over the same span, so joists have to be spaced closer, often 12 inches on centre where the boards run diagonally rather than the 16 inches wood would use. More joists means more lumber, more hangers and more labour, all of it under a surface nobody sees.
When does composite pay for itself?
It depends on your deck and on how diligently you would have maintained the wood one. This calculator does the arithmetic on your numbers rather than quoting a marketing figure, and it will tell you plainly when the answer is longer than ten years. The part the arithmetic cannot price is whether you would actually have done the sealing.
Can I put composite on my existing frame?
If the frame is genuinely sound and spaced correctly for composite, yes, and it is much cheaper than a new deck at roughly $35 to $55 a square foot. The frame has to be checked first, including the joist spacing, because composite on joists spaced for wood will feel bouncy and may void the board warranty. The replacement calculator prices that version.
Do composite decks need a permit in Herriman?
The material makes no difference. Herriman’s rule is about height: 30 inches or less to the lowest grade around the perimeter, with no roof over it and not serving the required exit, and no permit is required. Above that, the published fee is $432.39.
Is this a quote?
No. It is a planning estimate built from current Salt Lake Valley composite pricing and Herriman’s published requirements. A real number needs someone looking at your grade, your soil and the wall the deck attaches to.