ADU Site Prep Equipment in Utah
Key Takeaways
- Four phases, four machine roles. ADU site prep is clearing, grading, trenching, and slab base — each needs a specific machine.
- A day-by-day rental plan for a backyard ADU: which machine to rent each day and what it costs.
- Real Utah rental rates: walk-behind skid steers from $125/day, track skid steers $175–$375/day, mini excavators $250–$400/day, plate compactors around $100/day.
- The backyard-access trap adds $5,000–$8,000 to a sitework bill — learn which machines fit through a 36" or 48" gate.
- What site prep costs: roughly $1,600–$2,500 to rent the machines yourself versus $2,000–$15,000 to hire it out.
- Utah's 2026 ADU law (SB284) and the free Blue Stakes 811 locate you must do before any trench.
You got the ADU approved. Now someone has to clear the lot, cut it to grade, trench in water, sewer, and power, and build a compacted gravel base before the unit ever shows up — and that "sitework" line is where ADU budgets quietly blow up. The good news: nearly all of it is rentable equipment work, not specialty trades. Alpine Equipment Repair rents the full ADU site-prep lineup across Utah County and Salt Lake County — walk-behind skid steers from $125/day, track skid steers $175–$375/day, mini excavators $250–$400/day, and plate compactors around $100/day, with delivery at $165/hour. This guide maps each machine to each phase, then sequences it into a day-by-day rental plan you can hand to a crew or run yourself.
Utah's 2026 ADU Rules Changed — and Site Prep Is Now the First Real Step
Utah's SB284 rewrote the backyard-housing map. Every city with a population of 5,000 or more must now permit detached accessory dwelling units, and cities without an ADU policy have to adopt one by October 2026. If your lot is 11,000 square feet or larger, you may have a path to a detached ADU where none existed two years ago.
The specifics still belong to your city, and they matter for site layout:
- One ADU per lot (internal or detached), and it can't be sold off separately
- Owner-occupancy of the primary home or the ADU, recorded as a covenant
- Setbacks commonly around 5 ft on the side and 10 ft on the rear
- Size caps typically 800–1,000 sq ft, or up to 50% of the main house
- One added off-street parking space in most municipalities
Here's the part nobody tells you: zoning approval is not a green light to build. It's a green light to start spending money on dirt. Before a single wall panel arrives, the ground has to be cleared, graded, trenched, and based. That's site prep — and it's the first real, physical step of every ADU project.
The Four Phases of ADU Site Prep (and the Machine for Each)
ADU site prep breaks into four phases that happen in order. Each one has a primary machine and a tight-access alternative for backyards a full-size machine can't reach. This table is the whole article in one screen:
| Phase | What happens | Primary machine | Tight-access alternative | Typical days | Alpine daily rate |
|---|---|---|---|---|---|
| 1. Clearing | Demo old shed/slab, clear brush, strip & stockpile topsoil | Track skid steer + grapple/mulcher | Walk-behind skid steer (SK252) | 0.5–1 | $125–$375 |
| 2. Grading & pad excavation | Cut to grade, set drainage slope, dig the building pad | Mini excavator + track skid steer | Walk-behind skid steer + hand dig | 1–2 | $250–$575 combo |
| 3. Utility trenching | Trench water, sewer, electric from the house to the pad | Mini excavator or trencher | Walk-behind trencher | 0.5–1 | $250–$400 (trencher: call) |
| 4. Slab base | Spread road base, compact in lifts, fine-grade to slab elevation | Track skid steer + plate compactor | Walk-behind + plate compactor | 0.5–1 | $100–$400 |
Two things to note before the deep dive. First, Alpine includes pallet forks free with every skid steer — most yards charge $50–$100/day for the same attachment. Second, the rental clock runs independently for each machine, with a 4-hour (half-day) minimum, so you're not penalized for returning the skid steer at noon and keeping the mini ex until 4 PM. See the full skid steer and mini excavator lineups for sizes and attachments.
Phase 1 — Clearing the Site
Clearing means getting the footprint down to bare, workable dirt: demoing an old shed or slab, removing brush and scrub oak, pulling stumps, and stripping the organic topsoil layer so you're not building a base on material that will rot and settle.
The workhorse here is a track skid steer with the right attachment:
- Bucket or grapple — scoop debris, load it into a trailer, stack brush
- Forestry mulcher — chew through brush, scrub oak, and small trees in one pass (call for the attachment rate)
- Stump grinder — finish off the stumps the mulcher leaves behind
A 2,300 lb track skid steer like the Cat 279D ($300/day) handles a typical residential clear-and-strip in a half to full day. Tracks matter in Utah: they spread the machine's weight to roughly 3–5 PSI versus 25–35 PSI for wheels, so you're not carving ruts into the lawn you plan to keep — ruts that run $200–$500 to repair later.
If the backyard gate is the bottleneck, a walk-behind skid steer (the GIANT SK252 at $125/day) fits through a standard 36" gate and still loads, carries, and grades. Browse the compact track loader options for tight access — and see the full access guide further down, because gate width decides this whole project.
Phase 2 — Grading & Excavating the Building Pad
Grading does two jobs: it levels the building pad to a consistent elevation, and it establishes a drainage slope that moves water away from the new structure (code generally wants a fall of 6 inches over the first 10 feet). Then you excavate the pad and footing trenches to the depth your foundation plan calls for.
This is where people ask the wrong question — "skid steer or mini excavator?" — when the real answer is usually both. Here's how the three common machines compare:
| Factor | Track skid steer | Compact track loader | Mini excavator |
|---|---|---|---|
| Best at | Pushing, grading, hauling material | Same as skid steer, softer ground | Digging, trenching, pad excavation |
| Ground | Good on firm/compact | Best on wet, muddy, soft soil | Sits and digs anywhere |
| Use it for | Strip topsoil, rough/finish grade, move spoil | Grade on lawns and soft lots | Cut the pad, dig footings, trench |
| Alpine rate | $175–$375/day | $175–$375/day | $250–$400/day |
Best combo: a mini excavator digs the pad while a track skid steer grades and hauls the spoil — one productive day, two machines.
For a standard backyard ADU pad, a 5k–6k lb mini excavator ($275/day) paired with a 2,300 lb track skid steer ($300/day) is the sweet spot — about $575 for a combined grade-and-excavate day. The mini ex cuts the pad and footings; the skid steer moves spoil to the perimeter and runs the grade passes.
One Utah-specific warning: Wasatch-Front soils are heavy on expansive clay that swells when wet and shrinks when dry, and the benches see 150+ freeze-thaw cycles a year. That's exactly why getting the pad cut clean and the base compacted (Phase 4) is non-negotiable — it's the difference between a slab that sits flat and one that cracks in its third winter.
Phase 3 — Utility Trenching (Water, Sewer, Electrical)
A detached ADU needs its own utility runs from the main house or the street. Depths are set by code and frost, so check with your city, but these are the Utah ballparks:
| Utility | Typical trench depth | Notes |
|---|---|---|
| Electrical | 18–24 in | Warning ribbon 12 in above the conductor |
| Water | 12 in below frost line → ~24–30 in in Utah | Utah Valley frost line runs ~30 in |
| Sewer | Slope ¼ in per foot, min 12 in cover | Depth grows with run length |
| Separation | Water pipe ≥12 in above sewer | On a shelf 12 in to the side of the sewer |
Two machines do this job:
- Walk-behind trencher — fastest for straight, single-purpose runs in firm clay under ~200 ft. Cuts a clean narrow channel. (Contact Alpine for trencher rates — they vary by model.)
- Mini excavator — wins when you need depth past 30 inches, curved or L-shaped routes, or you want one machine that also handles spoil and doubles back to grade. A 5k–6k lb mini ex at $275/day digs to 8+ feet, so you'll never hit a depth limit on a utility run.
Before any trenching, call Blue Stakes 811. It's free, it's required by Utah law, and it gets every buried gas, power, water, and communication line marked before you dig. Cutting an unmarked line is a five-figure mistake and a safety hazard. Place the call at least two business days ahead. For backfilling the trench afterward, a jumping jack rammer (~$65–$110/day) is the correct tool — it drives compaction force straight down into the narrow trench, which a plate compactor can't do.
Phase 4 — Slab Base: Gravel, Compaction & Fine Grade
Do not skip this phase. Uncompacted sub-base is the number-one cause of slab cracking on the Wasatch Front, and a failed slab under an ADU is not a fix-it-later problem.
The recipe is well established:
- Compact the native subgrade first — dampen it, then run the compactor until your footprints stop denting it.
- Spread 4–6 inches of ¾" crushed road base with fines. The fines (stone dust) lock the angular rock together into a dense, stable mat. Don't use clean pea gravel — it shifts.
- Compact in 2-inch lifts. Wet each lift to optimum moisture and make about 4 passes. Build up to full depth one lift at a time — the 95% compaction rule means roughly 95% of maximum dry density before you pour.
- Top with a vapor barrier and a 1–2 inch sand leveling bed so the slab pours flat.
Use the right compactor for the material:
| Tool | Best for | Wrong for | Alpine rate |
|---|---|---|---|
| Reversible plate compactor | Gravel and road base (granular) — the slab base | Cohesive clay | ~$100/day |
| Jumping jack rammer | Trench backfill, footings, tight spots (cohesive soil) | Gravel base — it displaces instead of compacting | ~$65–$110/day |
A track skid steer ($300/day) spreads and screeds the road base fast; the reversible plate compactor (~$100/day) does the compaction. For the gravel base specifically, the plate compactor is the only correct choice — a rammer will push granular material to the sides instead of locking it down. When you move to the pour itself, the same yard that rents your skid steer and plate compactor also carries the concrete finishing tools, so you're not chasing a second supplier between phases.
The Day-by-Day ADU Site Prep Rental Plan
Here's the part no national rental chain or ADU builder publishes: a sequenced, machine-by-machine rental plan for a typical 600–800 sq ft detached backyard ADU on a standard lot with 48"+ side access. Site prep like this runs anywhere from a few days to about two weeks depending on lot size and conditions; this is the efficient four-day version.
| Day | Phase | Machine(s) | Alpine rate | What gets done |
|---|---|---|---|---|
| Day 1 | Clear & strip | Track skid steer (2,300 lb) + mulcher | $300 + attachment | Demo, clear brush, strip & stockpile topsoil |
| Day 2 | Grade + excavate pad | Mini excavator (5–6k lb) + track skid steer | $575 combo | Dig pad & footings, cut/fill, rough grade, set slope |
| Day 3 | Utility trenching | Mini excavator (5–6k lb) | $275 | Trench water/sewer/electric; jumping jack on backfill (~$75) |
| Day 4 | Slab base | Track skid steer + reversible plate compactor | $300 + $100 | Spread road base, compact in lifts, fine-grade to slab |
Machine subtotal: roughly $1,625, plus the mulcher attachment and delivery. At $165/hour with two delivery round-trips, figure about $1,950–$2,200 all-in for the equipment to take a backyard from raw to slab-ready. Tighten it further by returning each machine the moment you're done — the independent half-day clock means a noon return on Day 1 saves you, not the yard.
Tight-access variant: if your only way in is a 36" gate, swap the track skid steer for the walk-behind SK252 ($125/day) and hand-dig the footings. That version runs closer to $700–$1,200 in equipment — slower, but it fits where nothing else will.
Will the Equipment Even Fit? The Backyard-Access Reality
Access is the single most expensive surprise in backyard ADU sitework. The industry rule of thumb: if there's less than 8 feet of clear vertical access or the soil won't carry heavy equipment, expect costs to jump $5,000–$8,000. Most builders gloss over this. We'd rather you measure your gate before you book a machine.
| Clear gate / access width | What fits |
|---|---|
| Under 36 in | Hand tools, wheelbarrows, mini power tools only |
| 36–48 in | Walk-behind skid steer (GIANT SK252) — fits a standard 36" gate |
| 48 in+ | Compact track loaders (GIANT G950T at $175/day fits 48") |
| 60 in+ / open side yard | Full-size 2,300–3,100 lb track skid steers, mini excavators |
This is where a local yard beats a national chain. Alpine's walk-behind skid steer tows on a small trailer, fits through a 36" gate, and still moves real material — and someone on the phone will help you confirm it fits before it shows up. Two practical notes: lay plywood or ground mats to protect the lawn and driveway on the machine's path, and pick a staging spot up front for the spoil pile and the incoming road base so you're not double-handling material.
What ADU Site Prep Costs in Utah: Rent vs. Hire It Out
Sitework is the most opaque number in an ADU budget because most of it is quoted, not published. Here's the honest comparison.
| Approach | What you pay | What you get |
|---|---|---|
| Hire a sitework contractor | Clearing/leveling $2,000–$10,000 · Excavation $10,000–$15,000 · Grade + soil export $5,000–$10,000 · Poor access add $5,000–$8,000 | Turnkey. Their crew, their liability, their schedule. |
| Rent the machines (this plan) | ~$1,625 machines + delivery ≈ $1,950–$2,200 · Tight-access version ~$700–$1,200 | The dirt work done on your timeline — if you or your crew can run the equipment. |
In plain numbers: renting Alpine's full ADU site-prep lineup — track skid steer, mini excavator, and reversible plate compactor — runs about $1,625 in machine time plus $165/hour delivery, versus the $12,000-plus a sitework contractor typically quotes for the same clear-grade-trench-base scope in Utah.
The trade-off is real, and we won't pretend otherwise: hiring it out buys skill, speed, and someone else's insurance. Renting buys a five-figure savings if you have the operating ability and the time. For an owner-builder doing one ADU, or a GC who'd rather keep the sitework in-house than sub it out, the rental math is hard to argue with. What drives your number up or down: lot slope, soil (clay vs. sand vs. rock), how far utilities have to run, and — again — access. If you'd like a second opinion on which machines your specific lot needs, Alpine's equipment specialists will talk it through at (801) 701-7394.
Three Real Utah ADU Site Prep Scenarios
Scenario 1 — Lehi homeowner, detached ADU behind the house (access-limited)
The project: A flat quarter-acre lot in Lehi. The only way to the backyard is a 34-inch gate between the house and the fence. Owner-builder doing a 700 sq ft detached ADU.
Equipment rented: Walk-behind skid steer (SK252) at $125/day for clearing and material moves, two days. Reversible plate compactor at $100/day for the base. Footings dug by hand because nothing bigger fits.
How it works: The SK252 strips topsoil and hauls it out through the gate by wheelbarrow-and-bucket relay, then later spreads road base. It's slower than a full-size machine, but it's the only machine that physically fits. Total equipment: about $450 plus delivery. The access constraint saved this owner from a contractor's $5K–$8K "limited access" surcharge.
Scenario 2 — American Fork contractor, standard-lot detached ADU (full lineup)
The project: A GC in American Fork building a detached ADU on a lot with an open 10-foot side yard. Clear, grade, trench, base — the works.
Equipment rented: The full four-day plan above — 2,300 lb track skid steer, 5–6k lb mini excavator (combo day), reversible plate compactor. About $1,950 all-in.
How it works: Day 1 clear and strip. Day 2 the mini ex and skid steer run together — pad and footings dug, spoil moved, rough grade set. Day 3 trench the utilities. Day 4 base and compact. The GC bills four equipment days against what a sitework sub would have quoted at $12,000+, and keeps the schedule on his own calendar.
Scenario 3 — Saratoga Springs sloped lot, and the "don't rent that" call
The project: A sloped lot in Saratoga Springs needs real cut-and-fill to bench a flat pad before a detached ADU.
Equipment rented: A larger 10k lb mini excavator ($325/day) plus a 2,500 lb track skid steer ($350/day) for two days of cut/fill and grading.
The honest call: This crew almost rented a separate walk-behind trencher for the utility run. They didn't need it. The 10k lb mini ex was already on site and digs to 8+ feet — adding a trencher would've been a second rental for a job the excavator already covers. Don't rent what the machine you've got already does. One less unit, one less delivery, same finished trench.
How to Choose an Equipment Rental Company for Your ADU Project
You'll get a better outcome — from any yard, including ours — if you ask these before you book:
- Are attachments and pallet forks included, or extra? Alpine includes forks free; many chains add $50–$100/day.
- Is delivery a flat fee or hourly? Alpine is $165/hour; get the round-trip estimate up front.
- What's the rental minimum and how does the clock run? Alpine's minimum is 4 hours and each machine's clock runs independently — you're not billed a full day for a half-day job.
- Who fixes a breakdown mid-job? Alpine's in-house technicians service every machine they rent and respond fast — a dead machine on Day 2 shouldn't cost you Day 3.
- Can you confirm the machine fits my access? Give them your gate width. A good yard will steer you to the walk-behind before it shows up too big to use.
Notice these questions don't ask "who's cheapest." The daily rate is the smallest part of a sitework budget — downtime, surprise attachment fees, and a machine that won't fit cost far more than $25/day of rate difference.
Frequently Asked Questions About ADU Site Prep
How much does it cost to prepare a site for an ADU?
Hiring a sitework contractor typically runs $2,000–$10,000 for clearing and leveling, $10,000–$15,000 if significant excavation is involved, and $5,000–$8,000 more for poor backyard access. Renting the machines and doing it yourself costs roughly $1,600–$2,500 for a standard four-day plan, or about $700–$1,200 for a tight-access backyard. The biggest cost variables are slope, soil type, utility run length, and access.
What equipment do I need to build an ADU?
For site prep you need four machine roles: a skid steer (or walk-behind skid steer) for clearing, grading, and moving material; a mini excavator for digging the pad and trenching utilities; a trencher if your utility runs are long and straight; and a plate compactor for the gravel base. A jumping jack rammer handles trench backfill. Alpine rents all of them from one yard in American Fork.
How do you prepare the ground for an ADU foundation?
Clear and strip the topsoil, cut the pad to a level grade with a drainage slope away from the structure, excavate footings to plan depth, then build a compacted base: 4–6 inches of ¾" crushed road base with fines, compacted in 2-inch lifts to about 95% density, topped with a vapor barrier. Compact the native subgrade before you add any gravel.
How deep do utility trenches need to be for an ADU in Utah?
In Utah, electrical lines typically run 18–24 inches deep, water lines sit 12 inches below the frost line (roughly 24–30 inches in Utah Valley), and sewer lines slope ¼ inch per foot with at least 12 inches of cover. Water lines must stay at least 12 inches above sewer lines. Always confirm exact depths with your city, and call Blue Stakes 811 before digging.
How long does ADU site prep take?
Site prep — clearing, grading, trenching, and slab base — typically takes a few days to about two weeks depending on lot size, slope, and access. The efficient version is about four equipment days. The full ADU build that follows usually runs four to six months.
Do I need a permit to build an ADU in Utah?
Yes. Under SB284, cities with 5,000+ residents must permit detached ADUs (policy in place by October 2026), but you still need a building permit and your city sets setbacks, size caps, and parking. Check with your local building department — American Fork (801) 763-3060, Lehi (385) 201-1035, or Provo (801) 852-6400 — before you start.
What kind of gravel goes under an ADU slab?
Use ¾" crushed stone with fines (commonly called road base or ¾-minus), 4–6 inches deep. The fines are stone dust that lock the angular rock together when compacted, creating a dense, stable mat that won't shift under the slab. Avoid clean or rounded pea gravel — it migrates and won't hold compaction.
Should I rent a skid steer or a mini excavator for site prep?
For most ADU prep you'll want both, but for different phases. A skid steer is for clearing, grading, and moving material across open ground; a mini excavator is for digging the pad and trenching utilities. If you can only rent one, choose by your dominant task: dig-heavy job → mini excavator ($250–$400/day); move-and-grade job → skid steer ($175–$375/day).
How do you compact a gravel base?
Use a reversible plate compactor (about $100/day) for granular gravel base. Spread the road base in 2-inch lifts, wet each lift to optimum moisture, and make about four passes per lift until you reach roughly 95% compaction. Use a jumping jack rammer only for trench backfill and cohesive clay — it's the wrong tool for a gravel base because it displaces the material instead of locking it.
Can construction equipment fit in my backyard for an ADU?
It depends on your narrowest access point. Under 36 inches, you're limited to hand tools; a 36-inch gate fits a walk-behind skid steer like the GIANT SK252; 48 inches fits a compact track loader like the GIANT G950T; and 60 inches or an open side yard fits full-size machines. Measure your gate first — Alpine can confirm a machine fits before delivery. Call (801) 701-7394.
Do I need to call Blue Stakes before trenching?
Yes — it's required by Utah law and it's free. Call 811 (Blue Stakes of Utah) at least two business days before you dig, and crews will mark all buried gas, electric, water, and communication lines. Hitting an unmarked utility is a serious safety hazard and a five-figure repair you're liable for.
Can I do ADU site prep myself, or should I hire a contractor?
You can do it yourself if you can operate the equipment safely and have the time — renting the machines saves five figures versus hiring it out. Hire a contractor if your lot has steep slope, poor soil, complex drainage, or you're not confident running a mini excavator near utility lines. Many owner-builders split the difference: rent and self-perform the clearing and base work, and hire out the precision excavation.
Get Your ADU Site Prep Equipment in One Stop
Site prep is the first real money you spend turning an approved ADU into a built one — and it's almost all rentable equipment work. Clear it, grade it, trench it, base it, in four phases with the right machine for each. Alpine Equipment Repair rents the entire lineup — skid steers, mini excavators, trenchers, compact track loaders, and plate compactors — from one yard in American Fork, maintained by in-house technicians and delivered across Utah County and Salt Lake County — from Provo and Orem to Eagle Mountain and Saratoga Springs.
Tell us your lot, your access, and your timeline, and we'll line up the machines day by day. Call (801) 701-7394.
