Tree Protection During Construction: What Park City's Code Requires

The trees you lose to construction die three years later

That delay is the entire problem. If a bulldozer knocked a tree over on day one, everybody would see the damage and somebody would be held responsible. Instead, the excavator cuts a trench for the new water line, clips a few structural roots on the uphill side, the project finishes, the landscaping goes in, and the tree looks fine for two full growing seasons.

Then the crown starts thinning. Bud break comes late. Fall color arrives in August. By the time anyone connects it to the trenching, the contractor is long gone, the warranty has expired, and the homeowner is paying to remove a mature tree that was healthy before the project started — plus a stump grind, plus a replacement planting the code may well require.

Extension services are consistent about this lag. Soil compaction damage can take several years to become evident. Decline and dieback appear gradually over a period of years. Trees may take several years to adjust to the site changes construction imposes, and some never do.

Park City and the Heber Valley are in a sustained building and remodeling cycle, on steep wooded lots where the trees are a large part of what the property is worth. This is a guide to keeping them — what the city actually requires, how the protected area is calculated, what damages a tree, and where the leverage sits in a contract.

Park City regulates this, and the mechanism surprises people

Most owners assume tree protection during a build is a matter of goodwill. In Park City it is partly a matter of code, and the instrument is the Limits of Disturbance.

“Significant Vegetation” is a defined term

Park City’s Land Management Code defines it, and the wording varies slightly by chapter — which is itself worth knowing, because the measurement differs:

• In the residential districts: large trees six inches in diameter or greater measured four and a half feet above the ground (standard DBH), plus groves of smaller trees, and clumps of oak or maple covering fifty square feet or more measured at the drip line.
• In the subdivision requirements chapter: large trees of six inch caliper or greater, groves of five or more smaller trees, or clumps of oak or maple covering fifty square feet.

Caliper and diameter-at-breast-height are not the same measurement, so the chapter that applies to your project matters. Six inches is a low threshold either way — on a wooded Wasatch lot, a large share of your trees qualify, and the oak and maple clump provision catches the Gambel oak thickets that cover most south-facing slopes here.

Limits of Disturbance, and a posted security

Where staff determines there is Significant Vegetation on a site, Limits of Disturbance lines are shown on the plats. Under the subdivision chapter, a separate plan addressing Limits of Disturbance, vegetation protection during construction, and re-vegetation of disturbed areas is required. The rule at the lot level is blunt: all construction activity must be contained within the Limits of Disturbance line, with the balance of the parcel remaining undisturbed.

And the part that gives it teeth: a security must be posted to ensure compliance with the Limits of Disturbance plan. That converts tree protection from a conversation into money that does not come back if the plan is ignored. In the residential zones, the Planning Director determines the Limits of Disturbance and may require mitigation for loss of Significant Vegetation.

There is also an inspection hook — the city references a Limits of Disturbance inspection in its permit process, which means the line is meant to be verified on the ground and not just drawn on a plat.

Removed trees generally have to be replaced

Plat notes and architectural guidelines have required that Significant Vegetation removed be replaced in kind, with an allowed alternative of multiple trees whose combined caliper is equivalent to what was taken out. Disturbed areas get topsoil and revegetation.

Budget this at the start. Replacement planting at equivalent caliper is not a trivial line item, and discovering it at final inspection is considerably worse than pricing it during design.

One useful provision alongside all of this: a 2023 ordinance establishes that Significant Vegetation preservation is prioritized, but that it may be removed or replaced where applicable to comply with Firewise Landscaping and/or Defensible Space regulations. If your WUI obligations and your vegetation protection appear to contradict each other, the code anticipates that. Our HB 48 and WUI code guide covers the defensible-space side.

Verify before relying on any of this. These provisions sit across several chapters and have been amended repeatedly between 2019 and 2023, chapter numbering has shifted, and we could not confirm the current security amount or release conditions. Confirm with Park City Planning or in the current municipal code. If your lot is outside city limits, your jurisdiction’s rules differ — Summit County, Heber, Midway and the rest each handle this their own way.

How big is the area you actually have to protect?

This is where most protection plans fail, because people fence the trunk and call it done. The thing that needs protecting is the root zone, and it is much larger than it looks.

The ISA Rocky Mountain Chapter gives the working definition: the critical root zone (CRZ) is a radius of one foot per inch of trunk diameter, measured at four and a half feet above grade. A twenty-inch tree has a twenty-foot CRZ radius. Then also measure the drip line, and use whichever gives the larger area.

Some jurisdictions and extension services use a more protective multiplier — commonly 1.0 to 1.5 feet per inch, with 1.0 for younger, healthier, more construction-tolerant trees and 1.5 for older, less healthy, or more sensitive ones. Others cap it. Use your jurisdiction’s number where one exists.

Two facts explain why the zone is so large:

• The majority of feeder roots sit in the top twelve to eighteen inches of soil— exactly where equipment traffic and grading do their damage.
• Roots commonly spread to two or three times the tree’s height, far beyond the drip line. The canopy edge is a convenient marker, not a root boundary.

A caution on the online CRZ calculators: they are inconsistent. We found tools using multipliers from 1.5 to 2.0 and inventing thresholds that appear in no extension or municipal source. Use them for rough planning only; have an ISA-certified arborist set the protection radius for the species and site.

What actually kills the tree

Soil compaction — the quiet one

Equipment, material storage, and even repeated foot traffic compress soil most severely near the surface, which is where the roots are. Compaction collapses the pore space roots need for oxygen and water. ISA guidance is unambiguous: never compact soil within the CRZ.

The specific prohibitions inside the root zone are worth posting on site, because “we only parked there” is a real conversation:

• Stockpiling materials, debris, soil, or mulch
• Parking vehicles or equipment
• Trenching, or changing grade by cut or fill
• Dumping concrete washout or vehicle fluids
• Installing impervious paving
• Nailing or attaching anything to trees
• Wounding trunks with vehicles, equipment, or mowers
• Fire or excessive heat

Concrete washout deserves its own mention. It is strongly alkaline, it is routinely dumped wherever is convenient, and it does long-lasting damage to soil chemistry in the root zone.

Raising the grade

Fill over a root zone cuts off oxygen. The thresholds are tighter than most builders assume:

• ISA guidance: fill of two to four inches may cause less damage if it is coarser than the existing soil. Never place fill or organic material against the trunk.
• Extension guidance runs from “six inches or less probably will not harm a fill-tolerant tree, especially good topsoil” to a more conservative no more than two inches in a given year. One extension service warns that as little as two inches of clay can do irreparable damage to a fill-intolerant tree.
• Temporary fill counts.Even a few days of stockpiling soil over a root zone can cause long-term harm. The pile that is “only there until Thursday” is still damage.

Lowering the grade

Scraping removes absorbing and transport roots, strips nutrient-rich topsoil, and exposes the remaining roots to drying. General guidance is to remove no more than six inches within the CRZ, and less on shallow soils. Where soil must come off, retaining walls or terraces limit the loss and exposed roots should be mulched.

If grade must be lowered, the sequencing matters: prune roots cleanly four to six months beforethe construction activity, with regular irrigation before, during, and after. That gives the tree a chance to respond on its own schedule rather than mid-crisis. On a steep Park City lot, grade change and drainage are usually the same conversation — see our erosion and drainage guide.

Root severance and trenching

The rules here are specific and easy to hand to a contractor:

• Never cut roots wider than four inches— those are structural, and severing them is both a health problem and a stability problem. A tree that stays alive but loses its anchorage on one side is a failure waiting for the first heavy wet-snow load.
• Make clean cuts with sharp tools. Do not tear roots out with a backhoe. A torn root is a far worse wound than a cut one.
• Avoid trenching through the CRZ at all. Where it is unavoidable, tunnel at least eighteen inches below the root zone or bore the pipe.
• Protect trunks to a height of at least eight feet during trenching, and keep backfill and equipment off the trunk.
• Cover exposed roots with wet burlap and backfill the same day where possible. Roots left open to dry air for a day are roots you have lost.
• Root pruning and any work inside the CRZ should be supervised by an ISA-certified arborist. Our guide to what ISA training changes on a job site covers why that supervision is not a formality.

What a real protection plan looks like

Not complicated, but it has to exist on paper before mobilization.

• A tree inventory.Every tree at or above the Significant Vegetation threshold, located, measured at DBH, identified by species, with condition noted. This is also the document the city’s vegetation-protection plan requires.
• Keep, protect, or remove — decided in design. ISA criteria suggest considering removal for trees within ten feet of the proposed structure, trees that cannot be adequately protected, trees with less than a quarter of their height in crown, and trees with more than a third of the trunk wounded. Deciding this at design stage is dramatically cheaper than discovering it with an excavator on site.
• Fencing at the CRZ, not the trunk. Chain link or similar, with highly visible signage, in place for the life of the project. Fencing that comes down for the landscaping phase is fencing that failed at the moment the most equipment is on site.
• One route in, one route out. A single designated access and exit confines compaction to a corridor you have already written off.
• Padding on high-value trees— stem, branch, and root protection for the specimens you most want to keep.
• An irrigation plan. Provide supplemental water when rainfall falls below roughly one inch per week. A stressed tree in a dry Wasatch summer, mid-project, is a tree you are losing.
• A designated washout and staging area well outside every CRZ.
• Dated photographs before mobilization. This is your baseline, and it is the only thing that settles an argument about whether a tree was healthy in March.

Get the arborist in before the architect finishes

Extension guidance is explicit that an ISA-certified arborist should be involved at the beginning of the planning phase, and that is the single highest-leverage recommendation in this article.

The reason is that almost every decision that determines which trees survive is made on paper: where the driveway runs, where the utility trench goes, where material gets staged, where the excavator parks, whether the garage shifts eight feet. All of those are nearly free to change during design and effectively impossible to change once the foundation is in.

By the time an arborist is called to “look at the trees” after site work has started, the honest answer is often that the decisive damage already happened and will surface in three years.

The contract language worth having

Tree protection fails in practice because the cost of violating it is zero for the person doing the violating. Fix the incentive:

• Make the protection plan a contract exhibit, not a verbal understanding.
• Put a dollar figure on a protected tree. Liquidated damages per protected tree damaged or removed without authorization. A number in the contract changes behavior in a way that a fence alone does not.
• Require subcontractor acknowledgment. The excavation sub and the utility sub are usually the ones who cause the damage, and they frequently never saw the plan.
• Name who may authorize work inside a CRZ, and require it in writing.
• Tie a retainage release to a post-construction tree inspection rather than to substantial completion.

None of this is adversarial. Good builders in this market generally want the trees to survive too — mature trees are a large part of what makes a finished Park City property photograph the way the renderings promised.

If the damage already happened

Not everything is lost, and some interventions genuinely help:

• Get an assessment now, with the damage documented and dated, while causation is still provable.
• Decompact where possible. Air excavation around the root zone and radial trenching backfilled with good soil can restore pore space without further root loss.
• Mulch the root zone— out in the yard, not against the trunk, and keeping the first five feet around structures non-combustible per firewise landscaping guidance.
• Irrigate deliberately through the first several seasons after disturbance.
• Reduce other demands on a stressed tree. Avoid heavy pruning, which removes photosynthetic capacity exactly when it is needed.
• Monitor on a schedule and re-inspect annually. Construction-stressed conifers are also more vulnerable to bark beetle attack, and stress is what invites the first hit.

Where a tree is beyond saving, understanding the real cost is part of planning — our 2026 pricing guide covers removal ranges and stump grinding is worth deciding on up front. If you have just taken on a property where somebody else did the building, our year-one playbook covers what to look for.

Working with us on a build

Canyon Cutters works alongside builders, architects, and owners across Park City and the Heber Valley on exactly this: the inventory, the protection plan, the fencing layout, the supervised root pruning, the selective removals that design decisions genuinely require, and the on-site chipping that keeps the material from being hauled down the canyon.

We would rather be the call that happens during design than the second opinion three years later. If you have a project in planning — or a tree that has started declining since one finished — reach out through our contact page or call (201) 960-8275. The first visit is free, the inventory and assessment come in writing, and the written plan is the document your permit review is going to ask for anyway.

This article summarizes publicly available arboricultural guidance and our reading of Park City code provisions that span multiple chapters and several amendment cycles. It is not legal advice or an official code interpretation, and it is not a substitute for a site-specific protection plan. Confirm current requirements, thresholds, and security provisions with Park City Planning, or with your own jurisdiction if your property lies outside city limits.