The Hill Country Roadway Overlay (HCRO), established under Austin Land Development Code (LDC) Section 25-2-1185 and related chapters, imposes mandatory spatial, material, and environmental standards along some of Austin’s most ecologically sensitive and scenic corridors. Each discipline of plan production, from site grading to elevations, schedules, and landscape plans, is impacted by these overlays. Precision in HCRO drafting practices-on setbacks, building heights, material percentages, impervious cover, grading, lighting, and vegetation, as codified and enforced by the City of Austin-drives permit approval, cuts plan-review rounds, and translates into code-conforming construction.

Dimensioning HCRO Setbacks and Height Datum on Site Plans and Elevations: LDC 25-2-1185 Compliance

Setback Representation on the Site Plan

Austin’s Hill Country Roadway Ordinance, LDC 25-2-1185, dictates that structures along designated HCRO corridors must be positioned a minimum of 100 feet from the Hill Country roadway right-of-way (front yard setback), with 25 feet minimum at side and rear yard property lines. These dimensions are observed regardless of base zoning. The correct setback lines must be shown as bold dashed lines on architectural or civil site plans, explicitly dimensioned from the correct legal reference points:

  • Front setback: Dimensioned perpendicular from the right-of-way line, not from back-of-curb or pavement edge. The plan must label the surveyed right-of-way boundary (“Hill Country Roadway ROW per Survey”) and align the 100’ minimum setback line accordingly.
  • Side/rear setbacks: Dimensioned from the property boundary as shown in the site’s ALTA or boundary survey.

Common redline:

  • “Proposed structure encroaches into the required 100-foot front yard setback as per LDC 25-2-1185. Revise site plan to comply.”

Multiple setbacks should use legible, nested dashed lines or colored hatches in the legend. Each setback line must be labeled (“Required 100’ HCRO Setback”, “25’ Side/Rear Setback”) and dimensioned in plan view using continuous leadered dimensions to the nearest face of proposed improvements.

Height Datum and Elevation Details

The maximum building height allowed within HCRO boundaries is 28 feet above the natural grade at the building perimeter; no variances, administrative modifications, or allowances apply (LDC 25-2-1185(C)(2)). The LDC is specific: “building height is measured from the natural grade at the building perimeter.” This precludes using finished grade or average grade, a common error noted by plan reviewers.

  • On all exterior elevations, drafters must show a heavy dashed line for the natural grade, labeling it as “Natural Grade at Building Perimeter (Surveyed 2' Intervals).”
  • Elevation tickmarks should indicate both the natural grade and the finished floor. Call out the maximum dimension from the natural grade (at each face of the building) to the highest point of the proposed roof (“28'-0" max above natural grade - LDC 25-2-1185(C)”).
  • On sections, detail any necessary cut/fill so the grade line datum and structure are interpreted correctly by plan reviewers.

Common redlines for elevation sheets:

  • “Height measurements must be taken from natural grade at building perimeter. Provide revised elevations with accurate height datum.”
  • “Building height exceeds the 28-foot maximum allowed under HCRO regulations. Adjust elevations accordingly.”

Zoning Overlays and Amendments

While HCRO overlays take precedence, certain districts-such as those under LDC 25-2-1406 and the Lake Austin (LA), Barton Springs (BS), or Scenic Roadway (SR) overlays-may further modify height and setback rules. In these cases, drawings must reference both overlay and base district requirements, with tables on the site plan listing both base and overlay restrictions and referencing the exact LDC sections (“See LDC 25-2-1185; see also LDC 25-2-1406 for LA/BS overlays”).

All setback and height lines must be included in the site and floor plan sheet indexes, with cross-references to detail and elevation sheets, supporting a consistent code-trail for plan reviewers and future field verification.

Critical Sheet Legends, Dimensions, and Code Call-Outs

  • Dimension setbacks explicitly: “100.00’ min to ROW”, “25.00’ min to property line”.
  • Height datum: “Elevation 0.00’: Natural Grade at Building Perimeter (surveyed date XXX)”; “Proposed Building Height: XX’-X" (max. allowed 28'-0")".
  • Contour intervals on site/civil sheets: use 2’ intervals; bold contour for natural grade.

Plan sets missing these conventions often stall in plan review, with reviewers returning for revised, code-anchored dimensions and datum call-outs (Austin LDC Subchapter C, Article 11).

Drafting Exterior Material Schedules and Call-outs for HCRO Visual Compatibility

HCRO Schedules: Percentages, Reflectivity, and Documentation

Beyond spatial controls, the HCRO enforces visual harmony with the Hill Country landscape. The plan set’s exterior material schedule anchors this compliance. It must show:

  • Clear percentage breakdowns for each exterior material (masonry, stone, stucco, fiber-cement, wood, metal, etc.) for each façade, explicitly noting coverage area and percent of wall surface. (Ex.: “West Façade: 65% Lueders limestone, 30% wood siding, 5% fiber-cement trim.”)
  • Material reflectivity ratings: Each finish surface (roofing, cladding, glazing) must specify Solar Reflectance (SR) and, where applicable, aged SR, as well as Emittance per ASTM standards. For example, “Roofing: Class A composite shingle, SR = 0.70 initial, 0.55 aged per ASTM E903-96; Emittance = 0.75 per ASTM C1371-04a.”

For roofing specifically, Austin amendments and the Hill Country Overlay draw on Austin Energy’s reflective roof requirements: dark colors and low-reflectivity finishes are generally required for walls, while “cool roof” coatings are required for flat roofs. Where roof pitch brings portions into view from the protected corridor, ensure reflectance below 0.30 unless otherwise approved by DSD.

Plan Sheet Call-Outs, Notation Standards, and DSD Review Criteria

  • All elevations and architectural sheets: Place keynotes at every material transition (“Stone veneer: 3" min. thickness, rough-face, color to match Hill Country limestone-SR<0.3”.)
  • Reflectivity: List reflectivity/thermal emittance in finish schedules (“Metal coping: colored finish, SR 0.32, Emittance 0.81, ASTM E903-96/C1371-04a.”) Cross-reference to cut sheets in the appendix or on detail sheets.
  • Material percentages table: Place on cover sheet and in each elevation-some reviewers ask for a chart per exposure, not just overall.
  • Detail sheets: Show enlarged wall/roof section details with labeled layer build-up, expanded keynote for cladding type, fastener, and weather barrier.

Typical reviewer comments:

  • “Non-compliant materials specified for HCRO. Revise schedule to show min. 60% stone/approved masonry, max. 40% painted surfaces.”
  • “Insufficient documentation of reflectivity/emittance for all roof surfaces. Provide manufacturer spec sheets and indicate ASTM test compliance.”

Materials banned or restricted typically include bare metal and high-gloss surfaces. Cool Roof Rating Council datasheets support code documentation.

Critical Specs, Dimensions, and Plan Sheet Elements

  • Masonry: 3” minimum thickness, stone or brick with natural colors, rough face preferred.
  • Wood/fiber-cement siding: Max. 6” exposure for clapboards. Colors must be earth tones/blend with native context.
  • Roofing: For sloped roofs, dark composition shingles; for flat roofs, “cool roof” products at initial SR 0.70 and aged SR 0.55 or better per ASTM E903-96.
  • Reflectivity cut sheets: Attach manufacturer documentation showing SR/emittance for each exterior surface.

Plan sets that fail to annotate material percentages, omit reflectivity ratings, or lack precise legend correlations routinely face re-review. Reference Austin DSD’s Building Technical Codes and Local Amendments.

Calculating and Detailing HCRO Impervious Cover Limits on Site Plans

Impervious Cover Limits: Code and Zoning Context

Impervious cover within HCRO areas is strictly limited by both water quality and scenic overlay codes, enforced through permit review by DSD and Environmental Review. As established in LDC 25-8-423:

  • Single-family residential use (most common): 30% impervious cover on net site area, up to 40% only with transferred development intensity (see LDC 25-8-424 for TDI criteria).
  • Commercial, multifamily, or mixed use: 40% impervious cover, up to 55% if TDI is invoked (rare in residential overlays).

“Net site area” excludes dedicated rights-of-way, floodplain, and protected slopes, and must be shown as a calculation table on the site plan (“Net Site Area Calculation (per LDC 25-8-2): Lot area = X, less ROW = Y, less FP = Z, Net Area = Q”).

Drawing Material Breakdown and Legends

  • All impervious areas-buildings, driveways, walks, patios, concrete, and even paver areas atop compacted base-are to be hatched in a standard pattern, keyed to a legend (“IC-1: Concrete (hatch ###) ... IC-2: Asphalt (hatch ###) ... IC-3: Pavers (hatch ###)”).
  • Decks: Uncovered wood decks above pervious soil with spaces between boards are counted at 50% of plan area per LDC 25-8-63.
  • Paths, gravel, and landscape areas used solely for pedestrian or ornamental purposes, without compacted subbase, are not IC but must be indicated in the site legend and/or materials table as “pervious.”

Common plan reviewer comments:

  • “Incomplete impervious cover calculations. List all IC elements and their areas; confirm exclusions per LDC 25-8-63.”
  • “Site plan legend missing hatch patterns and area table for IC elements.”

Impervious Cover Table and Compliance Documentation

  • Tabulate each IC element: “Main house: 2,130 SF; Garage: 450 SF; Driveway: 950 SF; Walkways: 120 SF ... Total IC:”
  • Total IC as % of Net Site Area: Add as a summary row: “Total IC: 3,650 SF = 28.3% of net site area (max allowed: 30%).”
  • Include code reference: “Impervious cover calculations per LDC 25-8-423, 25-8-63.”

Delays in review often stem from omitted or ambiguous area calculations, or missing exclusions (sidewalks in ROW, un-compacted gravel, etc.). Calculations must be defensible and correlated directly with the materials legend and site drawing. (See also the Environmental Criteria Manual for further clarifications.)

Detailing Materials and Dimensional Specs

  • Concrete/asphalt elements: Show thickness (e.g., “4" concrete slab w/ 4" compacted crushed limestone base”), slope for drainage (“1% min. slope, away from structure”), and location markers aligned to setbacks.
  • Pervious vs. impervious: Detail in legends, with dashed vs. solid hatch for field clarity; call out exceptions-“Stone path, uncompacted, pervious per LDC 25-8-63.”

Drafting HCRO-Compliant Site Grading and Retaining Wall Details

Retaining Wall Heights and Permit Thresholds

Retaining walls within HCRO districts demand careful site grading coordination. Under Austin-adopted IRC section R105.2 (2024 edition, as amended), retaining walls up to 4 feet high (measured from the bottom of footing to top of wall) do not require a permit if not supporting a surcharge or sited within a flood hazard area. Walls over 4 feet always require an engineer’s stamp and a permit (“City of Austin Code 25-12-243”).

  • All wall heights must be dimensioned on both elevation and section views (“Proposed segmental block wall: 42” AFF, total 48” from base to cap”).
  • Engineered walls (over 4'): Call out “Top of footing elevation (XX.XX)”; “Top of wall elevation (YY.YY).” Reference structural sheet set (“See S2/S3”).

Common permit-stage redlines:

  • “Provide engineered drawings for all walls exceeding 4' in height per City Code 25-12-243 and IRC R105.2.”
  • “Retaining wall details must specify finished and natural grade at all faces.”

Material Specifications Relevant to HCRO Character

  • Limestone or masonry: “Dry-stack or mortar-set Texas limestone blocks, 4-6” H x 12-24” L x 8” D, rough face to exposure per HOA/overlay requirements.”
  • Concrete block: “Segmental, split-face CMU, color to blend with native stone; system to include interlocking pins and geogrid if wall exceeds 4’ or supports surcharge.”
  • Poured-in-place concrete (engineered): “3,600 psi min. strength, face finished with natural stone veneer or integrally colored texture; see detail 4/A201.”

HCRO overlays almost always require that wall materials visually harmonize with the Hill Country terrain. All elevations, wall legends, and detail sheets must call out material by proprietary name, color range, thickness, installation detail, and finish treatment.

Site Grading, Drainage, and Erosion Control Details

  • Sections and details must show filter fabric separation, subsurface drainage (“4” perf. drain tile at base, sloped 1% to daylight or storm outlet”), and minimum 12” backdrain clean gravel.
  • Slope to daylight at ends of walls or incorporate weep holes at 10’ o.c. Detail these in both plan and sections.
  • Temporary erosion controls: Silt fence, mulch socks, or filter berms-label on grading/landscape sheets as “ESC-1: Silt Fence at Toe of Slope - Per ECM §1.4.”

Permanent revegetation post-construction must be specified on plan note (“All disturbed soils to be seeded and stabilized per ECM §1.7, certification required for CO.”)

Critical Dimensions, Reinforcement, and Drawing Conventions

  • For walls under 2’: Compacted gravel base, 6-8” D x 18” W min. Show section marker “See 3/L-501.”
  • 2-4’ walls: Concrete strip footing, 12-18” D x 24-30” W min., #4 bar continuous, refer to detail “See S5/S6.”
  • Drainage swale: Call out grade break, slope arrow, and tie-in elevation (“Swale invert elev. = XX.XX; slope 2% min. to street ROW”).

Incorrect or incomplete wall details, ambiguous calls for natural vs. finished grade, and lack of stamped engineered sheets for tall walls cause delays at permitting and inspection. Reference Austin Transportation Criteria Manual, Section 13 for public ROW grading.

Specifying and Detailing Dark-Sky Compliant Lighting and Native Landscaping in HCRO Plans

Lighting Fixture Schedules, Photometrics, and Code Compliance

HCRO overlays systematically restrict outdoor lighting to address both environmental and scenic impacts. Austin’s LDC Chapter 25-2, Subchapter E §2.5 as locally amended enforces the following:

  • Fixtures must be full cut-off or fully shielded-emit zero upward light and comform to dark-sky standards. All exterior luminaire schedules must be annotated as “Full cut-off, dark-sky compliant per LDC 25-2-891.”
  • Fixture schedule: Tabulate all luminaires: tag (e.g., “L1, L2”), manufacturer/model, lamp type/wattage, mounting height, shielding details (“shielded wall sconce, 9’ AFF, downward only, 12W LED max”).
  • Photometric plan: Overlay photometric isolines on site/landscape plan, with max/min levels and cross-lot spill indicated (“Max at property line: [X] lux, Max up-light: 0.0% per fixture spec”).

Reviewer redlines:

  • “Provide catalog cuts for all fixtures; verify fully shielded/full cut-off. Revise lighting plan to show photometric isolines and property line compliance.”
  • “Lighting schedule does not note fixture shielding; revise to indicate dark-sky compliance.”

Native Landscaping Spec, Tree Preservation, and Plan Sheet Notation

  • Tree preservation: All trees ≥19” diameter at 4.5’ height are “protected.” Show with bold trunk symbol; dimension critical root zone (“CRZ”) radii and call out “Tree Protection Fence (orange safety fence at CRZ, 4’ min. height)” on both site and landscape plans.
  • Vegetation cover: At least 20% of the street yard must be vegetated (not hardscape); show in table (“Street yard area = XX sf; 20% = YY sf vegetated (lawn/shrubs/trees); mulch/gravel ≤4%.”) Grass areas count but must be native species as specified on plant schedule.
  • Tree planting: Schedule must list new plantings by caliper/species (“Quercus fusiformis; 3.5” caliper, native live oak; planting per ECM §3.5.2”).
  • Details: Call out planting pit dimensions, soil spec, mulch depth, staking, and maintenance requirements (“2x diameter of rootball; mulch 3” depth; top of root flare at finish grade.”)

Omissions in tree CRZ fencing, incorrect grass species, or lack of minimum vegetated coverage are among the most flagged issues by reviewers for HCRO frontages.

Plan-Review and Permit Comments: Avoiding Redlines

  • “Non-compliant fixtures: provide catalog cuts and annotation for full-cutoff dark-sky compliance.”
  • “Photometric plan missing; provide full site photometrics showing no upward light or property line trespass.”
  • “Tree protection fencing not shown at full critical root zone; detail required on L1.02.”
  • “Street yard vegetation below min. 20% per LDC. Revise planting plan and provide updated table.”

Dimensions, Fixture Ratings, Plant Materials, and Drawing Sheet Structures

  • Lighting: 12’ max mounting height for area lights; 9’ max for entries. Lumen output per area type and fixture, with “Full cutoff/BUG-rated B0-U0-G1” notation in schedule.
  • Tree/planting dimension: Trees at 3” caliper min., native; shrubs at 5-gal. container min.; identify location and spacing per ECM specification.
  • Landscape plan must overlay root protection areas and annotate with “Protected Tree-see EC-2/3/L-501 for root zone fencing & no-disturb notes.”
  • Include a legend for all plant material and lighting symbols; cross-reference catalog sheets and photometric plots.

Supportive code links: cityrulelookup.com-outdoor lighting, Austin DSD-Residential Plan Review.

Integrated Sheet Structure and Plan Set Conventions for HCRO Compliance

Consistent, code-referenced detail across disciplines is critical in HCRO-responsible plans. The full sheet set must:

  • Correlate site, architectural, civil, and landscape plans via explicit legends, zone overlays, and cross-referenced schedule tables.
  • Dimension all setbacks, building heights (using correct datum), and IC limits directly with code citations in close proximity to their call-outs.
  • Embed material percentages and ratings on both elevations and cover/finish schedules; include referenced ASTM/IECC documentation.
  • Show wall and grading cross-sections with spot elevations, drainage, erosion control, and wall reinforcement, all linked to both architectural and civil sheets.
  • Detail dark-sky lighting with photometrics, BRG/BUG ratings, schedule, and cut sheets all collated in one sheet and cross-included in general notes.
  • Annotate tree preservation, native planting, and critical root zone boundaries on landscape sheets, with expanded notation in legend and plan notes.
  • Tabulate, on a code summary/cover sheet, all compliance metrics: setbacks, max height, IC %, material percentages, vegetation %, tree preservation counts, and lighting controls, each with LDC/IBC section references.

Final plan sets reflecting these detailed conventions, matched with up-to-date code citations and precise sheet references, substantially streamline DSD reviews and field implementation under the Hill Country Roadway Overlay regime. For technical code text and interactive overlays, see Austin LDC Subchapter C, Article 11 and corresponding permit links at the City of Austin Development Services Department.

Every hill country project lives or dies on sheet-to-field specificity-precise setbacks, dimensional elevation links, material reflectivity, impervious coverage, wall and drainage structure, and environmental protections built into the base drawings and reviewed detail. No “back of napkin” compliance gets through DSD’s overlay review queue.

Kingsway Drafting & Design delivers this level of detail-driven compliance for HCRO sites on every project, every plan sheet.