Surveys & Assessments

Stone Surveys 101: How to Document Historic Masonry Conditions

Learn what a stone survey is, when it is required, and how architects document masonry conditions for preservation, safety, and compliance with Layer.

Mike Lee

Updated: Jan 6, 2026

Stone surveys are a required part of many preservation, façade, or safety-driven projects involving historic buildings. If your background is in new construction, this may be unfamiliar. The intent of a stone survey is to document how masonry materials have performed over time, not how they were designed or originally built.

This guide explains the purpose of stone surveys, where they are most often required, and how to prepare for this type of work as an architect.

What is a stone survey?

A stone survey is a visual and structured assessment of the condition of stone used in a building façade or structure. The goal is to identify the types of stone present, document how they were installed, evaluate signs of deterioration, and classify existing damage by location and severity.

Unlike traditional as-built documentation, stone surveys focus on how materials have aged over time and whether repairs or monitoring are necessary. The results typically inform repair design, preservation scope, or regulatory compliance.

Stone surveys are frequently required for:

Local safety inspection programs, such as New York City’s FISP (Façade Inspection & Safety Program, formerly Local Law 11), which mandates visual and close-up inspections of buildings over six stories every five years.
Historic preservation approvals, such as those required by local landmarks commissions in cities like Boston, Philadelphia, or Chicago.
Restoration scope development for public buildings, universities, or religious institutions undergoing capital improvement projects.
Documentation prior to adaptive reuse or envelope upgrades on masonry buildings.

The role of the architect in a stone survey is to document, not diagnose. You are not specifying repairs or confirming structural adequacy. Rather, your objective is to capture high-quality data that supports others in making informed decisions.

Topics to clarify with your client

Before conducting a stone survey, you should confirm the scope and expectations with the project lead, owner, or preservation consultant. These factors will shape how you plan the survey, what tools you use, and how much time is required.

Here is a checklist of questions you can lean on for that discussion:

Clarifying these items early will determine whether you are tagging every stone unit, mapping conditions by elevation, or creating a condition index tied to sample areas. This will also inform access requirements, team size, and whether digital survey tools are appropriate.

Where are stone surveys are most common?

Stone surveys are common in cities and regions where traditional stone construction was widely used and where long-term maintenance or historic preservation is a factor. If you’re practicing in residential architecture in Houston, you may never need to think about documenting stone condition because most buildings are stick built. If you work in New York City, you might see signs of a facade inspection on an almost daily basis in contrast.

The table below compares how local climate, building age, and regulatory environment shape the need for stone surveys in North America.

City or Region	Historic Construction Type	Common Stone Materials	Why Stone Surveys Are Common
New York City	Load-bearing and veneer façades on pre-war buildings	Limestone, brownstone, granite	Required by FISP law for buildings over 6 stories
Boston	Traditional masonry with frequent freeze-thaw cycles	Granite, sandstone, brownstone	Historic districts and preservation review processes
Chicago	Heavy masonry in early 20th century high-rises	Limestone, granite, terra cotta	Aging façades in severe climate; local ordinances
Philadelphia	Colonial and early industrial masonry	Schist, brick with stone trim	Landmark oversight; aging institutional buildings
Washington, DC	Civic and institutional stone buildings	Limestone, marble, granite	High concentration of historic public structures
Baltimore	Rowhouses and public buildings	Sandstone, brick with stone	Widespread stone detailing in early neighborhoods
San Francisco	Stone accents on seismic-retrofitted buildings	Granite, sandstone	Preservation boards; seismic work often triggers review
Houston, Phoenix, Orlando	Primarily modern framed construction	Limited exterior stone use	Stone surveys are rare due to climate and building type

In general, stone surveys are most relevant in northern or coastal cities where masonry buildings are older, exposed to moisture and freeze-thaw conditions, and subject to regulatory oversight.

Common stone types in historic construction

Architects are not expected to identify the exact mineral composition or origin of stone materials. However, being able to recognize general stone types and their behavior is essential to documenting existing conditions and supporting repair planning.

Stone Type	Typical Use	Common Issues	Notes
Granite	Civic buildings, foundations, stoops, water tables	Joint failure, cracking, staining	Durable stone often paired with softer mortar. Staining may result from metal anchors or atmospheric pollutants.
Limestone	Institutional façades, monuments, masonry veneer	Surface erosion, sugar decay, acid damage	Susceptible to uneven weathering and black crust formation in urban environments. Sensitivity varies by grain and finish.
Brownstone	Rowhouses and walk-ups in northeastern U.S.	Spalling, delamination, large-scale erosion	Soft, layered sandstone that retains moisture. Frequently patched or consolidated due to maintenance challenges.
Sandstone	Regional use in civic, religious, and residential buildings	Granular loss, erosion at corners, differential weathering	Varies widely in durability. Documentation should note differences in bedding orientation and finish.
Marble	Ornament, base courses, monuments	Staining, bowing, surface dissolution	Rare on full façades. Sensitive to humidity and acid rain. Bowing may occur in thin panels.

Always note transitions between stone types and identify areas with visible replacement or past repair. This is especially important for stone units that have been patched, substituted, or resurfaced.

Conditions to record

A stone survey documents visible deterioration. Your responsibility is to describe what is present; not to explain why it occurred or how to fix it. Use consistent terminology and include location-specific notes to support follow-up analysis.

Condition	Description
Cracking	Linear breaks in the stone or at mortar joints. May include surface hairline cracks, through-body fractures, or stepped cracking related to movement. Record orientation, length, and depth if observable.
Spalling	Loss of stone material from the surface, often exposing coarse texture or aggregate. Typically caused by freeze-thaw cycles, moisture, or embedded metals.
Scaling	Superficial flaking or exfoliation of the stone face. May signal early-stage deterioration or precede deeper loss like spalling.
Delamination	Separation of stone layers along natural bedding planes or weak lamination. Often found in brownstone or sandstone. May appear blistered or hollow.
Efflorescence	White or gray crystalline deposits of salts. Indicates active or past moisture movement. Often seasonal or related to drying patterns.
Biological growth	Presence of moss, lichen, algae, or mold. Most often appears in shaded or damp areas. May retain moisture and obscure underlying conditions.
Joint failure	Mortar that is cracked, recessed, missing, or deteriorated. Joint failure accelerates water ingress and stone deterioration.
Displacement	Stone units that are out of plane, bulging, rotated, or otherwise shifted. Can suggest movement, settlement, or anchorage failure.
Past repairs	Includes Dutchman inserts, epoxy fills, mechanical pins, or patching compounds. Note material compatibility, color match, and condition.
Incompatible materials	Use of cement-based mortars or rigid sealants that are harder than the surrounding stone or historic mortar. May cause adjacent failure or staining.

Each condition should be mapped by location and tied to a consistent code or legend. Avoid speculative descriptions. When in doubt, photograph and annotate rather than interpret.

Why mapping is critical

While photographs record appearance, maps communicate location, frequency, and severity. A comprehensive stone survey creates a shared reference for all project stakeholders and allows condition trends to be analyzed across elevations.

Effective survey mapping includes:

Elevation drawings or façade photos to serve as a base
A standard set of condition symbols or color-coded tags
Linked annotations for severity, location, and repair history
A numbering or ID system for traceability
Cross-referenced photographs tied to mapped tags

Mapping supports coordination between design teams, preservation reviewers, and contractors. It also allows for phased repair documentation and comparative analysis across time if follow-up surveys are conducted.

Access considerations

The method you use to inspect a building directly affects how much can be documented and how accurate your observations will be. Before determining how to access a façade or roofline, confirm whether there are specific regulatory requirements or inspection protocols that apply to the project.

Start by identifying:

Whether physical access is required by a governing body
Whether certain façade zones must be observed at close range
Whether you are permitted to conduct visual-only surveys
Whether photography alone will meet documentation standards

Once the requirements are clear, determine what access is practical and permitted based on building height, site conditions, schedule, and safety.

Access Method	Use Case
Visual survey from grade	Suitable for low-rise buildings or for ground-floor and setback façades. Often used when access is restricted or when only representative conditions are being collected.
Binocular or zoom-assisted survey	Common for preliminary assessments or when full elevation coverage is not required. Conducted from sidewalks, terraces, or rooftops. Provides moderate visibility but may miss fine-grain deterioration.
Lift or boom access	Required for close-range inspection or when regulations mandate physical access. Enables touch-level examination of cracks, joints, or repairs. Confirm safety procedures, lift permits, and anchor points ahead of time.
Drone photography	Best used for general documentation and to capture hard-to-access elevations. Valuable for mapping and coordination but should not be used to classify material conditions unless paired with physical inspection.

Access planning affects time on site, staffing, and equipment needs. Confirm with the owner or consultant what level of access is expected and what documentation standards must be met before mobilizing.

Digital documentation methods

Mobile documentation platforms reduce time spent on annotation and help maintain consistency across large surveys. Teams using Layer often standardize stone condition surveys using the following workflow:

Upload annotated PDFs, façade drawings, or elevation photos as a base layer
Create structured fields for condition type, severity, and notes
Tag each condition location directly on the drawing
Attach reference photos, detailed notes, or comments to each tag
Export survey data to a report format or sync to Revit if applicable

This method ensures that all documentation is tied to specific geometry, minimizes manual data entry, and supports collaboration with consultants or regulatory reviewers.