ASTM C1496-01

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Designation:C1496–01
Standard Guide for
Assessment and Maintenance of Exterior Dimension Stone
Masonry Walls and Facades
This standard is issued under the fixed designation C1496; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 This guide outlines how to visually assess exterior stone 3.1 Terms used in this guide are defined in Terminology
masonry walls and facades to determine their general condi- C119.
tion. Examining key features of the construction can help 3.2 Definitions of Terms Specific to This Standard:
identify and diagnose problems which require repairs or 3.2.1 crack monitor—any of the several two-part devices
corrective action. Such an examination can expose conditions that can be attached to stone masonry in such a way that they
which may be addressed with maintenance and minor repairs, can span cracks in order to periodically measure changes in
or may require expert assistance. This guide is not intended to crack width thereby indicating movement.
be used for buildings requiring major exterior rehabilitation or 3.2.2 dutchman—repair used to patch stone masonry with a
structural repairs. section of new stone. The damaged area within a particular
1.1.1 This guide applies to walls of solid stone or dimension stone element is removed. The remaining void is trimmed to a
stone used as a cladding. Stone cladding is typically connected regularshape.Anewpieceofstone,or“dutchman,”iscutfrom
to a backup material with a variety of anchoring methods, matching stone cut slightly smaller than the area to be filled. It
including traditional hand-set masonry anchors such as straps, is installed using dowels or some other mechanical attachment,
dowels, cramps, hook-and-eyes, dove-tails, wire ties, and the then adhered, or mortared into place.
like. Joints between stones in these types of buildings are 3.2.3 exfoliation—deterioration or loss of stone in the form
usually filled with mortar or sealant. Sealant-filled joints are of flakes, scales, and layers.
usuallydesignedtoaccommodatestructuralandthermalmove- 3.2.4 professional assistance—independent opinions and
ments. recommendations provided by persons having expertise in the
1.2 Thisguidespecificallyexcludesdimensionstoneusedin assessment and repair of stone masonry. Such professionals
interior building surfaces, flooring or paving, slate dimension may include independent consultants such as architects, engi-
stone used as roofing. Though they share some similar assess- neers, material scientists such as mineralogist or geologists, or
ment and maintenance concerns, thin stone (less than 2 inches stone masonry contractors.
nominal thickness) exterior cladding, and stone cladding at- 3.2.5 thick—stones with a nominal bed-depth of 2 in. (5
tached to metal flames are also excluded due to their unique cm.) or more.
design characteristics and performance requirements.Although
4. Significance and Use
procedures and cautions listed herein may apply to walls and
4.1 This guide attempts to provide information to assist
facades containing semi-dimension, or partially sized, stone in
the form of split-face, or rubble and to stone-facade concrete buildingownersandmanagerswithlimitedknowledgeofstone
construction to recognize basic problems with performance of
panels, the guide is not specifically directed to such stone use.
It does not address removal of small-area stains. facades, and to keep them in good condition through periodic
inspections and maintenance. Increased awareness of the
2. Referenced Documents
behavior of stone masonry facades and associated materials
2.1 ASTM Standards: can reduce maintenance and replacement costs by addressing
C119 Terminology Relating to Dimension Stone problems and deterioration early.
4.2 The objective of all maintenance should be to limit
1 deterioration through early intervention. When it appears
This guide is under the jurisdiction of ASTM Committee C18 on Dimension
damage to stone support elements has occurred, professionals
Stone and is the direct responsibility of Subcommittee C18.07 on Environmental
Properties, Behavior and Cleaning.
should be consulted to evaluate the support conditions, as well
Current edition approved April 10, 2001. Published July 2001. DOI: 10.1520/
as recommend methods to restore the building’s integrity and
C1496-01.
2 preserve public safety.
Annual Book of ASTM Standards, Vol 04.07.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C1496–01
5. Introduction suspended or fixed scaffolding, mobile work platforms, or
personnel lifts to adequately observe existing conditions.
5.1 An effective maintenance program for exterior stone
masonry should incorporate preventive maintenance among its
7. Procedure for Evaluation of Stone Conditions
key elements. Early attention to problems, and simple mea-
7.1 At a minimum, the following procedure should be used
sures to remedy them, will often avoid costly renovation later.
as a guide to decide an appropriate course of action for
This guide is intended to help interested personnel locate such
observed deficiencies as part of an inspection and maintenance
problem areas, better understand potential causes of stone
program for stone masonry facades.
deterioration, and identify appropriate corrective measures for
7.1.1 Identify and document the defects.
the observed deficiencies.
7.1.2 Note the extent of the defects, patterns or concentra-
5.2 Maintenance supervisors should understand how their
tions of distress.
building is constructed to apply this guide and better maintain
7.1.3 Postulate the likely causes.
their buildings. Employing a professional to assist them in
7.1.4 Perform necessary maintenance or obtain assistance
interpreting pertinent drawings and documents, and initially
with repairs:
inspecting conditions should help them become effective
7.1.4.1 If the condition is stable and does not appear to be
observers of stone performance.
progressive, perform appropriate maintenance, and simple or
5.3 This guide lists many typical problems that can affect
temporary repairs.
stone masonry, facades. It describes likely causes, and dis-
7.1.4.2 If the cause is not apparent, and the condition
cusses common repair methods. All initial attempts at repairs
appears stable and not progressive, monitor the condition and
should be done under the observation of a professional to
consult with professionals to determine the cause and appro-
ensure the use of proper materials and techniques.
priate repairs.
7.1.4.3 If the observed conditions are considered dangerous
5.4 Personnel responsible for stone facade maintenance
or progressive, obtain professional assistance immediately.
should be familiar with the systems used in the construction of
their buildings on at least an elementary level. Prior to
8. Maintenance
inspections, they should be briefed by personnel knowledge-
8.1 Routine Maintenance—Many problems can begin or
able about the building and its construction, particularly the
worsen due to neglect of routine maintenance. Stone masonry
stone wall system.This background should help in determining
itself, when used in an exterior application, requires periodic
when the engagement of a professional should be considered.
joint repairs, such as sealant replacement, tuck pointing, and
cleaning. Stone facade components can also be affected by a
6. Guidelines for Inspections
lack of maintenance of other building systems, such as roofs,
6.1 Schedule Inspections—Schedule and perform semi-
parapets, windows, and flashing.
annual inspections of stone wall elements. Inspect all eleva-
8.2 Cleaning—Regular cleaning is also critical to the long
tions of the building. A walk-around visual survey with a
term durability of natural stone facades, as well as their
camera and binoculars should be a minimum procedure. Use
appearance. Cleaning methods should be selected that do not
adjacent buildings’ roofs and windows to gain same-level
damage the stone. Cleaning methods and materials should be
access, to examine building facades and associated elements.
first tested, from the least to the most aggressive, to determine
Use building windows and set-backs where possible for
the mildest treatment that provides satisfactory results. Prior to
additional vantage points. If the available access is not suffi-
implementing a cleaning technique building-wide, test areas
cient to perform the inspections, then consider methods, as
should be cleaned using the proposed methods. The areas
outlined in 6.3. Photograph any observed distress or problem
should be evaluated for a minimum period of six weeks to
areas for later reference in determining appropriate repairs.
assess the results. Improper selection of cleaning chemicals
6.2 Condition Documentation/Monitoring—Keep accurate
and procedures will produce unsightly and irreversible damage
and cumulative records of inspection findings. Buildings con-
to the appearance, and potentially the structural integrity, of the
structed of thick dimension stone with mortar or sealant-filled
stone facade components.
joints react slowly to environmental forces. Knowledge of the
9. Areas of Focus for Inspection
timingofacondition’sonsetandunderstandingitsprogressaid
in assessing the distressed condition. Monitor critical or
9.1 Moisture or Water Staining—Look for signs of moisture
deteriorated areas between scheduled inspections. Use mea-
entranceoninteriorandexteriorsurfaces,aswellasthroughout
surements or crack monitors to measure changes in cracks,
the stone wall system. Water penetration can lead not only to
increasing lippage between stones (stones projecting or retreat-
deterioration of interior finishes, but also to stone and joint
ing in plane from the adjacent stones), or other changes and
material degradation and corrosion of anchor system compo-
displacements in stone position. Well-kept records will aid in
nents if the water is trapped behind or within the wall or facade
the diagnosis of the specific causes of the conditions observed,
system for prolonged periods. Water absorbed into stone and
should more experienced professionals be required.
joint materials can cause dimensional changes, potentially
6.3 Tall Buildings—Inspections of buildings with heights reducing clearances and creating stress concentrations.
that exceed those readily observable with binoculars, or with Trapped water can freeze and expand, causing the stone to
limited vantage points require more detailed planning. It will weaken, and eventually spall or crack. Joint materials may also
be necessary to view representative areas of the facades from deteriorate as a result.
C1496–01
9.1.1 Water can also carry minerals, chemicals, or other tems aggravate the effects of freeze-thaw cycling Both calcium
contaminants that can be deposited on or within the stone and chloride (CaCl ) and sodium chloride (NaCl) are commonly
joints, causing discoloration, staining, or deterioration. used. Both will cause damage to stone surfaces.
9.1.2 Wetness, staining, or darkening may be due to trapped 9.4 Facades—Sight along walls for bulging areas, particu-
moisture. Discoloration or deposition of efflorescence (a pow- larly in those containing smaller stones. Look for areas of
dery white or gray accretion on stone faces) may also be different, or changing, colors. Compare colors before and after
evidence of moisture entry, or “rising damp.” Rising damp is a rains; a continuing damp appearance for some time after a rain
condition in which the stones appear darker due to water may suggest a leak. Cracks across stones, or diagonally along
wicking into the stone by capillary action from a water source mortar joints, may suggest unaccommodated expansion and
along one or more edges of the stone, such as at the base of a contraction or structural movements.
building. 9.5 Unique Details and Fenestration of the Building—Look
9.2 Joints—Every inspection should include a review of particularly at parapets, copings, building returns and corners,
each joint between stones. Document anomalous and suspect andprojectingorcorbeledcourses,fordampnessandmisalign-
conditions photographically, especially in areas of accelerated ment. Check all facades at their bases for the appearance of
deterioration. Where a problem is suspected, it is useful to rising damp. Compare the appearance of joints and stones at
compare photographs taken at various times to establish the and near openings. Due to the typical uniqueness of their
progression and rate of deterioration. installation, soffit stones deserve special attention to their
9.2.1 Look for missing mortar and sealant, for cracks in alignment, color retention, and joint conditions.
mortar, for partings between mortar or sealant and the stone, 9.6 Building Components Not Fabricated from Stone—
for non-uniform joint sizes due to tight, closed or opening Many problems on buildings occur in the roof/parapet areas,
joints, and for lipped stones. Connections between stones and near openings, and at grade. Look carefully at the inside
non-stone materials such as windows and other openings are surfaces of parapets; check the flashing and counter-flashing;
often particularly susceptible to racking and eccentric move- the cant-strip and blocking; the mortar of masonry, back-up or
ment. Check for plugged weep holes throughout the wall under the coping; the coping head joints; expansion joints; and
system. Compare the width of expansion, control, and con- the roof membrane. Inspect roof valleys, particularly at their
struction joints. Look for wider or narrower tops and bottoms ends, where they terminate into drams and down spouts. Check
of such joints. for functioning dram leaders and down spouts. Also note any
9.3 Stone—Cracks and spalled areas at or near joints may cracks and open joints at and near windows and doors.
indicate excessive compression loading, anchor failure, and
10. Common Problems and Typically Recommended
environmental deterioration, among other things. Misalign-
Repairs
ment of stone across a series of joints may indicate local or
structural building movements. 10.1 The following section lists a number of common
9.3.1 Surface deterioration may take the form of exfoliation problems that can occur with exterior stone wall construction
(where the surface is lost in thin layers), spalling, powdering, which can be identified and addressed, at least in early stages,
or chipping. These condit
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