ARCHITECTURAL PRECAST CONCRETE JOINT DETAILS Reported by PCI Committee on Architectural Precast Concrete Joint Details Raymond J. Schutz Chairman James Engleҟ Albert Litvin James G. Gross ҟ R. L. Pare Abraham Gutmanҟ John S. Parrish J. A. Hansonҟ Irwin J. Speyer Kai Holbekҟ Ivan L. Varkay Felix Kulkaҟ Lloyd Wright Correct joint design and proper selection of materials and installation are vital for the successful performance and esthetic appeal of precast concrete wall systems. This report recommends the proper precast concrete joint details and sealants for specific situations. In writing these recommendations, architectural treatment and economy in mold design were considered but are not included, since these are covered in the PCI Manual on Architectural Precast Concrete. Following these recommendations will result in a good design and a durable, waterproof, and economical joint. 10
ARCHITECTURAL PRECAST CONCRETE JOINT DETAILS
Apr 07, 2023
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Reported by
Raymond J. Schutz Chairman
James Engle Albert Litvin James G. GrossR. L. Pare Abraham GutmanJohn S. Parrish J. A. Hanson Irwin J. Speyer Kai Holbek Ivan L. Varkay Felix Kulka Lloyd Wright
Correct joint design and proper selection of materials and installation are vital for the successful performance and esthetic appeal of precast concrete wall systems. This report recommends the proper precast concrete joint details and sealants for specific situations. In writing these recommendations, architectural treatment and economy in mold design were considered but are not included, since these are covered in the PCI Manual on Architectural Precast Concrete. Following these recommendations will result in a good design and a durable, waterproof, and economical joint.
10
CONTENTS Chapter1—Joint design ................................... 12
1.1 Scope 1.2 Types of joints 1.3 General design concepts for
joints 1.4 Number of joints 1.5 Location of joints
Chapter 2—Planning check lists ............................ 14 2.1 Definitions 2.2 Joint planning 2.3 Water runoff planning
Chapter3—Joint details ................................... 15 3.1 General 3.2 One-stage joints 3.3 Two-stage joints 3.4 Cavity wall 3.5 Floor and roof slab joints 3.6 Precast parapets 3.7 Precast panel window details
Chapter 4—Sealant materials ............................... 24 4.1 General 4.2 Field-molded sealants and
their uses 4.3 Accessory materials 4.4 Preformed sealants and
their uses 4.5 Compression seals and
their uses 4.6 Joint design 4.7 Determination of joint
movements and locations 4.8 Selection of butt joint widths
for field-molded sealants 4.9 Selection of butt joint shape
for field-molded sealants 4.10 Selection of size of compression
seals for butt joints 4.11 Limitations on butt joint widths
and movements for various types of sealants
4.12 Lap joint sealant thickness
References ............................................... 36
1.1 Scope
The design of joints must be exe- cuted as an integral part of the total wall design. Some specific guidelines for joints do govern their ultimate suc- cess. This chapter highlights and illus- trates several cases of interdependence with other wall design criteria.
In all cases, the designer should as- sess his requirements for joints realisti- cally with respect to both performance and cost. If joint designs and details are contemplated which differ from those normally used in the area where the project is located, local producers should be consulted.
The following discussion will deal mainly with joints which are designed to accommodate local wall movements only, rather than an accumulation of such movements which would require properly designed expansion joints.
1.2 Types of joints
Joints between precast wall panels may be divided into two basic types:
1. One-stage joints 2. Two-stage joints
A cavity wall design is considered a further application of the two-stage joint.
1.2.1 One-stage joints. As the name implies, this joint has one line of de- fense for its weatherproofing ability. This occurs normally in the form of a sealant close to the exterior surface. The advantage of this type of joint is
that it generally provides the lowest first cost, and it is suitable for use be- tween precast panels as shown in Figs. 3.2.1 to 3.2.6.
The success of one-stage joints de- pends on the quality of materials and proper installation at the building site. This type of joint is in common use in most of North America. One-stage joints should be regularly inspected and may demand fairly frequent mainte- nance to remain weathertight.
1.2.2 Two-stage joints. These joints have two lines of defense for weather- proofing. The typical joint consists of a rain barrier near the exterior face and an air seal normally close to the interior face of the panels. The rain barrier is designed to shed most of the water from the joint and the air seal is the de- marcation line between outside and in- side air pressures. Between these two stages is an equalization or expansion chamber which must be vented and drained to the outside. Section 3.3 gives typical details of two-stage joints. It can be seen that the simplest form of a hor- izontal two-stage joint is the well prov- en shiplap joint.
The rain barrier prevents most of the rain and airborne water from entering the joint. If airborne water (wind-driv- en rain) penetrates this barrier, it will drain off in the expansion chamber as the kinetic energy is dissipated and the air loses its ability to carry the water. Any water which penetrates the rain barrier should be drained out of the joint by proper flashing installations.
In order to avoid vertical movement of the air in the expansion chamber
12
(stack effect) caused by wind or outside air turbulences, it is advisable to use these flashing details as dampers and provide them at regularly spaced inter- vals along the height of the vertical joints. Such flashing is sometimes in- stalled at each floor level, but a greater spacing (two or three stories) may be sufficient for low-rise buildings and in areas with moderate wind velocities.
Since the air seal is the plane where the change in air pressures between the outside and inside atmospheres occurs, it would normally be subject to water penetration through capillary action. Inasmuch as the outside air reaching this seal has lost its water content, no moisture can enter by such action.
The danger of humidity traveling from inside the building and through the air seal should be investigated for buildings with relatively higher interior humidity, and for tall buildings, where the interior air pressure may occasion- ally be substantially higher than the outside atmospheric pressure. This con- dition is normally solved by using a cavity wall design.
A cavity wall (Fig. 3.4.1) is the most effective wall for the optimum separa- tion and control of both outside and in- side air and humidity conditions. When precast concrete wall panels are used in cavity wall designs, they will normally serve as the rain barrier. An air space is maintained between the precast exteri- or and the interior wall. Insulation, when required, is applied to the outside face of the interior wall, eliminating condensation problems and, thereby, making the inner wall subject only to the relatively constant interior tempera- ture. Cavity wall construction is nor- mally expensive when compared with conventional walls. On the basis of their lower maintenance costs and their ex- cellent performance records, they may well be justified for specific types and locations of buildings.
The two-stage joint is gaining accep- tance particularly for buildings subject to severe climatic exposure or tempera- ture and humidity control.
A disadvantage of the two-stage joint for concrete wall panels is the higher cost. For projects with good repetitive joint design properly integrated with other panel details, and having efficient production and erection procedures, it may well approach the cost of one-stage joint installations. In these instances, the safety factors and lower mainte- nance costs should also be considered.
A minimum precast wall panel thick- ness of 4 in. (10.2 cm) (with field- molded sealants), preferably 5 in. (12.7 cm) (with gaskets and compression seals), is required to accommodate both the rain barrier and the air seal. For two-stage joints with compression seals, connection detail allowance should be made for slight horizontal movements of the panels after initial fastening for air seal compression.5 The joints must be fully accessible from the inside of the panels for later installation of the air seal. The simplest form of a horizon- tal two-stage joint is the shiplap joint.
1.3 General design concepts for joints
The purpose of joint design is to pro- vide weathertightness of the joint con- sistent with the exposure of the joint. In addition, as part of the overall perfor- mance requirements of the building, the purpose for which the building is built will also determine design require- ments for the joint.
Thus, joint design will be governed by its exposure (orientation and climatic conditions), the purpose of the building, and appearance. The following guide- lines must all be evaluated in relation to the relative importance of these cri- teria.
PCI Journal/March-April 1973 13
1.4 Number of joints It is generally advantageous to plan
for the fewest number of joints, due to the lower overall joint cost, potentially lower maintenance cost, and the econ- omy of large panel erection.
Optimum panel sizes must, however, also be determined from erection condi- tions and established limitations of weight and sizes for transportation.7
If the desired appearance requires additional joints, this may be achieved through the use of false or dummy joints. In order to match the appear- ance of both false and real joints, an applied finish should be chosen to sim- ulate sealants or gaskets in the real joints. Caulking of the false joints adds an unnecessary expense.
1.5 Location of joints Joints are easier to design and exe-
cute if they are located where maxi- mum panel thickness occurs. Except for one-stage joints and joints in precast panels performing as rain barriers in cavity walls, the minimum panel thick- ness at joints should be 4 in. (and pref- erably 5 in.) for panels which can be
manufactured and erected to close tol- erances. Hence, it is recommended that joints be placed in any ribbed projec- tions of panels.
If ribs are too narrow to accommo- date joints, the full rib may be located in one panel only (Fig. 3.2.6). Another solution is to design every second panel with ribs at both edges using the bal- ance as infill units.
An important factor in locating and detailing joints is a proper assessment of the predicted weathering pattern for the structure. To limit weathering ef- fects on the building, it is advisable to emphasize the joints by making them wide and recessed from immediately adjacent surfaces. 8 Joints in forward sloping surfaces are difficult to weather- proof, especially where they may col- lect snow or ice. When these surfaces cannot be avoided, the architect should include a second line of defense against water penetration. This may be achieved by sealing the front of the sur- face and using a two-stage joint. If a one-stage joint is used, the owner must accept regular inspection of such joints and be prepared to perform frequent maintenance.
CHAPTER 2—PLANNING CHECK LISTS
2.1 Definitions Joint planning is recognition of, and
provision for, movement or isolation of movement in a building or other struc- ture based on an analysis of esthetic, structural and mechanical require- ments.
Water runoff planning is the visuali- zation of the paths that moisture may take, or its entrapment, and the provi- sions of safe channels for its flow and discharge.
2.2 Joint planning 1. Determination of amount of
movement that can be anticipated. A. Initial movement
1. Shrinkage 2. Foundation 3. Elastic deflection 4. Other
B. Life of structure movement 1. Temperature 2. Moisture 3. Wind
14
5. Live load deflections 6. Creep 7. Other
2. Architectural (esthetic) considera- tions
A. Accentuated jointing B. Hidden joints C. Spacing (a few large or many
small) D. Environmental needs
1. Water control 2. Air control (circulation) 3. Temperature control 4. Noise (vibration control)
3. Structural considerations A. Elimination of stress in structur-
al materials through relief of al- lowed movement.
B. Design to resist movement through the accumulation of stress.
C. Location of expansion-contrac- tion joints to maintain the struc- tural integrity. 1. Expansion-contraction joints 2. Construction joints 3. Articulating joints
4. Mechanical considerations A. Differential movement potential
1. Differing coefficients of ex- pansion
2. Differing heat absorption rates
3. Differing moisture absorption
moisture B. Isolation of vibrations
1. Internal (machinery or activ- ity)
2. External C. Other
1. Mastics 2. Thermoplastics 3. Thermosetting 4. Accessory materials
B. Preformed sealants 1. Rigid waterstops 2. Flexible waterstops 3. Gaskets
C. Other 6. Tolerances
2.3 Water runoff planning 1. Resistance to penetration
A. Seal B. Shape of joint
2. Channelization of moisture and discharge
A. Planned channelizing joints (two-stage system)
B. Channelization of inadvertent or seepage penetration (one- stage system)
CHAPTER 3-JOINT DETAILS
3.1 General This chapter shows typical details for
one-stage and two-stage joints, for floor and roof slab joints, for precast concrete parapets, and for windows in precast concrete panels. The committee recog- nizes that other details can be devel-
oped within the recommendations of this report that will provide satisfactory service. Thus, it is not intended that these details be used to the exclusion of all others, but rather that they be taken to illustrate the features of good joint planning and design.
PCI Journal/March-April 1973 15
.D. b.
p • P O p ' 6 a G DD 1 s p'
D
3/$ MIN. VERTICAL HORIZONTAL JOINT WIDTHJOINT WIDTH ° • °p.pD ^ ap • b.
pDp °P D^.p.D•D ., P
p•'p `p. D `p o 'a 'p D • D
Fig. 3.2.1. Recessed vertical butt joint Fig. 3.2.2. Recessed horizontal butt joint
b •• : DV •°
• ° •-'p JOINT WIDTH
a
•
° 'a
Fig. 3.2.3. Flush butt joint Fig. 3.2.4. Recessed corner joint
D• D ,p,° Z_
'• D- 'd. ^'
JOINT WIDTH oaa o >
Fig. 3.2.6. Joints in panels with narrow
Fig. 3.2.5. Corner joint detail ribs
16
3.3 Two-stage joints
AIR SEAL : CLOSED CELL SPONGE NEOPRENE SQUARE STRIP OR ROPE 1.5 TIMES THE THEORETICAL JOINT WIDTH
^4 ^2 I EXPANSION CHAMBER
w ^• D Via. ° rn a ^
•d. .•d, • \N \N W K
^' d. Q • 'p^ ^N -0J^W Z Wr-
f W
iD v
EXTERIORRAIN BARRIERFACE
Fig. 3.3.1. Two-stage joint vertical Fig. 3.3.2. Two-stage joint horizontal gaskets gasket
'2"MIN. z
• 1 d'
• D'D .Pe D•9 SEALANT(IF USED)MUST BE DISCONTINUED AT INTERVALS
SEALANT DISCONTINUED (VERTICAL JOINTS) TO DRAIN
AT HORIZONTAL JOINT AREA BETWEEN IT AND AIR SEAL
Fig. 3.3.3. Two-stage joint vertical Fig, 3.3.4. Two-stage joint horizontal sealants sealants
3.4 Cavity wall
2 I j2„ SEALANT-ALTERNATE RAINBARRIERS(TUBE)
Fig. 3.4.1. Horizontal section through cavity wall
PCI Journal/March-April 1973 17
PREFORMED ELASTOMER (STEEL REINFORCED)
.. a • ' D D
Fig. 3.5.2
STEEL PLATES
p , 0 D 1. D D. 0 D• D •p'
O' D
PREFORMED COMPRESSION SEAL NEOPRENE (SOMETIMES COMBINED WITH P.V.C. SHEET OR SHEET NEOPRENE SECONDARY SYSTEMS.)
Fig. 353 Fig,3.5.4
•a•4 ° ••d'DDS• °•° v°.• a g o d- p D
TREATED NEOPRENE
WIDTH OF NEOPRENE OR HYPALON SHEET SHALL EQUAL JOINT WIDTH PLUS ANTICIPATED MOVEMENT PLUS I INCH PLUS BOND AREA
Fig, 3.5.5
COMMERCIAL P.V.C. FLASH. OVER P.C. PANEL JOINTS. SECURE WITH COMPATIBLE
JOINT GASKET
SECTION A-A
PCI Journal/March-April 1973 19
r'
^Ia
o o
20
D
ol^ ,d .', D .a
CLOSED CELL NEOPRENE SPONGE - HOLD IN PLACE WITH MASTIC ADHESIVE
2 PC. MET. FLASH.
"— ADVISABLE TO PROVIDE P.V.C. FLEXIBLE FLASHING ACROSS PANEL JOINT POINTS
Fig. 3.6.3. Precast parapet with flush roof flashing
FIELD-MOLDED SEALANT
R SEAL
PCI Journal/March-April 1973 21
AN is" -SHIA11,
HEAD
CAULK
JAMB
CAULK
PANEL
SILL
am
-PVC
22
PREFORMED SEALANTS NEOPRENE
concrete panel
PCI Journal/March-April 1973 23
CHAPTER 4—SEALANT MATERIALS
4.1 General No one material has the perfect com-
bination of properties necessary to fully meet each and every one of the require- ments for each and every application. If there were, and its price were reasona- ble, obviously it would be in universal use. It therefore is a matter of selecting, from among a large range of materials, a particular material that offers the right properties at a reasonable price to satisfy the job requirements.
For many years oil-based mastics or bituminous compounds and metallic materials were the only sealants avail- able. For many applications these tra- ditional materials do not perform well and in recent years there has been ac- tive development of many types of elas- tomeric sealants whose behavior is largely elastic, rather than plastic, and which are flexible rather than rigid at normal service temperatures. Elasto- meric materials are available as field- molded and preformed sealants. Though initially more expensive, they may be more economical over an ex- tended period due to longer service life. Furthermore, as will be seen, they can seal joints where considerable move- ments occur which could not have been sealed by the traditional materials. This has opened up new engineering and architectural possibilities to the design- er of concrete structures.
No attempt has been made in this chapter to list or discuss every attribute of every sealant on the market. Discus- sion is limited to those features consid- ered important to the designer, speci- fier, and user so that the claims made for various materials can be assessed and a suitable choice for the application can be made.
4.2 Field-molded sealants and their uses
The following types of materials list- ed in Table 1 are currently used as field-molded sealants:
4.2.1 Mastics. Mastics are composed of viscous liquid rendered immobile by the addition of fibers and fillers. They do not usually harden, set or cure after applications, but instead form a skin on the surface exposed to the atmosphere.
The vehicle in mastics may include drying or nondrying oils (including ole- oresinous compounds), polybutenes, polyisobutylenes, low-melting point as- phalts, or combinations of these mate- rials. With any of these, a wide variety of fillers is used, including asbestos fi- ber, fibrous talc or finely divided cal- careous or siliceous materials. The func- tional extension-compression range for these materials is approximately ± 3 percent.
They are used in buildings for gener- al caulking and glazing where only very small joint movements are anticipated and economy in initial cost outweighs that of maintenance or replacement. With passage of time, most mastics tend to harden in increasing depth as oxida- tion and loss of volatiles occur, thus re- ducing their serviceability. Polybutene and polyisobutylene mastics have a somewhat longer service life than do the other mastics.
4.2.2 Thermoplastics (cold-applied, solvent or emulsion type). These mate- rials are set either by the release of sol- vents or the breaking of emulsions on exposure to air. Sometimes they are heated to a temperature not exceeding 120 F (49 C) to facilitate application but usually they are handled at ambient
24
temperature. Release of solvent or wa- ter can cause shrinkage and increased hardness with a resulting reduction in the permissible joint movement and in serviceability. Products in this category include acrylic, vinyl and modified bu- tyl types which are available in a vari- ety of colors. Their maximum exten- sion-compression range is ± 7 percent. Heat softening and cold hardening may, however, reduce this figure.
These materials are restricted in use to joints with small movements. Acryl- ics and vinyls are used in buildings pri- marily for caulking and glazing.
4.2.3 Thermosetting (chemically cur- ing). Sealants in this class are either one- or two-component systems which cure by chemical reaction to a solid state from the liquid form in which they are applied. They include polysul- fide, silicone, urethane and epoxy-based materials. The properties that make them suitable as sealants for a wide range of uses are: resistance to weather- ing and ozone; flexibility and resilience at both high and low temperatures; and inertness to a wide range of chemicals including, for some, solvents and fuels. In addition, the abrasion and indenta- tion resistance of urethane sealants is above average. Thermosetting, chemi- cally curing sealants have an expansion- compression range of up to -!- 25 per- cent depending on the one used, at temperatures from —40 F to +180 F (-40 C to +82 C). Silicone sealants re- main flexible over an ever wider tem- perature range.
These sealants have a wide range of uses in buildings and containers for both vertical and horizontal joints, and may be used in pavements. Though ini- tially more expensive, thermosetting, chemically curing sealants can accom- modate greater movements than other field-molded sealants, and generally have a much greater service life.
4.2.4 Thermosetting (solvent re-
lease). Another class of…
Raymond J. Schutz Chairman
James Engle Albert Litvin James G. GrossR. L. Pare Abraham GutmanJohn S. Parrish J. A. Hanson Irwin J. Speyer Kai Holbek Ivan L. Varkay Felix Kulka Lloyd Wright
Correct joint design and proper selection of materials and installation are vital for the successful performance and esthetic appeal of precast concrete wall systems. This report recommends the proper precast concrete joint details and sealants for specific situations. In writing these recommendations, architectural treatment and economy in mold design were considered but are not included, since these are covered in the PCI Manual on Architectural Precast Concrete. Following these recommendations will result in a good design and a durable, waterproof, and economical joint.
10
CONTENTS Chapter1—Joint design ................................... 12
1.1 Scope 1.2 Types of joints 1.3 General design concepts for
joints 1.4 Number of joints 1.5 Location of joints
Chapter 2—Planning check lists ............................ 14 2.1 Definitions 2.2 Joint planning 2.3 Water runoff planning
Chapter3—Joint details ................................... 15 3.1 General 3.2 One-stage joints 3.3 Two-stage joints 3.4 Cavity wall 3.5 Floor and roof slab joints 3.6 Precast parapets 3.7 Precast panel window details
Chapter 4—Sealant materials ............................... 24 4.1 General 4.2 Field-molded sealants and
their uses 4.3 Accessory materials 4.4 Preformed sealants and
their uses 4.5 Compression seals and
their uses 4.6 Joint design 4.7 Determination of joint
movements and locations 4.8 Selection of butt joint widths
for field-molded sealants 4.9 Selection of butt joint shape
for field-molded sealants 4.10 Selection of size of compression
seals for butt joints 4.11 Limitations on butt joint widths
and movements for various types of sealants
4.12 Lap joint sealant thickness
References ............................................... 36
1.1 Scope
The design of joints must be exe- cuted as an integral part of the total wall design. Some specific guidelines for joints do govern their ultimate suc- cess. This chapter highlights and illus- trates several cases of interdependence with other wall design criteria.
In all cases, the designer should as- sess his requirements for joints realisti- cally with respect to both performance and cost. If joint designs and details are contemplated which differ from those normally used in the area where the project is located, local producers should be consulted.
The following discussion will deal mainly with joints which are designed to accommodate local wall movements only, rather than an accumulation of such movements which would require properly designed expansion joints.
1.2 Types of joints
Joints between precast wall panels may be divided into two basic types:
1. One-stage joints 2. Two-stage joints
A cavity wall design is considered a further application of the two-stage joint.
1.2.1 One-stage joints. As the name implies, this joint has one line of de- fense for its weatherproofing ability. This occurs normally in the form of a sealant close to the exterior surface. The advantage of this type of joint is
that it generally provides the lowest first cost, and it is suitable for use be- tween precast panels as shown in Figs. 3.2.1 to 3.2.6.
The success of one-stage joints de- pends on the quality of materials and proper installation at the building site. This type of joint is in common use in most of North America. One-stage joints should be regularly inspected and may demand fairly frequent mainte- nance to remain weathertight.
1.2.2 Two-stage joints. These joints have two lines of defense for weather- proofing. The typical joint consists of a rain barrier near the exterior face and an air seal normally close to the interior face of the panels. The rain barrier is designed to shed most of the water from the joint and the air seal is the de- marcation line between outside and in- side air pressures. Between these two stages is an equalization or expansion chamber which must be vented and drained to the outside. Section 3.3 gives typical details of two-stage joints. It can be seen that the simplest form of a hor- izontal two-stage joint is the well prov- en shiplap joint.
The rain barrier prevents most of the rain and airborne water from entering the joint. If airborne water (wind-driv- en rain) penetrates this barrier, it will drain off in the expansion chamber as the kinetic energy is dissipated and the air loses its ability to carry the water. Any water which penetrates the rain barrier should be drained out of the joint by proper flashing installations.
In order to avoid vertical movement of the air in the expansion chamber
12
(stack effect) caused by wind or outside air turbulences, it is advisable to use these flashing details as dampers and provide them at regularly spaced inter- vals along the height of the vertical joints. Such flashing is sometimes in- stalled at each floor level, but a greater spacing (two or three stories) may be sufficient for low-rise buildings and in areas with moderate wind velocities.
Since the air seal is the plane where the change in air pressures between the outside and inside atmospheres occurs, it would normally be subject to water penetration through capillary action. Inasmuch as the outside air reaching this seal has lost its water content, no moisture can enter by such action.
The danger of humidity traveling from inside the building and through the air seal should be investigated for buildings with relatively higher interior humidity, and for tall buildings, where the interior air pressure may occasion- ally be substantially higher than the outside atmospheric pressure. This con- dition is normally solved by using a cavity wall design.
A cavity wall (Fig. 3.4.1) is the most effective wall for the optimum separa- tion and control of both outside and in- side air and humidity conditions. When precast concrete wall panels are used in cavity wall designs, they will normally serve as the rain barrier. An air space is maintained between the precast exteri- or and the interior wall. Insulation, when required, is applied to the outside face of the interior wall, eliminating condensation problems and, thereby, making the inner wall subject only to the relatively constant interior tempera- ture. Cavity wall construction is nor- mally expensive when compared with conventional walls. On the basis of their lower maintenance costs and their ex- cellent performance records, they may well be justified for specific types and locations of buildings.
The two-stage joint is gaining accep- tance particularly for buildings subject to severe climatic exposure or tempera- ture and humidity control.
A disadvantage of the two-stage joint for concrete wall panels is the higher cost. For projects with good repetitive joint design properly integrated with other panel details, and having efficient production and erection procedures, it may well approach the cost of one-stage joint installations. In these instances, the safety factors and lower mainte- nance costs should also be considered.
A minimum precast wall panel thick- ness of 4 in. (10.2 cm) (with field- molded sealants), preferably 5 in. (12.7 cm) (with gaskets and compression seals), is required to accommodate both the rain barrier and the air seal. For two-stage joints with compression seals, connection detail allowance should be made for slight horizontal movements of the panels after initial fastening for air seal compression.5 The joints must be fully accessible from the inside of the panels for later installation of the air seal. The simplest form of a horizon- tal two-stage joint is the shiplap joint.
1.3 General design concepts for joints
The purpose of joint design is to pro- vide weathertightness of the joint con- sistent with the exposure of the joint. In addition, as part of the overall perfor- mance requirements of the building, the purpose for which the building is built will also determine design require- ments for the joint.
Thus, joint design will be governed by its exposure (orientation and climatic conditions), the purpose of the building, and appearance. The following guide- lines must all be evaluated in relation to the relative importance of these cri- teria.
PCI Journal/March-April 1973 13
1.4 Number of joints It is generally advantageous to plan
for the fewest number of joints, due to the lower overall joint cost, potentially lower maintenance cost, and the econ- omy of large panel erection.
Optimum panel sizes must, however, also be determined from erection condi- tions and established limitations of weight and sizes for transportation.7
If the desired appearance requires additional joints, this may be achieved through the use of false or dummy joints. In order to match the appear- ance of both false and real joints, an applied finish should be chosen to sim- ulate sealants or gaskets in the real joints. Caulking of the false joints adds an unnecessary expense.
1.5 Location of joints Joints are easier to design and exe-
cute if they are located where maxi- mum panel thickness occurs. Except for one-stage joints and joints in precast panels performing as rain barriers in cavity walls, the minimum panel thick- ness at joints should be 4 in. (and pref- erably 5 in.) for panels which can be
manufactured and erected to close tol- erances. Hence, it is recommended that joints be placed in any ribbed projec- tions of panels.
If ribs are too narrow to accommo- date joints, the full rib may be located in one panel only (Fig. 3.2.6). Another solution is to design every second panel with ribs at both edges using the bal- ance as infill units.
An important factor in locating and detailing joints is a proper assessment of the predicted weathering pattern for the structure. To limit weathering ef- fects on the building, it is advisable to emphasize the joints by making them wide and recessed from immediately adjacent surfaces. 8 Joints in forward sloping surfaces are difficult to weather- proof, especially where they may col- lect snow or ice. When these surfaces cannot be avoided, the architect should include a second line of defense against water penetration. This may be achieved by sealing the front of the sur- face and using a two-stage joint. If a one-stage joint is used, the owner must accept regular inspection of such joints and be prepared to perform frequent maintenance.
CHAPTER 2—PLANNING CHECK LISTS
2.1 Definitions Joint planning is recognition of, and
provision for, movement or isolation of movement in a building or other struc- ture based on an analysis of esthetic, structural and mechanical require- ments.
Water runoff planning is the visuali- zation of the paths that moisture may take, or its entrapment, and the provi- sions of safe channels for its flow and discharge.
2.2 Joint planning 1. Determination of amount of
movement that can be anticipated. A. Initial movement
1. Shrinkage 2. Foundation 3. Elastic deflection 4. Other
B. Life of structure movement 1. Temperature 2. Moisture 3. Wind
14
5. Live load deflections 6. Creep 7. Other
2. Architectural (esthetic) considera- tions
A. Accentuated jointing B. Hidden joints C. Spacing (a few large or many
small) D. Environmental needs
1. Water control 2. Air control (circulation) 3. Temperature control 4. Noise (vibration control)
3. Structural considerations A. Elimination of stress in structur-
al materials through relief of al- lowed movement.
B. Design to resist movement through the accumulation of stress.
C. Location of expansion-contrac- tion joints to maintain the struc- tural integrity. 1. Expansion-contraction joints 2. Construction joints 3. Articulating joints
4. Mechanical considerations A. Differential movement potential
1. Differing coefficients of ex- pansion
2. Differing heat absorption rates
3. Differing moisture absorption
moisture B. Isolation of vibrations
1. Internal (machinery or activ- ity)
2. External C. Other
1. Mastics 2. Thermoplastics 3. Thermosetting 4. Accessory materials
B. Preformed sealants 1. Rigid waterstops 2. Flexible waterstops 3. Gaskets
C. Other 6. Tolerances
2.3 Water runoff planning 1. Resistance to penetration
A. Seal B. Shape of joint
2. Channelization of moisture and discharge
A. Planned channelizing joints (two-stage system)
B. Channelization of inadvertent or seepage penetration (one- stage system)
CHAPTER 3-JOINT DETAILS
3.1 General This chapter shows typical details for
one-stage and two-stage joints, for floor and roof slab joints, for precast concrete parapets, and for windows in precast concrete panels. The committee recog- nizes that other details can be devel-
oped within the recommendations of this report that will provide satisfactory service. Thus, it is not intended that these details be used to the exclusion of all others, but rather that they be taken to illustrate the features of good joint planning and design.
PCI Journal/March-April 1973 15
.D. b.
p • P O p ' 6 a G DD 1 s p'
D
3/$ MIN. VERTICAL HORIZONTAL JOINT WIDTHJOINT WIDTH ° • °p.pD ^ ap • b.
pDp °P D^.p.D•D ., P
p•'p `p. D `p o 'a 'p D • D
Fig. 3.2.1. Recessed vertical butt joint Fig. 3.2.2. Recessed horizontal butt joint
b •• : DV •°
• ° •-'p JOINT WIDTH
a
•
° 'a
Fig. 3.2.3. Flush butt joint Fig. 3.2.4. Recessed corner joint
D• D ,p,° Z_
'• D- 'd. ^'
JOINT WIDTH oaa o >
Fig. 3.2.6. Joints in panels with narrow
Fig. 3.2.5. Corner joint detail ribs
16
3.3 Two-stage joints
AIR SEAL : CLOSED CELL SPONGE NEOPRENE SQUARE STRIP OR ROPE 1.5 TIMES THE THEORETICAL JOINT WIDTH
^4 ^2 I EXPANSION CHAMBER
w ^• D Via. ° rn a ^
•d. .•d, • \N \N W K
^' d. Q • 'p^ ^N -0J^W Z Wr-
f W
iD v
EXTERIORRAIN BARRIERFACE
Fig. 3.3.1. Two-stage joint vertical Fig. 3.3.2. Two-stage joint horizontal gaskets gasket
'2"MIN. z
• 1 d'
• D'D .Pe D•9 SEALANT(IF USED)MUST BE DISCONTINUED AT INTERVALS
SEALANT DISCONTINUED (VERTICAL JOINTS) TO DRAIN
AT HORIZONTAL JOINT AREA BETWEEN IT AND AIR SEAL
Fig. 3.3.3. Two-stage joint vertical Fig, 3.3.4. Two-stage joint horizontal sealants sealants
3.4 Cavity wall
2 I j2„ SEALANT-ALTERNATE RAINBARRIERS(TUBE)
Fig. 3.4.1. Horizontal section through cavity wall
PCI Journal/March-April 1973 17
PREFORMED ELASTOMER (STEEL REINFORCED)
.. a • ' D D
Fig. 3.5.2
STEEL PLATES
p , 0 D 1. D D. 0 D• D •p'
O' D
PREFORMED COMPRESSION SEAL NEOPRENE (SOMETIMES COMBINED WITH P.V.C. SHEET OR SHEET NEOPRENE SECONDARY SYSTEMS.)
Fig. 353 Fig,3.5.4
•a•4 ° ••d'DDS• °•° v°.• a g o d- p D
TREATED NEOPRENE
WIDTH OF NEOPRENE OR HYPALON SHEET SHALL EQUAL JOINT WIDTH PLUS ANTICIPATED MOVEMENT PLUS I INCH PLUS BOND AREA
Fig, 3.5.5
COMMERCIAL P.V.C. FLASH. OVER P.C. PANEL JOINTS. SECURE WITH COMPATIBLE
JOINT GASKET
SECTION A-A
PCI Journal/March-April 1973 19
r'
^Ia
o o
20
D
ol^ ,d .', D .a
CLOSED CELL NEOPRENE SPONGE - HOLD IN PLACE WITH MASTIC ADHESIVE
2 PC. MET. FLASH.
"— ADVISABLE TO PROVIDE P.V.C. FLEXIBLE FLASHING ACROSS PANEL JOINT POINTS
Fig. 3.6.3. Precast parapet with flush roof flashing
FIELD-MOLDED SEALANT
R SEAL
PCI Journal/March-April 1973 21
AN is" -SHIA11,
HEAD
CAULK
JAMB
CAULK
PANEL
SILL
am
-PVC
22
PREFORMED SEALANTS NEOPRENE
concrete panel
PCI Journal/March-April 1973 23
CHAPTER 4—SEALANT MATERIALS
4.1 General No one material has the perfect com-
bination of properties necessary to fully meet each and every one of the require- ments for each and every application. If there were, and its price were reasona- ble, obviously it would be in universal use. It therefore is a matter of selecting, from among a large range of materials, a particular material that offers the right properties at a reasonable price to satisfy the job requirements.
For many years oil-based mastics or bituminous compounds and metallic materials were the only sealants avail- able. For many applications these tra- ditional materials do not perform well and in recent years there has been ac- tive development of many types of elas- tomeric sealants whose behavior is largely elastic, rather than plastic, and which are flexible rather than rigid at normal service temperatures. Elasto- meric materials are available as field- molded and preformed sealants. Though initially more expensive, they may be more economical over an ex- tended period due to longer service life. Furthermore, as will be seen, they can seal joints where considerable move- ments occur which could not have been sealed by the traditional materials. This has opened up new engineering and architectural possibilities to the design- er of concrete structures.
No attempt has been made in this chapter to list or discuss every attribute of every sealant on the market. Discus- sion is limited to those features consid- ered important to the designer, speci- fier, and user so that the claims made for various materials can be assessed and a suitable choice for the application can be made.
4.2 Field-molded sealants and their uses
The following types of materials list- ed in Table 1 are currently used as field-molded sealants:
4.2.1 Mastics. Mastics are composed of viscous liquid rendered immobile by the addition of fibers and fillers. They do not usually harden, set or cure after applications, but instead form a skin on the surface exposed to the atmosphere.
The vehicle in mastics may include drying or nondrying oils (including ole- oresinous compounds), polybutenes, polyisobutylenes, low-melting point as- phalts, or combinations of these mate- rials. With any of these, a wide variety of fillers is used, including asbestos fi- ber, fibrous talc or finely divided cal- careous or siliceous materials. The func- tional extension-compression range for these materials is approximately ± 3 percent.
They are used in buildings for gener- al caulking and glazing where only very small joint movements are anticipated and economy in initial cost outweighs that of maintenance or replacement. With passage of time, most mastics tend to harden in increasing depth as oxida- tion and loss of volatiles occur, thus re- ducing their serviceability. Polybutene and polyisobutylene mastics have a somewhat longer service life than do the other mastics.
4.2.2 Thermoplastics (cold-applied, solvent or emulsion type). These mate- rials are set either by the release of sol- vents or the breaking of emulsions on exposure to air. Sometimes they are heated to a temperature not exceeding 120 F (49 C) to facilitate application but usually they are handled at ambient
24
temperature. Release of solvent or wa- ter can cause shrinkage and increased hardness with a resulting reduction in the permissible joint movement and in serviceability. Products in this category include acrylic, vinyl and modified bu- tyl types which are available in a vari- ety of colors. Their maximum exten- sion-compression range is ± 7 percent. Heat softening and cold hardening may, however, reduce this figure.
These materials are restricted in use to joints with small movements. Acryl- ics and vinyls are used in buildings pri- marily for caulking and glazing.
4.2.3 Thermosetting (chemically cur- ing). Sealants in this class are either one- or two-component systems which cure by chemical reaction to a solid state from the liquid form in which they are applied. They include polysul- fide, silicone, urethane and epoxy-based materials. The properties that make them suitable as sealants for a wide range of uses are: resistance to weather- ing and ozone; flexibility and resilience at both high and low temperatures; and inertness to a wide range of chemicals including, for some, solvents and fuels. In addition, the abrasion and indenta- tion resistance of urethane sealants is above average. Thermosetting, chemi- cally curing sealants have an expansion- compression range of up to -!- 25 per- cent depending on the one used, at temperatures from —40 F to +180 F (-40 C to +82 C). Silicone sealants re- main flexible over an ever wider tem- perature range.
These sealants have a wide range of uses in buildings and containers for both vertical and horizontal joints, and may be used in pavements. Though ini- tially more expensive, thermosetting, chemically curing sealants can accom- modate greater movements than other field-molded sealants, and generally have a much greater service life.
4.2.4 Thermosetting (solvent re-
lease). Another class of…
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