MM1 Exam 2
Masonry Tie and joint Reinforcing
Corrugated tie z-tie adjustable tie Adjustable stone tie two wire ladder tie ladder loop tie three wire truss tie Dovetail anchors with concrete backup Steel Column Anchor
Tooling of Joints
Exterior use Concave Joints Vee joint Interior Weathered joint Raked Joint Flush Joint Stripped Joint Struck Joint
Three major methods for molding bricks
soft mud dry press Stiff mud
Mortar Ingredients
* Most characteristic type is cement-lime mortar, made of portand cement, hydrated lime, an inert aggregate and water. • Portland Cement - the bonding agent in mortar. It is a blend of lime, iron, silica, and alumina. Crushed stone is pulverized and heated in kilns to create dry (dehydrated) powder cement. • Lime - added to mortar to impart smoothness and workability. Produced by burning limestone or seashells (calcium carbonate) in a kiln to drive off carbon dioxide and leave quicklime (calcium oxide). • Aggregate - sand, which must be clean and screened to eliminate particles that are too coarse or too fine. • Water - chemically involved in the curing of the cement and lime. ▫
Spanning Openings- Lintels
- Arching action of masonry above opening supports wall load outside of load triangle - lintel carries less wall load than normal load triangle. -lintel must carry an additional load if a concentrated load or floor or roof loads fall within normal load triangle. -horizontal thrust from any arching action must be resisted by the wall mass on either side of the opening.
Glass mullion systems
- Glass is installed onto metal bars by means of screws on the four corners of the glass - Gives the appearance of floating glass due to being unframed - Used in lobbies and airports.
Making Brick
- Winning -crushing -pulverizing - screening -forming and cutting -storage and shipping -Firing -drying -coating or glazing
Timbrel Ribbed Vaulting
-Antoni Gaudi, Casa Mila (La Pedrera) Barcelona, Spain, 1905-10. -Antoni Gaudi, Crypt of the Colonia Guell Barcelona, Spain, 1908-15.
Raw material preparation
-gathering raw materials -storage of raw materials -crushing -grinding -Screening -Pug Mill
Non-Loadbearing Prefabricated Panelized Masonry Facade
290 Mulberry SHoP Architects, New York, NY, USA
Thermal Insulation
A Detour Back to Concrete: Low Density Insulating Concrete (pumice as lightweight aggr.) R/in = .55 ft2-hr-F/BTU-in.55 x 17.7in = 9.8 R-value wall.55 x 25.6in = 14.1 R-value roof
Butt-Joint glazing
A glazing system in which the glass panes or units are supported at the head and sill in a conventional manner, with their vertical edges being joined with a structural silicone sealant without mullions.
Firing of Bricks
After molding, bricks are dried for one to two days in a low-temperature dryer kiln. They are then ready for firing or burning. • Today, bricks are usually burned in either periodic or continuous tunnel kilns. • Periodic kiln is a fixed structure loaded with bricks, fired, cooled, and unloaded. • Long tunnel kilns are used for higher productivity. Bricks are passed continuously through long tunnels on special railcars to emerge at far end fully burned. • First stage of firing is dehydration. Next stages are oxidation and vitrification, where temp rises to 1800 to 2400°F and clay is transformed into a ceramic material. May be followed by flashing for color. • Last step is controlled cooling. Entire process takes 40 to 150 hours.
MCW 3
Cavity airspace Foil-faced Polyisocyanurate insulation wall tie weephhole Flashing membranes
Structural Glazing
Glass held with strong sealants and carrying some wind load. Sealant may be used to bond it to concealed metal rails to give an all glass facade that has good weather resistance and is easy to maintain.
History (continued)
Medieval civilizations in Europe and the Islamic world brought masonry vaulting to a very high plane of development: palaces, markets, mosques, glazed tiles, fortresses, and cathedrals. In Central America, South America, and Asia, civilizations were evolving techniques in cut stone. • Industrial revolution in Europe and North America: • Mechanization of mining, transportation, and production techniques • Portland cement entered widespread use, allowing greater strength • Late 19th century, masonry displaced by iron or steel frames and reinforced concrete required for tall buildings in the city. • 19th century development - invention of hollow concrete block - much cheaper than cut stone and less labor than brick. • 20th century developments - steel-reinforced masonry, high-strength mortars, higher structural strength masonry units, and new types of masonry units. ▫
Nominal Sizes for Common Shapes (Facing + Building)
Modular Engineer Modular Closure Modular Roman Norman Engineer Norman Utility
Flashing
Needed at: • Top • Base • Openings • Structural support • Geometry changes • Material changes
Thermal Insulation
R-values/Additive Calculations for Wall Assemblies•R-values for each layer of an assembly may be added to calculate the total R-value of the wall or roof assembly.
Structural Bonds and Patterns
Running Bond common bond stack Bond Flemish Bond English bond
Masonry
Simple building technology: Mason stacks pieces of material (bricks, stones, or concrete blocks, collectively called masonry units) atop one another to creates surfaces (typically walls) and resists forces .• Many materials possible, though most common are clay, stone, and concrete .• Varied techniques, colors, textures, and patterns; small units allow for many formal possibilities .• Masonry is the material of earth. • Ancient building technology. • Material Cost varies with type and quality • Labor intensive. • Durable material. If detailed correctly, it can be a low-maintenance material, scarcely affected by water, air, or fire. It can last for many generations. ▫
Tinted Glass
Tinted glass is made by adding small amounts of selected chemical elements to the molten glass mixture to produce desired hue and intensity of color in greys, bronzes, blues, greens, and golds. • Visible light transmittance (VT) is measured as the ratio of visible light that passes through the glass relative to the amount of light striking it. • Clear glass has visible light transmittance of 0.80 to 0.90, meaning that 80 to 90 percent of the visible light striking the glass passes through it. • By tinting glass, visible light transmittance is reduced.. • Visible light transmittance ranges from 0.75 in light tints to 0.10 for dark grey. • To evaluate effectiveness of glass in reducing heat gain (infrared radiation), a measure called the solar heat gain coefficient (SHGC) is used. • SHGC is the ratio of solar heat admitted through a particular glass to the total heat energy striking the glass. • Clear glass has SHGC of 0.90 to 0.70; tinted glass SHGC of 0.70 to 0.35. ▫
Modular brick size
W=4 h=2 2/3 l=8 vertical crossing 3C=8 in. Mortar joints=3/8" thick actual= 7 5⁄8 × 3 5⁄8 × 2 1⁄4 inches
Point-supported Glass System
a detail of the glass roof supports. notice the four point and two point stainless steel spider fittings that attach the glass components to each other and to the metal supporting structure
Laying Bricks - The Basics
course is the row wythe is a vertical layer of masonry units, one unit thick bed joints run above and below the course and head joint are between each brick collar joint for a double wall brick position -stretcher header -soldier -rowlock
Spanning Openings- Arches
jack Arch Segmented arch roman arch
Efflorescence
• A fluffy crystalline powder, usually white, that sometimes appears on the surface of a wall of brick, stone, or concrete masonry. • Consists of one or more water-soluble salts that were originally present either in the masonry units or in the mortar. • Salts were brought to the surface and deposited there by water that seeped into the masonry, dissolved the salts, and then migrated to the surface and evaporated.▫ • Can be avoided by: • Choosing masonry units that do not contain water-soluble salts • Using clean ingredients in the mortar • Minimizing water intrusion into the masonry construction ▫
Timbrel Vaulting (Catalan Vaulting)
• Adhesion of multiple layers of clay tiles produces a cohesive layered surface able to withstand and redirect out-of-plane stresses (vaulting action). • Able to be constructed at lower profiles than a Roman arch. • Depth of plane typically only 2-4 in. thick. ▫
Detailing Masonry Walls: Flashings and Drainage (continued)
• At the outside face of the wall, the flashing should be carried at least 3⁄4 inch beyond the face of the wall and turned down at a 45-degree angle. • This creates a drip, allowing water draining from the flashing to drip free of the wall rather than being drawn under the flashing by capillary action and returning into the wall. • Capillary action is the pulling of water through a small orifice or fibrous material by the adhesive force between the water and the material. • A capillary break is a slot or groove intended to create an opening too large to be bridged by a drop of water and, thereby, to eliminate the passage of water by capillary action. The drip at the outside edge of flashing functions as a capillary break. • Copper and stainless steel are the best flashing materials in masonry walls; galvanized steel, aluminum, and lead are unsuitable in masonry construction.
Insulation on the Inside Face
• Can be insulated by attaching wood or metal furring strips to the inside of the wall. • Furring strips may be of any desired depth to house the necessary thickness of fibrous or foam insulation between the furring strips. • Gypsum wallboard or other interior finish material is then fastened to the furring strips. • Furring also creates spaces in which electrical wiring and plumbing can easily be concealed. ▫
Fritted Glass
• Created by imprinting the surface of glass with silk-screened patterns of ceramic-based paints. • The paints consist primarily of pigmented glass particles called frit. • After the frit has been printed on the glass, the glass is dried and then fired in a tempering furnace, transforming the frit into a hard, permanent ceramic coating. • Many colors are possible in both translucent and opaque finishes. • Typical patterns for fritted or silkscreened glass are various dot and stripe motifs, but custom-designed patterns and text are easily reproduced. • Often used to control the penetration of solar light and heat into a space. ▫
History (continued)
• Cylinder Process: • Sphere, heated to a molten state, was swung back and forth, pendulum fashion, on the end of the blowpipe to elongate it into a cylinder. • Hemispherical ends were cut off and remaining cylinder was slit lengthwise. • Then reheated, opened, and flattened into a rectangular sheet of glass later cut into panes of any desired size.
History
• Earliest examples: low walls of stacked stones or caked mud taken from dried puddles. Mortar was mud pressed into joints for stability. • By fourth millennium B.C., peoples of Mesopotamia were building palaces and temples of stone and sun-dried brick. • In third millennium B.C., Egyptians erected the first of their stone temples and pyramids. • Fires built against mud brick walls brought a knowledge of the advantages of burned brick, leading to the invention of the kiln. • Masons learned the art of turning limestone into lime, and lime mortar gradually replaced mud. • Greek temples of limestone and marble. • Romans: first large-scale use of masonry arches and roof vaults in temples, basilicas, baths, palaces and aqueducts.
Masonry Cavity Walls
• Every masonry wall is porous to some degree. • A cavity wall prevents water from reaching the interior of a building by creating a hollow space between the inside and outside wythes of the wall. • Two wythes are separated by a continuous airspace spanned only by ties made of corrosion-resistant galvanized steel or stainless steel that hold the wythes together. • When water penetrates the outer wythe, it is conducted down the cavity and out at the bottom by flashing and drained through weep holes to the exterior of the building. • Water-repellent coating, or dampproofing, is applied to the cavity side of the interior wythe of the wall to further protect against water penetration. • Board insulation can be added into the cavity to slow the flow of heat through the wall. ▫ In a loadbearing cavity wall, the backup wythe normally carries the structural loads while the outer wythe serves as a nonstructural facing or veneer. • In a nonloadbearing cavity wall, the interior wythe still braces the outer wythe stucturally against seismic or wind loads. ▫
Surface Divider Joints
• Expansion joints - intentionally created slots that can close slightly to accommodate the expansion of surfaces made of brick or stone masonry. • Control joints - intentionally created cracks that can open to accommodate shrinkage in surfaces made of concrete masonry. In common usage, control joints are specific to a singular surface material, and do not transmit through the entire building. • Movement joints - sometimes called "construction joints" or "isolation joints," and are placed at junctions between masonry and other materials, or between new masonry and old masonry, to accommodate differences in movement. In common usage, movement joints are often "building separation joints" operating through ALL of the surfaces and material systems of a building at a particular location.
Types of Masonry Walls
• Five Broad Categories or Types of Masonry Walls: • Composite Masonry Walls • Masonry Cavity Walls • Masonry Load-Bearing Walls • Reinforced Masonry Walls (vs. unreinforced) • Note: These types of walls are not mutually exclusive (excepting composite and cavity walls) - masonry walls are often hybrids between multiple types.
Insulating Glass (continued)
• For improved thermal performance: • Introduce gasses with lower thermal conductivity between sheets of glass. Argon and krypton are most commonly used. • Vacuum-insulated glazing units rely on evacuation of most of the air from the space between the glass sheets, and are currently under development. • Performance as a thermal insulator is quantified as its U-Factor. U-Factors are mathematical reciprocals of R-values. Lower U-Factors = improved thermal performance.
Spandrel Glass
• Frits are used to create special opaque glasses for covering spandrel areas (the bands of wall around the edges of floors) in glass curtain wall construction. • Uniform coating of frit is applied to what will be the interior surface of the glass. • Many suppliers can apply thermal insulation on the interior of the glass, complete with vapor retarder.
Basic Terminology
• Glazing - refers to the installing of glass in an opening or to the transparent material (usually glass) in a glazed opening. • Glazier - installer of glass. • Lights or lites - individual pieces of glass. • Glass • Major ingredient of glass is sand (silicon dioxide or S02). • Sand is mixed with soda ash, lime, and small amounts of alumina, potassium oxide, and various elements to control color, then heated to form glass. • Finished material while seemingly crystalline and convincingly solid is, is actually a supercooled liquid or amorphous solid. It has no melting point and an open, noncrystaline microstructure. • When drawn into small fibers, glass is stronger than steel but not as stiff. • In larger pieces, imperfections reduce useful strength, esp. in tension. ▫
Glazing Large Lights (continued)
• Glazing materials most commonly used between the mullions and glass include wet glazing components and dry glazing components. • Wet components • Mastic sealants and glazing compounds. • With good workmanship, is more effective in sealing against penetration of water and air. • Dry components • Rubber or elastomeric gaskets. • Faster, easier, and less dependent on workmanship than wet glazing. • Two types are often used in combination to utilize best properties of each. • Weep holes should be provided to drain water from the horizontal mullions to the exterior of the window frame. ▫
Tempered Glass
• Has higher residual stresses than heat-strengthened glass. • Is four times as strong in bending as annealed glass. • If it breaks, the sudden release of its internal stresses reduces tempered glass instantaneously to small, square-edged granules. ► ► • This characteristic, combined with its strength, qualifies it for use as safety glazing in situations of possible occupant impact. • Used for as safety glazing - for all-glass doors that have no frame at all, hockey rink enclosures, basketball backboards, etc. • More costly than standard annealed glass. • Often has noticeable optical distortions created by the tempering process. • All cutting to size, drilling, and edging must be done before the heat treatment of the glass. ▫
Wood Joist Construction
• Hybrid System (Filigree + Solid) • Floors and roofs are framed with light wood joists and rafters and supported at the perimeter on masonry walls. • Essentially balloon framing where outer walls of wood are replaced with masonry bearing walls. • Balloon framing is used for interior loadbearing partitions to minimize the sloping of floors that might be caused by wood shrinkage along interior lines of support. ▫
Concrete Masonry Exterior Bearing Wall with Open-Web Steel Joists
• Hybrid System (Filigree + Solid) • Structural steel, either light gauge steel or framing steel may be combined depending on the design intentions.▫
Heavy Timber or Mill Construction
• Hybrid System (Filigree + Solid) • Uses heavy timbers rather than light joists, rafters, and studs. • Uses thick timber decking rather than thin wood panel sheathing and subflooring. • Because heavy timbers are slower to catch fire and burn than small light frame members, larger floor areas and greater building heights are permitted with Mill Construction than Ordinary Light Wood Frame Construction. ▫
Concrete Block Exterior and Interior Bearing Walls with Precast Hollow-Core Slabs
• Hybrid System (Solid + Solid) • Sitecast concrete, and precast concrete are frequently used in combination with masonry bearing walls.
Insulation Within the Wall
• If cavity is wide enough, masons can insert slabs of plastic foam insulation against the inside wythe of masonry as the wall is built. • Hollow cores of a concrete block wall can be filled with loose granular insulation or with special molded-to-fit liners of foam plastic. • Insulating the cores of concrete blocks does not retard passage of heat through the webs of the blocks, however, and is most effective if coupled with a continuous, unbroken layer of insulation in the cavity or on one face of the wall. ▫
History (continued)
• In 1959, English firm of Pilkington Brothers Ltd. started production of float glass. • Has since been licensed to other glassmakers and has become the worldwide standard, replacing both drawn glass and plate glass. • Float glass: • Ribbon of molten glass is floated across a bath of molten tin, where it hardens before touching a solid surface. • Ordinary window glass is annealed, meaning it is cooled slowly under controlled conditions to avoid locked-in thermal stresses. • Resulting sheets of glass have parallel surfaces, high optical quality (virtually indistinguishable from that of plate glass), and brilliant surface finish. • Has been produced in U.S. since 1963 and now accounts for nearly all of domestic flat glass production. ▫
Advanced Glazing Systems
• In butt-joint glazing, head and sill of the glass sheets are supported conventionally in metal frames, but vertical joints are eliminated. Vertical joints between sheets of glass are made by injection of a colorless silicone sealant • In structural glazing, metal mullions lie entirely behind the glass, with the glass adhered to the mullions with structural silicone sealant, or a mechnical fastener. • In glass mullion systems, tempered glass sheets are stabilized against wind pressure by perpendicular stiffeners, also made of tempered glass, or by systems of tension cables. • In point-supported glass systems metal fittings are used to join corners and edges.
history of Glass and glazing
• Initially a material for colored beads and small bottles, glass was first used in windows in Roman times. • Largest known piece of Roman glass, a crudely cast sheet used for a window in a public bath, was nearly 3 by 4 feet in size. • By 10th century A.D., Venetian island of Murano had become the major center of glassmaking, producing crown glass and cylinder glass for windows. • Both processes began by blowing a large glass sphere (drawn glass). • Crown process: • Heated glass sphere was adhered to an iron rod opposite the blowpipe. • Sphere was reheated and glassworker spun the rod rapidly, causing centrifugal force to open the sphere into a large disk, or crown, 30 inches or more in diameter. • When crown was cut into panes, one pane always contained the "bullseye." ▫
Insulating Glass (continued)
• Insulating glass units (IGUs) • Hermetically sealed at time of manufacture with dry air inserted in the space between the glass lights. • Hollow metal edge spacer (also called a spline) is inserted between the edges of the sheets of glass. • Edges are closed with an organic sealant compound. • Small amount of chemical drying agent, or desiccant, is left inside the spacer to remove any residual moisture from the trapped air. • Standard overall thickness for large lights of double glazing is 1 inch, which results in an airspace 1⁄2 inch thick if 1⁄4 inch glass is used. ▫
Fire-Rated Glass (continued)
• Intumescent interlayer laminated glazing • Made of thin layers of transparent intumescent material sandwiched between multiple layers of annealed glass. • When heated, intumescent interlayer reacts to form opaque, insulating layer. • Resists passage of flame and smoke, but also limit the rise in surface temperature of the glass on the side opposite the fire and prevent radiant heat through the glass. • Suitable for use in larger sizes and in broader range of applications. • Fire resistance ratings of up to 2 hours can be achieved. ▫
Brick Masonry
• Is made of clay (fine-grained non-organic mineral). • Is dug from pits, crushed, ground, and screened to reduce it to a fine consistency. It is then mixed with water to produce a plastic clay ready for forming into bricks. • Among masonry materials, brick is unique in its fire resistance. • Traditional bricks are shaped and dimensioned to fit the human hand. • Because of their weight and bulk, they are expensive to ship over long distances. • Bricks are produced by a large number of relatively small, dispersed factories from local clays. ▫
Composite Flashing
• Laminated, combining multiple layers of various materials. • Intermediate in price. • Most consist of a heavy foil of copper or lead laminated with polyester film, glass fiber mesh, bitumen-coated fabric, or waterproofed kraft paper. • Many composite flashings are very durable. ▫
Tinted Glass (continued)
• Light to Solar Gain (LSG) ratio • Useful measure of overall energy-conserving potential of glass • Defined as the visible light transmittance divided by the solar heat gain coefficient. Visible light transmittance (VT) Solar heat gain coefficient (SHGC) • Glass with high LSG admits a relatively large portion of visible light in comparison with the amount of solar heat admitted, combining the greatest daylighting potential with the least solar heating potential. • Green- and blue-tinted glasses tend to have high LSG ratio values, while those of bronze, gold, and grey tints tend to be lower. ▫
MLW
• Loadbearing, unreinforced brick masonry walls • 16-stories: walls are 18-inches thick at top and 6-feet thick at the base of the building
Low-Emissivity Coated Glass
• Low-emissivity (low-e) coatings • Ultrathin, virtually transparent, and almost colorless metallic coatings. • Selectively reflect solar radiation of different wavelengths, especially infrared radiation (heat). • Most often used as one of the two lights in double glazing, where it offers several benefits: • Overall thermal transmittance of glazing unit is reduced. • Can simultaneously provide high visible light transmittance with low solar heat gain, allowing units to achieve highest light to solar gain ratios of any insulated glass type. ▫
Heat-Strengthened Glass
• Lower-cost than tempered glass. • Induced compressive stresses in the surface and edges of heat-strengthened glass are about one-third as high as those in fully tempered glass (5000 psi compared with 15,000 psi for tempered glass). • Twice as strong in bending as annealed glass and is more resistant to thermal stress. • Usually has fewer distortions than tempered glass. • Breakage behavior is more like that of annealed glass than tempered glass. • Cannot be used where safety glazing is required except in laminated form.
Laminated Glass
• Made by sandwiching a transparent polyvinyl butyral (PVB) interlayer between sheets of glass and bonding the three layers together under heat and pressure. • When laminated glass breaks, the soft interlayer holds the shards of glass in place rather than allowing them to fall out of the frame of the window. Useful for skylights and overhead glazing, because it reduces the risk of injury to people below in case of breakage. • Qualifies as safety glazing, since it does not create dangerous, loose shards of glass when it breaks. • PVB interlayer may be colored or patterned to produce a wide range of visual effects.
Thicknesses of Glass
• Manufactured in a series of thicknesses, typically ranging from 3/32 inch, through 1/8 inch, up to as much as 1 inch, depending on the manufacturer. • For a particular window, glass thickness is determined by the size of the light and the expected maximum wind loads on the glass. • For low buildings with relatively small windows, glass 1/8 inch thick is usually sufficient. • Thicker glass is generally required for larger windows and for windows in tall buildings, where wind velocities are high at higher altitudes.▫
Spanning Systems for Masonry Bearing Wall Condition
• Masonry is largely unable to span long horizontal differences (floors + roofs). • Often combined with another horizontal system to create a hybrid structure system. • Hybrid Systems - 4 Principal variations combined • Wood Joist Construction • Heavy Timber • Steel - Light Gauge and Post + Beam • Concrete - Prefabricated and site cast
Special Problems of Masonry Construction: Expansion and Contraction
• Masonry walls expand and contract slightly in response to changes in both temperature and moisture content. • New clay (brick) masonry units tend to absorb water and expand under normal atmospheric conditions. • New concrete masonry units usually shrink somewhat as they give off excess water following manufacture. • Expansion and shrinkage in masonry materials are small compared to the moisture movement in wood or the thermal movement in plastics or aluminum. • Must provide surface divider joints to avoid an excessive buildup of forces that could crack or spall the masonry. ▫
Glazing Small Lights
• May be glazed by simple means since they are not subjected to large wind force stresses or large amounts of thermal expansion and contraction. • In traditional wood sash, glass is first held in place by small metal glazier' s points and then sealed on the outside with glazing putty, a oil compound that gradually hardens by oxidation of the oil. • Putty is protected from weather by subsequent painting, and tends become brittle with age. • As an alternative to glazing putty, newer latex and silicone caulking compounds can be applied more quickly and need not be painted. • Synthetic rubber gaskets can also be used
Mortar Hydration
• Modern masonry mortars are made with hydraulic cements. These are cements that cure by chemical reaction with water, a process called hydration (similiar to cement). • Once hydraulic cements harden, they become water insoluble. • If unused mortar is more than 2 ½ hours old, it must be discarded because it has already begun to hydrate and water cannot be added without reducing its final strength. In some projects, extended life admixtures may be used. ▫
Brick Classifications
• Most common bricks are facing brick, building brick, or hollow brick. • Facing bricks are used where appearance is important. • Building bricks used where appearance doesn't matter. • Facing and Building Bricks may be 100% solid but are more often cored to reduce cracking during firing and reduce weight. • Hollow bricks are up to 60 percent void. -Reinforced: to enable the insertion and grouting of steel reinforcing. -Unreinforced - To construct light infill walls or reduce thermal transmission in exterior walls. ▫
History (continued)
• Neither crown glass nor cylinder glass was of sufficient optical quality for the fine mirrors desired by the 17th-century nobility. • For this reason, plate glass was first produced in France in late 17th century. • Molten glass was cut into frames, spread into sheets by rollers, cooled, then ground flat and polished with abrasives, first on one side and then on the other. • Result was a costly glass of near-perfect optical quality in sheets of unprecedentedly large size. • Mechanization of grinding and polishing operations in 19th century reduced price of plate glass to level that allowed it to be used for storefronts in Europe and U.S. ▫
Color of Bricks
• No two bricks are identical. • Color depends on the chemical composition of the clay or shale and the temperature and chemistry of the fire in the kiln. • Higher temperatures produce darker bricks. • Iron prevalent in most clays turns red in an oxidizing fire. • Other chemical elements interact in similar ways in the kiln to make other colors. • For bright colors, faces of bricks can be glazed like pottery either during the normal firing or during a subsequent firing process.
Heat-Treated Glass
• Produced by reheating annealed glass in an oven and then cooling (quenching) both of its surfaces rapidly with blasts of air while its core cools much more slowly. • Process induces permanent compressive stresses in the edges and faces of the glass and tensile stresses in the core. • Resulting glass is stronger in bending than annealed glass and more resistant to thermal stress and impact. • Useful for windows exposed to heavy wind pressures, impact, or intense heat or cold. • By adjusting quenching process, greater or lesser degrees of residual stress may be introduced into the glass, producing products referred to as either "tempered" or "heat-strengtened glass." ▫
Insulation on the Outside Face
• Relatively recent development. • Usually accomplished by means of an exterior insulation and finish system (EIFS), which consists of panels of plastic foam that are attached to the masonry and covered with a thin, continuous layer of polymeric stucco reinforced with glass fiber mesh. • Appearance is that of a stucco building. • Masonry is completely concealed and can be of inexpensive materials and/or unrefined workmanship. • Thin coatings are not very resistant to damage, and can allow substantial moisture leakage into the walls of the building. ▫
Mortar
• Serves to cushion the masonry units, giving them full bearing against one another despite their surface irregularities. • Seals spaces between units to keep water and wind from penetrating the wall. • Adheres the units to one another to bond them into a monolithic structural unit. • Important to the appearance of the finished wall. ▫
Thermal Insulation of Masonry Walls
• Solid masonry wall is a good conductor of heat, which means it is a poor insulator. • Three general ways of insulating masonry walls: • On the outside face • Within the wall • On the inside face ▫
Glazing Large Lights
• Those lights over 6 square feet (0.6 m2) in area require more care in glazing. • Wind load stresses are higher and glass must span farther between supporting edges. • Basic design objectives for large-light glazing systems: • Support the weight of the glass in such a way that the glass is not subjected to intense or abnormal stress patterns. Since glass is poor in tension, glass is almost always held from underneath rather than hung from the top. • Support the glass against wind pressure and suction. • Allow for expansion and contraction of both glass and frame without damage to either. • Weight of glass is often supported in the frame by synthetic rubber setting blocks, normally two per light, located at the quarter points of the bottom edge of the light.▫
Composite Masonry Walls
• To balance appearance and economy, solid masonry walls of multiple wythes can be constructed of multiple materials. • Composite masonry walls have an outer wythe of stone or face brick and a backup wythe of another material, often hollow concrete masonry. • Two wythes are bonded by horizontal steel reinforcement or steel tiles, and the space between can be filled with mortar. • Can be loadbearing or non-loadbearing. • Separate wythes are intimately bonded so that they behave as a single mass. • Evaluate differential thermal and moisture expansion characteristics of the two materials to be sure that the wythes expand or contract at similar rates. • In loadbearing applications, consider differential strengths and elasticities of the materials.
Detailing Masonry Walls: Flashings and Drainage
• Two general types of flashing are used in masonry construction: • External flashings - prevent moisture from penetrating into the masonry wall at its exposed top or where it intersects the roof. • Internal flashings (also known as concealed or through-wall flashings) - catch water that has penetrated a masonry wall and drain it through weep holes back to the exterior. • External flashing at intersection of flat roof and wall parapet is usually constructed in two overlapping parts: • Base flashing - often formed by the roof membrane itself. It is normally turned up for a height of at least 8 inches vertically. • Counterflashing or Cap Flashing - embedded in the masonry wall above the base flashing and extends downward, lapping over the base flashing. • Two parts allow for ease of installation and movement. ▫
Reinforced Masonry Walls
• Unreinforced masonry walls: • Cannot carry such high compressive stresses as reinforced walls. • Have little ability to resist tension forces. • Unsuitable for use in regions with seismic risk or for walls subject to strong lateral forces (wind or earth pressures). • Steel-reinforced masonry loadbearing walls: • Combine complimentary materials to resist both compression (masonry) and tension (steel). • Can be constructed thinner than comparable unreinforced walls. • Savings in materials, labor, and floor area required for tall walls. • In contemporary construction, all but the smallest and simplest masonry walls are reinforced. ▫
Fire-Rated Glass
• Used in fire doors, fire windows, and fire resistance rated walls. • Must maintain its integrity as a smoke and flame barrier even after it has been exposed to heat for a period of time. • 3 principle fire-rated glass solutions: wired glass, ceramic glass, intumescent layer glass • Wired glass • Produced by rolling a mesh of small wires into a sheet of hot glass. • When it breaks from thermal stress, wires hold sheets of glass in place so that the glass continues to act as a fire barrier. • Carries a fire resistance rating of 45 minutes. • Optical-quality ceramic (crystalline vs. amorphous solid) • More stable against thermal breakage than any type of glass. • Can achieve fire resistance ratings ranging from 20 minutes to 3 hours.
Masonry Loadbearing Walls
• Usually simply called bearing walls. • Walls constructed of brick, stone or concrete can be used to support roof and floor structures of light wood framing, heavy timber framing, steel, sitecast concrete, precast concrete, or masonry vaulting. • Loadbearing masonry walls can be built with or without reinforcement. ▫
Buildings of Layers
• Walls, skin, and enclosure must typically perform a number of functions: • Express and/or embody formal design intent, the making of inhabited space, and the mediation of interior and exterior, both visually and physically. • Structural - gravity (live + dead loads) and/or lateral loads. • Thermal resistance - slow movement of heat energy. • Moisture resistance - water + water vapor/humidity/moisture. • There are few (if any) magic materials that perform all of these functions well. • The many different functions are typically addressed through different layers within wall, roof/overhead, and floor assemblies. • Each layer is often a different material, addressing the diverse functions of enclosure. • The particular way that layers are brought together is an opportunity to impart meaning and intent within the work.
Masonry Cavity Walls 2
• Width of wall cavity: • Minimum recommended separation between wythes of a cavity wall is 2 inches (1 inch when insulation is installed). • Allows enough space for masons to keep the cavity free of mortar obstructions. • Weep holes: • Allows for any water that enters the wall cavity to be redirected back to the exterior (in combination with flashing). • Should be immediately on top of flashing to keep bottom of cavity dry. • Can be made with rope, plastic tube, or unmortared head joint. • Masonry Reinforcing and Ties (Lateral): • Typically installed within the width of the mortar joint. • Typically constructed of welded wire. ▫
Insulating Glass
• Window glass is a poor thermal insulator. • Single glazing • 1 sheet of glass • Conducts heat 5 times as fast as 1 inch of polystyrene foam insulation and 20 times as fast as a well-insulated wall. • Double glazing • 2 sheets of glass with an airspace between them. • Cuts rate of heat loss in half. • Triple glazing • 3 sheets of glass, with airspaces between each sheet. • Reduces rate of heat loss to about a third of the rate through a single sheet. • Still loses heat six times as fast as the wall in which it is placed. • Double- or triple-glazed units are called insulating glass units (IGUs). ▫
Vapor Retarder(continued)
•Commonly used vapor retarder materials are polyethylene plastic sheet, craft paper facing on glass fiber batt insulation, aluminum foil facing on various types of insulation, and special paint primers with low water vapor permeability.•In low-slope roof construction, vapor retarders are often made of roofing felts layered in hot asphalt or of adhered rubberized asphalt sheets.•Where vapor retarders are used, the cooler side of the assembly, opposite the vapor retarder, must be breathable,or designed so that any moisture that does find its way into the assembly can be dispersed through vapor-permeable materials.•Assemblies with multiple vapor-impermeable layers should be avoided; they can trap moisture and provide no means for the moisture to escape.
Sustainability Considerations in Exterior Wall Systems
•Design of the exterior wall has a greater effect on lifetime (operational) energy consumption than almost any other factor. •Glass should be used where it can supply day lighting and provide views, but also limited to prevent overheating, glare, or excessive heat loss through the envelope. •Windows that can be opened and closed by the occupants can help reduce energy costs, in some cases. Note humidity issues + cooling/heating lag. •Opaque areas of the exterior wall should be well insulated. •Thermal bridges should be eliminated from the exterior wall. •The entire envelope should be detailed for air-tightness. Fresh air to be provided by building ventilation system, not by air leakage through ext. wall. •South-facing glass can be used to provide solar heat to the building in winter, but must avoid glare, local overheating, + UV deterioration of interiors. •Consider using south-facing surfaces for electrical energy generation.
Water Vapor and Condensation (continued)
•Dew pointsvary based on humidity of air masses (for a given temperature): •More humid rooms have a high dew point, meaning the air would not need to be cooled much before it reaches 100% humidity. •Dry rooms have a lower dew point, and the air can be cooled to a lower temperature before it reaches saturation. •When air is cooled below its dew point, it can no longer contain all its water vapor and some of the vapor turns to liquid. This process of converting water vapor to liquid by cooling is called condensation.
Steep Roofs
•Drain themselves quickly, giving wind and gravity little opportunity to push or pull water through the roofing material.•Materials can be small, overlapping units:•Shingles, of wood, slate, or artificial composition.•Tiles of fired clay or concrete.•Small units are easy to handle and install.•Repair of localized damage is easy.•Effects of thermal expansion and contraction, and of movements in the structure that supports the roof, are minimized.•Water vapors can vent themselves easily through the loose joints in the roofing material.
Forces that Move Water Through a Wall
•Gravity •Momentum •Surface Tension •Capillary Action •Air Currents and/or Pressure Differentials
Stiff mud
•High-production method most widely used today. •Moist lay is extruded through rectangular die, rectangular column of moist clay is then sliced into bricks by wires of automatic cutters, and then dried. -Extruder - Core Hole Die on Extruder -Column of Clay is Extruded -Extruding -Extruded Column of Green Clay - Reel Cutter for Slicing Brick -Separating Sliced, Green Brick Dry, Green Brick Emerges From Dryer
Conceptual Approaches to Watertightness in the Exterior Wall
•In order for water to penetrate a wall, three conditions must be satisfied simultaneously:•There must be water present at the outer face of the wall.•There must be an opening through which the water can move.•There must be a force to move the water through the opening.•If any one of these conditions is not satisfied, the wall will not leak.•Four basic responses to preventing a leak:•Keep water away from the wall, if possible via overhangs or projections.•Try to seal every opening. This barrier walltypically proves unreliable.•Eliminate or neutralize the forces that move water through a wall.•Provide strategies for internal drainage or secondary defense, via cavities within the wall assembly that allow for drainage (pressure equalized designand rainscreen design.
Detailing Masonry Walls: Flashings and Drainage (continued)
•Interior flashings are installed by masons as they construct the wall. •Where an internal flashing crosses the wall cavity, it should be turned up 6 to 9 inches at the back face of the cavity and penetrate the inner wythe by at least 2 inches. •If the cavity is backed up by a concrete beam or wall, it may terminate in a reglet, a horizontal slot formed in the face of the concrete. ▫
Vapor Retarder Usage (continued)
•Key points to remember:•Warmer air = more moisture = higher vapor pressure•Cooler air = less moisture = lower vapor pressure •Moisture will move from areas of high pressure towards areas of lower pressure.•If properly designed and located (on warm/humid/high pressure side), vapor retarder may slow movement of moisture into the wall assembly, reducing likelihood of condensation occurring within the cavity.
Thermal Insulations
•Material added to a building assembly to slow the conduction of heat through the assembly.•In the winter, it is warm inside a heated building and cold outside. In summer the relationship reverses. In both cases the temperature varies according to the materials and insulation in it.•A materials effectiveness in resisting the conduction of heat is called its thermal resistance, abbreviated as Rand expressed as square foot-hour-degree Fahrenheit per BTU (ft2-hr-F/BTU). (Remember: R = 1/U)•The higher a material's R-value, the higher its resistance to heat flow and the better its performance as a thermal insulator.•The thermal performance of a complete building assembly depends on the sum of the thermal resistances of the materials from which it is made.•Metals are poor insulators, and concrete and masonry are only slightly better. Wood has a substantially higher thermal resistance, but not nearly as high as that of commonly used insulating material
Design Requirements for the Exterior Wall
•Principal Design Issues :•Convey design intent and meaning •Define the character of the project -further spatial and formal qualities •Negotiate and define social relationships •Primary Functional/Performative Requirements of Enclosure: •Keep Water Out •Keep Water Out •Keep Water Out •Prevent Air Leakage •Control Light •Control the Radiation of Heat •Control the Conduction of Heat •Control Sound
Roofs
•Protect buildings and people from precipitation and solar radiation(both visible spectrum and ultraviolet radiation).•Are subject to intense temperature differentials, with surface temperatures ranging from below freezing to boiling hot within many 12-hour cycles.•Are potentially more important than walls in the thermal performance of a building envelope (heat rises).•Are constructed of many different materials.•Can be generally organized into two groups: low-slope roofs and steep roofs.
Design Requirements for the Exterior Wall (continued)
•Secondary Functions: •Resist Wind Forces •Control Water Vapor •Accommodate Movement •Thermal Expansion/Contraction •Moisture Expansion/Contraction •Structural Movements •Resist Fire -sometimes a primary function, depending on context •Address Installation Requirements for the Exterior Wall •Allow for Maintenance •Weather Gracefully
Vapor Retarder
•Sometimes inexactly referred to as a vapor barrier.•Material that is used to slow the diffusion of water vapor through a building assembly.•Continuous sheets or coatings made of plastic, metal foil, coated paper, or any other material resistant to the passage of water vapor.•Located toward the warmer sideof the insulation in a building assembly.•Restricts the diffusion of water vapor into the assembly from the side of higher vapor pressure, limiting chances for dew point conditions and condensation to occur within the assemblys cooler portions.•Where heating conditions predominate, place vapor retarders toward interior, heated side of the insulation in the assembly.•In humid regions where warm-weather cooling predominates, locate vapor retarder toward the exterior side of insulation.•In mild or balanced climates, vapor retarder may not be necessary.
Thermal Bridging vs. Thermal Break/Thermal Barrier
•Thermal bridging occurs when a part or parts of a building envelope assembly with low thermal resistance penetrate the thermal barrier. •Common occurrences are cantilevered concrete slabs, steel beams, and older window assemblies. •Greatly reduces the overall thermal performance of the overall building assembly and should be avoided by detailing thermal breaks.
Water Vapor in Building Assemblies (continued)
•Under summertime cooling conditions in hot, humid weather, diffusion of water vapors is reversed -water vapor is driven from the warm, damp outside air toward cooler, drier air inside. •In most of North America, this summer condition is not as severe as that in winter, and heating conditions predominate. Control of water vapor in building assemblies focuses primarily on the flow of vapor from interior to exterior. •In Florida, the southern U.S., and the Hawaiian Islands, however, the summer condition is the more severe. The flow of water vapor from exterior to interior is the predominant problem to be solved.
Low-Slope Roofs
•Water drains relatively slowly from the surfaces.•Membranes that cover low-slope roofs must be absolutely watertight.•Small errors in design or construction can cause them to puddle and/or hold water.•Small punctures, tears, or gaps in seams can cause large quantities of water to enter the building structure and its interior.•Major advantages of low-slope roofs:•Can cover a building of any horizontal dimension, whereas a steep roof becomes uneconomically tall when used on a very broad building.•Much simpler geometries make them easier and less expensive to construct.•Can serve as balconies, decks, patios, landscaped gardens, or parks.
Water Vapor and Condensation
•Water exists in three physical states, depending on temperature and pressure: solid (ice), liquid, and gas (vapor). •Air always contains some water in the form of water vapor, an invisible gas. •The higher the temperature of the air, the more water vapor it can contain. •At a given temperature, the amount of water vapor the air contains in proportion to the maximum amount of water that it can contain is the relative humidity of the air. •As air cools, its capacity to hold water vapor diminishes, leading to an increase in relative humidity (even though the amount of water vapor is unchanged). •If air continues to cool, it will reach a point where relative humidity is 100%. This is the temperature at which the air is fully saturated with water vapor, also known as the dew point.
Water Vapor in Building Assemblies
•Water vapor is a gas and exerts pressure, called vapor pressure, on the surfaces that contain it. The more water vapor an air mass contains, the greater the vapor pressure. •Under wintertime heating conditions, the air inside a building is at a higher temperature and contains more water vapor than the air outside. This is especially true in areas where occupants are cooking, bathing, washing, etc. •Result is a net difference in vapor pressure acting from inside to outside, causing water vapor to diffuse outward directly through the various material layers of the enclosing assembly. •If the rate of diffusion is high enough and the change of temperature within the assembly great enough, water vapor will reach its dew point and condense within the assembly. •If moisture accumulates, damage and deterioration of materials will occur.
