BCN 3224 – Construction Techniques Exam 3 Review

Material Covered: Chapters- 27-29, 33-34. Rebuild, Guest Lectures, Roofing Video.

Chapter 27 – Exterior Wall Cladding – I (Principles of Rainwater Infiltration Control):o Exterior walls are one of the major determinants of the appearance of a building. They

convey images such as strength or solidity, and a sense of movement or activity. More importantly, the importance of the buildings performance of the exterior walls is even greater. Together, they provide the buildings envelope, providing separation btw inside and outside and serving to maintain an acceptable interior environment.

o The exterior walls can only function if they are able to perform well under a range of environmental conditions. They must: Prevent water infiltration from rain and snow Control heat loss and heat gain Control air leakage and water vapor transmission Resist fire Control sound transmission Accommodate movement due to thermal, moisture, and other causes

27.1 – Rainwater Infiltration Control - General Principles:o 3 major forces that affect water infiltration through exterior walls are gravity, the

capillary effect, and wind. Because these forces frequently act on an assembly simultaneously, multiple strategies must be used in the same assembly to counter water infiltration. 1. Gravity-Induced Infiltration: gravity generally affects water penetration through an

exposed horizontal surface of a wall and can be countered by providing a nominal slope in the surface. The purpose of the slope is to drain water away from vulnerable areas of the building.

2. Capillary-Induced Infiltration: water molecules are subjected to forces of attraction btw them, creating an intermolecular cohesive bond btw them. In addition, water molecules experience forces of attraction from the molecules of the surface with which they are in contact, forming an adhesive bond. Cohesive and adhesive forces create the capillary effect, which is responsible for suction forces that occur in tiny spaces btw two surfaces, being sucked btw the surfaces.

Capillary break: the space that is introduced in larger spaces to prevent capillary suction in narrow joints of 1/4” or wider.

3. Wind-Induced Infiltration: providing an overlap btw members meeting at a joint is another joint is a common measure. The force of wind can impart kinetic energy to water, causing the water to travel horizontally as well as vertically in the joint.

The Importance of Joint Sealants: Filling joints with sealants is another commonsense used strategy to keep water

from penetrating joints btw bldg. components. However, because they degrade quickly, they cannot be the only water-resistant element.

27.2 – Rainwater Infiltration Control and Exterior Walls:o Water Resistant Walls can be divided into 3 types:

1. Walls with overhangs This system depends on protective floor and roof overhangs to prevent water

penetration. However, the depth of overhangs is a limitation since they at times must be very large.

2. Barrier Walls Face-Sealed Walls and Reservoir Walls:o Barrier walls are those that function as the primary structure, and at the same

time, performs as the building envelope. This wall type resists water infiltration either by a) providing an impervious barrier or “face-sealed wall” or b) by functioning as a water reservoir – “reservoir wall”.

3. Drainage Walls A relatively more water-resistant exterior wall consisting of an exterior cladding,

inner backup wall, and an intervening air space btw. Any water that leaks through the cladding collects in the air space and is drained out through small openings at the bottom of the cladding called weep holes.

Important Features:o Exterior claddingo Air spaceo Water-resistant backupo Weep holeso Flashing: continuous waterproof membrane providing continuous barrier.

Collects and channels water back to exterior. 27.3 – Rain-Screen Cladding:o This system includes the basic principles of the drainage wall system, but it also

addresses the issues of water penetration due to unequal distribution of air pressure on the ext. of the wall in the air space btw the cladding and backup wall. In order to reduce the suction of water, the pressure should be equalized as much as possible.

o Wind Load On The Cladding Of A Pressure-Equalized Wall: Rain screen: the exterior cladding in a pressure-equalized wall.

o Practical Limitations: It isn’t possible to achieve a completely load-free cladding.

There is a time-lag btw a change in the outside pressure and the corresponding change in air space pressure, at which the cladding is subjected to wind load.

o Airtight Backup Wall: Once the pressure in the air space is equalized with respect to the pressure on the

walls façade, not air movement will occur in the space, however, will ONLY work if it is airtight.

o Compartmentalization Of The Air Space: Another cause of air movement in an intervening air space is where the action of the

wind produces positive pressure on the windward façade and the sides under negative pressure. Therefore, the air space of a pressure-equalized drainage wall must be closed at wall corners. A closed-cell compressible filler such as neoprene sponge may be used as closure material.

o Summary: an ideal rain-screen wall should consist of the following 3 water-infiltration-control features: 1. Voids in cladding for pressure equalization in the air space 2. Compartmentalization of the air space 3.Airtight backup wall

Chapter 28 – Exterior Wall Cladding – II (Masonry, Precast Concrete, and GRFC):o Anchored Masonry Veneer and Adhered Masonry Veneer:

Masonry veneer can either be a) anchored masonry veneer or b) adhered masonry veneer.

o 28.1 – Anchored Masonry Veneer Assembly – General Considerations: Brick veneer is by far the most popular contemporary cladding systems. This is due

to: durability, fire-resistance, aesthetic appeal, and low-maintenance. Generally consists of singly-wythe brick wall (4” nominal thickness). Back-up walls can

be load or non-load bearing walls and consist of: Wood or cold-formed steel stud (residential) Concrete masonry (commercial) Reinforced concrete (commercial)

Anchors: Steel anchors connect the veneer to the backup wall which transfers the lateral

load from the veneer to the backup wall. They are made of 2 pieces which are secured to the backup and the other embedded in the horizontal mortar joints. Anchors should not be spaced more than 32” O.C. horizontally or 18” vertically.

Air Space: An air space of 2” clear is recommended for brick veneer. This reduces the effects

of excess mortar in the space. Wood-stud-backed wall assemblies use 1” spacing. Support For Brick Veneer – Shelf Angles Anchored To Structural Frame:

Brick ledge: a 1.5” depression commonly created in the foundation to receive the first course of the veneer, which further prevents water intrusion into the backup wall.

Shelf angles/relieving angles: supports veneer in mid to high-rise buildings and are anchored to the buildings structure.

Lintel Angles – Loose-Laid: Lintels generally used as additional supports for dead loads over an opening in

brick veneer and are of steel angles and placed loosely on the veneer. Locations of Flashings and End Dams:

Flashings must be provided at all interruptions in the brick veneer:o At foundation levelo Over a shelf angleo Over a lintel angleo Under a window sill

Joints btw flashings must be sealed, and all flashings much be accompanied by weep holes.

Flashing Materials: Must be:o Water-resistanto Puncture/tear/abrasion resistanto Durableo Flexibleo Corrosion resistanto Ultraviolet radiation resistant

Common materials:o Stainless steelo Copper sheeto Plastics (Neoprene, PVC, EPDM)o Composite flashing

Construction and Spacing of Weep Holes: Weep holes must be provided immediately above flashing. Generally spaced 24”

with open-head joints and 16” with wick or tubes. The simplest and most effective weep hole is an open vertical mortar joint in the

veneer (open-head joint). Joint screens may be used to resist bugs and debris.

Mortar Droppings In The Air Space – Mortar Catching Device: Mortar droppings must be minimized to ensure efficient air space functions.

Mortar Capturing Device: place immediately above the flashing consisting of a mesh which traps droppings and suspends them permanently above the weep holes.

Continuous Vertical Expansion Joints in Brick Veneer: Continuous vertical expansion joints at intervals are required due to the post-

construction expansion of brick walls. Max. Spacing is 25’. Mortar Type and Mortar Joint Profile:

Type N: generally specified in all-brick veneer except seismic zones. Concave joints yield veneer with more water-resistance.

28.2 – Brick Veneer With A CMU Or Concrete Backup Wall: See FIGURE 28.19 Air And Water Resistance of CMU Backup Walls:o The exterior face of CMU backup walls need to be suitably treated to resist the

flow of air and water while allowing water vapor to pass through. Several proprietary liquid-applied air weather barriers are available.

28.3 – Brick Veneer With A Steel Stud Backup Wall: Differs from CMU mainly in the anchors used for connecting the veneer to the

backup. Various types of anchors can be used in different situations. Steel Stud Backup Wall as Infill Within The Structural Frame:o Figure 28.28 shows a detailed section of brick veneer applied to a steel stud

backup wall with a reinforced-concrete structural frame. Steel Stud Backup Wall Forward Of The Structural Frame:o In low-rise buildings, putting the steel stud backup wall on the outside of the

structure allows it to cover the structural frame. Thus, the studs are continuous from the bottom to top, requiring no shelf angles. Slip connections must be used to connect the studs with the floor or roof, so the roof and structural frame can move independently.

Air and Water-Resistance of A Steel Stud Backup Wall:o 1. Wrap-type air-weather retardero 2. Liquid-applied air-weather retarder (commercial)

28.4 – CMU Backup Vs. Steel Stud Backup: Steel Benefits:o Lightweighto Economy

Concerns:o Only performs well if the stud wall is sufficiently stiff. Increasing stiffness of

studs increases costs. o Condensation Corrosion

CMY Benefits:o Does not depend on screws more forgivingo Anchors are embedded in mortar joints no corrosiono Inherent stiffness

28.6 – Precast Concrete (PC) Curtain Wall: Panelized construction where panels are constructed off-site under controlled

conditions and transported to site in ready-to-erect conditions, reducing time and costs.

Favored in harsh climates where low temperature affect curing process. Used for most building types, but more often high-rise hospitals, apartments,

garages, office buildings, etc. Supported on and anchored to the buildings structural frame and hoisted by

cranes into position. Panel Shapes and Sizes:o Window, spandrel, etc.o Generally made as large as possible and extend from column to column

Concrete Strength:o The 28-day concrete strength should be reasonably high so that when the panel

is removed from the form, it can resist the stresses during removal and handling processes. Most common is 5,000 PSI.

Panel Thickness:o Governed by the erection stresses rather than load stresses. Cannot be less

than 5”. Mock-Up Samples:o Architect requires precast plant to prepare and submit for approval, and kept

onsite for reference. 28.7 – Connecting The PC Curtain Wall To A Structure:

The connections of a PC curtain wall panels to the buildings structure are among the most critical items in a PC project and are typically designed by the panel fabricator. 2 types are required in each panel:o 1. Gravity Load Connections (bearing supports: only 2)

Bearing supports: a section of steel tube, partly embedded in the panel and partly projecting out of panel.

o 2. Lateral Load Connections (tiebacks: 2+ per panel) Tiebacks: resists horizontal forces on the panel from wind etc. Allows

movement within the plane of the panel. Clearance Of Panels From The Structural Frame:

o PCI recommends a min. horizontal clearance of 2” of precast panels from the building structural frame.

28.8 – Brick And Stone-Faced PC Curtain Wall: PC curtain walls may be faced with thin clay bricks at the time of casting the

panels. (3/4” -1”). They are placed in patterns in the form and concrete is placed over them.

PC curtain walls may also be faced with natural stone veneer. 28.9 – Detailing a PC Curtain Wall:

A typical PC curtain wall is backed by an infill steel stud wall, which provides the interior finish and includes insulation, as well as electrical and other utility lines. A fairly lightweight backup wall is adequate.

Water Intrusion Control and Joints Between Panels:o PC curtain walls are much more resistant than brick-veneer walls, so only joints

btw panels must be treated with a backer rod and sealant. Outer seal provides weather barrier and contains weep holes. Inner seal provides air barrier.

Insulated, Sandwich Panels:o PC curtain wall panels with rigid plastic foam insulation btw two layers of

concrete may be used in cold regions. Nonstructural purposes only. 28.10 – Glass Fiber-Reinforced Concrete Curtain Wall (GFRC):

Ingredients:o Portland cemento Sando Glass fibers (provide tensile strength)o Water

Does not require steel reinforcing. GFRC Skin And Cold-Formed Steel Frame:o Consists of 3 main components:

1. GFRC Skin (1/2”-3/4” thick) Cold-formed steel backup frame Anchors that connect skin to steel backup frame

Flex Anchors:o The skin is hung 2”+ away from the face of the frame using bar anchors,

providing an essential gap for differential movement btw the skin and frame for evaporation etc.

o Bonding pad: the skin which is thickened around the anchor embedment.o Anchors transfer both gravity and lateral loads from the skin to the frame.

28.11 – Fabrication of GFRC Panels: Preparing the mold: plywood or plastic mold per required shapes.

Applying the mist coat: a tin cement-sand slurry coat is sprayed which gives an even and flat surface to the concrete.

Applying the GFRC mix: consists of white Portland cement and sand slurry mixed with 5% glass fibers.

Frame placement: cold formed steel support frame is placed against skin Bonding pads: formed at each anchor Removing the panel from the mold and curing: removed after sufficient strength is

achieved. 28.12 – Detailing a GFRC Curtain Wall:

Requires 2+ bearing connections and tieback connections. Connection hardware is lighter. Because the skin is thin, a water drainage system should be in place from behind the skin in the panels.

Chapter 29 – Exterior Wall Cladding – III (Stucco, Adhered Veneer, EIFS, Natural Stone, and Insulated Metal Panels): This chapter continues the discussion of exterior-wall cladding systems.o 29.1 – Portland Cement Plaster (Stucco) Basics:

Plastering walls makes them fire-resistant, water-resistant, as well as smooth and paintable.

Consists of cementitious materials, sand and water. Gypsum boards have largely replaced plaster. Common Stucco uses:

Cold-formed steel stud walls Wood stud walls Masonry walls Concrete wallso Require appropriate temperature conditions (40+)

Mix Composition For Stucco Coats: Typically applied in 2 coats over a wall, called the base and finish coats. In some cases, the base coat can be applied in the scratch and brown coat. 2 types of factory-blended mixes for the finish coat are available:o 1. Portland cement-based mixo 2. Acrylic polymer-based mix (more common finish coat)

o 29.2 – Stucco On Steel- Or Wood-Stud Walls: The anatomies of wood and cold-formed steel frame walls with a stucco finish are

essentially identical. They both require exterior sheathing, water-resistant membrane, and a self-furring metal base. The stucco is the first line of defense vs water. The membrane is the 2nd.

In most projects, two layers of asphalt-saturated building paper or one layer of No.15 asphalt-saturated roofing felt is used as the water resistant membrane. It is applied horizontally with laps btw sheets.

The metal base generally consists of self-furring galvanized steel lath (expanded metal lath) these provide a bonding feature for stucco.

Application of Stucco: Generally consists of 2 coats (scratch and base) each approx. 3/8” thick and

approx. 1/8” thick finish coat = total thickness of 7/8”. Stucco is mixed in a mixer, connected to a pump and delivered to point of

application through a long pipe terminating in a nozzle that sprays the mix. A 24-48 hour time interval is used btw scratch and brown coats for correct drying. A longer interval is required btw brown and finish coat of 7-10 days to allow for

shrinkage. Control Joints And Expansion Joints:

Control Joints: (1-piece) since shrinkage is an inherent feature of stucco, leading to cracking, it is controlled using closely packed control joints.

ASTM requires that the area btw control joints in stucco applied on a stud-wall assembly not exceed 144 sqft. They should be provided around all openings in walls.

Expansion joints: (2-piece accessory) needed in a stucco finish which responds to large movements in the building structure. They should be provided at each level in the exterior wall in a multistory building to absorb the movement in the spandrel beam.

Stucco Stop: a casing bead used at the terminal edge of a stucco surface to prevent chipping on corners etc.

Rigidity Of The Stud Wall Assembly: Due to the relatively thin and brittle fully cured stucco surface, it is important that

the backup wall assembly be sufficiently rigid. One-Coat Stucco:

Includes glass fibers in addition to Portland cement and lime. ½” thick and is applied on the lath but is finished smooth.

Reduces labor, time, and cracking. 29.3 Stucco On Masonry And Concrete Substrates:

Masonry is an excellent substrate for stucco because it is far more rigid, and provides a much better bond for stucco finish, therefore, not needing lath.

Stucco applied on a masonry wall usually consists of 2 coats (base/finish) with a total thickness of 3/8” – 5/8”.

Because masonry is porous, it may suck water from the mix, leaving insufficient water in stucco, therefore, a prewetting may ne required.

Light sand-blasting followed by application of a liquid bonding coat is required on the concrete walls.

Joints In Stucco-Finished Masonry And Concrete Walls:o Due to its higher rigidity, the control joints can be spaced farther apart.

29.4 – Limitations And Advantages Of Stucco: Lacks the ability to drain rainwater out of assembly if penetrated. Thin and light for drying in wet regions Because it is adhered finish, it better resists vibrations and movements. Clarity of form that results from its use and variety option of colors.

29.5 – Adhered Masonry Veneer: Masonry veneer that is adhered to the backup wall instead of being anchored to it,

in which the masonry units are very thin. The most common type consists of manufactured stone (1.5” thick) Benefits: lower costs, lightweight, large variety. Veneer Anatomy And The Construction Process:o Similar to that of stucco.o A 3/8” thick scratch coat on metal furring lath is the backup used for the veneer.

After 24 h, veneer units are adhered to the coat using Type S or N masonry mortar.

Adhered Masonry Veneer With Portland Cement Board Backup:o An alternative in which a ½” thick Portland cement board applied over exterior

sheathing replaces the metal furring lath and scratch coat. 29.6 – Exterior Insulation And Finish System Basics (EIFS): “Synthetic stucco”

Consists of a layer of rigid polystyrene foam insulation, a fiberglass-reinforcing mesh, a polymer-based base coat, and a polymer-based finish coat. The reinforcing mesh is embedded in the base coat.

2 categories:o 1. “soft-coat EIFS”o 2. “hard-coat EIFS”

29.7 – Application of Polymer-Based EIFS: EIFS is a versatile cladding used for all types of projects. The use of rigid foam insulation in EIFS has 4 major advantages:o 1. Energy efficient o 2. Foam insulation allows a great deal of detail work to be easily completed on

façadeo 3. Large variety of colors

o 4. Does not require control joints Negatives:o Low impact resistanceo Inability to breathe

Installation of Insulation:o Adhere the insulation over the liquid-applied air-weather retarded placed over

the substrate.o Adhesive is applied to back of insulation in ribbons using trowel.o Board is pressed against substrate and clings to.o Boards are arranged in running-bond pattern to avoid continuous joints.o Insulation boards are sanded smooth (rasping).

Application Of The EIFS Lamina (Base Coat, Mesh, and Finish Coat):o Before the base coat is applied, the terminal edges of insulation boards are

wrapped with reinforcing mesh, a process known as backwrapping.The reinforcing mesh is embedded in the base coat.

Movement Control In An EIFS Wall:o Since it is a relatively flexible membrane, no control joints are necessary, but

expansion joints are. 29.8 – Impact-Resistant And Drainable EIFS:

Created in address impact and drainage issues. Impact Resistant EIFS:o Consists of 2 layers of base coat. The first layer is embedded in a thicker

reinforcing mesh, with the 2nd layer having the same mesh as the standard EIFS. Drainable EIFS:o 2 types available:

1. The system with insulation adhered to the substrate having vertical drainage grooves at the back of the insulation.

2. The other system has insulation mechanically anchored to the substrate and a thin drainage mat and an air-weather retarder behind the insulation.

Both systems require a perforated plastic track at the bottom to allow water to weep at the base.

29.9 – Exterior Cladding With Dimension Stone: Granite, marble, and limestone Min. recommended thickness is 20 sqft. Or less. Field installation can be done by 2 methods:o 1. Standard-set installationo 2. Vertical channel support installation

29.10 – Field Installation Of Stone –Standard Set Method:

In this method, each stone slab is directly anchored to the backup wall with its own dead-load and lateral-load supports. Tieback anchors provide lateral-load supports.

Bayonet clip : a stainless steel bent-plate clip commonly used substitute for a stone liner block.

29.11 – Field Installation Of Stone – Vertical Channel Method: The anchorage of stone slabs is substantially simplified by using continuous vertical

support channels. They are anchored directly to the CMU backup wall and are spaced at quarter points extending from floor to floor.

29.12 – Prefabricated Stone Curtain Walls: Instead of installing stones slab by slab to a backup wall, they can be anchored to a

steel truss frame at the construction site. The stone-frame assembly forms a panel, which is lifted into position by a crane and hung from the building’s structure like any other curtain wall panel, extending from column to column.

29.13 – Thin Stone Cladding: Another form of panelized stone cladding uses and extremely thin (1/4” thick)

stone veneer bonded to an aluminum honeycomb backing. Standard panel size is 4’x8’. They are ideal due to lightweight, high ductility, and bending strength for seismic

areas. Anchorage:o Utilizes 2 continuous interlocking channels, with one installed to the back of the

panel, and the other is field anchored to the backup wall. Prefabricated Stone-Honeycomb Curtain Wall Panels:o They can be prefabricated into curtain wall panels, extending from column to

column and hung from the buildings structure like any other curtain wall. 29.14 – Insulated Metal Panels:

Another type of lightweight exterior cladding system consisting of metal/steel panels with 2-3” factory-installed polyurethane foam insulation btw metal skins. They are available in a wide array of colors as well as galvanized/stainless steel.

These panels have a high R-value due to the insulation core, therefore additional insulation my not be necessary.

Chapter 33 – Roofing – I – (Low-Slope Roofs)o The roof is one of the most critical components of a building, and covers 75% of all

litigations against architects.o They are replaced on average about every 12-14 years. This is due to severe chemical,

physical and environmental degradation.o 33.1 – Low-Slope And Steep Roofs Distinguished:

Classified into 2 types: 1. Low-slope roofo Water-resisting roof consisting of a continuous roof membrane over a relatively

flat roof surface.o A low-slope roof has a slope of less than 3:12 (25%) and greater than ¼:12 (2%

slope)o Commercial/industrial buildings. Relatively easy maintenance.

2. Steep Roofo Also called a “water-shedding” roof typically consists of small individual roofing

units (shingles) that overlap each other. The roof surface must be sloped so that he water is shed off the rood by gravity.

o Despite the greater durability of a steep roof, the market share of low-slope roofs is nearly twice as large as that of steep roofs.

33.2 – Low-Slope Roof Fundamentals: Components:o Roof membrane; including protective cover tor coating above the membrane,

where needed.o Insulationo Roof decko Flashings

Roof Membranes:o The most important part of a roof because it is the waterproof layer. o 3 general categories:

1. Built-up roof membrane Consists of 3-5 layers of felt with intervening moppings of asphalt, covered

by an aggregate cover. 2. Modified bitumen roof membrane

Similar to a built-up roof membrane and comprises 2-3 layers of modified bitumen sheets with intervening moppings of bitumen, followed by protective aggregate.

3. Single-ply roof membrane Consists of only 1 sheet of a synthetic plastic and does not require a

protective aggregate cover. Roof Insulation:o In a typical low-slope roof, the insulation is sandwiched in btw the membrane

and the deck. Apart from reducing energy costs, insulation provides a suitablesubstrate for the roof membrane. Over a steel roof deck, insulation provides the necessary surface flatness as well.

Roof Deck:o A low-slope roof deck may be of steel, wood, cast-in-place concrete, precast

concrete, gypsum concrete, or wood-fiber-cement deck. Steel and concrete roof decks are more commonly used in low-slope roofs.

Roof Flashings:o Play an integral part of a low-slope roof. They are required at roof terminations,

parapets, roof expansion joints, and penetrations. Low-Slope Roof – A System Of Compatible Components:o Roof design must be considered a system design. It should consider the

interaction btw rood components and the effects of external factors such as climate, etc.

33.3 – Built-Up Roof Membrane: Consists of a number of felt layers, separated by interplay moppings of bitumen. The greater the number of layers, the stronger and more durable the membrane. 3-5 layers is generally the norm. Felt works as a reinforcing material, giving the required tensile strength to the

membrane, as well as stabilizes the bitumen against flow. Organic And Fiberglass Roof Felt:o A built-up roof felt consists of fibers or strands pressed into a sheet. A felt may

be either organic felt or inorganic felt, depending on whether the fibers are organic or inorganic. Organic felt is made from paper or wood fibers. Inorganic is made from glass fibers.

Types of Fiberglass Felt:o 1. Asphalt-treated fiberglass felt: classified by either Type IV (44 lb./in.) or VI (60

lb/in.)o 2. Coal tar-treated fiberglass felt: the use of tar-treated fiberglass felt has been

decreasing. Bitumen – Asphalt And Coal Tar:o 2 types of bitumen – asphalt and coal tar – are used in built-up roofing.

Asphalt: waste product obtained from the distillation of crude oil. Coal tar: obtained from distillation of coal.

Types Of Roofing Asphalt:o ASTM specifications divide roofing asphalts into 4 types:

I, II, III, IV. The most important property that distinguishes one type from another is the

softening point temperature (SFT) of asphalt: SPT: the temperature at which asphalt begins to flow, directly related to

the weathering characteristics of asphalt.

Amount required: approx. 25lb of asphalt per roof square is recommended for interply moppings and 60lb per roof square for the flood coat.

Built-Up Roof Surfacing:o Since both coal tar and asphalt degrade over time due to sun exposure, the

topmost layer must be protected with stone aggregate. This also increases fire-resistance, and other weathering effects.

o 33.4 – Modified Bitumen Roof Membrane: Similar to built-up roof felt because the waterproofing agent is the bitumen, to which

a polymer has been added to modify the bitumen’s properties. This increases the sun resistance and other temperatures.

2 most common asphalt modifiers: 1. SBS (more flexible, cold-resistant) 2. APP (UV-resistant)

Carrier: a reinforcing mat which is impregnated and coated with modified bitumen on both sides of a modified bitumen sheet.

Dual-carrier: a sheet that has both fiberglass and polyester reinforcements.o 33.5 – Single-Ply Roof Membrane:

Types of roof membrane with only one ply and do not require the cumbersome use of hot bitumen, making an easy installation process. It is made of a polymeric material.

The polymers can be divided into 2 main categories: 1. Thermosetting polymer (unweldable plastic): does not soften on heating. 2. Thermoplastic polymer (heat-weldable plastic): softens on heating, and hardens

on cooling over and over again. Advantages:

Highly flexible – can withstand large elongation before failure Wider and longer rolls – less laps – less failure spots Temperature-resistant

Disadvantages: Absence of 2nd, 3rd, or additional plies. Less waterproof

EPDM Membrane: Because it is a synthetic rubber, it is essentially similar to the material used in

automobile tires. Typical thickness is 45-60 mil. PVC Membrane:

The most versatile plastic available in 2 types:o 1. Rigid PVC (pipes, siding, window sashes)o 2. Soft, Pliable PVC (shower curtains, raincoats, electrical wire, roof insulations)

The primary advantage of PVC membrane is that the seams in the membrane can be heat fused. It is also inherently fire-resistant. (Avg. thickness is 45-80 mils).

TPO Membrane: Also a thermoplastic, it has the heat weldability of its seams. It is more economical

than PVC. TPO combines the advantages of EPDM and PVC, which explains the increasing

popularity of TPO among the single-ply membranes.o 33.6 – Rigid-Board Insulation And Membrane Attachment:

A type of insulation commonly used in a low slope roof consisting of semi rigid boards. There are 2 common semi-rigid board insulations:

1. ISO boardo Have a much wider applicability than XPS board

XPS boardo Chemically incompatible with some membranes (PVC).

Cover board: an intervening medium btw the roof membrane and the insulation used to provide compatibility. Perlite is a common board used which adds to the R-value of the system (1” thick).

Insulation Attachment – Built-Up And Modified Bitumen Members: The insulation used with built-up and modified bitumen membranes is ISO board

covered with perlite board. This prevents bridging through insulation joints. Insulation Attachment – Single-Ply Membranes:

With a single-ply membrane, the combination of ISO board and cover board in staggered layers is generally used and is attached to one of the 3 systems:o 1. Fully adhered

Manufacturer-provided adhesive is applied to the underside of the entire membrane, and double-sided tape is used to join the laps. Well suited for high wind regions

o 2. Mechanically fastened Consists of screws and a continuous bar (batten bar) through which screws

are applied.o 3. Ballasted

The entire membrane is laid loose over the insulation, followed by a loose-laid single-ply membrane. It is the most economical single-ply system

o 33.7 – Insulating Concrete And Membrane Attachment: Low-slope roof insulation (other than the rigid boards) is lightweight insulating

concrete or foamed concrete. Insulating concrete is poured over a roof deck in wet format and becomes monolithic with the deck after hardening.

Insulating Concrete:

Where insulating concrete is used over a steel deck, the use of a slotted deck is recommended, allowing moisture to depart from the concrete.

Followed by:o Asphalt-treated base sheet fastened to concreteo After fastening, it is mopped to the base sheet

Major advantage: the roof slope can easily be provided in the insulation easily.o 33.8 – Low-Slope Roof Flashings:

Flashing: provides additional strength at roof-wall junctions and integrates the roof membrane with the wall and further waterproofs the system.

Flashing is also required around penetrations in the roof such as drains, gutters, vents, stacks, sun lights, expansion joints,etc. 3 main types:

1. Base flashings 2. Curb flashings 3. Flange flashings

o 33.9 – Base Flashing Details: Base flashing occurs at the junction of a roof and a wall that rises above the roof. 5 important components:

1. Membrane base flashingo Provides additional reinforcement to the roof membrane and extends the

waterproofing ability to the roof to the highest anticipated water level. Most commonly used type is SBS-modified bitumen sheet.

2. Perimeter wood nailerso Used at the base. Add strength and provide a nailable surface to which

membranes and flashings are attached. 3. Cantso Pressure treated wood or Perlite board adhered to the nailer to prevent

cracking during service. 4. Counter-flashingo Generally made of sheet metal, is removable and reusable components that

allow for reroofing without demolishing other components of the detail. They lap over the top of the membrane flashing to prevent the entry of water btw membrane flashing and the parapet wall.

5. Parapet copingo Sheet metal, which wraps over a continuous metal cleat on the outside face of

the parapet and fastened to the parapet nailer with fasteners. Most are spring loaded so they can be snapped to continuous cleats on both sides of the coping.

o 33.10 – Curb And Flange Flashing Details:

Curb Flashing : occurs at the curb placed at the building expansion joint, around a roof opening such as skylight, or under rooftop equipment.it must extend vertically up the curb and en 8” above the roof level.

Flange Flashing: does not extend vertically, but lies in the plane of the roof. Occurs at the edge of the roof and used for supporting a structural frame under rooftop equipment.

o 33.11 – Protected Membrane Roof: In PMR, the insulation is laid loose over the roof membrane, which is generally

installed straight on the deck. Also called an “inverted roof” because the order of insulation and membrane is

reversed compared to others. Followed by:o Leveling boardo Type of membrane (built-up, modified-bitumen, or single-ply)o Covered with insulationo Covered with ballast (gravel or pavers)

Insulation In A Protected Membrane Roof: Insulation is a more critical component of the assemblyo Required characteristics:

Water-impermeable Freeze-resistant High compressive strength High dimensional stability

Filter Fabric:o Another important component of PMR, which consists of a porous plastic

membrane, laid over the insulation to keep silt and small debris from flowing into insulation joints and restricting the insulations movements. Protects roof drains vs. blockage as well.

o 33.12 – Low-Slope Roof Design Considerations: With so many types of low-slope roofing systems available (membranes, insulation

types, and decks) which system is most appropriate for a project? Some of the major factors that affect the selection of an appropriate roofing system are:

Locally available roofing technology Systems suitability to local climate Curved roofs and roofs with large slopes (use fully-adhered single-ply membrane) Chemical environment on the roof Roof warranty Long-term cost and sustainability aspects of the system

Life-Safety Issues in Low-Slope Roof Design: Fire-safety:o Separated into 3 classes:

1. Class A (least) 2. Class B 3. Class C (most)

Wind/hail-resistance:o Min. factor of safety is 2.0.(FMRC)

Drainage Design Chapter 34 – Roofing – II – (Steep Roofs)o A steep roof has a slope greater than or equal to 3:12. o Of the various types of steep roofs, asphalt shingle roofs are the most commonly usedo Architectural sheet metal roofs are used in both low-slope and steep roofs.o 34.1 – Steep-Roof Fundamentals:

The basic components of a steep roof: Shingles Underlayment Ice dam protection membrane (where needed) Deck Flashings

Roof Shingles: Commonly used varieties:o Asphalt:

“Composition shingles” have the largest market because of low cost and acceptable life span. Light weight, reduces costs.

o Slate: Longest recorded histories of use. Perform well in cold climates and can last

75+ years. Expensive.o Concrete/Clay:

Good looking because they are available in large variety of shapes. Very durable. Quality control can affect durability. Concrete tiles can also fade in color over time.

o Wood: Pose a fire hazard.

o Metal Has a small market, but offers a large variety of metal shingles in

contemporary roofs. Roof Underlayment:

A water-resistant layer that is required under shingles throughout the roof as a second line of defense against water leakage. Requirements are based on type of roof materials and slope.

A valley requires a valley underlayment since it is more vulnerable to water damage.

Ice Dam Protection Membrane: A special type of underlayment which is used at eaves in colder climates.

Roof Deck: It is the most important structural element of the roof. Consists of plywood or oriented strand-board panels.

Flashings: Used as additional waterproofing components to create watertight seals at

terminations and transitions in the roof. Critical areas include valleys, eaves, rakes, chimneys, and other penetrations.

Flashings around roof penetrations such as a chimney or pipe are very critical because water is redirected and compressed on a smaller area of the roof as it flows around the penetration.

o 34.2 – Asphalt Shingles And Roof Underlayment: Manufactured in strips of 36”x12” with up to five cutouts. Vary in weight of 200lb-400lb per roof square. Composed of a fiberglass mat, saturated and coated with asphalt and surfaced with

mineral granules (color choice). Each is lined with a self-sealing adhesive, which is activated by the sun.

Standard Slope : btw 4:12 – 21:12. Recommended Roof Underlayment: No. 15 or heaver asphalt-treated organic felt. Drip Edge: a sheet metal drip edge used at all eaves and rakes and mechanically

fastened to the deck (galvanized steel) applied before the underlayment is appliedo 34.3 – Installation Of Asphalt Shingles:

After the underlayment and ice dam protection member have been installed, the roof is ready to receive shingles.

Begin with starter course laid from one end of roof to the other First course of shingles is laido 6” offset method : the pattern of shingles generate by a half-tab procedure.o to improve the performance of the roof, it is desirable to include a course of

bleeder strips at the rake, similar to a startar course. Fasteners:o Shingles are fastened with 11 or 12-gauge galvanized steel roofing nails with

3/8-7/16” diameter nail heads. Each shingle stirrup requires a min. of 4 nailes.

o 34.4 – Valley Treatment In An Asphalt Shingle Roof A valley occurs where 2 pitched roofs meet and water converges. In asphalt shingle

roofs, there are 3 types of valley treatments to be used: 1. Open valley 2. Woven valley 3. Closed-cut valley

Regardless of the type of valley, each valley requires: Valley underlaymento Consists of a full-width asphalt-treated organic felt (No.15+) secured with a

number of nails. Valley flashing

Open Valley – Roll Roofing Material As Valley Flashing: In an open valley, the shingles are held away from the centerline of the valley so

that the valley flashing is exposed to view, providing a smooth/rapid exit of water. Open Valley – Sheet-Metal Valley Flashing:

Galvanized steel sheet metal is placed over the valley underlayment with special metal clips that allow movements.

Woven Valley: Shingles from the 2 adjacent roofs weave into each other, covering the valley

flashing. More durable than open valleys, but reduce flexibility. Closed-Cut Valley:

The shingles from one side of the valley are cut parallel to the line of the valley so that the valley is partially closed. A closed-cut valley combines the advantages and disadvantages of the other 2 valley types, so it is more commonly used. It is also more fire-resistant.

o 34.5 – Ridge And Hip Treatment In An Asphalt Shingle Roof: Asphalt shingles from both sides are butted against each other at the ridge, which is

then capped with ridge shingles. The treatment of a hip is similar, where the hip is capped with the same shingles as a

ridge, and the shingles are installed from the bottom of the hip to the top.o 34.6 – Flashings In An Asphalt Shingle Roof:

Step flashing : a sloping roof plane that abuts a vertical side wall is flashed with metal shingles placed over the end of each asphalt shingle course in an L-shape.

Flashing Around A Masonry Chimney: Consists of 4 component sheet-metal flashings, where the sheet metal is generally

prepainted steel or other compatible metal:o Apron flashing

Placed over the downslope side of the chimney and tightly wrapped around.

o Step flashing Installed on the side walls of the chimney

o Cricket flashing Formed with plywood or oriented strand-board before shingles or etc.

o Counterflashingo One edge of the counterflashing laps over the flashing, and the other is inset

into the masonry mortar joints. Raggle : a cut in appropriate mortar joints.

o 34.7 – Essentials Of Clay And Concrete Roof Tiles: The service life spans of clay and concrete are much longer than asphalt and produce

appealing roofs due to a wide variety of colors and shapes. Clay And Concrete Roof Tile Profiles:

Mission tile profile : semicircular barrel profile S-shape tile profile: integrates the pan and cover of the mission tile into one unit.

Water Absorption And Strength Of Tiles: Unlike asphalt shingles, clay and concrete absorb water, which can eventually

damage the roof. Roof Underlayment And Tile Roofs:

Because a tile roof is relatively long-lasting, the underlayment should match the durability of the tiles.

Ice Dam Protection Membrane: Should be specified in all climates, particularly cold climates.

o 34.8 – Clay And Concrete Tile Roof Details: The easiest and most common method of fastening tiles is to nail them to the

substrate. Nails should be of similar lifetime and stainless steel or copper. The best installation of tiles is achieved with a network of battens and cross-battens

of treated wood nailed to the deck over the underlayment. The tiles are then nailed to the top battens.

The space under the tiles allows for rapid drying Eave Treatment:

Unlike an asphalt roof, the drip edge is not necessary because the eave tiles can be made to project enough off the roof.

Rake, Ridge, and Hip Treatments: Specially prepared curved rake tiles are generally used to weatherproof the rake.

The construction of the hip and ridge is similar.o 34.9 – Types of Sheet-Metal Roofs:

The development of durable coatings on sheet steel, coupled with a vast array of nonfading coating colors has increased the popularity.

Sheet metal roofs are of 2 types: 1. Structural sheet-metal roofso Double as a roof covering and also a structural deck. Commonly used in low-

cost industrial buildings in what are generally referred to as pre-engineered metal buildings.

2. Architectural sheet-metal roofso Require a supporting deck and an underlayment. 2 types:

1. Traditional architectural metal roofs Custom metal roofs

2. Contemporary architectural metal roofs Manufacturer-specific.

o 34.10 – Contemporary Architectural Metal Roofs: Require a deck and underlayment. The deck can be any one of the deck types used in low-slope roof applications

(concrete, steel, plywood, oriented strand-board). Fabrication of Contemporary Architectural Metal Roof Panels:

Shop-fabricated On-site fabrication to required profile (reduces transportation costs)

Anchoring Panels: The panels are fastened to the substrate by metal cleats, based on the

manufacturer.o Fixed type: cleats that do not allow movemento Expansion cleat: required if panels are 40’+ which allow movement.

Ridge And Eave Details: Ridges typically consist of a continuous Z-shaped sheet-metal closure set in sealant

and soldered to the underlying metal panels. A preformed ridge cap engages into the closure. And ice dam protection membrane is adhered over the ridge directly below the

roof panels. Roofing Video: o Rock/gravel is used on roods for thermal protection and against the elements etc.

Lighter-colored rock is used to deflect the sunlight and decrease roof temp.o How can you tell if a new roof is needed?

Roof leaks, plywood warpage/movement, soft spots etc. Lifespan around 15-20 years on average.

o There is no such thing as a purely flat roof.o What are Single-ply Roofing Advantages?

Single ply roofing offers a number of benefits over traditional BUR (built up roofs). It is has a long life span (up to 40 year life expectancy), provides strength, durability, is Eco-friendly, and is available in a variety of materials and colors. Single ply roofing systems offer the advantages of rapid installation and lightweight construction. These systems provide high puncture and tear resistance, excellent dimensional stability, and high tensile strength. They offer superb resistance to ozone and UV exposure, extreme weather conditions, chemicals, and fire. During installation, no heavy equipment is required and the membrane can be applied during inclement weather.

o Study Basic Sketch of Ridge-Board Insulation:o

o Study Base Flashing Detail Diagram:

o What 3 things are inspected on a roof?o Deck (Sheath)o Paper (Felt)o Shingle (Asphalt)

o Study Stucco Application Diagram:

o Know:o Brick Experienceo Rebuildo Guest Lectureo Roofing Videoo Framing Cube

o Study Window/Door Frame in a wall: