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Lesson 23 - Lesson 23 BCN 1001 Building Construction...

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Unformatted text preview: Lesson 23 BCN 1001 Building Construction Interior Walls and Partitions — Chapter 23 — Pgs 883 — 921 Types of Interior Walls Fire walls — Extend from foundation to roof — Divide building into segments considered to be a separate buildings Fire barriers — Between distinct uses that require separation — Typically extend from floor to underside of structure above Shaft walls — Enclose multistory spaces - elevator shafis, stairwells, and chases (vertical corridor for utilities) Fire Walls Divide a building into smaller units — Each of which may be considered a separate building when calculating allowable heights and areas under a bUIIding code Forms a required separation to restrict the spread of fire through a building Must either — Meet a noncombustible roof sthcture atthetop — Or extend through and above the roof by a specified minimum distance Sufficient structural stability to withstand collapsing Openings are restricted in size and must be closed with fire doors or fire-rated glass. Chapter 23 - Interior Walls and Partitions - This chapter — Explains the types of interior walls and part'rtions defined by the building codes — Describes the more common assemblies actually used - Special emphasis is given to gypsum plaster and gypsum board constructions Types of Interior Walls - Smoke barriers — Institutional buildings where occupants cannot readily leave in case of fire - Hosp'rtals‘ prisons. etc. 7 Provide a barrier to fire — Sealed against the passage of smoke - Other non bearing partitions — Do not bear a structural load — Do not play a role in preventingthe spread offire Fire Barriers Used within a building to separate — Mixed occupancies Tenant spaces in commercial buildings Dwelling units in multiple dwellings Guest rooms in hotels and dormitories "o enclose required stainvays and exitway corridors Restrict the spread of fire Unlike Fire Walls — Do not necessarily extend from foundation to roof — But cannotterminate at a suspended ceiling Openings in fire barriers are restricted in size and must be closed with fire doors or firerated glass The required fire resistance ratings for the various types of fire barriers are listed in several places in the IBC Shaft Walls - Enclose a multi-story opening, such as: — An elevator shalt — Shaft for ductwork, conduits. or pipes - Elevator shafl walls — Withstand the air pressure and suction loads of the elevator cars — Reduce the noise ofthe elevator machinery - IBC required fire resistance ratings are — 2 hours for buildings four siJJries or more — 1 hour for shorter buildings Smoke Barriers - A smoke barrier Continuous from one side ofthe building tothe other Continuous from the top of a floor slab to the bottom ofthe slab on the floor above Sealed at all edges Penetrations for air ducts must be protected with dampers - Close automatically it smoke is detected in the air Other penetrations must be sealed airtight Doors - Close fitting - Without grilles or louvers - Close automatically Partitions Partition framing - If applied over a masonry wall; Finish may be spaced away from the wall with either wood or metal iurring strips — Allows for the installation ofa fiat wall finish — Provides a concealed space for installing - Plumbing - Wiring - Insulation Smoke Barriers - Institutional occupancies, where occupants are unable to leave the building - Divide floors in such a way that occupants may take refuge in case of fire by moving to the side of the smoke barrier that is away from the fire - Is a 1-hour partition Partitions Partition framing - Partitions finished in plaster or gypsum board are usually framed with — Wood - Used only as allowed by combustibility requirements otthe building code - Fire—retardant—treated wood is allowed for partition framing in all types of construction — Provided it is used as part of a partition assembly that has been tested and cerlified to have the required overall fire resistance — Or metal studs - Ught—gauge steel studs and runner channels - Open—thss Wll'e studs for plaster partrtions only - Neither is very strong structuraly until restrained by the plaster or sheet material Plaster Plaster is a generic — cementitious substances that are applied to a sun‘ace in paste form, alter which they harden into a solid material Plastering began in prehistoric times with the smearing of mud over — masonry walls — or over a mesh of woven sticks and vines - wattle (mesh ) and daub (mud) Egyptians and Mesopotamians developed finer, more durable plasters based on gypsum and lime Portland cement plasters evolved in the 19th century Plasters of gypsum, lime. and portland cement used today Gypsum Plaster Gypsum is an abundant mineral in nature Crystalline hydrous calcium sutf‘ate Quarried, crushed, dried, ground to a fine powder Calcined - Heated to 350 degrees Fahrenheit (175°C) - Drive off about three—quarters of its water of hydration Ground to a fine white powder, is known as plaster of paris When mixed with water, it rehydrates and recrystallizes rapidly - M it hardens, it gives ofi heat and expands slightly Gypsum Plaster When a subjected to fire A thin surface layer is calcined and gradually disintegrates It absorbs considerable heat and gives off steam, both of which cool the fire "he fire slowly works through the gypsum "he uncalcined gypsum never reaches a temperature more than a few degrees above the boiling point of water Fire resistance can be increased by — Increasing the thickness ofthe gypsum as necessary — Adding lightweight aggregates to reduce its thermal conductivity — Adding reinforcing fibers to retain the calcined gypsum Gypsum Plaster Common types of base coat gypsum plasters: . Ordinary gypsum plaster, in various formulations suitable for either hand or machine application Wood-fibered gypsum plaster, gypsum plaster blended with chopped wood fibers for lighter weight, and greater strength and fire resistance Light—weight gypsum plaster with perlite or vermiculite aggregate. for lighter weight and greater fire resistance High-strength base-coat plaster, for use under high- strength finish coats Gypsum Plaster Gypsum - Disadvantage — It is soluble in water - Advantages — Durable Light weight as compared to many other materials Resists the passage of sound betterthan most material Easily worked in either its wet or dry state Can be fashioned into surfaces that range from smooth to heavily textured Very inexpensive Highly resistant to the passage offire Gypsum Plaster Calcined gypsum is formulated with admixtures to control its setting time and other properties Gypsum plaster is made by mixing dry plaster with — Water — Aggregate - Fine sand - Or lightweight aggregate such as vermiculrte or periite Because 01 its expansion during setting, gypsum plaster is very resistant to cracking Gypsum Plaster Finish-coat plasters are typically a blend of gypsum plaster and lime - The lime provides — superior workability — finishing qualities - The gypsum provides — greater hardness and strength — prevents shrinkage cracking Li me and Portland Cement Plasters comm on types offinlsh coat gypsum plasters: Portland cement—lime plaster, aka stucco - Readwlxed l'lnlsl‘l plaster - Used where the plaster is likely to be subjected to — Factory-blended lime and other ingredisrls moisture — Exterior yrs! surfaces Gauglng plaster _ Commercial kiohens — Gypsum plaster Ttll' [Ob-shit! moung Iir'ltl'l hydrated TH'IIE-l'lll'lg lIl'l‘lE _ lnmfirial plans _ _ — Shower rooms High-strength geugu‘lg plaster — Funlulalcd to produce a Eris-l1 plaster will: lighter compressive slreno'rh Gypsum Plaster - Not as easy to apply and finish . Shrinks slightly during curing. so it should be installed Kama! cement wllh frequent control Jolnls — Fl Dlflflflfltfi MUQII'IQ DEBIEI' ll'lflli HUME-5 an mentionslly dense. crac assisted. lowbsorbomy finish Molding plaster — A fastsetling. line-textured material For mold'ng plaster omsment and running carries Plastering Plaster Lathing Plaster can be applied either hy Plaster" may be applied . Directly to a masonry surface 1 To any of a group of plaster poses known collectively as: lath - Machine — Machine application is essentiallyI a spraying process - Hand: application is done with very simple tools — Hal-ill: in one hand Io hold a small quantity ofplaster TYPE“ Elf lath — Tromel'il the olherhandto lil the pleaterfremthe hawk. apply it - WWI-t on trame _ Iothesurtace. and smooth i into place — Thlrr stops ol'woo-d nailed to wood Earning . After machine or hand application — Small spaces loll bah-men mallow — Dent}: a straighlcdoe. drawn across ilto level it Keying ET the plaster _ Trourel is. used again Io smooth Ihe surfsce - Until a Few cloned-:5 ago. “1': mail common Form of lath It @311}... 3|.- .s‘l‘lfi. I a. Plaster Lathing F'laster Lathing Types of lath . Expanded metal — Sheets or steel alloy silt and stretched lo prodtae a mesh of memos-shaped openmgs _ applied Tn + Dram—trusswtestudsuth lrllennt'tent mama sleet me . Lighl-galrpcslccl studs aih sell-drilling. sall—taqzlpiru sum-rs + 'I'U'DDICI swam Paige—header: lilting nus. _ lath rated with mnhnd cemenl stucco is galvanized to deter corrosion Types of lath . Preformed gypsum hoards — Sheels 16 Inches by 4-3 lnchfi — Thicknesses ofiiI'Fl mo 11? inch — Hardened gypsum plaster Faced Irrith fllIEl' layers of a special absorbent paper - lnrlcl layers of walcl-Irmslanl paper to protect the gypsum cone - Mathsdlo - Tnlssstuoseflh spasm metal cl'os - Eteel 111'de Elm-15W 511M!!- — Cannot be used as a base for firms plaster till liltll'tlifl‘fl cement stucco Plaster Lathing Types of lath - Veneer ptaster base — Paper—faced gypsum board — 4 feet wide and 8 to 14 feet long — Attached to - Wood or steel studs with screws - Wood studs with nails — Base for the application of veneer ptaster Plaster over expanded metal lath Applied in three coats - The first. called the scratch coat — Troweled on rather roughly — Cannot be made completely flat because the uncoated lath moves under the pressure of the trowel — Scratched while still wet. uslng a notched darby, a broom. ora special take to create a rough surface to which the second coat can bond mechanically ° The second, called the brown C03! — Build strength andthickness — Present a level surface for the application of the third or finish coafi — Leveled by drawing a long straightedge across the surfaces of the grounds (the edge beads, corner beads, and control joints) - The third, called the finish coat 7 The finish coat is about 1f16 inch thick 7 May be troweled smooth or worked into any desired texture Plaster Over Gypsum Lath - Three coat system — The bestquality — Economically advantageous over metal lath - Gypsum lath replaces much the thickness of the scratch coat - Two coat system — Gypsum lath is sufficiently rigid to replace scratch coat — Only a brown coat and a finish coat need be applied — The elimination of the scratch coat has obvious economic advantages Plaster Lathing Trim accessories are used at the edges of a plaster surface to make a neat, durable edge or corner — Edge beads — Corner beads — Control joints - Mounted over seams in the lath at predesigned intervals to control cracking — Grounds - Tn'm accessories used as lines that gauge the proper thiclcness and plane - Straightedge may be run across them to level the wet plaster Produced as — Stamped and bent galvanized steel — Extrusions of plastic or aluminum Tradesperson who applies lath and trim accessories is known as a lather Plaster over expanded metal lath Advantages — Extremely strong — Resistant to fire Disadvantage — Cost, largely clue to labor involved in applylng Plaster Applied to Masonry Plaster is applied directly over brick. concrete masonry, or poured concrete walls The walls should be dampened thoroughlyin advance of plastering A bonding agent may have to be applied to some types of smooth masonry surfaces The number of coats of plaster required to cover a wall is determined by the degree of unevenness of the masonry surface Veneer Plaster Least expensive Competitive in price with gypsum board finishes The veneer base and accessories create a very flat surface Specially formulated dense plaster Applied in a "doubleback" process — Thin coat — Followed immediately by a second "skim" coat that is finish troweled to the desired texture Hardens so rapidly that it may be painted the next day Stucco - Exterior applications over metal or wood studs — Applied over sheathing - Asphalt—saturated felt paper applied as an air and moisture barrier - Self—fun'ing galvanized metal lath attached with nails or screws — Without sheathing - Wall is laced tightlyr with Strands of line wire a few inches apart - Paperbacked metal lath is attached to the line wire - Exterior applications over masonry — Same as plaster over masonry Gypsum board - Advantages Least expensive of all interior finishing materials for walls and c eilings Retains the fire—resistive characteristics of gypsum plaster ls installed with less labor by less skilled workers than lathers and plasterers Eliminates some ofthe delay that associated with curing and drying of plaster Stucco - Portland cement stucco shrinks and is prone to cracking — Provide with control joints at frequent intervals - The curing reaction in stucco is the same as that of concrete — Must be kept moist for a period of at least a week before it is allowed to dry - Applied — In three coats — Either with a hawk and trowel or by spraying Gypsum board - Gypsum board, aka: wallboard. plasterboard, dry-wall. and Sheetrock® — Core of - Calcined gypsum - Starch - Water - Pregenerated foam (to reduce the density of the mixture) - Various addrtives — Sandwiched between special paper faces — Manufactured in widths of 4 feet and lengths of B to 14 feet - In recent years, a gypsum board that has no paper faces — Contains an admixture of cellulose fibers that greatly strengthen the hardened material Types Of Gypsum Board Regular gypsum board — Used for the majority of applications Water-resistant gypsum board (aka: green board) — In locations exposed to moderate amounts of moisture — Water—repellant paper facing and a moisture—resistant core formulation Type X gypsum board — For many types of fire—rated assemblies — Core material reinforced with short glass fibers - Fibers hold the calcined gypsum in place to continue to act as a barrier to fire Type C gypsum board — Proprietary formulation that is more fire resistant than Type X — Thinner board of Type C may be substituted for Type X Types Of Gypsum Board Foil—backed gypsum board — Eliminate the need for a separate vapor retarder in outside wall assemblies — Acts as a thermal radiant barrier ifthe back of the board faces a dead airspace at least 3M inch thick Predecorated gypsum board — Has been covered with paint, printed paper, or decorative plastic film — Used in a numberof systems of demountable office partitioning Coreboard — 1—inch—lhick panel — Used for shalt walls and solid gypsum board partitions — Fabricated in sheets 24 inches wide High—impact gypsum board — slam-2n Type X panel that has a polycarbonate film bonded to its back — Useful in buildings that are exposed to rough usage Thicknesses Of Gypsum Board 1l2-inch board — Most common thickness. It is used for stud and joist spacings up to 24 inches SIB-inch board — Limited to stud spacings of not morethan 24 inches — Often used where additional fire resistance or structural stiffness is required 3l4—inch Type X board — 2—hour partitions with a single layer of gypsum board on each face — 4—hour partitions that include two layers on each face 1-inch-thick board is made only as coreboard Installing Gypsum Board Gypsum Association's standardized levels of gypsum board finish — Enable the designer to specify the minimum level of finish that is acceptable Level 0 — Just the boards, without taping, finishing, or accessories — For temporary construction, or where finishing is postponed Level 1 — Joints covered with tape set in joint compound — Areas not open to view‘ such as above ceilings, in attics, and in service corridors Level 2 — Level 1 plus coat of Joint compound over the accessories and fasteners — Thin coat of compound over the tape — garages, warehouses, storage areas, and for board used as a baclcer for tile Thicknesses Of Gypsum Board - 1l4-inch board — Gypsum backing board in certain sound control applications — Produced by some manufacturers to be used fortight—radius bends - 5H 6-inch board — For manufactured housing, for weight reduction to facilitate shipping - 3l8-inch board — Double—layer wall finishes — Permitted over studs 16 inches apart by some building codes Installing Gypsum Board Hanging the board - May be installed over — Wood - Either screws or nails to fasten to mod — Heads a'e driven to a level slightly below the surface at the bead, but notenough to loathe paper surface — Ught—gauge steel studs - Serf-drilling, self—lapping screws to fasten to steel - Usually installed with the long dimension of the boards horizontal — To minimize the length ofjoinls — To create the stiffest wall possible - The longest possible boards are used 7 To eliminate or at least minimize end joints between boards - When two or more layers of gypsum board are installed on a surface — Joints between layers are staggered in order to create a stiffer wall — A mastic adhesive is o‘lten used to join the layers to one another Installing Gypsum Board Gypsum Association’s standardized levels of gypsum board finish Level 3 — Adds another coat of compound over tape, accessofies, and fasteners — Surfaces that will be textured or covered with heavy wallcoverings Level 4 — Adds another coat of joint compound over taped seams, fasteners, and accessories. — Surfaces to be finished with flat paints, light textures, or thin wallcoverings Level 5 — Adds very thin skim coat over the entire surface of the board thickness — Surfaces receiving gloss or semigloss paints — Surfaces lit in such a way as to cast shadows from slight imperfections Gypsum Board Partition Systems Gypsum Shaft Wall Systems Examples in Figure 23.35 page 913 - Walls around elevator shafts, stairways, and mechanical chases can be made of any assembly that meets fire Fire reSIstance ratings up to 4 hours resistance and structural requirements Acoustic performance to STC 59 Provisions to isolate panels from structural loadings - Gypsum shaft wall systems offer several advantages — Movements in the load—bearing frame ofthe building — Lighter in weight Structural deflections — Installed dry Concrete creep — BUilt entirely from the floor outside the shalt Moisture expansion — Any of a number of designs may be used depending on: Temperature expansion and contraction - The requirements for fire resistance rating Sealant to eliminate sound transmission around the ' Airp'essqre'esmame edges - STC reqUIrements - Floor—to—ceiling height Demountable partition systems — Concealed mechanical fasteners — Used when partitions must be rearranged at frequent intervals Wall and Partition Facings Wall and Partition Facings Ceramic tile facings for reasons of: - Facings of granite, limestone, marble, or slate — Appearance — Durability — Public areas of major buildings — Sanitation — Moisture resistance — Fastened per Figure 23.42 page 918 Best quality — Tile facings applied to a base of metal lath and portland cement ' Woodwainscotingand paneling _ mortar — Limited quantities In fire—resistant bUIldings — Mounted over a backing of plaster or gypsum board to retain fire— LWer_c°51 resistive qualities — Eliminate the mortar base in favor ofspecial tile base panels of fiber—reinforced lightweight concrete Lowest-cost — Water—resistant gypsum board, The tiles are mounted to the mortar or concrete panel base with mortar, and to the gypsum with organic adhesive. After the tiles have become fully adhered, a cementitious grout of any desired coloris wiped intothe tile joints with a rubber—faced trowel Assignment Page 921 Review Questions 2, 3, 8: 4 If yo...
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