Concrete Tabby Plaster Stucco

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1 Concrete Tabby Plaster Stucco

2 Concrete Raw materials easily available Does not rot or burn Relatively low cost Used for every building purpose foundations, walls, pavement, interior finishes Has no form of its own Has no useful tensile strength, but has high compressive strength

3 Roman Concrete Invented by Romans Volcanic rock and ash from Pozzuoli (near Naples), called pozzolan Ground it up Mixed Pozzolana cement (naturallyhydraulic) with lime Burned the mixture Added sand When mixed with water, it hardened under water better than in the air

4 Roman Concrete, cont. Changed the way Romans built Masonry of stone and brick used for surface layers Hollow interiors were filled with concrete

5 Roman Brick Wall Construction

6 Pantheon, Rome,

7 Pantheon Current version built by Hadrian, Original built by Marcus Agrippa in 27 BCE; destroyed by fire in 80 CE Largest unreinforced concrete dome in the world Weight 5000 tons Thickness varies from 21 feet at base to 4 feet at the oculus Height = Diameter = 142 feet Coffering decorative but also reduced the weight of the ceiling

8 Coffered ceiling with oculus

9 Knowledge of concrete construction virtually lost during Middle Ages Late 18 th - early 19 th century, British and French inventors experimented with cements 1824 Joseph Aspdin invented Portland cement st modern poured gravel wall construction

10 Sidney Root-Joseph E. Brown house; 159 Washington Street, Atlanta; unreinforced concrete (?); 1858 Sebastopol; West Court Street, Seguin, Texas; unreinforced concrete, 1854

11 1867 Joseph Monier (France) patented iron reinforcing bars (rebar) Added the tensile strength of the metal to the compressive strength of the concrete 1886 Rotary kiln introduced made production of cement more practical st ASTM tests for cement (American Society of Testing and Materials)

12 Re-bar in CMUs (concrete masonry units)

13 Unity Temple; Oak Park, Illinois; pre-cast, reinforced concrete; 1906; Frank Lloyd Wright

14 Terminal Building, Dulles International Airport; Washington, DC; ;Eero Saarinen

15 Site-cast, reinforced concrete

16 Deterioration of Concrete Prolonged contact with water Freeze/thaw problems Corrosion of iron reinforcing bar or ties Absorbs CO 2 from atmosphere deteriorates Poor materials impure aggregates (e.g., beach sand); seawater Not poured property Historic: tamping, rolling left voids Modern: vibrated as poured Joints between pours Improper/no maintenance

17 Problems Cracking Spalling Deflection Erosion Corrosion of re-bar Solutions Fill cracks Patch Call engineer Replace Remove & replace All fills, patches, replacements should be compatible with the original for appearance and durability. Iron re-bar should be replaced with galvanized (steel coated with zinc) or epoxy-coated re-bar.

18 Water penetrating through concrete leaches out calcium oxide, forming crystalline calcite (stalactites)

19 TABBY Coastal Concrete From Spanish word tapia meaning earth compacted between boards First used in North America by the Spanish in the 1500s English began using tabby or tappy in the early 1700s

20 Tabby Composition Lime the binder (glue) Shells the aggregate Sand prevented shrinkage and cracking of the tabby mixture. Channel (river) sand was used; beach and dune sand contained too much salt Water had to be fresh Ash by-product from burning the shells; increased hydraulicity (ability of a binder to harden in contact with water); contributes to tabby s durability

21 Making Tabby Ingredients: Equal parts lime, sand, water, and shells, plus small amounts of wood ash Mix into a slurry Pour into a mold Let set until hardened Apply stucco or whitewash finish coat

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23 Advantages of Tabby Used inexpensive local materials No skilled labor required Versatility of form and application Poured into a mold, blocks, bricks, floors, ceilings, columns, arches Durability in a humid climate. Can be re-used

24 Disadvantages of Tabby Extremely labor intensive; a cheap source of labor was necessary to make tabby construction practicable (i.e., slaves) Susceptible to water damage, unless a finish coat of stucco or whitewash is applied Not fire resistant

25 Four Types of Tabby Oglethorpe tabby Spalding tabby Tabby Revival Pseudo-Tabby (faux tabby) 1950-Present

26 Oglethorpe Tabby Fort Frederica, 1736, St. Simons Island, GA

27 Spalding Tabby slave quarters; 1840s; Ossabaw Island, GA

28 Spalding Tabby slave quarters; 1840s; Ossabaw Island, GA

29 Tabby Revival Hollybourne Cottage, 1890, James Day, Jekyll Island, GA

30 Faux Tabby

31 Coquina is not Tabby

32 Coquina Spanish word for little shells A sedimentary rock composed of the shells of invertebrates Particles must be 2mm or larger in size Quarried and used as a building stone in Florida for over 400 years

33 PLASTER Generic term for cementitious substances applied to a surface in paste form that harden to a solid material Prehistoric plaster mud smeared over masonry walls or over a mesh of woven sticks and vines (wattle & daub) Egyptians and Mesopotamians developed fine plasters based on gypsum and lime Portland cement added in late 1800s Chosen wall surface until ca. World War II, replaced by drywall (gypsum board)

34 Gypsum Quarried, crushed, dried, ground to fine powder, heated to 350 F to remove most of the moisture (calcining) Calcined gypsum ground to fine powder is Plaster of Paris (discovered by Egyptians) When mixed with water, rehydrates and recrystallizes rapidly, giving off heat as it hardens, and expands

35 Early Plaster Clay and water Sand added to reduce shrinkage Straw, grass added as reinforcement

36 Lime Plaster Composed of non-hydraulic lime, sand, fiber or hair, and water Can be applied directly to masonry or over wood or metal lath More water resistant than early plaster Used in finish coats

37 Gypsum Plaster More rigid than lime plaster Requires furring strips against masonry More vulnerable to water damage Has more sculptural potential than any other architectural material

38 Characteristics of Plaster Major disadvantage water soluble Durable Lightweight Somewhat soundproof Easy to work, wet or dry Fashioned into a variety of shapes and textures Inexpensive Highly resistant to fire

39 Historically, plaster applied by hand using hawk and trowel; now usually sprayed on

40 Plaster Application Can be applied directly to masonry surface Most often applied to lath Wood strips nailed to wood framing with small spaces in between allowing keying of the plaster Hand split lath, accordion lath, sawn lath Metal lath, must be attached with furring strips

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42 Three-coat application SCRATCH BROWN 3. FINISH

43 The scratch coat forms keys when it oozes between the lath. These help hold the plaster onto the wall.

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45 Ornamental Cast Plaster Poured into molds Running with a template to make linear ornaments

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47 Problems with Plaster It is rigid, will crack Structural movement, settling, vibrations Lath movement Poor workmanship; e.g., too much sand crumbling Improper application Improper curing Lath set too closely, keys cannot form Water - softens plaster, rots wood lath, corrodes nails, causes iron lath to rust

48 Solutions Filling cracks Patching Re-plastering Veneer plaster replacement system All fills, patches, replacements should be compatible with the original for appearance and durability.

49 STUCCO Before 1870s: slaked lime, water, sand, straw or hair Old stucco was usually whitewashed annually for protection 1870s-present: Portland cement added, straw/hair can be omitted Harder, more like modern masonry mortar Used on surfaces exposed to moisture More than a veneer

50 Widely used on residences in U.S. in 17 th and 18 th centuries A. J. Downing advocated its use in 1850 Renewed use in 1890s-early 20 th century Prairie, Art Deco, Streamline Moderne, Spanish Colonial Revival, Mission Revival, Tudor Revival Modern stucco gypsum instead of lime Color depends on sand used, or from added pigments

51 Cliveden; Philadelphia; stone main façade; stucco over rubble, scored to resemble ashlar on side; 1764

52 Richardson-Owens-Thomas House; Savannah, GA; stucco over tabby, scored to resemble ashlar; 1817; William Jay

53 Swan House; Atlanta; stucco over terracotta block with cast stone trim and reinforced concrete fountain; 1928; Philip T. Shutze

54 Characteristics of Stucco Provides weather protection Somewhat fire resistant Can be worked to simulate stonework Used over less-costly substrate Can be applied directly to masonry or on lath over wood Same three-coat application as plaster Many ways to finish it

55 Modern stucco being sprayed over expandable metal lath

56 Stucco Repairs Identify the type of stucco before attempting repair Patch rather than replace when possible Repair/replacement should be compatible to the historic stucco in durability, color, and texture Repairs should be applied with similar method to the historic stucco

57 Staff Invented in France ca Plaster of Paris, cement, glycerin, dextrine mixed with water Cast in molds lined with hemp or jute fiber Usually ½ thick, off-white in color Casting to resemble cut stone, rock, faced stone, any masonry Can be bent, sawed, bored, nailed Impervious to water Reinforced with concrete for strength

58 Columbian Exhibition; Chicago; Most buildings in the White City were temporary structures built of staff