ConSpec Associates, Inc.

ARCHITECTURAL TERRACOTTA

HISTORYMANUFACTURING

ATTRIBUTESFLAWS

DETERIORATIONINSTALLATIONANCHORING

REPAIR

REPLACEMENT ALTERNATIVES

Mission Statement

To combine technology with tradition in both methods and materials for innovative, cost

effective, engineered solutions to the repair segment of the built

environment.

WHAT IS TERRACOTTA?

Terra-Cotta refers to a high grade of weathered or aged clay which,

when mixed with sand or with pulverized fired clay (GROG),

can be molded and fired at high temperatures to a hardness and compactness not obtainable with brick. Simply put, terra-cotta is

an enriched molded clay brick or block.

HOW IS IT MADE?

Hand Pressed Units: Clay is rolled out in order to remove the air from the raw clay material. The clay is then applied into high-grade gypsum plaster mold. When applying the clay into the mold, workers meticulously hammer and beat the clay, by hand, into all corners, reliefs and profiles of the mold.

HOW IS IT MADE?

Extruded Units: The raw clay materials are mixed into a plastic state and sent through a vacuum chamber to remove the air within the clay. Then the plastic clay material is pushed through a steel die and the terra cotta units are cut to length. This method is the least labor intensive and is most cost effective.

HOW IS IT MADE?

Ram Pressed Units: Ram pressing terra cotta units is very similar to the traditional hand pressing; however, a hydraulic ram presses the clay into a mold in lieu of a workers hand. This method of production is less labor intensive and is cost effective with medium to large quantities of repetitive units.

HOW IS IT MADE?

Slip Casting: Slip casting terra cotta units is also similar to the traditional hand pressing, except that the chemistry of the raw clay material is modified to create slip or clay slurry that is poured into a fully enclosed plaster mold.

How Long Does It Really Take

to Get Terracotta on a

Project?

PROCESS CYCLE

Contract Date 05/10/13 Receive Color Sample 05/17/13 Receive Survey Info 05/13/13 Receive Fragments 05/17/13 Initial Color Submittal 07/16/13 Arch Review 1st Color 07/26/13 12X12 Color sample 08/15/13

PROCESS CYCLE

Arch Approval 12X12 08/25/13 Shop Drawing Sub 06/14/13 Approved Shops 06/24/13 App Shops Received 06/26/13 105 Day Init Ship 10/09/13 Final Ship 134 Units 11/24/13

ATTRIBUTES

Shapes and designs, limited only to the imagination of the designer

This glass like glaze is durable and impervious to moisture penetration

Glazed surfaces are very dense and do not attract dirt and/or atmospheric deposits, resulting in a nearly self-cleaning surface

ATTRIBUTES

Fired clay material is fireproof Maintenance of the fired and

glazed surface is easy; it never needed paint and periodic washings restored its original appearance.

Durability and permanence – 100+ year life cycle

Manufacturing Defects

Air in material Poor Body Mix – Clay vs. Grog Delamination in Hand Pressed Warping – Aesthetic Only Improper Drying Inadequate Firing Improper Cooling – Body

Cracks Glaze Application

DETERIORATION

“The root of deterioration in glazed architectural terra-cotta systems often lies in a misapplication of the material”

PRESERVATION BRIEFS #7National Park Service

The Preservation of Historic Glazed Architectural Terra-

Cotta

DETERIORATION

Moisture Penetration Associated Material

Deterioration Corrosion of Underlying Steel Moisture Expansion Thermal Movements

DETERIORATION

Deterioration of Mortar Joints Cracking Spalling

– Glaze spalls – Freezing and thawing of entrapped

moisture Question – Grout fill or leave

terracotta empty?

DETERIORATION

Crazing - stresses caused by moisture expansion of the clay body exceed the tensile capacity of the glaze

Glaze shivering: glaze formulation not compatible or “fit” with the clay body shrinkage ratio during firing. glaze will be in tension without complete adhesion of glaze to the clay body.  This can result in glaze peeling

DETERIORATION

Improper repair techniques typically cause the most severe deterioration to a terra cotta facade (cladding material and underlying structure).

Note: As Arch Terracotta is considered impermeable it was once thought that no weep system was needed! WRONG!

INSPECTION

Visual Inspection Sounding – Wood – Acrylic –

Rubber - Metal Tests for Impurities Borescope

– Filled or not filled– Anchor & Steel Condition

INSPECTION

Probe Holes Metal Detection Infrared Scanning Sonic Testing Crack Monitors Rhylem Tests

INSTALLATION

Question? – Match TC pieces line for line, cure for curve?

OR True lines that “should” be

straight – sills, watertables, etc?

INSTALLATION

Questions? What Happens When Anchor

Holes Don’t Align? Mockup for complicated

sections? If so how does it impact

schedule as produced units are 3-4 months out?

Albany Capitol Mock-up

MAIN CAUSES FOR FAILURE

Use of Tanking or Backfill in the Units

Type of Mortar Used Inconsistent or Sloppy

Workmanship– Missing Ties– Mortar allows water ingress– Flashing, Caulking, Support, etc

Anchor Types

Mechanical - Off The Shelf Mechanical - Custom Chemical Cementious

Materials

Anchor Types

Impediment– Split Tail– Undercut– Pin– Swelling Sock

Adhesive– Epoxy– Resin

Mechanisms

Support– Angle/Channel– J Hook– Clamp– Clip– Bracket– Rod

Manufacturers

Mechanical

Holman & Barnard

Dur-O-Wall Heckmann Helifix

Cementitious

Ambex Cintec

Manufacturers

Epoxy

Hilti Powers Rawl Sika ITW Red Head

Resin

Hilti Celtite

Anchor Details Supplied at Bid By

Structural Engineer of Record - Sub Consultant to SE of R - Terracotta Manufacturer - Contractor - Anchor Supplier - Terra Cotta Standard

Construction 1927Typical or Detail?

40%40%

10%

0%

10%

Design Process

New Construction– Control

conditions for assembly design for both terracotta and substrate

– Set the needs for the anchoring system

Restoration– Discover

conditions for assembly design

– Examine existing conditions through visual inspection of in-place materials

Anchor Type & Source Percentage

TYPE

Catalog – Custom -

DETAIL

Structural Eng -

Architect -

Manufacturer -

Contractor -

70%

30%

10%

30%30%

30%

Contributors

Engineers Robert Silman SGH RRJ Thornton

Tomasetti WJE

Architects WASA Vitetta

Contributors

Manufacturers Gladding

McBean Cintec Helifix

Contractors Union Stone

Comments

1. Specify as much as we can to take it out of the contractors hands.

2. We are typically cleaning up messes.

3. Have to take it building by building.

1st Engineer

Comments

1. Tough to get beyond what contractors want to use.

2. You can provide complete specs but will it get done?

3. Spec doesn’t matter as you must find an anchor that fits in the field.

4. Danger is if specified and can’t be used contractor will ask for more money.

5. Mention anchor but hold pricing as pricing seems to override engineering.

2nd Engineer

Comments

1. Terracotta Standards circa 1927 ok for massive masonry structures.

2. Transitional steel frame construction, details are inadequate and must be redesigned upon restoration

3nd Engineer

Review Process

The choice of fixing details for terracotta depends on many things – not simply on whose specifying it:

Type of terracotta construction eg. load bearing mass masonry; transitional steel frame/load bearing masonry or reinforced concrete or steel and terracotta cladding

Forms of deterioration i.e. structural cracking; cracking of face of blocks alone; spalling etc

Type of remediation – wholesale replacement; partial replacement; patch repair

Exposure of the repair i.e. in seismic or high wind areas; marine climate; desert climate etc

Logistics i.e. high rise and forms of access Costs of repair In response to these factors, fixing details have to provide structural

support and/or restraint, and yet account for movement (terracotta being notoriously poor in shear and tension). There are no standard details for all of this.

4th Engineer

Systematic Approach1. Anchor system is designed and included on the contract

drawings2. Contractor is required to coordinate with the terracotta

manufacturer to provide pieces for mockups3. Typically an engineered system4. Mockups and shop drawing details required on all

anchoring5. Number and location of all anchors detailed6. Main problem is contractor doesn’t see how tight

schedule is as mockups of production pieces of terracotta are required and this time element must be taken into account.

7. Manufactured terracotta may have holes or slots in the wrong location for the infield condition necessitating additional holes or slots drilled into the production pieces.

8. Complete process is quite rigorous.9. Mockups in many cases being done during actual

fabrication of the terracotta10. Contractor produced anchors are open for review but

typically only engineered systems are acceptable

PHOTOS

PHOTOS – Goodwin Hotel

PHOTOS – Goodwin Hotel

PHOTOS – PS 238

DETAILS

DETAILS

DETAILS

DETAILS

DETAILS

DETAILS

DETAILS

APPLICATION

Concrete Backup

Custom Fabrication Process

Custom Fabrication Process

Custom Fabrication Process

Custom Fabrication Process

Custom Fabrication Process

Photos courtesy of John Lindner of Union Stone – Hoboken NJ

REPAIR

Crazing - stresses caused by moisture expansion of the clay body exceed the tensile capacity of the glaze

Glaze shivering: glaze formulation not compatible or “fit” with the clay body shrinkage ratio during firing. glaze will be in tension without complete adhesion of glaze to the clay body.  This can result in glaze peeling

2003Ritz Carlton HotelSan Francisco

20095 Years After Repair

Concerns

New Construction– Longevity of System Performance– Match Anchor to both Substrate and

Unit Capacity

Concerns

New Construction“Structural steel when erected

frequently varies from the exact figured dimensions, for this reason all supports for terracotta including angles, rods anchors, etc. should be designed so as to permit easy adjustment to the reasonable requirements of construction when the materials are being set” – Terra Cotta Standard Construction 1927

Concerns Restoration

– Longevity of System Performance 25 – 50 – 100 years

– Match Anchor to both Substrate and Unit Capacity

What is Substrate? Is Capacity of Substrate Diminished? Is Substate

– Solid or Hollow– Strong or Weak

“Anchors don’t fail substrates fail”

– Are Anchors Fire Rated?

Concerns Restoration

– Need for Replacement Units Deterioration Unstable Anchorage - Sometimes Rust Jacking due to Steel Corrosion

– Replace Steel– Apply Cathodic Protection to Steel

Concerns Restoration

– Replacement in kind may negate need for new anchorage design

– Replacement Material Durability Anchorage Requirements Aesthetic & Color Retention

– How do you inset single unit into existing structure?

– New codes may require Seismic upgrade

Replacement Materials

In Kind Stone Fiberglass Cast Stone Other

Longevity – Color - Cost

What Now?

Terra Cotta Standard Construction 1927– Covers Massive Masonry

Applications– Not as good for Transitional

Buildings More Standard Details for

Transitional Buildings?From Where?

Where?

– The Masonry Society– ICRI

Masonry Strengthening & Stabilization Committee

– APTI– SEAoNY– National Parks Service– Manufacturers, Engineers,

Contractors and Conservators

Preservation Engineering Who Restoration

Engineers What Master’s Degree When 4th Semester in

Progress Where Manhattan College Why Less than 5% of

Civil/Structural Engineers understand existing structures for restoration not Rip-Out-And-Replace

THANK YOU

Remember

“Combine Tradition with Technology”