Reinforcing Loose Terra Cotta Units And Patches
REINFORCING LOOSE TERRA COTTA UNITS AND PATCHES
THIS PROCEDURE SHOULD BE PERFORMED UNDER THE DIRECTION OF AN
HISTORICAL ARCHITECT OR ENGINEER TO DETERMINE THE MOST EFFICIENT
AND LEAST DESTRUCTIVE MANNER FOR EXECUTING THE WORK. APPROVAL
FROM THE REGIONAL HISTORIC PRESERVATION OFFICER IS REQUIRED.
A. This procedure includes guidance on installing bent wire
armatures or studs in terra cotta to additionally
reinforce and anchor existing patches that are more than
1/2" thick, or any patch which is approximately fist
B. This procedure requires substantial intervention and is
only to be used to secure large patches to already
damaged terra cotta surfaces. If not properly anchored,
large patches are particularly vulnerable to failure and
separation due to weight, thermal expansion and bond
C. See 01100-07-S for general project guidelines to be
reviewed along with this procedure. These guidelines
cover the following sections:
1. Safety Precautions
2. Historic Structures Precautions
4. Quality Assurance
5. Delivery, Storage and Handling
6. Project/Site Conditions
7. Sequencing and Scheduling
8. General Protection (Surface and Surrounding)
These guidelines should be reviewed prior to performing
this procedure and should be followed, when applicable,
along with recommendations from the Regional Historic
Preservation Officer (RHPO).
A. Sika Corporation
B. Abatron, Inc.
A. Stainless steel or bronze wire armature, or threaded rods
and bolts. Threaded rods shall be sized according to the
need and loading requirements. Consult with structural
engineer and RHPO.
1. Wire shall be 12-gauge or heavier.
2. Stainless steel shall be AISI Type 316.
3. The use of a wire armature or threaded rods shall
be determined by size, depth and thickness of patch
being stabilized. To be determined by structural
engineer and RHPO.
B. Moisture insensitive, structural epoxy or polyester resin
adhesive as recommended by adhesive manufacturer (Sika
Corporation, Abatron, Inc., or approved equal).
C. Acrylic-cement finish.
A. Masonry drill with diamond tipped coring bits.
B. Electric drill with mixing paddle to pre-mix epoxy
C. Clean pail in which to mix epoxy adhesive.
D. Pressure-injection equipment as may be required.
E. Mixing nozzle: As recommended by adhesive manufacturer,
the resin components may be automatically mixed by a
nozzle that is secured to the component cartridges.
3.01 ERECTION, INSTALLATION, APPLICATION
1. The drill holes should be sized according to the
wire or rod used. Typically, the hole shall be no
greater in diameter than 1/8-inch or 1/4-inch
(depending on the adhesive used) larger than the
pin to be embedded, and ten to fifteen bar
2. Drill shall be non-impact type rotary drill with a
3. Depth of hole shall be sufficient to reach sound
4. Space wire armature reinforcing at approximately
2-inches on center, arranged in a grid or mesh where
applicable, or as recommended by structural engineer.
5. Clean holes with high pressure air.
B. Protection: Protect surfaces around holes from contact
with adhesives. Use petroleum jelly, modeling clay or
polyethylene sheets as required.
1. Verify the rod length as appropriate for the depth.
2. If using automatic pressure-injection equipment,
resin shall be automatically measured and mixed in
the mixing nozzle.
3. If mixing by hand, mix each component by volume as
directed by manufacturer into clean pail.
Components shall be used straight, without any
additives. Mix thoroughly for time specified by
manufacturer with low-speed drill (400-600 rpm)
fitted with appropriate paddle. Blend until
uniform color is achieved.
4. Pack or place the resin into holes.
5. Slowly insert the wire armature or threaded rod
into the resin to the full depth of the hole.
Countersink head of rods.
6. Do not disturb the anchor until the adhesive has
cured. Follow manufacturers instructions.
7. No gaps shall be visible between the rod and the
D. Plug counter-sunk holes and build-out face of damaged
patches as required flush with surrounding surfaces using
patching mortar as described in HBPP procedure 04214-01-R,
"Patching Small Holes, Minor Chips and Spalls in Terra Cotta".
A. Immediately remove spills and excess adhesive with
absorbent material and flush with water.
B. Uncured material can be removed with solvent as
recommended by adhesive manufacturer.
C. Do not allow excess material to cure as cured adhesive
can only be removed mechanically.
A. Apply one coat colored masonry acrylic-cement finish to
protect and repair damaged surface areas.
B. Apply this protective, coloring, coating to existing old
patch areas where the color does not match the terra
END OF SECTION