Historic Building Strengthening With Hidden FRP Repairs
Carbon FRP that can be painted over, or NSM carbon rods and strips set into grooves, so repairs stay out of sight. FRP keeps historic structures close to their original size and appearance.
Churches, mosques, courthouses, government buildings, theaters and museums were built long before modern building codes. Most projects start with one of these problems.
1
Older seismic and wind codes
Most historic buildings do not meet current seismic or wind design requirements and must be upgraded for those loads.
2
Age and deterioration
Decades of exposure, aging materials and corrosion weaken walls, floors, beams and columns.
3
A change of use
A floor converted to a museum gallery, for example, may need to carry much heavier loads than it was built for.
4
Repairs that change the look
Conventional steel or concrete strengthening can alter the building's historic character, so review boards often reject it.
HOW IT WORKS
How Hidden FRP Repairs Work
Thin sheets of carbon or glass FRP fabric, typically about 0.05 in. (1.3 mm) thick, are bonded to the surfaces of beams, columns, walls and floors. They add significant strength with very little added thickness or weight, so the structure keeps its original size and appearance.
Once cured, the FRP can be painted or coated with an architectural finish, which makes the repair hard to see. Where even that is too visible, Near Surface Mounted (NSM) carbon rods or strips are set into narrow grooves cut into the surface. Once the grooves are covered, the reinforcement is completely hidden.
Our team works with owners, architects, the engineer of record and preservation reviewers. We recommend the right QuakeWrap® system, including PileMedic® or SPiRe®+ where they fit, and provide specifications and sample details for your engineer, whose drawings go to the preservation boards and agencies for review.
Carbon or glass FRP fabric bonded to the surface
NSM carbon rods or strips hidden in grooves
Finished with paint or architectural coatings
Specifications for your engineer of record
typical FRP fabric thickness (1.3 mm)
0.05 in.
typical increase in member size (13 mm)
Under 1/2 in.
ADVANTAGES
Advantages of FRP for Historic Preservation
Walls, floors, beams and columns
One family of materials strengthens every major structural element.
Minimal added size
Members typically grow less than 1/2 in. (13 mm).
Hidden from view
Repairs can be painted, coated or set into grooves.
Fast, low disruption
Installation is quick, with minimal disruption to the building.
Lightweight
The materials add little load to the structure.
Blends with existing finishes
Finished surfaces can be painted or coated to match.
Planning a historic renovation?
Tell us about the building, the elements that need strengthening and what must stay visible. Our team will recommend the right QuakeWrap® system and provide specifications for your engineer.
Fox Tucson Theatre: Masonry Walls Strengthened Behind the Finishes
Built in 1929, the Fox Theatre in Tucson, Arizona was closed for more than 30 years before a $12 million renovation. Many unreinforced masonry walls and parapets, the basement concrete beams and the lobby floor slab needed strengthening, and the lobby slab also needed waterproofing. The retrofit could not disturb the historic character of the building.
QuakeWrap® glass fabric was used to increase the shear capacity of the masonry walls and the flexural capacity of the parapets, and to strengthen the basement beams that support the lobby floor. The lobby slab was strengthened and waterproofed from the top in a single operation, after the slab was redesigned as a cantilever so the FRP could also serve as the waterproofing.
After the walls were strengthened, the historic interior panels were reinstalled. The project was completed in April 2005 and was featured on the History Channel's "Back to the Blueprint."
Over 7,000 sq ft of masonry wall converted to shear walls
Over 8,500 sq ft of QuakeWrap® glass fabric
2006 SEAoA Award for Excellence in Structural Engineering (Retrofit)
2007 ICRI Award of Merit
CASE STUDY
LA Museum of Natural History: Roof Slabs Retrofitted Under the Tiles
During a major seismic retrofit of this Los Angeles landmark, the inclined roof slabs of the museum wings were found deficient in resisting in-plane seismic forces (diaphragm action). The strengthening system could not alter the building's historic features.
The ceramic roof tiles were removed, and the roof slab was repaired and smoothed. Carbon FRP fabric was installed directly on the repaired roof to resist the design in-plane seismic forces. The refurbished tiles were then reinstalled over the retrofit, giving the building its original appearance. The work was completed in July 2007.
Your structural engineering services were second to none in terms of cost efficiency and constructability… QuakeWrap has done a top-notch job on a challenging project. Your efforts have exceeded expectations per the drawings and the tight budget. The level of quality demonstrated in your craftmanship has not gone unrecognized here.
SMSteven Mitchell, AIAProject Manager, Historic Fox Tucson Theater Renovation, Concord General Contracting, Tucson, AZ
ARCHITECT“
Architecturally, this product is very unobtrusive. It doesn't interfere with the looks of anything you apply it to.
JCJohn Cataldo, AIA, CSIPresident, Cataldo Architects, Pasadena, CA
Historic Preservation FAQs
Will an FRP repair be visible in a historic building?
Usually not. FRP fabric is about 0.05 in. (1.3 mm) thick and can be painted or coated with architectural finishes. NSM carbon rods or strips set into grooves are completely hidden once the grooves are covered. At the Fox Tucson Theatre the interior panels were reinstalled over the strengthened walls, and at the LA Museum of Natural History the roof tiles were reinstalled over the FRP.
Can FRP strengthen unreinforced masonry walls?
Yes. Glass or carbon FRP fabric bonded to unreinforced masonry walls increases their shear capacity. Over 7,000 sq ft of masonry wall at the Fox Tucson Theatre and 11,000 sq ft at 219 High Street in Ebensburg, PA were converted to shear walls this way.
How much does FRP add to the size of a member?
Typically less than 1/2 in. (13 mm), and the materials add very little weight, so the building keeps its original proportions.
Who prepares the drawings for the preservation board?
Your engineer of record. Our team recommends the QuakeWrap® system and provides product data sheets, specifications and sample design details that your engineer uses in the drawings submitted to preservation boards and regulatory agencies.
Can you provide specifications and design details for our engineer?
Yes. Our team will recommend the right QuakeWrap® system and provide product data sheets, specifications and sample design details for your engineer of record.
