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Special Inspections

Twining is the most recognizable name in testing and inspection. It has been our core service for over 125 years, and while we have grown to encompass a multitude of other Engineering Consulting services, we take pride in being the preferred provider for special inspection and materials testing in the regions we serve.

Our team has the resources to staff every project with experienced and professional inspection personnel. These highly skilled men and women have been selected for their depth of knowledge and for their ability to work with clients to achieve maximum performance at minimum cost.

Our team currently consists of more than 150 inspectors throughout California, more than 80% of whom hold multiple inspection certifications in various aspects of construction.

Special Inspection Services

The disciplines our inspectors cover include:

Structural Steel

High Strength Bolting
Curtain Wall Attachments
Shop Fabrication Inspection
Welding Procedure and Welding Qualifications


Placement Inspection
Rebar Placement
Shotcrete Sampling
Batch Plant Inspection
DSA Shotcrete

Roofing and Waterproofing

Existing Properties
New Construction

Spray-Applied Fireproofing

Cementitious Fireproofing
Intumescent Fireproofing


Source Inspection
Placement Inspection
Rebar and Tendon Placement
Pre and Post Tension Stressing
Concrete Sampling
Sampling of Reinforcing Steel
Precast Plant Inspection
Batch Plant Inspection
DSA Concrete


Inspection of Layup
Block and Brick Sampling
Mortar Sampling
Grout Sampling
Precast Plant Inspection

Drilled-In Anchors

Epoxy Anchors
Mechanical Anchors


Wood Framing

Our considerable pool of inspectors enables Twining to provide our clients with the inspection support they need at any location, for any shift, as project needs arise. Our dispatch office is available 24 hours a day, 7 days a week.

Twining’s long-standing relationships with steel fabrication shops throughout the world allows our inspectors to provide seamless shop fabrication inspection no matter where it may take place. Our experienced staff has inspected the fabrication of structural steel as far away as Japan and Taiwan.

Nondestructive Examination

The field of nondestructive testing is undergoing rapid change, bringing technologies that had previously been the subject of research into the arena of practical application. Twining has been at the forefront of these applications, from participating in the post-Northridge SAC committees through being the first firm to fully implement the requirements of FEMA 353 and now AWS D1.8, to the field implementation of the latest technologies such as Phased Array Ultrasonics and Time of Flight Diffraction. Twining is fully compliant not only with ASNT SNT-TC1A, but with the stricter certification standards of CP-189.

Dye Penetrant
Magnetic Particle
Ground Penetrating Radar
In-Place Concrete Soundness
Floor Flatness and Levelness

Twining’s core testing services are overseen by Robert M. Ryan, CWI, ASNT NDT Level III, who has been with Twining and its affiliated companies since 1977. Robert possesses vast experience in all areas of field inspection and is a leading expert on all aspects of structural steel construction and nondestructive testing. Robert also provides strategic counsel and technical direction for many of our largest projects and has worked on some of California’s most distinguished landmarks including the J. Paul Getty Museum, Walt Disney Concert Hall and Disney’s California Adventure.

Featured Projects

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