Hambro® Systems

Hambro D500 Structural Floor Joist System

Advantages & Cost Saving Benefits:

Fire Ratings:

Hambro® has superior U.L. Fire Ratings for 1, 2 and 3 hours, and eliminates the need for fire dampers.

Acoustical Properties:

Hambro has an STC 57, one of the highest in the industry, and an IIC 30 on bare concrete. Hambro’s IIC with soft vinyl is 55, and with pad and carpeting it increases to 69.

Mechanical Interfacing:

Features open web configuration, no bridging, and 4 foot to 5 foot joist spacing accommodates Mechanical Interface (mechanical distribution) within the joist plenum. Hambro permits full-length ducts and pipes, and virtually eliminates dropped ceilings and bulkheads.

A Variety of Bearing Systems:

Hambro is appropriate for a variety of bearing systems: steel studs, masonry, steel, concrete, and wood framing.

Composite Design:

Hambro’s composite design provides a floor that is 2 to 3 times more rigid, with one-third the deflection of a typical bar joist assembly. Hambro also provides 4 feet joist spacing without bridging and bracing. Typical bar joist assemblies are spaced at 2 feet or 2 feet-6 inches on center and require bridging, bracing, and metal deck.

Ease of Installation:

The Hambro System is easily installed by one of the many experienced installers who contract with you directly and package related scopes of work, or by your own unskilled forces, if you choose.


Hambro is well-suited to a variety of projects including: Apartments & Condominiums, Independent, Assisted, & Extended Care Facilities, Student Housing, Schools, Hospitality, Military Housing, and Office Facilities.

Slab Penetrations:

Slab penetrations are easy, using either sleeves, styrofoam or wood blocking prior to concreting. No tendons and fewer joists offer flexibility. A slender 3,500 psi slab makes coring simple, if necessary.


Hambro’s Typical Details have been developed as an aid to specifying professionals and are conveniently provided as a basic guide of suggested practice for the Hambro system.

And thanks to Swirnow Structures LLC:

  • Assistance is available every step of the way. We provide conceptual design and estimating, and we’re available at your job site when it counts.
  • A simple letter agreement without the fine print is usually all it takes to get started.
  • Guaranteed upfront pricing at the early stages of your design.
  • On most projects, a first shop drawing submittal can be made within 25 working days, and joist deliveries within 4 weeks.

Product Information:

The Hambro D500 Floor System combines composite joists with poured concrete, developing a hybrid concrete/ steel T-beam running in one direction, and an integrated, continuous slab in the opposite direction. The D500 System utilizes reusable Rollbars® and plywood forms.

The bottom chord (Fy 50 ksi) acts as a tension member during both the concreting stage and the service life. The web system, consisting of bent rods, (Fy 50 ksi) ties the top and bottom chords together and resists the vertical shears in the conventional truss manner.

Hambro D500’s patented 13-gauge S-shaped top chord section has four basic functions:

  1. It is the compression member of the joist during the non-composite concreting stage. The system does not require shoring.
  2. It is a “high chair” for the welded wire mesh, developing negative moment capacity in the concrete slab where it is required over the joist top chord.
  3. It supports the slab forming system.
  4. It automatically becomes a continuous shear connector for the composite stage.

The concrete slab is reinforced with welded wire mesh at the required locations and behaves structurally as a continuous, one-way, reinforced concrete slab.

The rigid ⅜ inch CDX plywood sheets and Rollbars, when locked into the D500 top chord section, not only act as simple forms for placing concrete, but provide the essential lateral and torsional stability to the entire floor system during the concreting stage.

The interaction between the concrete slab and Hambro joist begins to occur once the wet concrete starts to set. The necessary composite interaction for construction loads is achieved once the concrete strength, f’c reaches 500 psi (3.5 MPa). This will usually occur within 24 hours.

Even in the coldest of winter concrete pouring conditions, construction heating will maintain the concrete at temperatures necessary for this strength gain. When in doubt, concrete test cylinders can be used to verify strength.

Normally 4 feet-1-¼ inch to accommodate standard 4 foot-0-inch-wide plywood forms, but spacing of joists can be altered to suit job conditions.