spancrete-logo

FAQ

How far can I span without a beam?

The PCI Design Handbook recommends limits on span-depth ratios for the hollowcore slabs. For roof slabs, a span-depth ratio limit of 50 is suggested. In practice, a span-depth ratio of 45 is common for floors and roofs where fire endurance, openings, or heavy or sustained live loads do not control a design.

Example: 10″ Spancrete® roof with a span to depth ratio of 50

10″ x 50 = 500 /N
500 = 41.67 FT or 41’–8″

12

SMA Research Notes (stored as PDFs)

1021: Span Limitations – Floor Vibrations – Rhythmic Activity
1022: Span Limitations – Floor Vibrations – Heel Drop Response
1023: Span Limitations – Floor Vibrations – Flexible Supports

What design load do I need for my building?

Design loads are determined by applicable building codes and engineering judgment. It is recommended that you consult an architect, structural engineer, or local building code administrator. The following can be used as a rule of thumb. Residential garage floors are generally 80 pounds per square foot (psf), offices are 100 psf, general assembly spaces are 100 to 150 psf, mezzanines are a minimum of 125 psf, and residential loading is 50 psf.

What thickness of Spancrete® hollow core plank do I need?

Load tables indicate what service loads can be achieved at different spans. The capacity of the Spancrete Hollowcore® plank is dependent on the topping applied to the plank. Toppings are frequently used in conjunction with plank systems for cosmetic and/or structural purposes. A structural topping is applied to the plank such that it bonds to the plank to form a composite unit to enhance the load capacity of the system. A non-structural topping is used to compensate for camber, create drainage, or provide a wearing surface. Non-structural toppings may or may not be bonded to the plank but in all cases do not contribute to the structural load capacity of the plank.

The charts shown here (click to enlarge) indicate approximate Spancrete Hollowcore® plank sizes and capacities. The charts are intended to be an illustrative guide only. Please contact your local Spancrete® sales representative to determine the actual plank size required for your application.

Again, the charts are meant to be a guide; contact your local Spancrete® sales representative to determine a recommended plank size for your application.Example:
You want to install Spancrete Hollowcore® plank over a proposed 24-foot x 36-foot garage. It is assumed the plank will span the 24-foot direction. Whenever Spancrete Hollowcore® plank is exposed to the elements or wet environments, it is recommended that a waterproof membrane be installed over the plank system. This will keep the topping from bonding to the plank, as the topping is considered non-structural. A standard design load for a residential garage is 80 pounds per square foot (psf). A 2-inch concrete topping will add approximately 25 psf (or 12.5 pounds per inch of topping). The total superimposed load therefore is approximately 105 psf. A check of the chart labeled “Floor Without Structural Topping” indicates that a 24-foot span will require an 8-inch plank.

SMA Research Notes (stored as PDFs):

1016: Cantilever Load Distribution
1020: Load Distribution
1022: Span Limitations – Floor Vibrations – Heel Drop Response
1023: Span Limitations – Floor Vibrations – Flexible Supports

Span Notes (stored as PDFs):

How to Use Spancrete® for Inexpensive Space Under Your Garage
Building a New Home with Spancrete® is Easy

Where can I cut holes in my Spancrete® hollow core plank?

All holes and openings should be shown on construction drawings so that the openings can be engineered for the appropriate working loads. If possible, the holes should be located to cut the fewest number of reinforcing strands as possible. All openings should be reviewed by the Spancrete Engineering Department prior to cutting.

SMA Research Notes (stored as PDFs):

1001: Load Distribution Around Central Openings
1002: Load Distribution Around Multiple Central Openings
1004: Shear Design at End Openings

Span Notes (stored as PDFs):

Planning for openings in Spancrete®
Cutting and drilling openings in Spancrete® is easy

How do I cut holes in my Spancrete hollow core plank?

Holes can be core drilled or cut with a concrete saw. Larger openings are cut with a walk behind concrete saw. It is important to cut the holes only AFTER the plank has been erected and the grouted keyways have cured. In some cases, large openings are framed with a steel header. Be sure to get engineering approval before cutting any opening. Contact your local Spancrete Sales Representative for more information.

Span Notes (stored as PDFs):

Planning for openings in Spancrete®
Cutting and drilling openings in Spancrete® is easy

How do I anchor to the underside of my Spancrete hollow core plank?

Commercially available anchors can be drilled and sleeved into the bottom of the plank. Care should be exercised when selecting an anchor because different connectors can withstand varying degrees of pullout force. Drilling through the plank and bolting completely through the plank is often used to support heavy hanging loads. Anchors should be located under the Spancrete hollow core to avoid damaging reinforcing strands.

SMA Research Notes (stored as PDFs):

1029: Bottom Inserts – Powers Fasteners
1030: Bottom Inserts – Red Head
1031: Bottom Inserts – Hilti

How do I support my Spancrete hollow core plank?

Spancrete does not design the supporting structures and assumes no responsibility for their structural integrity. Walls must be concrete masonry units (CMU)/block or poured-in-place concrete. All CMU walls require a continuous bond beam (filled top course) for mounting the Spancrete® hollow core plank. Spancrete hollow core plank requires a 4-inch minimum bearing area on each end for both CMU and concrete. Steel beams are also often used to support Spancrete hollow core plank. Steel surfaces require a minimum of 3-inches of bearing area.

Span Notes (stored as PDFs):

Spancrete® and Structural Steel is a Proven System

How do I connect to a block/concrete masonry unit (CMU) wall?

The standard block or CMU wall connection is achieved with a 1/2″ diameter hole through the Spancrete into the bond beam (filled top course) at 4′ on center. A #4 (1/2″ diameter) rebar is then driven into this hole, thereby providing a positive connection between the Spancrete and the wall. This economical connection is capable of resisting relatively light loads as shown in the Research note listed below.

SMA Research Notes (stored as PDFs):

1015: Dowel Connections

How do I connect to steel?

A weld plate embed is cast into the plank at the time of manufacture and field welded to the steel beam. It is standard practice to only weld one end of a piece of Spancrete® hollow core plank.

SMA Research Notes (stored as PDFs):

1012: Bottom Weld Plates – With Stud Anchors
1013: Bottom Weld Plates – With Wire Loops

Span Notes (stored as PDFs):

Spancrete® and Structural Steel is a Proven System

Where do I find connection details?

Connection details are located on this website. You can download these AutoCAD® details directly into your drawing. Contact your local Spancrete Sales Representative if you are unable to find an applicable detail or have any questions.

SMA Research Notes (stored as PDFs):

1012: Bottom Weld Plates – With Stud Anchors
1013: Bottom Weld Plates – With Wire Loops
1015: Dowel Connections

Span Notes (stored as PDFs):

Spancrete® and Structural Steel is a Proven System

Go to AutoCAD® Details

Can I put a wall or column on my Spancrete® hollow core plank?

It depends on the application. Many columns, point loads, and wall loads can be supported by the plank. Spancrete’s Engineering Department will analyze each case of unsupported loads and will give you a specific recommendation for your particular project. Contact your local Spancrete Sales Representative to review your application.

SMA Research Notes (stored as PDFs):

1003: Width to Span Ration Effect on Load Distribution
1004: Shear Design at End Openings
1005: Shear Design for Edge Loads
1006: Shear Strength
1007: Shear Strength with Filled Cores
1008: Crushing Capacity of Plank Ends
1011: Diaphragm Shear on Untopped Spancrete Decks
1018: Concentrated Loads on Untopped Spancrete Decks
1019: Concentrated Loads on Topped Spancrete Decks
1020: Load Distribution

Do I need to fill the core ends?

The majority of core ends are not filled. In multi-story construction it may be required to grout the Spancrete cores to prevent crushing of the ends. However, in most buildings up to three or four floors, grouted cores are not required. Consult the Spancrete Engineering Department or the reference listed below for more information on when cores need to be grouted.

SMA Research Notes (stored as PDFs):

1008: Crushing Capacity of Plank Ends

How can I finish the underside of my Spancrete® hollow core plank?

The Spancrete® hollow core plank surfaces can be finished in a variety of ways to provide a durable, maintenance-free system. Click on the attached links to view more information concerning finished surface options.

Span Notes (stored as PDFs):

Attractive ceilings are easy with Spancrete®
Jointless textured ceiling applications on Spancrete® plank

How do I finish off the top of my Spancrete® hollow core plank?

With proper selection and installation, carpet can be installed directly over the hollowcore plank. Click on the attached links to view more information concerning finished surface options.

Span Notes (stored as PDFs):

Direct application of pad and carpet over Spancrete® saves time
Tile installation over Spancrete®
Topping off your Prestressed hollow core floor

What is the specification for structural topping?

Where structural topping is required, a minimum 2″ concrete topping must be bonded to the plank. Because the structural topping provides load capacity, it is imperative that the topping be of specified strength completely bonded to the plank uninterrupted by control joints or conduit. Topping must be designed for 28-day strength of 4,000 pounds per square inch (psi). When placing concrete topping, precautions must be taken to thoroughly clean and wet the plank’s top surface. Topping must be properly cured before continuing work on the surface.

It is further recommended that wire mesh be used in the concrete topping, with the mesh size to be determined by the architect/engineer. It should be noted that the 2″ minimum thickness topping is measured at mid-span (high point of camber) and therefore, additional concrete may be required at the perimeter to level the floor. All non-load bearing walls (CMU, Steel Stud or Wood Partitions) must be installed AFTER the concrete topping is placed and ON TOP OF the structural topping.

SMA Research Notes (stored as PDFs):

1019: Concentrated Loads on Topped Spancrete Decks
1020: Load Distribution

Span Notes (stored as PDFs):

Topping off your Prestressed hollow core floor

How much would Spancrete hollow core plank cost for my project?

Spancrete® hollow core plank is an engineered product and each project has unique requirements. Free estimates are provided upon request. Please contact your local Spancrete Sales Representative to discuss your unique application.

In what sizes is Spancrete® hollow core Plank offered?

Spancrete® hollow core plank is manufactured in standard 4’ wide dimensions. While it is most cost effective to utilize a 4’ increment, Spancrete hollow core plank can be split or cut, to achieve any design width or angle.

Span Notes (stored as PDFs):

How to Use Spancrete® for Inexpensive Space Under Your Garage
Building a New Home with Spancrete® is Easy

What is pre-stessed concrete?

Reinforced concrete members must carry their own weight as well as any applied loads. This means that conventional reinforced concrete planks must have short spans and thick section depths. Pre-stressing of precast concrete planks overcomes this limitation. In pre-stressing, high-tensile steel strands are stretched between abutments at each end of casting beds. Concrete is then placed to encase the strands. As the concrete cures, it bonds to the tensioned steel. When the concrete has reached a specified strength, the tensioned strands are released from the abutments. This exerts pressure upon the lower portion of the member, which stresses the concrete, and in effect relieves the precast plank from the need to support or carry its own weight. This pre-stress force gives Spancrete Hollowcore plank its slight upward arch or camber.

Span Notes (stored as PDFs):

Advantages of prestressed concrete