cmu guide

Size and Shape GuideConcrete Masonry UnitsFRANKLIN SERIES GRAY CONCRETE MASONRY • JEFFERSON SERIES ARCHITECTURAL COLOR MASONRY

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Concrete Block are commonly referred to as “CMUs” (Concrete Masonry Units), “Grey Block” or simply “Concrete Block.” The follow-ing are keyed names commonly used to further describe different types of concrete block.

A. Scored B. Stretcher End (Mortar Groove) C. Breaker D. Sash Groove E. Plain End F. Rectangular Core G. Pear Core H. Split Face* J. Bullnose (Double shown)

How to Calculate Fire Ratings for Concrete Block

International Standard Building CodeSouthern Building Code Congress International1996 Edition Chapter 31, Section 3103.1.1

3103.1. The fire resistance ratings of walls and partitions constructed of concrete masonry units shall be determined from Table 3103.1. The rating shall be based on the equivalent thickness of the masonry and type of aggregate used.

*Values between those shown in the table can be determined by direct interpolation.**Contact producer to verify aggregate and net volume. Certifications provided by each producer member as requested.

Thickness shown for concrete masonry is equivalent thickness defined as the average thickness of solid material in the wall and is represented by the the formula:

TE = Vn

L x H

Where:T

E = Equivalent thickness, in inches

Vn = Net volume (gross volume less volume

of voids), in cubic inches*L = Length of block, in inchesH = Height of block, in inches

Source: SBCCI

Table 3103.1Minimum Equivalent Thickness (Inches)

of Loadbearing or Nonloadbearing Concrete Masonry Walls*

Fire Resistance Rating (hours)

Type of Aggregate 1.0 2.0 3.0 4.0Expanded Shale, Clay** or Slate 2.6 3.6 4.4 5.1

*All split-face masonry units are available in grey and Block USA standard colors.

Concrete Block

Example: 8" cmu with a known 1100 psi gross area at 52% solids.

Compressive Strength (Gross Area) x 100 = Compressive Strength (%) Percent Solids (Net Area)

1100 psi x 100 = 2115 psi 52%

Example: 8" cmu (7.625 actual size) with a known 1100 psi gross area with an equivalent thickness of 4.0".

Compressive Strength Actual Compressive Strength (Gross Area) x Thickness = (Net Area) Equivalent Thickness 1100 psi x 7.625 = 2097 psi 4.0

Block manufacturers have gross-area psi data as well as solids and equivalent strength numbers. Most will have the net-area compressive strength psi with future test results.

Compressive Strength of Concrete Masonry (PSI*)

Gross Area to Net Area Conversion *Based on average of 3 units 4" height and above

Comment: ASTM C-90 is the standard of masonry production specifications in the United States. With the approval of ACI 530.1-88 specifications and the issue of ASTM C-90-91, there is one major specification change to note. In the past, block compressive strength (psi) was based on gross area requiring an average 1000 psi. The strength requirements have not changed but the measure-ments have. All new specifications now are based on net area of 1900 psi.

To assist you in calculating the net area, please follow the formula below.

Given the gross area compressive strength, you may determine the net area by knowing: (1) percent solids of unit, or (2) equivalent thickness of unit.

Dimensions

4-Inch Unit Configurations





2” Brick Units

2x4x8Concrete Brick

2x8x16Concrete Brick

2¼x8x16Concrete Brick

4” Units Grey Block Split-Face

4x8x16Solid Stretcher

4x4x16Solid StretcherHalf-High

4x4x16Hollow Stretcher

4x8x16Stretcher

4x8x16StretcherSingle Score

4x8x16Single Bullnose

4x8x16Double BullnoseOne End

4x8x16Double BullnoseOne Side

4x8x16Split Face Stretcher

4x4x16Split Face StretcherHalf-High

4x8x16Split Face StretcherSingle Flute

4x8x16Split Face StretcherTriple Flute

4x8x16Split Face StretcherEight Flute

4x8x16Split FaceReturn Corner

4x8x16Split Face ReturnCorner Single Flute

4x8x16Split Face ReturnCorner Triple Flute

4x8x16Split Face ReturnCorner Eight Flute

2-5/8-8x16Solid

* Available in Single Score * Single Score Available

6x8x16StretcherSingle Score

6x8x16Corner

6x8x16Split Face

6x8x14Split Face Corner

6x8x16Corner Sash

6x8x8Half Stretcher




6x8x16Solid Bottom Lintel

6x8x8Sill Block Smooth

6x8x8Split FaceSill Block

* Restricted Open/Solid Available


8x8x16Stretcher

8x8x16Corner Sash

8x8x16Corner

8x8x16CornerSingle Score

8x8x8Half Stretcher


8x8x8Half Double Bullnose





* Available in some locations * Available in some locations

10x8x8Half Corner

10x8x16Stretcher

10x8x16Corner Sash

10x8x8Half Sash

8x4x16Half High

8x8x16 RestrictedOpen Bottom Lintel

* Solid Bottom Lintel Available


8x8x16Conduit/ Deep Lintel

8x8x16Cut Header

8x8x8Sill BlockSmooth

8x8x8Split FaceSill Block


* Available in Some Locations


8x8x16Split Face Stretcher Single Flute

8x8x16Split Face StretcherThree Flutes

8x8x16Split Face StretcherEight Flutes

8x8x16Split Face Corner

8x8x16Split Face CornerSingle Flute

8x8x16Split Face CornerThree Flutes

8x8x16Split Face CornerEight Flutes

10x8x16Restricted Open Bottom Lintel


* Single Score Available



10x8x16Split Face Lintel

8x8x16 Split Face LintelOpen/Solid Bottom


* Open/Solid Bottom Lintel Available


12x8x12Pilaster Block

12x8x16Stretcher

12x8x16Corner Sash

12x8x8Half Sash


12x8x16Stretcher Single Score

* Available in Some Locations




12x8x16Restricted Open Bottom Lintel

12x8x16Split Face Stretcher Three Flutes

12x8x16Split Face Stretcher Eight Flutes

16x8x16Pilaster

16x8x16Flue Block

16x4x16Pier Pad

16” Units Grey Block

12x8x16Corner

12x8x16Conduit/Deep Lintel

12x8x16Split FaceStretcher

12x8x16Split Face Stretcher Single Flute



12x4x16Half-High

12x8x16Split Face Lintel

* Open/Solid Bottom Lintel Available

Midsouth Division1-800-338-7902

Gulf Coast Division1-800-888-9262

Georgia Division1-866-322-5625

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