Gemstone ground face masonry is a unit that has surged in popularity over the last few years. The natural aggregate of the block is brought forth by grinding the face of the unit to a smooth “polished” looking finish; a sealer is then applied to give the block an added sheen and to assist in the resistance of natural elements that may mar the surface. Gemstone units are used both inside and out because of their smooth, easily cleaned faces.

There are many standard sizes and shapes to select from and a variety of colors that show the natural beauty of the aggregate. They require no additional refinishing and will retain their color and appearance for the life of the product. Gemstone block, whether used as a veneer or in standard wall thickness, conforms to ASTM C90 standard specification for loadbearing concrete masonry units.

It is  fire resistant and acoustically and thermally massive, providing an alternative to many other more expensive building products. Many interior walls are constructed using only Gemstone block while exterior walls combine the uses of many architectural types for more dramatic results. As architectural lines and styles change, the Gemstone unit will continue to enhance design and offer a clean, striking appearance.

Shape Guide

Name : Stretcher CMU
York Building Products Stretcher CMU Shape for Gemstone® Masonry Products
Nom. Size  Code
 4x8x16  4F
 6x8x16  6F
 8x8x16  8F
 10x8x16  10F
 12x8x16  12F

Name : Universal Corner
York Building Products Universal Corner Shape for Gemstone® Masonry Products
Nom. Size Code
8x8x16 UC

Description : Use this unit for any depth corners.
Name : Open-Bottom Bond Beam
York Building Products Open-Bottom Bond Beam Shape for Gemstone® Masonry Products
Nom. Size Code
6x8x16 6OB
8x8x16 8OB
10x8x16 10OB
12x8x16 12OB

Name : Half-High
York Building Products Half-High Shape for Gemstone® Masonry Products
Nom. Size Code
4x4x16 44f
6x4x16 64F
8x4x16 84F
10x4x16 104F
12x4x16 124F

Name : Half Block
York Building Products Half Block Shape for Gemstone® Masonry Products
Nom. Size Code
4x8x8 48F
6x8x8 68F
8x8x8 88F
10x8x8 108F
12x8x8 128F

Name : Closed-Bottom Bond Beam
York Building Products Closed-Bottom Bond Beam Shape for Gemstone® Masonry Products
Nom. Size Code
6x8x16 6FU
8x8x16 8FU
10x8x16 10FU
12x8x16 12FU

Edge Codes

York Building Products B10C10 Edge Code for Gemstone® Masonry Products
York Building Products B11C11 Edge Code for Gemstone® Masonry Products
York Building Products B1C1 Edge Code for Gemstone® Masonry Products
York Building Products B2C2 Edge Code for Gemstone® Masonry Products
York Building Products B3C3 Edge Code for Gemstone® Masonry Products
York Building Products B4C4 Edge Code for Gemstone® Masonry Products
York Building Products B5C5 Edge Code for Gemstone® Masonry Products
York Building Products B6C6 Edge Code for Gemstone® Masonry Products
York Building Products B7C7 Edge Code for Gemstone® Masonry Products
York Building Products B8C8 Edge Code for Gemstone® Masonry Products
York Building Products B9C9 Edge Code for Gemstone® Masonry Products

York Building Products Division 4 Binder- Digital Version

Technical Data & Installation Guide



Part 1—General


Submit color samples for selection from manufacturer’s series. Submit product literature, certifications, test reports and full size sample(s) of each color specified.

Quality Assurance

Certifications (Split Face, Chiseled Face, Rustic Face, Temple Stone, Tudor Stone, Smooth Face):

Concrete blocks for finishing shall conform to ASTM C90. The provisions of ASTM C90 apply with regard to appearance.

Certifications (Gemstone®, Gemstone Plus®):

Concrete blocks for grinding shall conform to ASTM C90. The ground surfaces are produced with sealer. All units contain an integral water repellent and CMU admixture at the time of manufacture.

Fire Resistance: Define hourly ratings required as 1, 2, 3 or 4 hours.

Field Constructed Mock-Ups:

Construct a sample panel, no less than 4' x 4', of units of each color & size to be used in the project.

Delivery, Storage And Handling

Masonry units shall be delivered to the jobsite on covered banded pallets. Store pallets in single stacks on level ground and cover with waterproof covering (e.g., tarpaulins) to protect the blocks from inclement weather. Handle blocks carefully to avoid breakage and damage to the finished surfaces.

Project/Site Conditions

Protection of Work:

Cover tops of walls each day after installation to keep open walls protected and dry. After units are installed they should be protected from staining or other damage by covering the bottom of the walls with plastic.




Part 2—Products

Product Name

Architectural Concrete Masonry Units – All Finishes


York Building Products
950 Smile Way, York, PA 17404

Related Materials

Colored matching or contrasting mortar is available from Workrite. Refer to Division 4 Masonry Section for mortar type and specifications. In all exterior mortar, use water-repellent mortar additive available from York Building Products and follow manufacturer's instructions.

Sizes And Shapes

Nominal 2", 4", 6", 8", 10" and 12" standard block thicknesses are available, as well as all standard block shapes. High-strength units for special structural requirements are also available.

Masonry Cleaners

Use masonry cleaners such as Prosoco Masonry Cleaner for all finishes. Follow manufacturer’s instructions for proper mixing and application. Do not apply cleaner with pressure spray above 50 psi.

CAUTION! Never use Muriatic Acid solution on units.

Part 3—Execution


Lay blocks from more than one pallet at a time during installation. Lay units using the best concrete masonry practices. Lay blocks with the faces level, plumb and true to the line strung horizontally at the face. Complete masonry construction using procedures and workmanship consistent with the best masonry practices.


Make all unit cuts, including those for bonding, holes, boxes, etc., with motor-driven masonry saws, using either an abrasive or diamond blade. Cut neatly and locate for best appearance.

Mortar Bedding and Jointing:

• Lay units with full mortar coverage on head and bed joints, taking care not to block cores to be grouted or filled with masonry insulation.

• Tool all mortar joints -when thumbprint hard - into a concave configuration.

• Care should be taken to remove mortar from the face of masonry units before it sets.

• Tuckpoint the joints of scored units for proper appearance. All exterior scored units must be tuckpointed to prevent water penetration.


Installation Recommendations

• Cavity wall construction is recommended for exterior walls with proper flashing, venting and weep holes.

• A complementary or matching mortar color is recommended when using colored architectural units.

Flashing Of Masonry Work

Install flashing at locations shown in the plans and in strict accordance with the details and the best masonry flashing practices.

Weeps And Vents

Install weep holes and vents at proper intervals (32" O.C. above bed joints, typical) at courses above grade, above flashing and at any water stops over windows, doors and beams.


The unit faces shall be free from chips, cracks or any other imperfection that would detract from the overall appearance of the finished wall when viewed from a distance of twenty (20) feet at right angles to the wall with normal lighting.


Keep walls clean daily during installation using brushes. Do not allow excess mortar lumps or smears to harden on the finished surfaces. Harsh cleaning methods after walls have been erected may mar the surface of the blocks.

Final Cleandown

Always test a small, inconspicuous area before using cleaners. Do not use acids or abrasives on finished surfaces. Clean the completed walls with masonry cleaner APPROPRIATE FOR THE FINISH, strictly following the manufacturer's instructions including thorough rinsing.

Do not use acid or abrasives on the finished surfaces. Failure to strictly follow manufacturer's instructions can result in permanent damage to the finished faces.


Properly installed and cleaned architectural masonry units need virtually no maintenance other than routine cleaning with standard commercial grade cleaning agents.