Glass Block Mortar


TEC® Skill Set® Glass Block Mortar is a non-modified high-quality blend of portland cement, graded silica, additives and a unique, proprietary ingredient designed to prevent mortar from cracking.  It is intended for use with all glass block. For applications subjected to freeze/thaw conditions or whenever the enhanced performance of a latex-modified mortar is desired, mix Glass Block Mortar with a TEC Skill Set Mortar Additive.


  • Bright white
  • May contribute to LEED® certification project points
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Terms and conditions

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TEC® Skill Set® Glass Block Mortar Product Info


TEC Skill Set Glass Block Mortar is a high quality blend of portland cement, graded silica, additives and a unique, proprietary ingredient designed to prevent mortar cracking. It is intended for use with all glass block. For applications subjected to freeze/thaw conditions or whenever the enhanced performance of a latex modified mortar is desired, mix Glass Block Mortar with a TEC Skill Set Mortar Additive.


Key Benefits and Features

  • Use interior and exterior
  • Bright white


50 lbs. (22.68 kg) plastic bag White    Product #33-0027-3121


Coverage may vary according to substrate conditions and thickness of application. Figures listed below are presented only as guidelines. Approximate coverage per 50 lbs. (22.68 kg) Glass Block Mortar:


Block Size Approximate Coverage Number of Blocks
6" x 6"
(150 x 150 mm)
8-12 sq. ft.
(0.7-1.1 m2)
36 blocks
8" x 8"
(200 x 200 mm)
11-15 sq. ft.
(1.0-1.4 m2)
28 blocks
12" x 12"
(300 x 300 mm)
16-20 sq. ft.
(1.5-1.9 m2)
18 blocks



  • Glass Block Anchors - to secure installation to surrounding frame. When installing 6" (150 mm) block, set anchors 18" (450 mm) apart; for 8" (200 mm) block, set anchors every 16" (400 mm); and for 12" (300 mm) block, set anchors 24" (600 mm) apart. Attach short arm of anchor to jambs and heads, with long arm extending a minimum of 9" (225 mm) into the joint.
  • Glass Block Reinforcing - to strengthen glass block installation. Place in the same joint as anchors, along the entire length of joint.
  • Expansion Strips - made of dense, fibrous glass or white polyethylene, inserted at heads and jambs to allow panel expansion and contraction.
  • Glass Block Spacers - plastic or galvanized steel spacers speed installation and promote uniform joint spacing. Plastic spacers are used for vertical and horizontal joint alignment, galvanized steel spacers are used for horizontal joints only.
  • Asphalt Emulsion Adhesive - used for bonding expansion strips to head and jambs to isolate glass block from framing.


Store in a cool, dry area away from direct sunlight. Do not store open containers.


Shelf Life
Maximum of 1 year from date of manufacture in unopened package.


TEC Skill Set Glass Block Mortar should not be applied when the temperature of the area or materials is below 50°F (10°C) or above 90°F (32°C). Do not use over hardwood flooring, presswood, particleboard, chipboard, oriented strand board (OSB), Masonite, lauan plywood, pressure-treated or oil-treated plywood, or similar dimensionally unstable materials. Do not use to install glass tiles. Instead, use TEC Skill Set Glass Tile Mortar.


FIRST AID MEASURES: In all cases, seek medical attention if symptoms develop or persist. EYES: Flush with water for 20 minutes. SKIN: Wash with soap and water. IF VAPORS INHALED: Remove to fresh air. IF SWALLOWED: Do not induce vomiting. WARNING! This product contains chemicals known to the State of California to cause cancer, birth defects or reproductive harm. KEEP OUT OF REACH OF CHILDREN. For Medical Emergency Information, call 1-888-853-1758.


This Product Data Sheet has been prepared in good faith on the basis of information available at the time of publication. It is intended to provide users with information about and guidelines for the proper use and application of the covered TEC Skill Set brand product(s) under normal environmental and working conditions. Because each project is different, H.B. Fuller Construction Products Inc. cannot be responsible for the consequences of variations in such conditions, or for unforeseen conditions.

Physical Properties

TEC® Skill Set® Glass Block Mortar
Physical State Dry powder
Color White
Pot Life 1 hour
Initial Cure [at 72°F (22°C)] 16 to 24 hours
Final Cure 21 days

Surface Preparation
All framing, pocket recesses or chases must be complete, accurately placed and measured to correct dimension prior to receiving glass block. The opening should equal the nominal length and height [including the 1/4" (6 mm) mortar joints] of the total number of blocks that will fit, plus 1/2" (13 mm). Clean glass blocks, removing any foreign substances to promote a proper mortar bond. Pre-plan the installation to determine where anchors and reinforcing will be placed. Anchors should be cut to 12" (300 mm) lengths, bent to produce a short arm [3" (75 mm)] and a long arm [9" (225 mm)]. Attach short arm of anchor to jambs and head, with long arm extending into joint. Follow anchor spacing requirements as outlined in the accessories section above. Reinforcing should extend the entire length of the glass block row. When more than one reinforcing bar is required per joint, overlap the reinforcing at least 6" (150 mm).


Mixing-With Water
For best results, maintain all tiling materials, substrates, room and adhesives at 50°-70°F (10-21°C) for 24 hours before and 48 hours after installation. Avoid breathing dust and contact with eyes and skin. Avoid using high speed mixing, not to exceed 300 rpm, to prevent entraining air. Add powder to liquid for ease of mixing. Avoid adding excess liquid as this may cause glass block to sink into mortar during installation.

In a clean mixing container, slowly add product to 1.25 gallons (4.73 L) clean, cool water. Mix material for 2-5 minutes to a consistency that is drier than mortar used for ordinary masonry or tile work, then allow the mortar to stand for 10 minutes. Remix for 1-2 minutes and apply. Maximum working time of the mortar is approximately 1 hour at 70°F (21°C). Do not use antifreeze compounds or accelerators. Do not add additional water.


Mixing-With Latex Additive
For improved performance in any application, H.B. Fuller Construction Products Inc. recommends the use of TEC® Skill Set™ Mortar Additive in place of water. For installations subjected to freeze/thaw conditions the use of TEC Skill Set Mortar Additive is required.

When using a mortar additive, always follow label directions for detailed mixing and substrate recommendations.


Using a trowel, place a full mortar bed, at least 3/8"- 1/2" (10-13 mm) thick, on the base or sill. Do not furrow. Install first block snugly against expansion strip at the jamb location with spacers in place. Use a rubber mallet to tap blocks into place. Do not use steel tools on glass blocks for adjustments as surface may be scratched. Do not place mortar between expansion strips and glass block. For remaining blocks, apply approximately 3/8"-1/2" (10-13 mm) mortar to the vertical edge that will be in contact with the preceding block. Lay each block in place on the curb or sill with appropriate spacers. Set remaining courses as outlined above. Once the mortar has set (in approximately 2 hours), smooth all joints with a striking tool. Striking should leave all joints completely filled with mortar.

Anchors and glass block reinforcing are placed in the same joint as detailed above. Anchors should be securely fastened to the framing, with the expansion strip trimmed to cover the anchor short arm. When vertical expansion joints are present, reinforcing should neither continue through nor bridge them.


Clean tools and hands immediately, while mortar is still fresh, with warm soapy water. Remove surplus mortar from the faces of the glass block, at the time joints are struck or tooled, using a damp sponge or cheese cloth before the material hardens. Perform final cleaning about 15 minutes later by polishing off remaining haze with a clean, soft, dry cloth.


Protect finished installation from moisture or rain for 24 hours after installation.

Technical assistance

Information is available by calling the Technical Service Helpline.

Toll Free: 800-832-9023

TEC® Skill Set® Glass Block Mortar Safety Data Sheet


Download TEC® Skill Set® Glass Block Mortar Safety Data Sheet