What Mortar Is Used to Install Glass Block Windows?

History

• Hand-blown glass blocks were popular during the 1800s in shipbuilding, where they provided a thick light portal, allowing filtered light into the ship's cabin. These windows were constantly in need of maintenance, since the mortar used was traditional stone mortar and it would crack and crumble under the movement of the ship's walls and exposure to moisture. In 1930, mass production of glass blocks began, and gradually the mortar used to lay the blocks improved.

Types

• If you purchase a glass block kit, it will come with powdered mortar, to which you will add water or another form of adhesive, such as glass block glue or silicone. When laying a free-block window, choose a mortar specifically made for glass block installation. Glass block mortar comes in a dry powdered state and you will mix it before use. While you can use masonry mortar, it contains larger abrasive particles and may scratch the glass. Glass block mortar comes in different colors to match your design needs. (See Resources)

Features

• When laying a free-block window, you may choose the standard mortar method of placing the individual blocks, leveling each row individually and using a trowel to apply the mortar before laying another block. In this method, expansion mesh or fibrous strips are installed on the window sash and between the rows. Alternative methods utilize plastic spacers that ensure a uniform design or you may choose a mortarless method that involves the use of plastic channels and a sealant, instead of mortar.

Considerations

• When using the standard mortar method or the plastic spacer method, make sure all your tools are within easy reach before beginning. Mix only small amounts of mortar at a time and discard unused mortar if it begins to harden before you can apply it. Keep a large bucket of clean water and a soft silicone sponge handy to remove any mortar residue from the blocks as you lay them. Don't allow mortar to dry on the surface of the glass block.

Potential

• With the correct installation, glass blocks are valuable, not only for windows, but also for glass shower enclosures and for aesthetic design in residential and commercial applications.