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About Mortar for Glass Block Windows

Naima Manal
Table of Contents

An ideal security barrier, glass blocks suitably provide the ambiance of natural outdoor lighting filtered through textured glass. They provide light to otherwise dark spaces, and they are permanent alternatives to the standard window.

About Mortar for Glass Block Windows

Built right into an existing wall, they give an elegant appearance to any residential or commercial space. To attain the look and feel of a glass block feature, glass block mortar must be used to securely hold the glass blocks in place.


Glass Block Mortar

Glass block mortar is the most important component of building a glass block feature, after the glass blocks. It is composed of a cement base for its adhesive qualities, as well as line and sand for structure. Glass block mortar also has waterproofing ingredients, since glass blocks can be used for outdoor and indoor building projects. Glass block mortar typically only requires that you add water and mix to the consistency specified on the package.


Glass block mortar uses Portland cement, which does not have pebbles in it. The mortar has a very high adhesive and bonding quality, and when it dries it is water- and crack-resistant. Using a different type of mortar will not give the same effectiveness for a glass block wall construction, and you may be replacing the mortar sooner than expected, due to weather damage. If damage does occur to the mortar over time, glass block mortar can also be used to repair any water damage, weathering or cracks. Glass block mortars come in different grades; some are suitable for outdoor and indoor use, others only for indoor use. You need several supplies when using glass block mortar. If designing an opening through an outdoor wall, have on hand foam insulation spray or strips. In addition to the glass blocks, you will also need anchors, spacers, reinforcement bars and plastic connectors. These supplies will help anchor the glass to the existing structural wall, and the other supplies help to keep the blocks spaced evenly. Remember to use a level at every step, especially the first row, as this will be the leveling of the entire wall.


Glass block mortar needs the appropriate amount of time to dry and cure. It is ideal to construct a glass block wall in warm temperatures, and it should not be disturbed for three days. You have to clean away excess mortar while it is still damp to prevent the difficult job of scrubbing away dry clumps of mortar later on. Glass block mortar cleans up with soap and water very easily, so act fast for a simple cleanup. When purchasing glass blocks, take into consideration the amount of mortar you will need, so that you do not have to make an extra trip or two to the home improvement store. Depending on the size of the glass block, a 50-pound bag will set 40 six-inch square blocks, 32 eight-inch square blocks, 24 10-inch square blocks or 18 12-inch square blocks.


Glass Block Wall

Be careful when using glass block mortar. The powder form is hazardous to your lungs, so wear a face mask. In wet and powder form, the glass block mortar is a skin and eye irritant, so avoid direct contact. Wear protective clothing and eye protection as well, and seek medical attention immediately if any mortar gets into your eyes. Be careful to always read the warning label and handling instructions for glass block mortars.


An alternative to using glass block mortar is to use a glass block grid system. Made of an aluminum grid, the system allows you to snap the glass blocks in place. It is generally less expensive than hiring professionals to install the glass blocks with the mortar, and it may be a moderately easy project for the avid do-it-yourself-er.