How to Apply Glass Block Mortar

Lead Image
  • 2-6 hours
  • Intermediate
  • 200-350
What You'll Need
Shovel, or garden hoe
Dry mortar mix
Rubber mallet
Clean, dry cloth

Glass block mortar, unlike mortar used to install concrete block, is a special type of mortar that requires knowledge or experience relating to its use, preparation, mixing, and application for installation. This process is no simple thing. If you are a DIY enthusiast with no experience in applying this mortar, you will at least need information such as that you will find below.

Step 1 – Preparing for Application

To prepare for application of the mortar, check to be sure your framing and chases are in place and are clean and that all surfaces of glass blocks to be used are clean enough to ensure a good bond with the mortar. Refer to manufacturer guides for anchor and expansion strip placement. Cure all panels and sills that are painted with asphalt emulsion for at least 2 hours before applying your mortar.

Step 2 - Mixing the Mortar

An important element in knowing how to apply this special mortar is in knowing something about mixing it. As in a more standard mix, you will need a mixing container, such as a wheelbarrow in which you'll be able to see and work water and dry mix into a smooth mix of a consistency that will allow you to trowel it onto the proper joint or surface. Use a shovel or garden hoe to thoroughly mix the dry mortar mix with water. When your mortar batch is mixed, let it sit undisturbed for a maximum of 10 minutes, then before applying it, mix it one more time. This mix will need to be usable for a number of hours. When it begins to set, discard it and mix a fresh batch. After your batch has initially set, avoid adding more water. This additional water can reduce bonding strength and performance quality. For specific mixing instructions for individual mortar products, refer to manufacturer instructions.

Step 3 – Applying the Mix

Apply your mix to form a base on which your glass blocks will be laid. Allow a ¼ inch to 3/8 inch joint width and avoid furrowing the mortar in the joints. Once the glass blocks are placed on the mortar base, tap the blocks with a rubber mallet to better ensure the bond between mortar and block. Press reinforcing material to cover the top half of the mortar, then smooth the mortar with your trowel. Avoid using mortar to cover any expansion joint strip. Finish one glass block course before beginning the next course. Be careful to avoid letting the mortar set. In temperatures lower than 40 degrees F, delay laying the glass block until you have warmer temperatures.

Step 4 – Curing the Mortar

Allow the mortar to cure for a full day (24 hours), depending on ambient temperature and humidity. Refer to manufacture recommended curing time.

Step 5 – Cleaning up the Mortar

From glass block surfaces, clean off all excess mortar, using a damp sponge. Polish the glass with a dry, clean cloth. To remove mortar from your hands and tools, wash with a solution of warm water and detergent while the mortar on them is still wet and pliable.