Install Glass Block
Given their superior insulating qualities, glass blocks can be used to replace exterior windows or even to form "walls" with minimal heat loss. With some planning and patience, a do-it-yourselfer with an intermediate skill level and the right tools should be able to tackle this project with ease. Lowe's is happy to provide this information as a service to you.
Where to Use Glass Block
Glass block walls can be placed in virtually any location. However, they cannot be used as load-bearing or structural members of any building. You can use glass blocks to:
- Form large exterior windows that offer privacy while allowing natural light to enter the home.
- Make a shower wall that resists staining and cleans easily.
- Create an accent piece in walls, islands, windows and more.
Also available are specially-sized blocks that form tight curves, round corners and trim pieces. If you're planning to install a curved glass block fixture, consult a building contractor, glass block manufacturer or architect for advice on construction techniques.
Prepare the Installation Area
Follow the basic steps to make certain the area is fully prepared for your new glass block:
|Good idea: Plan ahead. Before beginning the project, make sure you have all the materials you'll need. |
Verify that the removal or modification of any existing structure will not affect the structural integrity of your home. If necessary, contact an architect or general contractor.
- Plan to reinforce the supporting floor as necessary. Large glass block walls require reinforcement of the underlying floor joists, so be prepared to add this procedure to your project. For more information about reinforcing floor joists, consult a building contractor familiar with building codes and practices in your area.
- Carefully measure the installation area. Blocks vary in size from 4" x 8" to 12" x 12" or more. Multiply the number of glass blocks you desire to use horizontally by the nominal width of the blocks themselves. Nominal width adds the actual width of the block and the average width of one mortar joint. Add approximately 1/4" to 1/2" (depending on manufacturer recommendations) to this number to allow for spacing at the end of the run. This process determines the width of the opening required. Repeat the process with a column of the vertical blocks to determine the height required. Remember to add 1/4" to 1/2" to this number.
(number of blocks X nominal width of blocks) + 1/4" = width of rough opening.
(5 blocks X 8" nominal width) + 1/4" = 40 1/4"
- Once you've purchased the blocks for the project, test fit them by stacking the blocks in the desired configuration without any mortar or adhesive.
- For floor-length projects, install a curb below the bottom row of glass blocks. The curb allows for the installation of moulding beneath the wall and protects the blocks from contact with vacuum cleaners or mop heads. You can make one from two 2" x 4" pieces of wood nailed together and cut to the horizontal length of the opening.
Install Glass Blocks with Mortar
- Adjust the spacers for the first row of blocks. Using tin snips, cut two "L"-shaped spacers for each corner and a series of "T"-shaped spacers for each joint along the bottom level of blocks. Cut spacers ahead of time to avoid pauses when mortaring your glass blocks.
- Prepare the panel anchors. Each panel anchor should be 12" in length with a right angle bend at the 3" mark. A panel anchor is attached to the jamb (side of the panel) and head (top of the panel) using drywall screws on top of every second row or after every second column of blocks. If you're attaching anchors to tile or concrete, use plastic screw anchors. Panel anchors are not used at the first or top two layers of blocks, or on the curb/sill (bottom of the panel).
- Measure and cut the expansion strip based on the locations of panel anchors. The strips are inserted between the glass blocks at the jambs and head between the panel anchors. The flexible expansion stripping allows the blocks to expand without cracking the mortar and also allows a weathertight seal.
|The mortar should have the consistency of bread dough and stick to the vertical side of a glass block.|
Cut the panel reinforcing wire to a length matching the width of the glass block installation. If more than one strip is needed, overlap the pieces by 6". Apply panel reinforcing wire to each horizontal row that has panel anchors.
- Mix the glass block mortar. The mortar should have the consistency of bread dough and stick to the vertical side of a glass block. Avoid direct skin or eye contact with the mortar, as it can cause skin irritation.
- Lay a 1/2" deep layer of mortar on the surface where you will place the first layer of blocks. Place an "L"-shaped spacer at the corner of the opening and a "T" spacer one block-length away on the freshly-mortared base surface. Don't let the mortar cover the spacers. Place an un-mortared glass block between the spacers. Sandwich a piece of expansion strip between the jamb and block and push the block into place.
- Place another "T" spacer on the mortar one block length away from the previous "T" spacer. Apply a 1/2" coating of mortar to the vertical edge of the next glass block and place it snugly against the previous block. Repeat this procedure until you complete the row.
|Check the level and plumb of the first row. |
Install the final block in the row in the same manner as the block installed in step 7. Press any excess mortar back into the joints using the foam brush. Check the level and plumb of the first row. Level the row as necessary by tapping it with the rubber mallet. Be careful not to hammer any block too far down, as you may have to pull the block out and start the row over.
- Apply a 1/2" coating of mortar to the top of the first layer of blocks. Insert "T" spacers at each jamb and uncut spacers at each joint between the jambs. Be careful not to smear mortar on the top of any spacer, as this will cause the blocks to sit unevenly.
- Place the first block of the new row at one of the jambs. Be sure to sandwich an expansion strip between the jamb and the glass block. Do not put mortar on this block. Install the next block by applying a 1/2" layer of mortar to the vertical edge which will contact the previous block installed at the jamb. Continue this process until you finish the row. Check the level and plumb of this row and correct if necessary.
|The top of every second row of blocks requires panel reinforcing wire and panel anchors at both jambs.|
The top of every second row of block requires panel reinforcing wire and panel anchors at both jambs. Lay a 1/2" layer of mortar on top of the second row of glass block. Attach the 3" end of the panel anchor to the jamb with two 1" zinc-plated pan head screws. Press the long end of the panel anchor in the mortar on top of the second row. Embed the ladder-shaped panel reinforcing wire in the mortar on top of the second row. If your wall needs more than one strip of panel wire to cover its full length, overlap the strips by 6".
- Lay the next row of blocks in the same manner as the first two. Continue until you reach the next-to-last row, being sure to place panel anchors and reinforcing wire on top of every second row. The top two rows do not require reinforcing wire or horizontal panel anchors. Check the level and plumb of your panel as you finish each row.
- Finish the panel with the final row. Apply a 1/2" coat of mortar to the next-to-last row. When inserting spacers, remove the spacer tabs on one side of the block panel so you can slide the blocks in between the head and the next to last row.
|Attach a panel anchor to the head of the opening with the long end extending down into the vertical mortar joint.|
Insert an unmortared block at one of the jambs, sandwiching the expansion strip between it and the head of the opening. Mortar the vertical side of the next block and insert it beside the first block in the row. Attach a panel anchor to the head of the opening with the long end extending down into the vertical mortar joint. Continue the final row while placing vertical panel anchors at every second block in the row. The final block does not require a vertical panel anchor.
- Allow the mortar to set according to the manufacturer's instructions (usually one hour) and twist off the spacer tabs on both sides of the panel. Fill any holes from the spacers with mortar using the foam brush.
- Using a wet sponge, clean any mortar from the glass block before it fully dries. Rinse the sponge frequently to avoid smearing the mortar.
- Strike the joints by sliding the striking tool along the mortared joints to give it a smooth appearance. Follow the instructions provided by the tool's manufacturer. First strike the horizontal joints, then the vertical joints, or vice-versa to make sure the striking pattern is consistent. Fill any holes that may appear in the mortar and re-strike if necessary.
- Allow the mortar to cure based on the manufacturer's instructions. Caulk around the edges of the panel to create a weathertight seal.
- Clean the block with a nonabrasive cleaner and plastic scouring pad.
- Apply a coating of clear acrylic or silicone sealer over the mortar joints to help prevent mildew.
Install Glass Block with Silicone Adhesive
- Drill/driver and bits
- Measuring tape
- Tin snips
- Metal file
- Caulking gun
- Joint striking tool
- Glass block
- 1" zinc-plated drywall screws
- Silicone sealant/adhesive
Mortar-less installations are much easier to complete and require less time. Kits vary by manufacturer, but most include plastic or metal channels that surround the panel and interlocking spacers that fit between each block. These types of walls require support from all four sides, so they can only be used as part of an existing wall. Glass block panels should be assembled per the manufacturer's instructions and mounted permanently using a special silicone sealer/adhesive.
Generally, installations follow these basic steps:
- Prepare the opening according to the manufacturers instructions. Multiply the nominal width of each block by the number of blocks in the row or column to figure the size requirements of the opening. Size the opening as required.
- Test fit the panel area with the glass blocks.
- Attach mounting channels to the jambs, curb and head of the mounting area using the screws provided. You may want to paint the screw heads to keep them from showing through the adjacent blocks.
- Assemble the glass block wall using the provided interlocking plastic spacers.
- Caulk the edges and joints of the panel using the sealant/adhesive recommended by the manufacturer. Strike the joints as you would with a typical mortar installation.
|Good idea: If weight is an issue or if you cannot reinforce the mounting area, acrylic blocks are very similar to glass blocks in appearance, but weigh significantly less.|
Each manufacturer has special requirements and recommendations for silicone adhesive installation. If you choose to assemble your panel with silicone adhesive, familiarize yourself with the manufacturer's requirements before beginning the project.Was this information helpful? Please let us know your do-it-yourself experiences. We'd love to hear from you!