Covering up an old glass block window is a common renovation task, whether you’re tired of the dated look, need more privacy, or want to improve energy efficiency. This guide walks you through the process of covering glass blocks from the inside, using a simple framed panel method. It’s a practical, reversible solution that doesn’t require removing the existing blocks.
What You’ll Need
- Measuring tape
- Plywood or MDF board (cut to fit your window opening)
- Insulation board (optional, for added thermal performance)
- Wood screws or masonry anchors (depending on your wall type)
- Screwdriver or drill
- Level
- Paint or primer (if you want to finish the panel)
- Caulk or sealant
- Safety glasses and dust mask
Step-by-Step
- Measure the opening. Use a tape measure to get the exact width and height of the glass block window, measuring at several points because openings are often not perfectly square. Note the smallest measurements – your cover panel should fit within those.
- Cut the panel. If you’re using plywood or MDF, cut it to the measured size. For a cleaner look, you can cut a piece of insulation board to fit snugly inside the window frame and then attach the plywood over it. Always wear a dust mask when cutting.
- Dry-fit the panel. Place the panel against the glass blocks to ensure it fits properly. It should sit flush against the frame or the blocks, depending on your setup. If it’s too tight, trim it slightly; if it’s too loose, you’ll need to shim it later.
- Attach the panel. Hold the panel in place and use a level to make sure it’s straight. Then secure it with screws. If you’re screwing into wood framing, use wood screws. For masonry or metal frames, use appropriate anchors. Drive screws through the panel into the surrounding frame, spacing them a few inches apart along the edges.
- Seal the edges. Apply a bead of caulk or sealant around the perimeter of the panel where it meets the wall or frame. This will prevent drafts, moisture, and light from seeping through. Smooth the caulk with a wet finger or a caulk tool.
- Finish the surface (optional). If you want the panel to blend with your wall, paint it with a primer and then a finish coat. You can also wallpaper over it or cover it with fabric for a decorative touch.
Common Mistakes
- Skipping the level. A panel that isn’t level will look crooked and may not seal properly. Always check with a level before securing.
- Using the wrong fasteners. Screwing into drywall without anchors will pull out easily. For heavy panels, use proper wall anchors or screw into studs or the window frame.
- Not sealing the edges. Leaving gaps allows air and moisture to pass, which can cause condensation and mold. Caulk is essential.
- Cutting the panel too large. If the panel is slightly too big, it will bow or not fit at all. Measure twice, cut once – and always leave a small gap for expansion.
Tips
- For a removable cover, attach hinges to one side and a latch on the other, allowing access to the window if needed.
- If the glass blocks are in a bathroom or kitchen, use moisture-resistant materials like PVC trim or marine-grade plywood.
- Consider adding a layer of rigid foam insulation between the panel and the glass to improve thermal performance.
- If you’re covering a large window, use two smaller panels instead of one heavy sheet – they’re easier to handle and install.
- Paint the panel the same color as the wall to make it disappear, or use a contrasting color to create a feature.
Troubleshooting
- Panel won’t stay flush. If the panel bows or doesn’t sit flat, check for debris or unevenness in the frame. Add shims behind the panel to create a flat surface, then screw through the shims.
- Condensation forms on the inside. This indicates that moist air is reaching the cold glass. Make sure your panel is sealed tightly, and consider adding a vapor barrier (like plastic sheeting) between the insulation and the panel.
- Screws won’t hold. If the screws strip or pull out, use larger anchors or switch to a different fastening method, such as construction adhesive. For masonry, use tapcon screws.
- The panel looks crooked. Loosen the screws slightly, adjust the panel with a level, and retighten. If the opening itself is out of square, you may need to trim the panel to match.
- Caulk keeps cracking. Use a flexible, paintable caulk (like acrylic latex) and ensure the surface is clean and dry before applying. For large gaps, use backer rod first.
Frequently Asked Questions
Can I cover glass blocks from the outside?
Yes, but it’s not recommended because exterior materials must withstand weather and UV exposure. An interior cover is simpler and more durable.
Will covering the window block all light?
Yes, a solid panel will block all light. If you want some light, consider using a translucent material like frosted acrylic or installing a small window in the panel.
How do I remove the cover later?
If you used screws, simply unscrew them and patch the holes. If you used adhesive, you may need to pry the panel off and clean the residue. A hinged panel is the easiest to remove.
Can I cover the glass blocks with drywall?
Yes, you can install drywall over the blocks, but you’ll need to build a frame to attach it to. This is a more permanent solution and requires more work.
Do I need to insulate the cover?
Not necessarily, but adding insulation improves energy efficiency and reduces condensation. It’s especially helpful in colder climates.
What if the glass blocks are in a load-bearing wall?
Covering them from the inside does not affect the structural integrity, as you’re not removing the blocks. However, if you plan to remove them, consult a structural engineer first.