By Glass Block HQ | Updated 2026
The single most important factor in whether your glass block windows hold up for years or decades isn’t the blocks themselves — it’s how the finished panel is installed into your wall. Two methods exist in Ohio, and the difference in long-term performance is dramatic.
Modern glass block windows start as prefabricated panels. Individual glass blocks are assembled into a panel using silicone adhesive between each block. This is standard across the industry — virtually every glass block installer in Ohio uses silicone-bonded prefab panels. The silicone creates clean joints and holds the blocks together as a unit.
The panel assembly method is not where installations succeed or fail. What matters is how that completed panel gets attached to your wall.
At Glass Block HQ, we take the prefabricated panel and mortar it into your wall opening. High-strength mortar bonds the panel’s perimeter to the surrounding masonry structure — foundation block, poured concrete, or brick. This creates a rigid, permanent, structurally integrated seal between the glass block panel and your home.
The mortar perimeter is what makes the installation weathertight, secure, and durable for decades. It’s masonry bonded to masonry — the same principle that holds your foundation together.
This step requires real masonry skill. The opening must be properly prepared, the mortar mix must be correct for the substrate, and the panel must be set level and plumb with consistent perimeter coverage. Proper cure time matters. It’s not complicated, but it demands experience and care. For the full step-by-step process, see our installation guide.
Some installers skip the mortar entirely. They take the same prefabricated silicone-bonded panel and attach it to the wall opening using more silicone or caulk around the perimeter. The entire assembly — block-to-block joints AND the panel-to-wall connection — is held together with nothing but adhesive.
This is faster. It requires less skill. It’s cheaper. And it’s the reason we get so many replacement calls.
Ohio’s climate is particularly hard on silicone perimeter installations. The combination of freeze-thaw cycles, temperature swings from subzero winters to humid summers, and ground moisture puts extreme stress on adhesive-only connections.
Silicone contracts and expands with temperature changes. Over years of Ohio weather, this repeated movement creates gaps between the panel and the wall. Water gets into those gaps, freezes, expands, and makes them larger. Within 5 to 10 years, you can have active leaks, drafts, and a panel that’s pulling away from the wall.
Silicone degrades from UV and moisture exposure. The clean perimeter seal from installation day yellows, becomes brittle, and starts cracking and pulling away from surfaces.
Silicone provides no structural resistance. A panel held in by caulk can potentially be pushed inward by force — something that is extremely difficult when the perimeter is mortared into masonry.
| Factor | Mortar Perimeter (Our Method) | Silicone Perimeter |
|---|---|---|
| Panel assembly | Silicone-bonded prefab (industry standard) | Silicone-bonded prefab (same) |
| Panel-to-wall connection | Mortar — permanent masonry bond | Silicone/caulk — adhesive only |
| Water resistance | Durable long-term perimeter seal | Can degrade, crack, peel over time |
| Structural integrity | Panel is locked into the masonry | Panel can shift, pull away from wall |
| Security | Very difficult to breach | Panel can potentially be pushed in |
| Ohio winter performance | Mortar is stable in freeze-thaw | Silicone contracts in cold, opens gaps |
| Typical lifespan | Decades | 5–10 years before perimeter issues |
We replace silicone-perimeter glass block regularly across Ohio. The typical pattern: gaps between the panel and the wall, active water leaks during rain or snowmelt, drafts around the perimeter, and in advanced cases panels that have visibly shifted or can be rocked by hand. The blocks themselves are usually fine — it’s the connection to the wall that’s failed.
Homeowners consistently report it looked great for the first few years before gradually deteriorating.
Look at where the glass block panel meets the wall — the perimeter. If you see a bead of clear or yellowed flexible caulk, your panel was set with silicone. If you see gray or white rigid mortar filling the gap between the panel and the wall structure, it was mortar-set.
If the panel shifts or rocks when you press on it, the perimeter connection is failing — regardless of method.
We can replace failing silicone-perimeter installations with proper mortar-set perimeter work. Call for a free assessment.
For a broader look at all basement window options, see our basement guide.
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Yes, and so does virtually every glass block company in Ohio. Prefabricated panels with silicone joints between blocks are industry standard. The silicone holds the blocks together as a unit. What makes our installation different is the perimeter — we mortar the completed panel into your wall opening, creating a permanent masonry bond. Companies that cut corners use silicone for the perimeter connection too, and that’s where failures happen.
Ask them directly: “How do you attach the panel to the wall opening?” If they say mortar or masonry, good. If they dodge the question or say caulk/silicone/adhesive, that tells you the panel-to-wall connection will be the weak link. Any reputable installer will be transparent about their method.
Sometimes the perimeter can be re-mortared if the panel itself is still in good condition. In many cases though, the panel needs to come out and be reinstalled properly. We assess each situation individually — sometimes it’s a repair, sometimes it’s a replacement. We’ll give you an honest recommendation.
Slightly — but the difference is measured in hours, not days. And the result lasts decades longer. The small additional time is well worth it.
The cost difference is typically modest per window. Given that mortar-set perimeter lasts decades versus silicone-perimeter’s typical 5 to 10 year lifespan, the cost per year of service is dramatically lower with mortar.
Our team is ready to assist you. Call one of our offices using the phone numbers below or text us at (614) 324-9002
