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The 7 Biggest Blunders with Glass Block Bathroom Windows (and 7 Tricks to Fix Them)

Written by Mike Foti on . Posted in Bathroom Remodeling, Glass Block

Glass block window in bathroom or shower installation | Innovate Building Solutions | #GlassBlockWindow #BathroomWindows #GlassBlockDesign

I’ve been around the (glass) block (OK, I know that’s a bad play on words) a long time. I started in this business in 1989 (I like to tell people I was only 11 years old at the time, but nobodies buying it). In these 30 years I’ve seen a lot of glass block bathroom window jobs. Some supplied and installed by my business, others not.

Glass block is thought of as a ‘masonry’ product (mortared together block by block with an old, grizzly mason). Homeowners and contractors struggle with masonry-built glass block windows. They’re not sure how to design their window. They don’t know how it should be installed into a framed opening (since most bathroom windows aren’t installed into concrete blocks or poured walls, like basement windows).

This lack of knowledge (and the bad information they get along the way) results in some UGLY-looking jobs which don’t last. My business has seen (and fixed) many of these ugly jobs (or you can call them blunders).

The fact is these blunders (AKA crappy jobs) didn’t have to happen. In fact, glass blocks can be simple to design and install…if you know a few tricks.

In this article my goal is simple.

First, I want to identify the top 7 blunders I’ve seen in my waaaay too many years in the biz.

Second (and most importantly), I want to give you practical ideas (or tricks), so you don’t fall in the ‘bad project’ trap. I want you to have a bathroom window which looks sharp and is designed, fabricated and installed to last (I was going to say to Infinity and Beyond, but that sounded too corny).

So, let’s dig into the 7 biggest blunders (and practical ideas to fix them) of glass block bathroom windows.

Glass block bathroom window blunder #1 – You try to build your window block by block inside the window opening

Since window openings aren’t square, the sill is sloped, and they can be high off the ground, trying to install your blocks unit by unit inside the opening (after your old window is taken out) is a complete and total disaster.

To give you some idea of why this is a bad idea, my company (which was started in 1977) has NEVER installed even one glass block bathroom window block by block inside the opening.

So, if a company which has installed over 870,000 windows in our history has NEVER installed one in the opening, you may (correctly) conclude it’s a bad idea.

With this being said, it’s nice to know there’s a far smarter way to do it.

Glass Block Window Ultimate Guide

How to overcome blunder #1 – Use prefabricated glass block assemblies vs. installing block by block

The simplest way to overcome blunder #1 is to purchase (or have installed for you) a prefabricated glass block window. Prefab windows are built in one section (or multiple sections if you have a very large window). This preassembled process makes them far simpler to install. These sections are made with mortar or silicone between the blocks, or for maximum strength and energy efficiency use a ‘Protect-all’ vinyl stacking window.

A prefab glass block shower transom window installation | Innovate Building Solutions | #PrefabricatedGlassBlock #GlassBlockWindow #GlassBlockDesign

Premade windows install in less than 1/3 of the time of a block by block installation. Even more important, with premade window the joints sizes are consistent. Your job won’t look like your grandson or granddaughter put them together.

Glass block bathroom window blunder #2 – You installed your window, now you’re scratching your head on how to ‘finish around it.’

Glass block basement windows are MUCH simpler than their upper floor bathroom ‘brothers.’ In glass block basement windows first, you set the window in the concrete block or poured wall. Second, mortar ‘the puppy’ in. Slam, bam, thank-you-ma’am, you’re done.

Bathroom windows are not so simple.

If this window is going into the middle of your bathtub/shower, there’s ceramic tile or a shower wall surround you need to work around. On the outside (if you don’t have a brick veneer to mortar to) you’ll need a plan to finish to your siding or stucco.

The biggest blunder I see is owners and contractors assume all you need to do is ‘mortar this sucker’ in like a basement window. The problem with this is the moisture from the mortar will get absorbed into the wood studs around the opening and eventually crack. The joint on the inside (around ceramic tile or your shower surround) will also crack and can cause leaking into the wall cavity (and that would NOT be a good day!).

Here’s some ideas to fix these problems.

How to overcome blunder #2 – Use the right details to finish the inside and outside of your glass block bathroom window

Finishing the inside 

When finishing the inside of your glass block window it’s a good idea to use silicone caulk to join the edges of the glass blocks to the ceramic tile or wall surround. This will provide a seal, but also allow for flexibility as your home shifts. Around the perimeter you can use cultured stone, a vinyl window trim kit or run the window flush with the shower on the inside to eliminate any finishing at all.

Acrylic window trim kit around a high privacy glass block | Innovate Building Solutions | #AcrylicTrim #WindowTrim #GlassBlockWindow

Finishing the outside

Although the outside can be finished in many ways (depending on if the exterior of your home is wood, stucco, vinyl siding, brick etc.), the most common is a sided home. With sided homes, it makes sense to finish the outside edges of the glass block window in the same manner as a vinyl replacement window. Use an ‘aluminum coil wrap’ around the window which is sealed to your siding.

glass block window finished with coil stock on outside | Innovate Building Solutions | #GlassBlockWindow #Outsidetrim #GlassBlockBathroom

Glass block bathroom with coil stock capping | Innovate Building Solutions | #OutsideTrim #GlassBlockWindow #FramingGlassBlock

Glass block bathroom window blunder #3 – You didn’t make sure the opening fit the design you liked

IMHO, the biggest problem with glass blocks is you can’t cut them. You must work with the sizes available to drive your design.

The hottest trend in glass block window design is evolving away from the ‘same old, same old,’ where one block is stacked on another. Homeowners are flocking to ‘stained-glass-window-esque’ designs with various block sizes. You want to make a statement with your block window. You no longer want a generic job.

This is great…. except…when it’s not and the opening doesn’t (or won’t) fit the design concept you like. You may wonder how to get past this problem. Here’s how.

How to overcome blunder #3 and create a fun glass block window design which fits

As Steven Covey used to say (sort of), “With glass block design you’ve got to begin with the end in mind.”

With residential glass block bathroom windows you’ll either be designing with American sized blocks (which are 4” x 8”, 6” x 6”, 6” x 8” and 8” x 8”) or Metric sizes (which are 7 ½” x 7 ½” or 3 ¾” x 7 ½”). These sizes will drive your design. So, here’s what you need to do.

Multi glass block pattern design with color in bathroom | Innovate Building Solutions | #GlassBlockPatterns #BathroomWindows #GlassBlockWindows

First, develop (or find on Pinterest) a fun design you love. If it’s a design which exists already, call the glass block prefabricator and ask what the ‘pattern repeat’ is and the size of the design. Then, with your home builder or contractor figure out if your openings can be sized to work with the design. If not, you’ll need a new design.

Glass block shower window with a multi sized design | Innovate Building Solutions | #GlassBlockDesing #ShowerWindow #GlassBlockDesign

DO NOT – create the hole first and do the design second.

Glass block bathroom window blunder #4 – You’re ‘putting on’ an ‘unintended show’ for the neighbors

Glass block shower windows are perfect, except when they’re not and you realize you’re providing the neighborhood a ‘show’ in your birthday suit (and that ‘suit’ doesn’t look as hot as it did when you were in your 20’s!).

Privacy is personal (isn’t that redundant?). One person’s ‘completely private’ pattern is another person’s exhibitionist extraordinaire. You need to see what block feels right for you. This is where knowing your patterns (and processes) comes in handy.

How to overcome blunder #4, and not show more ‘skin’ than you’d like

With glass blocks there are ‘completely private’ patterns (Iceberg and Diamond, for example) and there are ‘partially private’ patterns (‘wave’ is most common). The amount of privacy which is right for you will also depend on where the window is located.

For example, if you have a first-floor bathroom window, smack dab in the middle of the shower (which anyone on the outside can walk up to), you obviously will want maximum privacy. On the other hand, if this window is on the second floor (even in the shower) a partially-obscure ‘wave’ pattern which blurs your outline, may offer enough privacy.

Iceberg privacy glass block bathroom window | Innovate Building Solutions | #PrivacyGlassBlock #GlassBlockWindow #Showerwindow #BathroomWindow

In addition, if you love the ‘wave’ look and want to use it on your first-floor window and maintain maximum privacy, you can use a frosted glass block window to improve privacy.

Frosted glass block window and wall in bathroom | Innovate Building Solutions | #FrostedGlassBlock #GlassBlockDesign #GlassBlockWall

No matter what, make sure the glass block pattern you choose feels right for you.

Glass block bathroom window blunder #5 – You bought a frameless premade glass block window for your new home or room addition but aren’t sure how to install it.  

Earlier in this article I talked about glass block premade windows. Now I’ll tell you while buying premade windows is a good idea, they aren’t all created equal.

The most popular glass block prefabs are frameless. In remodeling jobs in masonry openings, frameless glass blocks are perfect. However, in wood framed or new construction openings, not so much.

Contractors and DIY’ers struggle with how to finish around wood framed openings. They’re used to installing ‘nailing-flange’ vinyl windows. They ask, “what the heck (they don’t say it quite so nicely) am I going to do around the perimeter of this doggone window?”

This uncertain installation leads to crazy approaches to finish it.

What many new home builders, remodeling contractors and weekend DIY-warriors don’t realize is doing wood framed projects with glass blocks can be simple. Here’s how.

How to overcome blunder #5 using a vinyl framed glass block window

New construction glass block windows (for wood framed openings) can be ‘easy-peasy-lemon-squeezy’ (as one of the guys who works with me likes to say). Instead of buying an ‘unframed prefab glass block window,’ what you need is a vinyl framed glass block window.

With the vinyl framed window you can still create any type of design (see blunder #3), but the window is prefabricated into a vinyl frame with a nailing flange. With this unit the window is installed like a new construction vinyl window.

Don’t make a new construction glass block bathroom window job harder than it needs to be. Use the right window. Take the anxiety out.

Installating a vinyl framed glass block window | Innovate Building Solutions | #InstallglassBlock #Vinylwrapglassblock #VinylWrapFrame #GlassBlock

Glass block bathroom window blunder #6 – You have ‘buyer’s remorse’ after you go on Pinterest and see pretty, colored blocks

Inspirational ideas are wonderful if you see them at the right time.

Inspirations ideas are painful when you see them ‘after the fact’ and it’s too late to bring your dream bathroom to life.

I’ve dealt with bummed out people when they notice colorful block options too late in the remodeling or building process. Then the lead times are too long. Their designs (and window openings) won’t work with the available color options (which are usually in metric sizes). Frustration and FOMO (Fear of Missing Out) sets in.

Glass Block Window Ultimate Guide

How to overcome blunder #6 when you want color in your glass block window design

There’s no practical way to modify a clear glass block window after it’s been installed and add colors to it. It’s too expensive. It’s impractical to remove glass blocks from an existing window and put color in after the fact.

Blue frosted glass blocks inside a bathroom | Innovate Building Solutions | #GlassBlockWindow #ColorGlassBlock #BathroomWindow #BlueGlassBlock

The key to solving this problem is to develop your design before your bathroom is remodeled or new home windows are framed. Here’s what you need to do.

First, determine if the supplier you’re working with offers American or Metric sized colored glass blocks. In the United States today most of the colored blocks are metric sizes (the only American sized colored blocks are done with an aftermarket drilling and filling color process).

Second, develop your design and determine the rough opening you need.

Third, buy the colored glass block window.

Blue and green colored glass block shower window | Innovate Building Solutions | #ColoredGlassBlock #GlassBlockWindow #BathroomWindow

Colored glass blocks in a bathroom shower | Innovate Building Solutions | #ColoredGlassBlock #BathroomWindow #GlassBlockDesign

Glass block bathroom window blunder #7 – You try to ‘go it alone’

Even though I’ve been in the glass block business for a long time, if I’m being honest with myself, I know installing a glass block window (for most homeowners at least) is a once-in-a-lifetime experience. Most people (unlike installers in our company) don’t install multiple block windows in their lifetime.

So, what this means you’re likely doing the installation for the first time. I also know many people are stubborn and try to ‘figure it out themselves. Pride trumps (no political play on words here) practicality.

This ‘figuring it out alone’ thing leads to the 6 blunders mentioned previously. That’s not good.

How to overcome blunder #7 – Get free help.

Why go it alone when you can get help for free? Glass block is a niche business. There are a small handful of companies across the country who really know their glass block stuff. The good news is they’ll share it with you…for free!

Call an experienced company with glass block designers and installers who’ve been down the road before (even if they have more gray hair than they care to admit. Note, I resemble this remark, but my solution is $9.99 bottle of Just for Men hair coloring – but that’s just between you and me).

Glass block window design Columbus Ohio Installation | Innovate Building Solutions | #GlassBlockWindow #DesigningShower #BathroomShower #ShowerWindow


I hope these 7 blunders get you off the pot-hole filled dirt road of a bad glass block bathroom window installation. Use these 7 ideas to overcome the 7 biggest blunders and get ‘er done right the first time. If you need help click the links or call the numbers below. Me and my team would be delighted to assist you.

How can I (or my team) help you with this project?

For assistance designing, building or installing a glass block bathroom window, shower wall or bar call Innovate Building Solutions at 877-668-5888 for nationwide supply. For a local installation service and supply contact Columbus Glass Block at 614-252-5888 or Cleveland Glass Block at 216-531-6363.


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Mike Foti

President of Innovate Building Solutions a nationwide supplier and regional (Cleveland and Columbus) remodeling contractors. Some of our product lines include glass counters, floors, backsplashes, glass blocks and grout free shower and tub wall panels

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