News from the Block, Innovate Building Solutions Blog
News from the Block, Innovate Building Solutions Blog
Bathroom, Kitchen, Basement Design & Remodeling Ideas for the Nicest Home or Business on the Block
Bathroom, Kitchen, Basement Design & Remodeling Ideas for the Nicest Home or Business on the Block

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

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 brick block guide cover

Go Glass!

A Guide to Great Home Design with Glass Blocks and Glass Bricks

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 Guide cover

Ultimate Glass Block Window Guide

A Clear Way to Transform Your Home!

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 Guide cover

Ultimate Glass Block Window Guide

A Clear Way to Transform Your Home!

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.

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

Comments (38)

  • Michele – yes you can repair a grout joint (that’s assuming the deterioration wasn’t caused by metal rusting inside the mortared walls – which is an older method of installing the wall). If it’s not due to rusting of the metal a tuck pointing contractor (or grout repair company) can remove some of the old grout and put new in there. I’d recommend using a sanded or urethane grout between the joints – Mike

  • Hi Mike,
    I have a beautiful Glass Block Shower wall that was installed with mortar. The mortar inside of shower wall is showing signs of deterioration due to water damage from usage especially on the lower half of the glass block wall. Can the mortar be fixed or touched up before it erodes further? Also, how can it be sealed to prevent it from happening in the future?
    Thank you, Michele

  • Kathie it’s usually possible to replace just one block. What our installers do is to use duct tape over the block (inside and out). Then you break the block completely. Then you’ll insert the new block with the same material as was around the old block.

    I hope this helps you – Mike

  • I have a glass block window in the bathroom above the tub and bottom right hand corner has started cracking and I see moisture from raining currently can I fix it with window glue? Can’t find anyone to replace just one block.

  • Rick – thanks for your comment. I don’t recommend trying to tie in a glass door to a glass shower shower wall. I’d either have the entire glass wall system with glass blocks – or all with flat glass. Mike (feel free to call us if we can help more – 877-668-5888.

  • Hi. We eventually plan to remodel our bathroom, however that’s not a this year (and possibly not next) project. Our current shower is glass with a 30 year old brass frame. The front is full size sliding glass doors. The right side is about 2/3 height, and sits on the edge of the faux marble. The glass in that wall is “spidering”. We want to go with dark shower and fixtures when we change. However, if we go to a place to custom make a replacement that fits in our current shower, it will cost over $2k. Since we do not know if the remodel will be the same design and size, we are hesitant to invest this much. So brainstorming, can this short glass wall be replaced with a glass block wall. Then for the front, either an expensive sliding or swing open door, or possibly even just a simple shower rod with curtain. We are wondering if such a wall can be built inexpensively AND support a shower door or rod for a couple years. FYI – the back wall and tub surface (where the wall is mounted) are both the same faux marble. Thanks in advance for your input!

  • Minal – thanks for your question. It looks like you’ve had seal failure between the acrylic block units. I’d recommended using a ‘vinyl stack’ glass block window which has vinyl spacers between the glass blocks so you won’t get mold growth between the blocks. Here’s a link to show you this type of window. Let our team know if we can help further (877-668-5888) – Mike (now here’s the link –

  • Hi Mike,
    Thank you for all the useful information. We have a walk in shower with acrylic block fixed vinyl windows. After 10 years, some damage has occured with condensations within the some areas and green suff in couple of places. Is it better to replace these with glass block windows? Are they more durable?

  • Luanne – with this project I think it will be best to see some pictures to see what’s going on. Feel free to call our office and we can get you an email to send them to for more information. And I’m glad you’re finding the site of value to you! Mike (you can reach us at 877-668-5888)

  • Hi Mike,
    I am so glad I found your website! Thank you for helping people like me who need help they can’t find easily. We have a glass block wall in our bathroom that was installed 20 yrs. ago when the house was built. The outside has a lot of silicone around each of the blocks and the perimeter of the entire window area. The inside has shown wet stains on the windowsill. A contractor came out and told us it was from condensation around the window, no repair was needed. We are having a shower built around this window. I wanted to reseal the inside with silicone to make sure it didn’t leak or build up water in the grooves creating mold. I chipped out all the old mortar, and sprayed some beach water on some of the blocks. I now see that the mortar underneath some of the bricks has disintegrated. There is a metal or aluminum frame on the face of the blocks so it is not easy to apply silicone. If I squeeze as much silicone underneath the frame will that be sufficient? I am trying to avoid having the whole window redone. Thank for any advise you can give.

  • Jeff – while you could do this – I don’t know if I’d recommend it. The challenge may be you’ll get moisture in between the glass and the cement board – and it will also not look too nice from the outside. Mike

  • Can you cover in a glass block window from the inside? I want to put a shower in against the glass block window and cover it with cement board and tile over it? Is this possible?

    Jeff Hackett

  • Laura – I would either recommend using a urethane grout, a glass block mortar mix or using (if the joints are small enough) silicone between the blocks. These are the best options. Thanks for your nice comments – Mike

  • Hello!
    Awesone article!
    I removed all the grout in my shower glass block window, as I believe it was not sealed and was “chunking” out. Living in Central Montana, I presumed the extreme cold through the window could freeze any moisture remaining and this would continue to be a problem. Could I use a tub/tile caulk for between the blocks? Or would this prove to be the wrong choice?
    Thanks for your time!

  • Allesandro – our company’s expertise is in the glass blocks -and I’m guessing by ‘toughened glass’ you may be referring to what we call in the United States – ‘tempered glass.’ This doesn’t sound like a difficult installation. I would contact a ‘glazing contractor’ who works with metal frames and glass. They should be able to assist you with this. Mike

  • Hi Mike,
    I’m about to have my bathroom refurbished and I’m thinking of having a shower wall (will be created ex novo) with some openings to let the light in from the window opposite to it. In the project I’ve agreed with the company which created the layout, we initially thought of using some glass blocks to fill the openings of the shower wall. The openings are going to be 100mm wide, 100mm deep and around 1000mm height. My question is: can I use 8mm toughened glass instead of glass blocks? The idea is to install them flush to the ouside of the shower wall to create a sort of alcove from the inside. How would you fix the glass panel to the wall? Would you use a frame?
    Some companies I’ve spoke to seem to be a bit confused about the installation and the waterproofing of it.
    Thank you

  • No Jennifer – the glass block window should do fine in the shower. You will want to make sure the grout joints (if you have grout joints vs. silicone joints) are sealed – Mike

  • Michael – our crews use an aluminum coil stock to surround the outside of the wood trim (to protect it from rotting) and then we return the coil stock to the window and seal with silicone caulk. Hope this helps you – Mike

  • Mike – I’m putting a prefab glass block window in a remodeled shower area. There was no window in the old shower. I’ll be cutting out the window space, then will build a 2 x 4 frame. I have lap siding on the outside. My question is how to best Flash or waterproof the outside? I was going to put some 1 x 3 framing around the outside of the window opening – but I’m unsure how to best waterproof the window.

  • James with glass blocks we generally use a silicone caulk. If you want to get the specific brand/model number we use (or want to source this) call our office at 877-668-5888. Mike

  • The window outside is peeling the caulk away between each block starting from the bottom. What product is recommended to fill back in between the blocks?

  • Rose – the glass blocks themselves are waterproof, but you’ll want to look at the trim to make sure it’s waterproof also. If you have wood trim in there now you’ll want to remove it and then you can tile up to the glass block window. We’d recommend you use sealant between the glass block units and the tile. Mike

  • We want to replace a soak tub w/a walk in shower. There is already a glass block window above the tub. Do we have to do anything additional to it to make it water proof & sealed ? Or would it already be since it’s over the tub? And can we tile right up to frame/molding?

  • Armin – the reason the glass blocks are 7 3/4″ and the blocks are called ‘8″ x 8″ blocks’ is the 7 3/4″ is its nominal size. If you use a mortared system the standard visible joint would be 1/4″ bring the ‘finished size’ to an 8″ x 8″ increment. Let me know if I can help further – Mike

  • So we are building a bathroom that has very little natural light and thought of doing a glass block wall with artificial back-lighting in the shower. (This makes a sort of faux window.) 8 inch glass block was specified and then we bought 8 inch (tall) tile to match/line up. The tile was delivered, but alas, looking more closely we see that the glass block is really 7-3/4 inches. They won’t line up. What to do? Any thoughts?

  • Thanks Jason – I’m glad the article was of value to you. First of all to make a better determination if the window should be set flush to the outside it would be good to get inside and outside pictures, however with this being said we usually don’t put the glass block window flush to the outside. We will set them so there is a reveal on both the inside and outside. We don’t really like to have it flush because then more water will come right down on the window from the surrounding siding. I hope this helps you. Mike

  • Mike,

    First of all, great article and very informative. We are about to embark on a bathroom remodel journey. Our home is brick, and we’ve hired a mason to do the glass block window in our shower. I assumed that the glass block would be inset, like any other window. My mason says it will be flush with the brick. Is that the correct way to do it?

  • Andrea – although we don’t have a distributor in Missouri, we do prefabricated glass block windows and can ship a unit to you (either with or without a vinyl frame). Feel free to call our team at 877-668-5888 for more assistance. Mike

  • Great article as I research options for a window in my attic that I am going to have installed. I am contemplating the ready made drop in glass block, but I would like to have a window that I can see out of and possibly open on the bottom. I have an area of 47 x 47 to drop a window in with a lot of space on each side of the window. I live in Missouri, do you have suggestions for a distributor in the Columbia area? I am also a designer with a business license.
    Thank you for your suggestions and time,

  • Liz – we would recommend you buy a piece of solid surface material and angle it in the opening so it is pitched towards the shower. I hope this helps.


  • My hubby redid our shower with tile and then created a lovely glass block window. But the issue is the bottom of the window. Where is it slightly inset from the tile. It is flat now and we get water buildup there and now an orange coloring to the chaulk.

    How can we angle the trim/edget to keep that from happening?
    Chaulk alone is not enough we need to give it an angle?

  • Christie – I guess that can be both the ‘good and bad’ of standard glass blocks – they let in a lot of light. I do have 2 ideas for you though. The first (and probably the simplest) would be to work with a company who sells and installs window film. These films are often used on the inside of house windows to cut down glare and so furniture doesn’t fade. They can put the window film over the glass blocks from the inside. This has been done before. The second option (which I’m not sure if you can do since the glass block window is installed) is to see if a person can sandblast the blocks (while they’re in the opening). We have a process to sandblast (we call it frosted) before the window is built – but obviously your window is installed in the opening now. Let me know if I can help further – Mike – 877-668-5888. Good luck!

  • Mike:

    My husband’s parents put in a glass block backsplash in the kitchen and right now, I’m trying to find a “bandaid” to the problem until I can have it removed! It measures 80″ long by 16″ wide and unfortunately, there is so much sunshine that comes through in the morning, that I have to use sunglasses to cook! Can I paint the glass block? Would that help? Ideas?

  • Jackie -I’m glad you found this information about glass block bathroom windows helpful. There are a number of fun things you can do with them. Just for your information we can supply this product anywhere in the United States (or you can pick it up (we have a location in Cleveland Ohio which isn’t far from Ontario). Let us know if we can help further. Mike

  • Hi,
    Thank you Mike for this practical information. I didn’t really think there were colour options available. So glad there are. I am in the Niagara area of Ontario Canada and so far I haven’t come across a store that sells these ready made windows for my bathroom. After reading your idea fixes I will start to look around for someone who can make a small 20×20: shower window, with the vinyl edging. It may take a while but I don’t want to settle for something unattractive just because that’s all they say there is.

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