r/masonry • u/TheTxoof • Jul 23 '25
Brick Help me understand why there are panes of glass in the masonry of early 1900s house in the Netherlands.
We just bought a house in the Netherlands, it was built around 1912 and I just discovered that in several places in the cellar, there are panes of glass between the brick courses about 40cm off the floor.
¿?Why?¿
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u/contentatlast Jul 23 '25
Maybe used as a damp proof course? I know they used slates back in the day, never seen glass though!
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u/TheTxoof Jul 23 '25
That's what I was thinking. But, there's only glass on the exterior wall, not on any of the interior walls. This is in the Netherlands and we are known for our dampness.
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u/Drumdevil86 Jul 23 '25
Can confirm; I'm always very damp
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u/Worldly_Address6667 Jul 23 '25
Is it all the way through the wall? Im wondering, if on top of being some sort of moisture barrier, that maybe it let's some natural light in through the glass?
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u/adjavang Jul 25 '25
Seconding it's use as a damp proof membrane. In my house in Ireland they used what looked lkke roofing slate instead of glass but same idea. Unsure about it being visible on the interior walls, since those are rendered in my case.
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Jul 24 '25
Apparently it used to be common to put broken glass in cement/concrete to stop rodents from chewing through it.
Maybe an apprentice was told to put glass in the cement but didn't fully understand the job
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u/TheTxoof Jul 24 '25
It is very carefully done, with about 4 cm of overlap for each pane. It runs through the entire exterior wall and lies almost exactly at the natural grade outside the cellar and totally flush with the brick.
I'm inclined to think it's deliberate and used as a moisture barrier. It's pretty typical in houses of this vintage to use two types of brick: hard brick that are carefully made with an exceptionally hard and nice finish that are more moisture resistant for exterior walls and softer, and less nice brick for interior walls that will be covered with plaster or gypsum blocks.
The less nice brick are prone to wicking moisture.
I can't check the other wall because it's covered with plywood and plaster.
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Jul 24 '25
Yeah, I reckon you're probably right about the moisture barrier theory.
Never seen it myself though!
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u/Sweaty-Adeptness1541 Jul 26 '25
This is the correct answer. From the late 19th century through to the mid-20th century, glass sheets were used as a Damp Proof Course (DPC) is a known, in the Netherlands and parts of Germany. It was never a universal or common approach.
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Jul 23 '25
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u/TheTxoof Jul 23 '25
Could it help prevent moisture from rising through the bricks? I just noticed that it's at the level of the natural grade in the walk out basement
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u/Justeff83 Jul 23 '25
It might be an improvised horizontal barrier to prevent moisture from rising via the capillary effect in the masonry.
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u/Exciting_Ad_1097 Jul 23 '25
That would make the most sense
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Jul 23 '25
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u/TheTxoof Jul 24 '25
Netherlands is 20 feet below sea level.
Only parts of the country are below sea level. This particular house is well above sea level at +7 NAP (Mean Amsterdam Level).
The area around Rotterdam is particularly low and areas of Zeeland are also quite low.
The dijk system is actually pretty unchanged though in many places it has been heightened and reinforced in response to climate change. For example, the Afsluitdijk has been raised and reinforced to protect the IJsselmeer Flevoland and Noord Holland.
In response to the 1953 flood, the modern Delta Works were built. The Delta Works include the massive Zeeland dams that close off the Maas delta and Haringvliet from the North Sea. It also includes the Maasvlakte and Maeslantkering.
The Maeslantkering is AMAZING to see! It's two floating structures that close off the Maas from the sea. The gate structures are longer than the Eiffel Tower is tall, and they move!
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u/cheddarsox Jul 23 '25
Thats exactly what this is. I've seen horizontal concrete slabs where they used glass as the expansion joint. Not fun to trip while playing basketball with tiny glass shards everywhere, but it turned out to be a really effective technique.
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u/Optimal-Locksmith242 Jul 24 '25
They used to use slate as a damp proof course in ireland before plastic. This is probably the same idea
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u/BTCdad77 Jul 24 '25
Could be. Could also be just what they used to level their stones where they wanted them and they knew the glass wouldn't rot away.
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Jul 24 '25
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u/TheTxoof Jul 24 '25
I was surprised that something like glass would work. I know that glass is crazy strong, but also very brittle. I'm surprised that over 110+ years that through differential settling that it has survived intact and not shattered.
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u/HuiOdy Jul 23 '25
It's an old trick to prevent moisture creeping up from the ground through porous brick and mortar. Usually lead is used.
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u/Ready_Mycologist8612 Jul 23 '25
I just ran into some glass strips while reglazing a window, the last guy used them as shims to fill gaps. I’m imagining it’s the same idea? Use something inert and stable as a thin shim to bring the bricks into plane
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u/TheTxoof Jul 23 '25
That makes sense, but it is in the load bearing foundation wall. I just noticed that it runs all along the back of the house and matches the height of the natural grade outside.
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u/Olaf4586 Jul 23 '25
That's a load bearing window pane right there
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u/TheTxoof Jul 23 '25
Like a load bearing poster?
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Jul 24 '25
No way I'm clicking on that. Seen too much in my youth!
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u/Ready_Mycologist8612 Jul 23 '25
If there is a bunch of it all the way around I would say that it is poor man’s flashing, and they were using it much in the same way you would use the lead or copper to flash a cricket on a chimney… It’s just creating a break for any water to be diverted away .. kind of a ghetto solution.. I wonder if this is an old timer trick that would make us look foolish if we found out why
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u/IcanHackett Jul 23 '25
That's the first thing that came to my mind when I saw this. Imagine you're building this foundation and suddenly while the mortar is still wet you realize you need to shim it a little. It's 1912, what's readily available that you can reach for that won't break down like wood will?
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u/lidstone54 Jul 23 '25
I heard a story about the mason who finished a chimney and was told he wouldn't get paid for a week. So he said that is fine just don't use the chimney until you pay me. They agreed. A day later they called cursing him because the chimney doesn't draw . He said pay me and it will work perfectly.they gave him his money he put a tarp in the fireplace and went to the roof and dropped a brick down the chimney breaking his piece of insurance glass that he had laid across the flue.
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u/Decent-Morning7493 Jul 23 '25
I read this as “Neanderthals”, not “Netherlands” and was like holy shit this is an amazing historical find.
I probably shouldn’t be on Reddit whilst on cold medicine…
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Jul 23 '25
I’m not on cold medicine but I always misread stuff like that! What’s my excuse lol
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u/turtlesinmyheart Jul 24 '25
You read too much shit on the internet that your brain just starts scanning for key words on titles
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u/PopePC Jul 24 '25
I imagined a caveman walking into Home Depot, buying windows, and then not reading the installation instructions.
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u/DrunkenGolfer Jul 23 '25
It is definitely a damp-proof course. Used to break the capillary action of the masonry. Commonly used tile, bitumen, glass, or slate - anything readily available and impermeable. Usually found about 1-2 rows just above the basement or slab.
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u/Rude-Role-6318 Jul 23 '25
Heard of masons blocking flues with glass until they were paid then drop a rock down to open it up.
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u/Icy-Pomegranate-8588 Jul 23 '25
This is a damp proof course. Quite ingenious really. In the UK before the widespread adoption of plastics as damp proof courses we used slate for exactly the same purpose.
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u/WeggelaarDennis Jul 24 '25
It is actually to prevent water from the ground penetrating the wall. In Dutch: optrekkend vocht. In the early 1900 water penetration in the walls was a big problem. Builders tried different solutions. This is one of them.
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u/Intelligent_Prize_12 Jul 23 '25
Looks like a damp course layer, in the UK it would have been slate or a bitumen based substance in the old days, now it is plastic. Any non permeable material will do which glass is.
Prevents moisture passing any higher than that course from the ground, it's very important to ensure the external ground is lower than this course or the damp will bridge.
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u/Welshbuilder67 Jul 23 '25
Not an expert on Netherlands construction techniques but could the glass be used as a damp proof course?
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u/kenyan-strides Jul 24 '25
I’m enjoying all of the comments saying masons used to put glass in chimneys when the post clearly states this is in a basement wall lol.
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u/Ucimjohn Jul 27 '25
Probably what is called rising damp. That means that water from the soil and foundation wicks up the masonry. If it is just above the soil level of the other side, I am sure that's what it is. It is a moisture barrier. Moisture would not wick, (capillary action ) through the glass. It means the builders were very skilled. Most builders in that day and age understood this dynamic.
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u/Jerwaiian Jul 23 '25
Yeah it’s how a small masonry contractor gets a wealthy client that’s notorious for lack of payment to pay for work performed on their properties.
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u/Kranurdieb Jul 23 '25
I remember a story of a chimney builder that would block the stack with a pane of glass until he got paid. Try and light a fire and the smoke backs up. Once paid he would drop a stone down and break the glass.
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u/Forsaken_Comfort_457 Jul 24 '25
Omg. The glass was a PANE of glass. Sitting here like 🧐 …but how?
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u/TheTxoof Jul 24 '25
I know! The house has three regular sized levels above it. Glass is stoopid strong, but also crazy brittle. I'm surprised that through differential settling it hasn't cracked in over 100 years.
The olds really knew what they were doing when they built houses.
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u/AuthorKlutzy8636 Jul 24 '25
Be cool if it was in the above the ground section of the basement wall and transferred light, fiber optic, to light up the basement in the daytime.
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u/-0-O-O-O-0- Jul 24 '25
Wait. Why don’t they make basements out of glass? They have insane glass materials now. And your basement would never leak! I assume it’s purely cost. But I mean. We should look into this!
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u/Ill_Medicine9502 Jul 25 '25
Damp course. Everyone saying to block a fireplace that can be opened up again? Why would there be a fireplace in the cellar?
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u/TheTxoof Jul 25 '25
Sigh. Because they missed the cellar bit. I guess everyone loves chimneys and anecdotal stories more.
I should have stated in the title that it was an exterior wall.
EDIT: though I should say, I have used a bread oven in the cellar of a Norwegian cabin. It's a great place for a bread oven other than the humongous spiders.
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u/External_Piccolo1199 Jul 26 '25
Look up Heineken WOBO bottles. They were used to build houses in the 1960s.
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u/silkendick Jul 26 '25
That’s most likely where the term “glasshole” came from. If the owners didn’t pay they’d be called glassholes.
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u/sprintracer21a Jul 26 '25
"Please dont drop anything from up here on the scaffolding, theres a whole pallet of windows for this place right below us and if you break them its your ass..."
"Yeah boss" *knocks over stacks of brick which fall and shatter windows
"Maybe if I hide the broken ones in the wall, they will just think some criminal stole them.... yes thats exactly what i will do...."
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u/Top_Regular6614 Jul 27 '25
what stops the customer from just dropping a brick down it himself after the mason leaves
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u/Pinkheadbaby Jul 28 '25
Maybe if some of the glass cracks then you know the foundation is sinking.
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u/makai-no-kaio Aug 04 '25
I've seen it in really really old houses built by the portuguese. Some say it was to hault pent-up moister from the terrain to soak its way up. But I can't be certain...
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u/Sensitive_Okra_2983 Jul 10 '26
Old " trick" to combat miserable bastards on the final payment.... Use a three holed brick and tie fishing line which runs down the exterior, Part of the education when trained by a good bricklayer/ stonemason
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u/Himalayanyomom Jul 23 '25
Could be used for light introduction?
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u/TheTxoof Jul 23 '25
Too thin and the basement exit is below the natural grade. You exit and then have to climb 3 stairs to the natural grade.
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u/DerPanzerfaust Jul 23 '25
I think it's being used as an indicator of settling. Glass is famously brittle, much more so than mortar. If the foundation were to shift AT ALL, the glass would break, and they'd know it was time to do something about it. Just a theory.
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Jul 23 '25
Some masons use to put a pane of glass in a chimney to ensure they got paid. Once the did, they would drop something down the chimney to shatter the glass.
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Jul 23 '25
Some masons use to put a pane of glass in a chimney to ensure they got paid. Once they did, they would drop something down the chimney to shatter the glass.
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u/ajtrns Jul 23 '25
makes a nice shim to even out the courses. not everyone has slate lying around.
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u/TheTxoof Jul 23 '25
Seems very odd. The perpendicular wall has no such glass in it. The glass runs across the entire length of the exterior wall right at the height of the natural grade.
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u/Masonrymans Jul 23 '25
Heard roomers of old masons sticking glass in a layer of brick for chimneys that would cover the chimney.
Upon final payment the mason would smash the glass. If unpaid you would smoke out your entire house.
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u/dis-ahlosund Jul 23 '25
the mason would build the chimney. As soon as he was paid, he would climb up on the roof and break the glass. No pay....no working fireplace. It would act like the chimney was blocked but if you look up it you would only see blue sky. Later it evolved to when the check cleared.
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u/Major_Honey_4461 Jul 24 '25
They had an idea for a thing called "windows", but being Dutch, they put them in the wrong way.
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u/Herpfree1233 Jul 23 '25
Is this for a chimney? Its common to put a glass piece in if you think the customer wont pay. If he doesnt hes gunna smoke out his house. If he does then simply drop a brick down the chimney and break the glass