Ever notice how old houses have weirdly sized windows?

Also, I read somewhere that you’re supposed to measure from “jamb to jamb” and not include the trim, but honestly, sometimes it’s hard to tell what counts as trim or jamb in these old houses.

That’s a super common headache. Older homes are all over the place with what’s considered “trim” vs “jamb” - sometimes you’ve got layers of paint or weird molding that hides the real edges. Here’s how I usually tackle it:

- Look for where the window actually stops and the wall begins. The jamb is basically the side of the window frame that touches the window sash (the part that moves), not the decorative wood on top.
- If you’re unsure, pop off a piece of trim carefully (pry bar + patience). You’ll see the actual frame underneath. That’s your true measuring point.
- If removing trim isn’t an option, shine a flashlight along the edge - sometimes you can spot where things transition.

A few other things I’ve run into:

- Like you mentioned, always measure top/middle/bottom (and left/right if it’s a tall window). I’ve seen some windows bow out so much that there’s nearly half an inch difference from top to bottom.
- Don’t trust old blueprints or “standard” sizes. I once ordered a whole set of replacements based on what was supposed to be a standard 32" opening… turned out every single one was different by at least 3/8". Ended up trimming and shimming every last one.
- Watch for settled sills - sometimes they slope down toward the outside if there’s been water damage. Measure both inside and outside if possible.

One trick: If you’re ordering custom windows and your measurements are weirdly close to a standard size, go just a hair smaller. It’s way easier to shim/fill gaps than try to force a too-tight fit. And don’t forget - old houses move with the seasons, so leave yourself some wiggle room.

Funny enough, I’ve found more oddball sizes in 1940s bungalows than in Victorians. Maybe they just eyeballed it back then… or maybe my house is just extra quirky.

Hope that helps someone avoid a costly mistake.

I totally get the confusion with old houses - mine’s from the 1920s and every window seems like it was custom built for that exact spot, no rhyme or reason. I once tried to measure for a new sash and ended up discovering three different “jambs” under layers of caulk and trim. What finally worked for me was running my finger along the inside edge until I hit bare wood, then using a small mirror to double-check what I was actually measuring. Still had to shave down the new sash a bit, but at least it fit. It’s wild how nothing is ever square or standard in these places... makes you wonder how anyone managed before laser levels.

Had the same headache with my 1915 place. The window openings are all over the map - nothing is plumb or level. Measuring for replacement sashes turned into a full-on forensic investigation.

"I once tried to measure for a new sash and ended up discovering three different “jambs” under layers of caulk and trim."

I ended up using a digital caliper for the final measurements, but still had to custom plane the frame. Even then, it was a tight fit on one side and a gap on the other - had to use backer rod and flexible sealant to compensate. Laser levels help, but honestly, nothing beats just taking your time and expecting a bit of trial and error.

I kind of appreciate the quirks now, but it definitely makes any “standard” window part basically useless. Custom seems like the only way unless you want to completely reframe, which... no thanks.

I ended up using a digital caliper for the final measurements, but still had to custom plane the frame.

Standard parts rarely fit these old frames, and even custom orders can be a gamble if the opening isn’t square. I usually end up scribing the new jambs to match the existing opening. It’s tedious, but it avoids big gaps or binding sashes.

Standard parts rarely fit these old frames, and even custom orders can be a gamble if the opening isn’t square.

That’s exactly what I’m running into with my place. It’s kind of frustrating, but honestly, seeing it all come together after all the scribing and planing feels worth it. Nice to know I’m not the only one dealing with these weird angles.

Totally get what you mean about the satisfaction after all that fitting and trimming. Sometimes I wonder if these frames shifted over time or if builders just eyeballed it back then. Have you run into any spots where the old plaster or trim made things even trickier? That’s tripped me up more than once.

Definitely ran into that - old plaster is a wild card. Sometimes you pull off the trim and there’s a half-inch gap or weird buildup from past repairs. Makes it tough to get anything square. I’ve had to shim behind new casings just to get things to line up. It’s like every window tells its own story... and not always a good one.

Haha, yeah, I thought it was just me being clumsy with a pry bar, but every time I mess with the trim in my place (1920s), it’s like opening a weird time capsule. Sometimes there’s a random chunk of wood stuffed behind the plaster, or the window’s off level by half an inch. I tried to square up one frame and ended up shimming so much it looked like a game of Jenga. Guess “standard size” just wasn’t a thing back then...

- Had the same thing in my 1915 place - nothing lines up, and every window is a different height off the floor.
- Once pulled off some baseboard and found a brick just sitting behind it. No idea why.
- “Standard size” is a myth with these old houses. You end up custom ordering or hacking things to fit.
- Honestly, sometimes I wonder if the builders were just using whatever was lying around... but I guess it’s held up this long, so maybe there’s something to it.

Yeah, "standard size" is pretty much a joke in these old places. I had to trim down a new door just to get it to fit in my 1920s bungalow. Nothing in here is square, and the windows are all over the place - some barely above the floor, some almost at ceiling height. Makes it a pain if you want matching blinds or curtains.

That brick behind the baseboard... I've found random stuff too. Once pulled up a floorboard and there was an old horseshoe wedged in there. Maybe they just tossed in whatever was handy for shims or filler? Or maybe it was some weird good luck thing.

Curious if anyone's tried to actually level out window heights or just left it as part of the house's "charm"? I’ve thought about it, but seems like a huge hassle for not much payoff.

Curious if anyone's tried to actually level out window heights or just left it as part of the house's "charm"? I’ve thought about it, but seems like a huge hassle for not much payoff.

I get the charm thing, but I actually went down the rabbit hole of trying to even out two windows because the drafts were driving me nuts. Ended up realizing it was less about the height and more about the old frames leaking air everywhere. Honestly, all that work for symmetry didn’t do much for energy bills - caulking and adding storm windows made way more difference. Sometimes “charm” is just code for “needs a sweater indoors,” you know?

Sometimes “charm” is just code for “needs a sweater indoors,” you know?

That line made me laugh - so true. I’ve tried to “fix” the quirks in my 1920s place, but honestly, chasing perfect window alignment felt like a losing battle. Did you notice any issues with the walls themselves when you worked on yours? In my case, some of the weird window heights were hiding old settling problems, which turned into a bigger project than expected. Wonder if anyone else ran into that rabbit hole...

Yeah, I’ve definitely been down that road. My house is from the late 30s, and I thought the wonky windows were just a “character” thing until I started pulling off trim and realized the walls themselves had shifted over time. Turns out, what looked like a simple window replacement ended up with me sistering joists in the crawlspace. Sometimes it feels like these houses are just waiting for you to poke at something so they can reveal another secret problem.

- Not sure I totally buy that every weird window is just a sign of shifting walls.
- In my place (built 1942), most of the oddball window sizes were just a result of how materials were rationed and reused back then. Lumber lengths weren’t always standard, and sometimes they just made do with what they had on hand.
- Pulled apart a kitchen wall once and found two different types of framing around the same window - looked like it’d been re-framed at least twice. No major structural movement, just a series of “good enough” fixes over the decades.
- Sistering joists sounds rough, though. Guess some houses do hide bigger issues.
- But sometimes, it’s just a patchwork history of repairs and renovations, not necessarily a sign the whole place is shifting under your feet.
- I’d say, before assuming it’s all structural, check for old repair work or mismatched framing. Saves a lot of crawling around in the dirt if it turns out to be a cosmetic quirk.
- Still, these old places definitely keep you guessing...

Funny timing - just pulled some trim off a window in my place (late 30s build) and found three different types of nails holding it together. No sign of anything shifting, just a lot of “whatever works” over the years. Anyone else ever notice how sometimes the window frames don’t even match the rest of the house? Makes me wonder if folks just grabbed whatever was cheapest or left over from another project. I do get a little nervous when I see cracked plaster around them, though...how do you tell if it’s just age or something moving behind the scenes?

I do get a little nervous when I see cracked plaster around them, though...how do you tell if it’s just age or something moving behind the scenes?

Honestly, cracked plaster isn’t always a sign of trouble. My house is from the 40s and there are hairline cracks all over the place, mostly from settling or even just temperature swings. If the cracks are diagonal or keep getting bigger, that’s when I’d worry about shifting. But if they’re just little ones around the windows, it’s probably just old materials doing their thing. I wouldn’t stress unless doors start sticking or you see big gaps.

Cracks around windows can be tough to read, but here’s how I usually break it down: First, check if the crack is wider than a nickel - if it is, or if you notice it growing over a few months, that’s worth watching. Next, look at the direction. Vertical or horizontal cracks are often just from settling or expansion, but diagonal ones can sometimes mean shifting. I also like to press gently on the area - if it feels hollow or crumbly, might be old water damage or just age.

Curious if your window frames are original? Sometimes weird sizing comes from past repairs or retrofits that didn’t quite match the old rough openings. Have you noticed any spots where the plaster seems soft or bulging near those cracks?

Interesting point about the diagonal cracks - I've seen those pop up near windows in my 1920s place, and it turned out some of the sills were replaced with slightly different lumber. Have you checked if your window sashes sit flush or if there’s a gap at the corners? Sometimes gaps or misalignment are a clue that things got swapped out at some point. Also curious if any of your trim looks newer than the rest... sometimes it’s subtle but tells a story.

Funny you mention the trim - my living room has one window with chunky, bright-white molding and the rest are all that old, yellowed pine. The “new” one sticks out like a sore thumb. Anyone else find random shims jammed in to make things fit? That’s my house in a nutshell.