Getting precise measurements for weird-shaped windows (arches, triangles, etc.)

- 100% agree on contour gauges being more trouble than they’re worth with old plaster or uneven trim. They just don’t flex enough for those weird bumps.

- Cardboard’s my go-to, but I’ve actually had decent luck with kraft paper for tight arches - just tape it in place and run a pencil along the edge. It’ll wrinkle a bit, but you get a cleaner line.

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“tracing the outline, then flipping the template over to double-check for symmetry before cutting anything expensive”

- For really complex shapes, I use a combo: kraft paper for the curve, cardboard for the main body. Tape them together and you’ve got a flexible but sturdy template.

- One tip: if you’re working solo, use painter’s tape to hold your template in place while you trace. Masking tape can pull paint or fibers, especially on older walls.

- Never tried freezer paper, but now I’m curious. Might be easier to get into those tight corners than cardboard.

- Digital measuring tools are tempting, but unless your trim is brand new and perfectly square, they’re usually more hassle than help. Sometimes old-school is just simpler.

Funny you mention freezer paper - gave that a shot once when I was dealing with a weird half-moon window in the attic. It actually held its shape better than I expected and was easier to cut than cardboard for those tight inside curves. Still, I’m with you on digital tools. Tried one of those laser measuring apps last winter, and it got thrown off by every bit of wonky plaster.

“Sometimes old-school is just simpler.”

- Ran into a similar mess with an eyebrow window in our old place - nothing standard about it.
- Tried cardboard first, but it kept buckling at the curve. Freezer paper, like you mentioned, worked better than expected. Never thought I’d be raiding the kitchen for home repair supplies, but here we are.
- Digital measuring tools are hit or miss for me too. The app I tried couldn’t handle the lumpy plaster and weird angles - numbers were all over the place.
- I keep coming back to tracing with kraft or butcher paper. Lay it right up against the frame, mark everything out, then double-check with a tape measure before cutting anything expensive.
- Only thing I’ll add: sometimes I use painter’s tape to hold the template in place while tracing, especially if I’m working solo or on a ladder. Saves a lot of swearing.
- Old houses definitely keep you humble - there’s always some surprise behind every wall or window... but that’s half the fun, right?

Freezer paper, huh? That’s a new one for me, but it makes sense - never thought I’d be using kitchen stuff for window projects either. I’ve always defaulted to kraft paper or old wrapping paper rolls for templates, but sometimes it’s a pain getting it to stay put, especially if there’s a breeze coming through. Painter’s tape is my go-to for keeping things from sliding around too, though I’ll admit I’ve had it peel up some old paint here and there.

I totally hear you on digital tools. I bought one of those laser measure gadgets thinking it would be a game-changer, but our plaster walls are so wavy it just spits out numbers that make zero sense. Ended up trusting my tape measure and eyeballing more than I care to admit.

One thing I’ve wondered - has anyone tried using that flexible curve ruler stuff? The kind artists use for drawing odd shapes? I saw someone use it to trace the curve of an archway and then transfer it to plywood. Looked like it saved some headaches, but not sure if it’d work for bigger windows or just smaller trim jobs.

Old houses are definitely full of surprises. Last year when we redid a bedroom window, we found an empty hornet’s nest tucked in the frame and some weird newspaper from the 1940s used as insulation. Made me laugh, but also reminded me nothing is ever straightforward in these places.

Curious if anyone’s found a trick for getting measurements right when the molding isn’t even the same on both sides. Sometimes one side of the arch is just... off by half an inch compared to the other. Do you split the difference, or just pick a side and hope for the best?

I know a lot of people like to split the difference when things aren’t symmetrical, but honestly, I just pick the side that’s more square and run with it. Otherwise, I feel like you wind up with two sides that look off instead of just one. The flexible curve ruler is a cool idea, but I tried it once on a big window and it flopped around too much - ended up going back to cardboard templates. Sometimes old-school just works better.

The flexible curve ruler is a cool idea, but I tried it once on a big window and it flopped around too much - ended up going back to cardboard templates. Sometimes old-school just works better.

Yeah, I hear you on the floppy ruler. I bought one of those thinking I was about to revolutionize my window game, but it was basically a sad noodle by the time I got it up to the arch. Cardboard templates might not be fancy, but at least they don’t try to escape halfway through tracing.

I’m with you on picking the more “square” side, too. That whole “split the difference” thing sounds good in theory, but when you’re standing back looking at it, you just end up with two sides that are both a little bit wrong. I’d rather have one side that looks intentional and one that’s just...well, a little off. Honestly, most people won’t notice unless they’re the type who brings a level to dinner parties.

Here’s a trick I picked up from my neighbor (he’s a retired carpenter and has opinions about everything): blue painter’s tape. If you’re doing an arch or triangle, run strips of tape along the edge of the glass, then sketch your line right on the tape. You can tweak it until it looks right, then peel the tape off and slap it on your cardboard for a template. It’s kind of a hybrid old-school/new-school thing, and it’s saved me from having to cut five versions out of cereal boxes.

I’ve also tried that tracing paper stuff, but unless you’ve got a third hand, it’s just not worth the hassle. Cardboard holds its shape, and if you mess up, who cares? Grab another Amazon box and try again.

Anyway, just wanted to chime in because I’ve definitely wrestled with all these “precision” tools that end up being more trouble than they’re worth. Sometimes the simple stuff wins.

Painter’s tape is underrated for stuff like this. I did something similar when I had to fit a weird trapezoid window in our attic - ran tape, sketched the line, then transferred it to cardboard. Tried using tracing paper and it just slid everywhere. Cardboard’s sturdy enough that you can actually test-fit it a few times without it getting all floppy or torn. The only downside is if your window’s really high up, balancing everything gets a little sketchy... but tape plus cardboard has worked way better for me than any of those bendy rulers or “precision” gadgets.

Cardboard’s sturdy enough that you can actually test-fit it a few times without it getting all floppy or torn.

Yeah, cardboard templates are a lifesaver for odd shapes. I’ve tried those “contour gauge” tools and honestly, they’re more trouble than they’re worth - never seem to match the real curve, especially on old plaster. One trick I picked up: use hot glue to tack the cardboard pieces together if your window’s got multiple angles. Ever tried making a template for an arched window? Curious if anyone’s found a way to keep the center point accurate when you’re working solo.

Hot glue is a smart move - I’ve only used tape and it always peels off at the worst time. When I tried to template an arched window by myself, I ended up using a string tacked to the center point and kind of swinging it like a compass. It was fiddly, but it worked well enough for getting the curve right. Definitely not perfect, but better than freehanding. Honestly, working solo just means accepting a little bit of “close enough” sometimes.

That string compass trick brings back memories... I tried something similar with a cardboard template when I tackled the weird triangle window in our stairwell. I traced the shape by pressing the cardboard into the frame and just sort of marked it with a pencil. Not the most scientific approach, but it got me close enough for a blackout shade. I totally get what you mean about solo projects - sometimes “good enough” is really all you need, especially when no one else is going to notice those tiny gaps except you.

That’s pretty much how I handled the odd-shaped window in our attic. I tried to be precise at first - measuring angles, using a protractor, the whole deal - but honestly, it just got frustrating. Ended up doing almost exactly what you described: cardboard, pencil, and a bit of trial and error. It wasn’t perfect, but unless someone’s walking around with a flashlight looking for gaps, no one notices.

I get why people want everything to line up perfectly, but sometimes “close enough” is all you can expect with these weird shapes. Especially if you’re working alone and don’t have fancy tools. I do wonder if there’s some middle ground between the DIY cardboard method and hiring a custom installer... maybe 3D scanning or something? Though that sounds like overkill for most of us.

Anyway, if the blackout shade works and you’re happy with it, I’d call that a win. Perfection’s overrated when it comes to home projects like this.

I totally relate to the frustration - measuring those odd angles feels like a math class I didn’t sign up for. I actually tried using one of those angle finder apps, but it was more confusing than helpful. The cardboard method was way less stressful, even if it’s not perfect. I keep wondering if there’s some kind of template kit out there for this, or maybe something like peel-and-stick guides? 3D scanning sounds cool, but yeah, probably too much for most of us. At the end of the day, as long as it blocks light and looks decent, I’m not sweating the small gaps.

I’ve had my fair share of headaches with arched windows - ended up tracing the shape onto butcher paper and cutting a template. Not high-tech, but it worked better than any gadget I tried. Honestly, unless you’re after museum-level precision, close enough usually does the job.

Not high-tech, but it worked better than any gadget I tried.

That butcher paper trick brings back memories. I did something similar when we replaced the old leaded glass in our 1920s bungalow. Tried a digital angle finder first - ended up more confused than when I started. In the end, tracing the arch onto cardboard gave me the best fit, even if it was a bit rough around the edges. Funny how sometimes low-tech just wins out over all those gadgets. I get wanting precision, but like you said, unless you’re restoring a cathedral, “close enough” holds up just fine for most homes.

I get where you’re coming from - sometimes the old-school way just feels right, and for quick projects, it usually gets you close enough. But I’ll be honest, after years of patching up “almost perfect” fits, I’ve started leaning more on those digital gadgets. The learning curve is real, but once you get the hang of them, they save a ton of time (and headaches) when you need to match multiple arches or weird angles. Not saying cardboard is out, but for jobs where gaps really matter - like custom window inserts or trim - I’d rather wrestle with tech than redo a piece twice. Just my two cents...

I hear you on the digital gadgets making life easier - my cousin swears by his laser measurer and honestly, his projects always fit together like a puzzle. But I’ll admit, I still get a weird satisfaction out of tracing stuff with cardboard or that old cereal box from the recycling bin. There’s something kind of fun (and a little ridiculous) about crawling around with scissors and tape, trying to get that arch just right.

That said, I’ve had my share of “almost fits” turn into “why is there a draft in July?” situations. The last time I tried to DIY a window insert for our attic triangle window, I thought I nailed it… until the first rainstorm and suddenly it was like Niagara Falls in the corner. After that, I caved and borrowed my neighbor’s digital angle finder thingy. Not gonna lie, it felt like cheating at first, but wow - it saved so much time and swearing.

I still keep some cardboard handy for quick fixes or when I’m not feeling up for tech, but if I really care about getting it right (like with trim or anything that’s going to be visible), the gadgets are hard to beat. Plus, if you mess up digitally, at least you can blame the batteries or the app instead of your own eyesight.

Price is a thing though. Those tools aren’t cheap, especially if you’re only doing one or two windows. If you’ve got a neighbor who’s into this stuff already, maybe trade them some baked goods for borrowing their gear? That’s what I did - banana bread is basically DIY currency around here.

Anyway, both ways have their place. I guess it depends if you want to spend your Saturday measuring twice or cutting twice…