- Ran into the same thing with my 1940s place—plastic shims looked bulletproof when I put them in, but as soon as we hit that first freeze/thaw cycle, the gaps showed up.
- Wood’s got that “give” factor, but yeah, it turns into a science experiment if there’s any moisture. Pulled a few out last spring and they were basically compost.
- Tried a combo last time: plastic for the base (keeps the rot away), thin wood shims stacked on top for that little bit of flex. Not perfect, but better than either alone.
- One weird thing—my neighbor swears by composite shims (sorta like recycled plastic/wood blend). Supposedly they squish just enough but don’t soak up water. Haven’t tried ‘em yet, but might be worth a shot if you’re tired of playing shim roulette every season.
- Old houses are like living with a mischievous roommate—always moving stuff around when you’re not looking...
I’ve heard mixed things about those composite shims—some folks love them, but I’m not totally sold. Feels like they’d still get brittle with enough cold, no? Has anyone tried them through a full winter in a drafty old place?
I get the skepticism—composite shims sound great on paper, but I’ve had mixed results. My old farmhouse gets pretty drafty and last winter, the composite ones I used under a bathroom window held up fine...but I noticed a couple started to flex weirdly when it dropped below zero for a week. Didn’t actually snap, but they felt less solid than wood. If you’re worried about brittleness, I’d lean toward hardwood shims, especially for spots that see real temperature swings. They’re cheap, easy to trim, and haven’t let me down yet.
That’s interesting—I've actually had the opposite experience with composites, but I totally get where you’re coming from with the cold snaps. In some of the older homes I’ve worked on (think 1920s brick), composite shims did fine behind interior trim, but I did notice they got a bit “spongy” feeling when the temps dropped. Never had one snap, but it made me second guess using them on exterior windows or anywhere there’s a real draft.
With hardwood, I do like that you can shave them down exactly how you need, especially if the jamb is out of square (which is basically every old house I see). Only thing that bugs me about wood is if there’s any moisture—it’ll swell or compress over time. Have you ever run into that, say in a bathroom or laundry area? Sometimes I’ll throw a little silicone around wood shims in wetter spots just to be safe. Curious if anyone else has a workaround for that?
I hear you on the wood swelling—had a bathroom window where the shims basically turned into mush after a year. What’s worked for me is sealing them with a quick coat of polyurethane before install. Takes an extra five minutes, but they hold up way better in damp spots. Silicone works too, but sometimes it gets messy if you ever have to pull them out later... Learned that one the hard way.
Yeah, I’ve had shims basically dissolve in my old basement windows too. That damp air just eats them up, especially the cheap pine ones. Tried sealing them with shellac once—worked okay, but honestly I didn’t notice a huge difference after a couple years. Polyurethane might be tougher, though. I’ll give that a shot next time.
Silicone, though... I’m not totally sold. Had a contractor use it on a door frame and when I needed to adjust things later, it was a mess. The shims were glued in so tight I ended up cracking some trim just getting them out. Maybe it’s fine if you’re sure you’ll never need to touch them again, but I like being able to fix stuff without a ton of hassle.
I’ve also started using composite shims in spots that stay wet. They’re not perfect—sometimes they’re too slippery and don’t grip as well as wood—but at least they don’t turn to mush. Not the cheapest, but for a couple bucks more it’s less headache in the long run.
Honestly, I feel like nothing really lasts forever in a bathroom or basement. Moisture finds a way in no matter what you do. Just gotta keep an eye on it and be ready to swap stuff out every few years. That’s homeownership, right?
Honestly, I feel like nothing really lasts forever in a bathroom or basement. Moisture finds a way in no matter what you do.
That’s the truth right there. I’ve tried everything from cedar shims to heavy-duty composites and it’s always just a matter of time before something needs attention. Can’t say I’m convinced on silicone either—once it’s on, it’s on for good (or bad). Polyurethane might buy you a little more time, but even then, you’re just delaying the inevitable. At least swapping out composite shims is less of a pain than dealing with soggy wood. Sometimes I wonder if it’s just about picking the battles you want to fight.
Moisture’s relentless, especially in older homes where the vapor barriers aren’t what they should be. I’ve noticed that even with composite shims, if the humidity spikes or there’s a cold snap, things shift and you’re back adjusting. I do think polyurethane sealants hold up a bit better than silicone in damp spots, but yeah—nothing’s truly permanent. At this point, I’m more focused on making sure there’s good airflow and maybe investing in a dehumidifier for the basement. It’s not glamorous, but it seems to slow down the cycle of repairs... at least for now.
- Been there with the shifting shims. My house is from the 1950s, and even after swapping to composite, like you said, things move with the seasons.
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Yep, that’s exactly what happens here. It’s like fighting a slow leak—never really done.“even with composite shims, if the humidity spikes or there’s a cold snap, things shift and you’re back adjusting.”
- I’ve had better luck doubling up on shims (wood + composite) for spots that get more movement. Not perfect, but seems to hold longer between tweaks.
- Polyurethane does outlast silicone in my experience, especially around window frames where condensation collects. That said, neither one is magic—eventually it all needs another pass.
- Airflow makes a big difference. I put a vent fan on a timer in my basement last year. Not fancy, but it keeps things drier so the frames don’t swell as much.
- Dehumidifier helps too, though I had to remind myself to clean out the filter every couple months. Otherwise it just blows damp air around.
- One thing that helped: sealing up obvious gaps in the old vapor barrier with heavy-duty tape. Not a full fix, but slows down how fast moisture creeps in.
- If the window frame is sagging bad, sometimes it’s worth pulling off the trim and checking for rot or mold underneath. Found some nasty surprises when I finally looked behind mine.
- None of this is permanent—just stretches out the time between repairs. At this point, I just keep a box of shims and a caulk gun handy and deal with it as needed.
- Honestly, sometimes I wonder if it’s worth replacing the window entirely, but then I look at the price tag and just laugh...
Anybody else tried those adjustable metal shims? Curious if they actually hold up or just rust out faster than wood.
That’s reassuring to hear I’m not the only one chasing seasonal shifts. My place is early 60s, and the amount of “micro-movement” in the frames is wild—sometimes you can literally see where the caulk’s stretched thin after a humid week. Doubling up on shims makes sense. I tried wood plus plastic last fall on a door jamb, and it seemed to buy me a few extra months before things loosened up again.
I haven’t used the adjustable metal shims yet, but I did look into them. One thing that put me off was the potential for rust, especially since my basement gets damp in summer no matter what I do with fans and dehumidifiers. The idea of being able to tweak them without pulling off trim is tempting, though. If they came in stainless or some kind of coated finish, maybe that’d help?
And yeah, totally agree about checking for rot—found some sketchy stuff under a sill last year that explained a lot. It’s frustrating how these fixes are more about buying time than solving it once and for all. But honestly, keeping a stash of shims and a decent caulk gun handy seems like the most realistic plan for now.