Why Your House Creaks at Night

Wednesday, August 25 · 7 min read

Every house makes noise after dark that it doesn't make during the day, and almost none of it means anything is wrong. Tonight we're covering the actual physics behind the pops and ticks, the pipe that bangs when the washer shuts off, and the one number worth knowing about the air in your house.

Reply and tell us your house's strangest nighttime sound.

A house is bigger at 3pm than it is at 3am, just by a little.

Wood, drywall, framing lumber, even the nails holding it together expand when they warm up during the day and contract as the house cools overnight, and different materials expand and contract at different rates.

When two materials move against each other at their own pace, at a joint, along a nail, where a floorboard meets a joist, you get a small, sudden release of friction.

That release is the pop or tick you hear once the house has gone quiet enough to notice it.

This happens more in the evening specifically because that's when the temperature swing is fastest. The sun stops heating the roof and walls, the outside air drops, and the house's materials are all contracting at once, each at a slightly different rate. During the day the same movement happens more slowly and gets buried under normal household noise, so you only really notice the settling sounds once the house, and you, have gone quiet.

Wood framing adds a second layer to this: humidity. Wood absorbs and releases moisture from the air constantly, swelling slightly when it's humid and shrinking slightly when it's dry, completely separate from temperature. A floor that creaked all summer and goes quiet in a dry winter, or the reverse, is usually humidity working on the wood, not a structural problem showing up.

Then there's the house's systems, which make their own separate category of noise.

Ductwork ticks and pops as it heats and cools with the furnace or AC cycling on and off, for the same expansion-contraction reason as the framing. A water heater tank pops as sediment settles and reheats. None of this is the house settling; it's just metal and water doing what metal and water do.

The sounds actually worth a call to a professional are different in character:

A quick way to tell the two apart: ordinary settling happens on a schedule you could set a clock to, roughly the same time each evening, roughly the same handful of sounds. A problem worth investigating breaks that pattern, gets louder over weeks, or shows up alongside a visible change somewhere in the house, not just an audible one.

If you hear a loud, sudden bang in the walls right when the washing machine or dishwasher finishes filling and the valve snaps shut, that's water hammer: a column of moving water hitting a dead stop all at once, and the shockwave has to go somewhere, usually into the nearest pipe strap or wall cavity, loud enough to hear from other rooms.

It's common, not dangerous in the short term, but repeated water hammer stresses pipe joints over years and is worth fixing rather than living with.

The fix is a water hammer arrestor, a small cylinder with an air cushion inside that absorbs the shock instead of the pipe absorbing it. Many newer washing machine hookups have small arrestors built into the valve already. If yours doesn't, a screw-on arrestor threads onto the hose bib behind the machine in a few minutes, no plumbing experience or pipe-cutting required, just a wrench.

If the bang is coming from a less accessible spot, behind a wall, under a sink you can't easily reach, that's the one version of this worth a plumber rather than a DIY attempt, since accessing the pipe itself may mean opening a wall.

Indoor relative humidity has a target band, not a single ideal number: 30 to 50 percent, per guidance from the EPA and most HVAC manufacturers. Below that range, wood dries and shrinks, more creaks, more static electricity, cracking in wood trim and furniture.

Above it, you're in mold and dust-mite territory, and a room feels muggier at the same thermostat setting.

A hygrometer (see below for our reco) is the only way to actually know where you sit; guessing by feel is unreliable, because people adjust to whatever range they're in within a day or two. A basic digital hygrometer costs under $20 and gives you a number you can act on instead of a hunch.

Once you have a reading, the fixes are boring and cheap: a humidifier in a dry winter house, a dehumidifier or just running the AC longer in a damp summer one, and in both directions, keeping bathroom and kitchen exhaust fans actually vented outside, not into the attic, does more than people expect.

The number also explains a lot of the noise from the anchor above. A house on the dry end of the band is a house with wood that's actively shrinking, which is exactly when you'll hear the most settling sound.

Humidity affects how warm a room feels almost as much as the actual temperature does, because your body cools itself by evaporating sweat, and that evaporation happens faster in dry air and slower in humid air. The same 76 degrees can feel comfortable or sticky depending entirely on the humidity in the room.

The practical move: if your AC's fan mode lets you run a lower fan speed, the air stays on the cold coil longer and more moisture gets pulled out per pass, so the same setting produces drier, more comfortable air. That often means you can raise the thermostat a degree or two and feel the same, or better, for less.

Raising the thermostat by even a degree or two saves on cooling costs over a full season, and a drier room is what makes that degree feel free instead of felt. This is the same reason a stuffy, humid room feels hot even with the AC running: humidity, not the number on the thermostat, is the variable actually working against you.

Furniture legs are a major, boring source of both floor scratches and small creaking sounds, especially on hardwood or laminate, and the fix is a sheet of self-adhesive felt pads, a couple of dollars for enough to cover a whole room's worth of chair and table legs.

Peel, stick to the bottom of each leg, done. It stops the scratch marks that build up from chairs sliding in and out at a dinner table, and it quiets a surprising amount of the small creak-and-shift noise that comes from furniture settling against a hard floor rather than the floor itself.

Check them every six months or so. Felt pads compress and wear thin with heavy use, especially on rolling chair casters, and a worn pad stops protecting the floor well before it looks obviously bad.

This is the cheapest single fix in this whole issue, and it's the one most people mean to do and never quite get around to. Buy the pads once, do the whole downstairs in the same afternoon, and you likely won't touch it again for a year or more.

If the humidity band above sounds useful but abstract without a number in front of you, the TempPro TP50 Digital Indoor Thermometer & Hygrometer is a small, honest instrument for the job: temperature and humidity on a large backlit display, updating every ten seconds, accurate to about 2 percent relative humidity in the range that actually matters.

At $15.99, this isn't a smart-home purchase, it's a $15 sensor, and that's the point: you don't need an app or a subscription to answer "is my house too dry or too damp." You need a number on a shelf you glance at once a week.

It also tracks daily high and low readings, so you can catch a room that spikes at a specific time of day, right after a shower, say, rather than relying on a single spot check. It ships with three ways to place it: a tabletop stand, a magnetic back, or a hanging mount, so it fits a shelf, a fridge, or a wall equally well.

It runs on a single AAA battery and has Bluetooth (there is also a basic version for $5 less. The BT version stores data and doesn’t even require you to register with the app to log info.

We haven't run this exact unit through a full year of seasons ourselves. The accuracy and battery-life figures above are TempPro's own published spec. Full details are on the product page.

Reply and tell us your strangest nighttime house sound too, we're collecting the best ones for a future issue.

See you tomorrow.

The Home Wire.

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