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North Hills Monthly

What Bumps in the Night Can Tell You about Your Home

Jan 30, 2015 04:09PM ● By Matthew Schlueb
By Matthew Schlueb

Native Americans refer to this time of the year as the ‘popping trees’ moon. There is a quiet in the air that you don't find other times of the year, especially in the early mornings before sunrise—the time of day I find myself shoveling our driveway to clear a path through the overnight snowfall.

My own home is nestled in the woods; the slightest breeze gives the tall, slender trees a gentle sway, then you hear a crack, and a pop. The sound riffles through the air. Branches and trunks are frozen stiff; their movements creak like cracking knuckles.

Freezing temperatures impact the house, too. When it’s cold outside and warm inside, there can be as much as 70 or 80 degrees’ difference during a typical February day in Pittsburgh. This difference in temperature transitions in the walls, creating crackling sounds of its own. Lying in the dark at bedtime, there are many things going bump in the night. My boys' active imaginations run wild, thinking up things loose in the house that could be making such sounds from the deep shadows in the corners or under their beds.

A soft rush of air fires up from the furnace, followed by clicks and knocks from ducts buried in the walls. A steady rhythm taps as the forced air rushes through, warming them. Soon the framing has its turn—louder pops from the walls and the floors. At our house, even the roof joins in. As the temperature drops, composite tiles make the loudest cracking noises of all. Infrequent, the sudden sound startles, breaking the silence.

The sounds of a house are not quite the same as ‘popping’ trees, which creak from reluctant movement as their frozen trunks and branches blow in the wind. The materials of a house move on their own, expanding as they warm, contracting as they cool. Dissimilar materials adjacent to each other expand at different rates. Metal ducts extend further than the wood studs to which they are tied. The ties and fasteners that hold ducts and pipes—the mechanical workings of a house—are made to have expansion joints and shifting fittings to relieve the pressures of materials that must move with changing temperatures.

Without such relief measures built in, the consequences would be far worse than startling noises. Pipes and ducts would crack, leaking water and wasted heat. The entire house is designed to move, from the framing and drywall holding it up to the flooring and cabinetry materials. Decorative trim hides away slotted joints and shifting materials; out of sight, we forget a house is not a static thing. Knocks on a silent winter night, however, remind us that a house is alive with hundreds of materials all moving at differing rates.

In a bathroom in my own house, there is a hairline crack running down the wall of a tiled shower. In the summer, when temperatures are warmer and the air wetter, the wall framing and substrates swell to close the crack, making it nearly invisible. In the winter months, the materials shrink and open the crack. I use it like a built-in barometer, conveying the current state of temperature and humidity inside the wall based on the crack's width.

For me, a house changes daily, cyclical with the seasons and on a continuum as materials age. I use certain signals, like bumps in the night or cracks on a wall, as instruments to measure the changes and keep me in tune with its current state. As these signs become familiar over time, a house becomes a home.

Over the coming months, this series of articles will help you to understand the signals your house gives off so that you can become more aware of the inner workings and changes that are taking place. Ultimately, I hope to educate you on how to better care for your home so it will provide you with years of happiness and comfort, sheltering you from the elements.

However, if on one of those cold winter nights, you nestle in with the kids to watch a movie next to a warm crackling fire, it might be best to keep to a comedy or drama. I can't be responsible for a scary movie and the subsequent fears at bedtime, when bumps in the walls, creaking and popping, come alive in the dark.


Matthew Schlueb is a registered architect and owner of SCHLUEBarchitecture. For questions or comments, contact Matthew at This article is part of an ongoing series addressing architectural issues for homeowners.