Why does my house make cracking noises at night?

Almost always thermal movement — building materials expanding and contracting as temperature changes, with the sounds concentrated in the evening because that is when the temperature is falling fastest.

The mechanism. Every material in a house expands when warmed and contracts when cooled, and different materials do so at different rates. Timber, plasterboard, plastic pipes, metal ducting and masonry all change dimension at their own pace. Where two materials are joined, that differential movement creates stress at the joint, and the stress releases suddenly as a crack or pop when friction is overcome.

Why at night. During the day, sun and heating warm the structure. After sunset, and after the heating switches off, the building cools. That cooling is the fastest sustained temperature change of the day, and the contraction happens while you are indoors, awake and — crucially — in a quiet house. The same noises happen during the day and are masked by everything else.

The usual culprits:

Central heating pipework. Copper expands noticeably when hot water flows through it. Where a pipe passes through a joist or a clip that is too tight, it sticks and then slips with a click. This is the single most common cause, and it correlates with the heating switching on and off.

Timber framing and floorboards, particularly in newer homes still drying out.

Roof structure and tiles, which experience the largest temperature swings of anything in the building.

Ducting and flues, especially metal.

When it is worth investigating. Ordinary ticking and popping is harmless. Be more attentive if you also see new or widening cracks in walls, doors or windows that have started sticking, sloping floors, or noises accompanied by visible movement — those combinations can indicate subsidence or structural movement rather than thermal cycling.

Fixes are usually easing an over-tight pipe clip or packing felt where a pipe passes through timber.