Can Dry Weather Cause Your Walls to Crack?
London sits on clay, and clay shrinks in a drought. Here's why cracks appear in a hot summer, which ones matter, and how to repair them so they stay closed.
Yes — Prolonged Dry Weather Really Does Crack Walls
London sits largely on clay, and clay shrinks as it dries out. In a long drought that shrinkage pulls at foundations and produces new cracks in plaster and render.
Timber does the same on a smaller scale. Skirtings, architraves and staircases lose moisture, shrink and open up gaps at the joints.
Most of what appears during a hot dry summer is cosmetic seasonal movement that closes again when the ground rehydrates.
Hairline and Seasonal, or Structural
Fine hairline cracks in plaster, cracks that follow a plasterboard joint, and gaps between woodwork and wall are almost always harmless movement.
Cracks that are wider than a coin's thickness, run diagonally, step through brickwork, appear on both sides of a wall, or stick doors and windows deserve professional assessment.
Cracks that keep widening through the season are the ones worth taking seriously — take a photo with a date and compare over a few weeks.
Fill for Movement, Not Just for Looks
Rigid filler in a moving crack simply cracks again. Flexible acrylic filler and decorators' caulk absorb seasonal movement and hold the decoration intact.
Rake out the crack slightly, fill in layers rather than one deep pass, let it dry fully in the heat and sand flush before priming the repair.
For a crack that has reopened repeatedly, a flexible filler with reinforcing tape or mesh under the finish coat gives a far more durable result.
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