Appearance
- Small cracks – hairline cracks
- Plastic shrinkage cracks appear in the surface of cement renders and slabs within a few hours of placing, sometimes very soon after final trowelling and frequently before trowelling.
- They are often not noticed until the next day as they can develop after the tradesmen have left the site.
- They rarely impair the strength of the work, but they commonly form a treebranch pattern, a network of ‘mudcracks’, or sometimes tend to be straighter, in a pattern across the surface. They can be very short, ie. about 50 mm, but can be up to 1 metre or more in length.
Cause
Hairline cracks
- Pool took too long to fill (should be completely filled within 36 hours)
- Pool finished on a hot, dry (low humidity) or windy day.
- Normal cement shrinkage
Solution
- Small hairline cracks may appear in plaster due to normal shrinkage or flexing of the supporting structure and should not be considered a deficiency.
- Small hairline cracks heal themselves as the cement fully hydrates.
- If crack remains visible try rubbing with wet and dry sandpaper.