Across 70-80 cases of new plaster cracking in Bristol and Bath, 55% were caused by the heating being turned on too soon or too high — and in the majority of cases it’s not the plasterer’s fault.

What Most Guides Say vs What Our Callbacks Actually Show

Most online advice suggests that any cracking in new plaster is a sign of poor preparation or a bad mix. However, our data from 70+ callbacks tells a different story. While preparation is vital, environmental factors are the primary culprit for the vast majority of issues we see in local Victorian and 1930s properties. For more on identifying common issues, see our guide on Why Is My Plaster Bubbling?.

How to Read Your Cracks — What the Pattern Tells You

Understanding the shape of the crack is the first step in diagnosing the cause. A network of fine cracks across the whole surface usually points to rapid drying from heat. Cracks following trowel lines suggest the plaster dried too fast in a draughty room. Diagonal cracks from corners of openings or along joints often indicate substrate movement, which is common in older Bristol homes. For further diagnostic help, see Why Is My Ceiling Cracking?.

The 4 Most Common Causes We Find

Heating Turned On Too Soon or Too High

The most common mistake is turning the heating to full to “help the plaster dry faster” within the first few days. This causes the surface to skin over while the moisture remains trapped inside, leading to a network of fine cracks. This is almost entirely avoidable. For official drying guidance, refer to British Gypsum’s technical advice.

Plaster Dried Too Fast in Warm or Draughty Conditions

Even without central heating, warm weather or open windows creating a strong draught can cause the plaster to lose moisture too quickly. These cracks often follow the path of the trowel lines and are typically cosmetic.

Substrate Movement

In older properties, the underlying wall or plasterboard may move as the building settles. These cracks appear diagonally from corners or along joints. If you suspect your plaster is failing due to underlying issues, check our guide on Hollow Plaster.

Contaminated or Wrong Mix

While rare, a bad mix will show signs within hours. The plaster may feel soft or crumbly to the touch. This is one of the few scenarios where the issue lies with the application or materials.

Is It the Plasterer’s Fault?

It is rarely the plasterer’s fault when new plaster cracks. Our data shows 55% of cases are due to heating, 25% to environmental drying conditions, and only 20% to substrate movement or mix issues. If you see cracks, assess the pattern first. If they are diagonal or the plaster feels soft, it is worth discussing with your professional. For help evaluating your project, see our guide on Plastering Quotes.

What We Tell Every Customer After a New Skim

To ensure a perfect finish, follow these steps:

1. Leave the heating off or at a low background level (max 15-16°C) for 5-7 days.

2. Keep windows slightly open for airflow, but avoid strong draughts.

3. Do not use a dehumidifier; it pulls moisture out too aggressively.

4. Allow the plaster to dry naturally and slowly.

5. Wait 3-4 weeks for a full cure before applying a mist coat.

What New Plaster Cracking Repair Typically Costs

FAQ

Is it normal for new plaster to crack?
Minor shrinkage cracks can occur as plaster cures, but they are often avoidable with proper drying.

Why has my new plaster cracked after a week?
This is usually due to the heating being turned on too high or too soon, causing rapid moisture loss.

Should I turn the heating on after plastering?
Keep it off or at a low 15-16°C for at least 5-7 days to allow for natural drying.

How long before new plaster stops cracking?
Once the plaster has fully cured (3-4 weeks), the risk of shrinkage cracking significantly decreases.

Is my plasterer responsible for cracks in new plaster?
In 80% of cases, the cause is environmental or related to the substrate, not the plasterer’s workmanship.

What temperature should a room be after plastering?
Maintain a steady, low temperature of 15-16°C to ensure the plaster dries evenly.

Can I fill cracks in new plaster before painting?
Yes, once the plaster is dry, hairline cracks can be filled, but ensure the cause isn’t structural first.

Why is my new plaster cracking while drying?
It is likely drying too fast due to heat or draughts, causing the surface to shrink before the moisture has escaped.