When to worry about cracks in plaster walls

Explore the various factors that influence crack severity, including width and location. Also, learn about the main causes behind cracks in plaster walls and how to fix hairline cracks yourself. Read on to discover when to address cracks and when to seek expert advice.

Types of plaster cracks

There are many different types of plaster cracks you can find in your home, each varying in direction, width and length. Whether you encounter cracks on walls, door frames or ceilings, it’s essential to determine how significant they are. While some are nothing to panic about, others can be down to structural problems.

The types of plaster cracks are:

• Vertical cracks: These cracks are quite common, particularly in new builds, and occur when fresh plaster dries out. They’re easy to fill in, but don’t attempt to repair them immediately as more could appear – wait until everything is dry before resolving
• Horizontal cracks: Serious cracks which often form because of structural movement
• Diagonal cracks: These cracks resemble stair steps running along your wall. You should take them seriously as they could indicate structural damage.
• Ceiling cracks: Many things can lead to cracks in your ceiling, including damp, structural movement, unsettled humidity and plaster shrinkage. It’s best to get a professional to assess these types of cracks.

How can you tell if a plaster crack is structural?

When examining cracks in your plaster walls, it’s vital to figure out if they could indicate structural issues.

One way to tell if cracks in your wall are structural is if they run diagonally. This can be a sign that there’s been some structural movement that needs addressing.

Diagonal cracks of 3mm or more could be a sign of subsidence, which is when the ground underneath your house sinks and unbalances your foundations, causing cracks in the walls. So, if you spot any cracks like these, it’s always best to contact an engineer.

If you notice a crack wider than 15mm, it could be a sign of structural damage and require immediate attention from a professional. It’s also worth getting an engineer to investigate any cracks you may have above door frames – these can be signs of foundation damage.

What causes cracks in your plaster?

There are various reasons cracks can start appearing in your plaster walls. Here are some of the most common:

• Plaster shrinkage: As plaster dries, it loses moisture, which can lead to shrinkage. This shrinkage can result in small cracks appearing on the plaster’s surface
• New home: Fine cracks are common in newly built homes as the building settles into its foundations
• Old home: Ageing homes are also susceptible to developing cracks in plaster
• Temperature and humidity changes: Variations in heat and moisture cause plaster to expand and contract. As a result, the building’s structure can change and cause cracks in plaster walls
• Dampness and moisture: When your walls become damp, the moisture can weaken plaster and cause it to crack.

Got your tools together? Move all furniture out of the way and cover any surfaces you want to protect. Then, follow these steps to fix the cracks in your plaster walls.

1. Take your Stanley knife and score the crack to widen
2. Grab the drywall tape, cut a piece to match the length of the crack and put it to one side
3. Mix your drywall joint compound in a tray, ensuring you follow the instructions on the packaging
4. Add some of the mixture to your filling knife and spread a thin layer over the crack
5. Cover the crack with the piece of drywall tape you cut earlier. If you notice any bumps, use your filling knife to smooth
6. Add another layer of the mixture over the top of the tape and leave to dry
7. Sand down the area until it’s flat.

Remember, this advice is for hairline cracks and those below 5mm. For any cracks 5mm or above, it’s best to enlist professional help.

When to contact a professional to fix cracks in the wall

As previously mentioned, hairline cracks and cracks up to 5mm are typically not cause for concern, and you can address them on your own. However, if you notice cracks that are wider than 5mm or diagonal (stair-step) cracks, then the best thing to do is contact a professional.

When it comes to the structural integrity of your home, it’s always better to err on the side of caution. An engineer can assess the situation thoroughly and advise you on the best solution. It’s also important to have home insurance, which could help any costs incurred when you need to repair structural damage to your property.