Plastering can seem a bit daunting, especially if you’re dealing with cracks or you’re attempting to fix blown plaster. However, with the right tools and a step-by-step approach, it’s a task any beginner can tackle with confidence. In this post, we’ll walk you through how to handle these issues, ensuring a smooth and strong finish to your wall. Whether you’re patching a small area or trying to fix blown plaster, follow these tips to get it done right.
The best way to get the most from this is by watching the video above. The text below will outline which products to use with a brief summery of the process so watch and read to get the best experience.
But before we get into it, you need to…
Assessing the Damage
Before starting any plaster repair, it’s important to assess the condition of your wall. If you notice any suspicious cracks, particularly those that look like signs of subsidence or more significant issues, call in a structural engineer. It’s better to be safe than sorry.
Once you’re confident that the wall is structurally sound, you can begin the process of removing the loose plaster. Scrape back any areas that are flaking or blown to expose the damaged spots. You’ll often find cracks or hollow-sounding sections where the plaster has separated from the wall.
The Right Materials for the Job
For this repair, we’ll be using British Gypsum Bonding, which is a backing plaster that’s ideal for medium to low suction backgrounds. It’s perfect for areas where the brickwork isn’t exposed. On the other hand, if you have areas where the plaster has come off down to the bricks, you’ll want to use British Gypsum Hardwall instead. Hardwall is designed to handle high suction backgrounds like brickwork and provides a strong bond that can deal with high traffic area’s.
Here’s a quick rule of thumb:
- Exposed brickwork: Use British Gypsum Hardwall.
- Plaster base coat without brickwork: Use Bonding.
Step-by-Step Guide On How To Fix Blown Plaster
Step 1: Fill the Gaps
Start by applying a tight coat of bonding to the damaged areas. You want a thin, even layer—nothing too thick, as this can cause issues later. The goal here is to fill the gaps while keeping the coat tight to the surface.
Step 2: Level the Surface
Once you’ve applied your first coat, use a derby or any straight edge to smooth the surface. Hold the edge flat to the wall and scrape off any excess bonding. If you notice any low spots, fill them in and smooth again until the surface is even.
Step 3: Reinforce with Mesh
For areas with cracks, you’ll need to reinforce the wall to prevent the cracks from reappearing. Cut pieces of scrim tapeor mesh to the size of the wall section you’re working on. Apply another tight coat of bonding, this time using a slightly wetter mix. This allows the mesh to bed into the plaster more easily.
Once the bonding is applied, press the mesh into the plaster. Work in small sections (about 1 metre at a time) to ensure the plaster doesn’t dry too quickly. Smooth it out with your straight edge again, making sure the mesh is fully embedded.
Step 4: Finishing Touches
After your mesh is in place and the bonding coat has been applied, rule the surface flat again. This ensures that your patch is level with the rest of the wall, providing a smooth surface for the next steps.
Word Of Caution: Ruling Plaster IS TOUGH…
Ruling plaster flat can be challenging for several reasons:
- Uneven Surface: The wall might have imperfections, such as dips, bulges, or bumps, which makes it difficult to get a perfectly level surface. When your applying plaster, especially over patches or old walls, these irregularities can cause the plaster to pull unevenly as you smooth it out. This is a challenge you may face when you want to fix blown plaster.
- Plaster Consistency: If the plaster mix is too thick, it becomes harder to spread evenly, leading to lumps or ridges. On the other hand, if the plaster is too runny, it won’t stay in place and may sag, making it difficult to level out properly.
- Suction Variations: Different parts of the wall might have varying levels of suction (how much moisture the surface absorbs from the plaster). This can cause some areas to dry faster than others, making it harder to rule the plaster flat before it starts setting.
- Pressure Control: Applying consistent pressure while using a straight edge or derby can be tricky. If too much pressure is applied, you might remove too much plaster, while too little pressure can leave excess material, making the surface uneven.
- Time Constraints: Plaster dries relatively quickly, especially in high-suction areas or warm environments. You need to work efficiently and rule the plaster flat before it starts to set, which can add to the difficulty, especially for beginners.
These factors require experience and skill to master, which is why ruling plaster flat can be one of the more challenging aspects of plastering. So make sure you have some prior experience with a trowel beforehand.
If you’re completely new to plastering then check out of free training at the end of this article.
Dealing with Exposed Brickwork
If you have areas where the plaster has come off down to the brick, the process is slightly different. Instead of bonding, you’ll use Hardwall. Hardwall is perfect for brickwork because it relies on the suction from the bricks to form a strong bond.
Step 1: Wet the Brickwork
Unlike bonding, do not use PVA to prepare the brick surface. Hardwall needs the suction to work properly. Instead, simply splash some water on the bricks to ensure there’s enough moisture to help the plaster bond.
Step 2: Apply Hardwall
Start with a tight coat of hardwall, pressing it firmly into the brickwork. Use plenty of pressure to ensure the plaster gets a good grip. Once the initial coat is applied, you can begin building up the thickness.
Step 3: Smooth and Level
Just like with bonding, use a derby or straight edge to smooth the surface. Go over the area both vertically and horizontally to ensure it’s as flat as possible.
What’s Next?
Now that your blown plaster and cracks are filled and reinforced, you have two options. You can either patch plaster the area or, for a more professional finish, skim the entire wall. If you’re ready to learn how to plaster, check out our full guide here.
Ready to Enhance Your Plastering Skills?
If your learning how to plaster for the first time then you might be reading this to get some information together for when you finally start plastering for yourself. If you’re looking for some help then the fastest way to learn is by seeing.
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