Introduction
Bulging plaster walls are plaster that has pushed outward from the lath or studs. This article explains how to assess the damage, decide on a flatten, replace, or re-key approach, and stay practical on the job. You’ll learn how to inspect the condition, identify loose edges, and plan your repairs before you touch the wall.
We’ll walk through cleaning and preparing the wall surface and then cover flattening, replacing, or re-keying as your options. I’ll list the basic tools and materials you’ll need for each method and remind you to check manufacturer instructions and local rules. Keep expectations clear: fix what’s loose, address the underlying cause, and follow drying or setting times per product instructions.
Key takeaways
- Assess bulge cause by moisture, timing, and underlying framing before choosing method.
- Inspect wall surface, remove loose plaster, and protect floors to avoid damage.
- Re-keying preserves plaster where feasible; flatten or replace if backing is compromised.
- Flattening requires careful tapping, screeding, and feathered edges for seamless patch.
- Full replacement demands removing plaster, lath, and installing a proper backing.
- Wear eye protection, dust mask, and follow local rules during any repair.
Table of Contents
- Introduction
- Key takeaways
- Quick Overview: Diagnose the Bulge and Decide Your Approach
- Tools and Materials Checklist
- Prep Work: Protect, Expose, and Assess Thoroughly
- Re-Keying a Bulging Plaster Wall (Save Method)
- Flattening and Patch Repair Techniques
- Full Replacement: When and How to Remove and Install New Wall
- Finishing Touches: Priming, Painting, and Long-Term Maintenance
- Cost, Time, and DIY Vs Professional Considerations
- Conclusion
- FAQ
Quick Overview: Diagnose the Bulge and Decide Your Approach
A bulge in plaster walls shows up as distortion, cracking, or a raised skin with possible moisture clues. It helps to note where the bulge runs and whether it travels with gaps or hollow sounds behind the surface. Use these signs to narrow down the likely causes and your repair path.
Run a quick check for water leaks, moisture behind the wall, and the overall condition of the lath and plaster. Measure how widespread the bulge is and whether multiple areas are involved. The three repair paths are flatten, re-key, or replace, chosen by the wall’s integrity and moisture history.
Visual and tactile signs of a bulging plaster wall
First off, don’t just poke at the wall. You’ll do more harm than good. Instead, inspect carefully for these telltale signs:
Cracks are your first clue. They might be hairline or wide, diagonal or horizontal. Check if they’re dry and stable, or wet and worsening. Wet cracks usually mean moisture issues.
Next, look for haloing – a damp ring around the bulge. This could be due to plumbing leaks behind the wall. Also, check if the bulge is sagging or protruding. Sagging often indicates structural issues.
Now, grab a screwdriver and gently tap the wall. A hollow sound means there’s likely a void behind the plaster. If it sounds solid but feels soft, that’s a sign of moisture damage. Always be gentle to avoid making problems worse.
Decision framework: flatten vs replace vs re-key
Before you grab your tools, take a step back and consider these factors:
Bulge size: If it’s small (less than 1″ or 25mm), you might get away with flattening. Larger bulges need more serious attention.
Plaster thickness: Check the thickness at the bulge and elsewhere on the wall. If it varies greatly, replacing might be best.
Lathe condition: Feel for any give or movement in the lathe (the wooden strips behind the plaster). If it’s soft or wobbly, replacement is likely needed.
Underlying cause: Check for moisture, cracks, or other signs of structural issues. If you find any, don’t DIY – call a pro.
Budget: Flattening is cheapest, but it might not last. Re-keying and replacing cost more, but they fix the problem properly.
Now, let’s talk about your options:
Flattening: This just hides the bulge, like putting a band-aid on a broken leg. It’s quick and cheap, but it won’t last if the cause isn’t fixed.
Re-keying: This involves removing the damaged plaster, fixing the lathe, and applying new plaster. It’s more work, but it lasts longer than flattening.
Replacing: If the bulge is big or the lathe is shot, you might need to replace the whole wall. It’s the most expensive option, but sometimes it’s necessary.
Safety and permit considerations
Before you start tinkering with that bulging plaster wall, stop and think about safety. You’re dealing with old materials here, so expect the unexpected.
Lead dust is a real risk in older homes. If your home was built before 1978, assume it’s there until you’ve tested for it. Wear a respirator rated for lead, not just dust. Check product labels and follow manufacturer instructions to ensure you’re protected.
Plaster dust can be nasty too. Wear a proper dust mask, not just any old thing from the hardware store. And protect your eyes with safety glasses or goggles. You don’t want that stuff getting in ’em.
Falling plaster? Yeah, it happens. Clear the area before you start work. No need to have a mini avalanche on your hands. If the bulge is big, consider shoring up the wall temporarily until you can get to work.
Now, permits. You might need ’em, you might not. It depends on where you live and what you’re planning to do. Check with your local building department. They’ll tell you what’s required. Better safe than sorry when it comes to the law.
Tools and Materials Checklist
Here you’ll map tools to the three repair paths and note budget options. Core items cover trowels, knives, a level, and a straightedge, plus safety gear. Keep a drill with a paddle mixer and a grinder or multi-tool handy for tougher jobs.
Stock materials by budget tier: basic patching compounds, mid-range plasters, or premium patch systems. Also include bonding agents, mesh or lath, and finish coatings compatible with your wall type. Prep and clean-up supplies finish the list for a smooth job.
Tools for assessment and removal
Before you start any repair, use these tools to assess the damage and prepare for safe removal.
- Hammer: Tap gently to check wall stability. Hollow sounds indicate potential structural issues.
- Screwdriver: Gently probe for loose plaster or lath.
- Moisture meter: Check for excess moisture, which could cause further damage if not addressed.
- Dust mask and goggles: Protect yourself from dust during removal.
- Plastic sheets: Contain dust and protect floors and furniture.
- Utility knife: Carefully cut away loose plaster for easy removal.
- Demolition hammer (optional): For stubborn areas, use a demolition hammer with a chisel attachment. Be careful not to damage lath.
- Trash bags: Have plenty on hand for easy disposal of removed plaster.
Quick rule: Always prioritize safety first. Wear appropriate PPE and contain dust to minimize cleanup.
Materials for re-keying and patching
When re-keying or patching, use these materials to ensure a strong bond with existing plaster.
- Plaster keys/anchors: Choose compatible keys that match your existing plaster. Incompatible keys can cause future issues.
- Bonding agent: Apply a bonding agent to improve adhesion between new and old plaster.
- Plaster mix: Select a mix that matches your existing plaster’s composition for seamless blending.
- Base coat: Apply a base coat to provide a solid foundation for your patch.
- Fasteners (if needed): Use appropriate fasteners or screws if reinforcing lath is necessary. Ensure they’re compatible with your wall system.
- Putty knife: Use various sizes for applying and smoothing plaster.
- Trowel: For larger patches, use a trowel to apply and smooth plaster.
- Hawk: Hold plaster mix while working with a trowel.
Quick rule: Always match new materials to existing ones as closely as possible for best results.
Materials for replacement or skim-coating
When replacing or skim-coating, use these materials for a smooth, professional finish.
- Lath options: Choose between metal lath, wood lath, or gypsum board for backing. Each has its pros and cons, so choose based on your wall’s needs.
- Joint compound: Use a high-quality joint compound for filling seams and creating a smooth surface.
- Mesh tape: Reinforce joints with mesh tape to prevent cracking.
- Finishing plaster: Select a plaster that provides the desired finish, whether it’s smooth or textured.
- Screws (if using gypsum board): Use appropriate screws for attaching gypsum board. Ensure they’re long enough to penetrate into studs but not so long they protrude through the wall.
- Level and straightedge: Use these tools to ensure a smooth, even application of plaster.
- Sandpaper or sanding block: Lightly sand between coats for a smooth finish. Be careful not to sand too aggressively, which can damage the surface.
Quick rule: Always follow manufacturer instructions for best results and safety.
Prep Work: Protect, Expose, and Assess Thoroughly
Clearly define the scope by identifying the bulge source and what exposure might reveal in the backing. Decide if you’ll re-key, patch, or replace based on what you find behind the surface. Keep the goal to preserve structure while easing access for inspection.
Set up dust containment, protect floors and furniture, and isolate the area. Prepare for exposure by planning careful scoring and removal of loose plaster. Inspect lath, backing, and moisture signs to guide your next move.
Containment, PPE, and Dust Control
Protect your space and yourself before starting any work. Seal doors and vents with plastic sheeting to contain dust. Use negative air machines if possible.
Wear appropriate PPE: gloves for handling materials, goggles to protect eyes from debris, a mask or respirator for breathing protection, and hearing protection when using power tools.
When sanding or vacuuming, keep the area wet to minimize airborne dust. Always use HEPA filters in your vacuums to trap fine particles.
How to Safely Open and Evaluate the Damaged Area
Start by creating a small test hole, about 1-2 inches in diameter, using a utility knife or drill. This helps locate any hidden issues like wires or pipes.
Carefully remove loose plaster around the bulge using a putty knife or trowel. Be gentle to avoid damaging lath or backing further.
Inspect the exposed area: check for rot, corrosion, or water damage on lath and backing. Locate studs by tapping the wall – they sound solid when knocked. Mark their locations with a pencil.
If you find mold, stop work immediately and consult a professional. Mold can be harmful to your health.
Estimating Scope and Time
Measure the bulge area to determine how much material you’ll need for repair. For re-keying, estimate based on square footage. For replacement, add extra for waste during cutting.
Repair time varies depending on method:
- Re-Keying: 1-2 days (including drying time)
- Replacement: 3-5 days (including drying and sanding time)
Prepare a materials list based on your estimates. Include plaster, lath if needed, mesh, screws, tape, sandpaper, and any necessary safety gear.
Re-Keying a Bulging Plaster Wall (Save Method)
Re-keying is mostly for loose plaster with solid backing and no active moisture. It’s not for large detachment or damp conditions. Use this method when a quick bond restoration can hold without full replacement.
Check the substrate for soundness and moisture before starting. Gather plaster keys or anchors, adhesive or plaster cement, and basic tools to create shallow keyways and secure the plaster in place. Allow proper curing and monitor for movement after reattachment.
When re-keying works best
Re-keying is most effective on small, localized bulges. Here’s when it works:
Small bulge size: The bulge should be less than 1-2 inches in depth and width.
Intact plaster surface: If the plaster surface is still intact with no large cracks or holes, re-keying can help restore its bond.
Solid backing: Re-keying works best when the lath behind the plaster is solid and not damaged. It needs to provide a good base for the keys to grip onto.
Re-keying procedure
Here’s how to re-key your bulging plaster wall:
Drill: Using a masonry drill, create shallow keyways (about 1/4 inch deep) at regular intervals (every 6-8 inches) across the bulge.
Insert keys/anchors: Tap in plaster keys or anchors into these keyways using a hammer and chisel. Make sure they’re secure but not too tight.
Apply adhesive: Apply a bonding agent or plaster cement to the back of the loosened plaster and onto the keys/anchors. This helps create a strong bond.
Reattach and cure: Press the loosened plaster firmly back into place, ensuring it’s flush with the surrounding wall. Let it cure for at least 24 hours before touching or painting.
Finishing after re-keying
After re-keying, you’ll need to finish the area to blend it seamlessly with the rest of the wall:
Fill and level: Use a putty knife to apply joint compound or spackling to any gaps. Level it off with the surrounding plaster.
Sand: Once dry, sand the area smooth using fine-grit sandpaper. Be careful not to sand too hard and damage the plaster.
Prime and paint: Apply a primer to seal the repaired area and help paint adhere better. Then, paint the wall to match the surrounding color.
Flattening and Patch Repair Techniques
Flattening focuses on minor bulges and cracks with partial removal and stabilized patching. Decide if a skim coat will level the face after securing the patch. Keep layers thin to blend with the surrounding wall.
Detail the prep steps: remove loose material, apply bonding agents, and back-butter patches for solid adhesion. Use feathering to blend edges and skim coat for a uniform finish after curing.
Partial removal and re-backing
Start by removing loose plaster using a scraper or chisel, extending about an inch beyond the bulge to ensure you’ve reached solid material. Be careful not to damage the lath underneath.
Once you’ve exposed sound plaster, clean the area with a damp cloth to remove dust. Inspect the lath for any damage and repair as needed.
Apply a bonding agent or scratch coat to both the removed patch face and the surrounding wall. This ensures a strong bond between the new patch and the existing plaster.
Skim-coating and feathering techniques
Mix your skim coat plaster to a smooth, creamy consistency. Using a wide trowel, apply the first thin layer evenly across the patched area, working it into the edges.
Allow this initial layer to dry according to the manufacturer’s instructions, usually around 24 hours. Lightly sand any high spots with fine-grit sandpaper.
For subsequent layers, use a damp sponge or trowel to feather the edges of your patch, blending it smoothly into the surrounding wall. This ensures an invisible repair.
Common mistakes and how to avoid them
Even with careful planning, DIY plaster repairs can go awry. Here are some common pitfalls and tips on how to avoid them.
- Over-sanding: Be gentle when sanding between coats. Over-sanding can remove too much material, weakening the patch.
- Improper bonding: Always use a bonding agent or primer before applying new plaster. Skipping this step can lead to delamination.
- Skipping key prep: Thoroughly clean and prepare the surface before applying any new material. Dust and debris can compromise adhesion.
- Rushing drying times: Allow each layer to dry as recommended. Rushing this process can result in weak, crumbly patches.
By being aware of these common mistakes and taking the time to prepare properly, you’ll increase your chances of a successful repair.
Full Replacement: When and How to Remove and Install New Wall
Full replacement is considered for extensive damage, rotten lath, or repeated failures with moisture history. It’s a bigger job that changes how the wall finishes and performs long-term. Compare whether plaster on lath or drywall over studs is more suitable for your space.
Plan demolition with containment and dust control, then address framing or studs, moisture barriers, and the chosen substrate. Follow with proper finishing and curing to avoid recurring issues and ensure a solid surface afterward.
Safe Demolition and Disposal
Before you start, ensure everyone’s safety. Wear a respirator, gloves, and goggles.
Check for asbestos. If your home was built before 1980, test for asbestos in the plaster. If present, hire professionals to remove it.
Contain dust with plastic sheets around the work area. Wet down surfaces to minimize dust. Turn off power at the main panel before removing electrical covers.
Installing New Lath and Scratch Coat vs Drywall
For traditional plaster, install new wood lath on existing studs or replace damaged ones. Space them 1/8″ apart.
Apply a scratch coat, letting it dry before applying the final layer. This method provides excellent soundproofing and durability but is labor-intensive.
For drywall, install furring strips on existing studs if needed for spacing. Attach gypsum board with screws or nails, following manufacturer’s instructions. Drywall offers quick installation, easy finishing, and lower cost but less soundproofing.
Seam Finishing and Texture Matching
After installing the new substrate, tape seams with joint tape and drywall mud. Let it dry, then apply a second coat.
Sand lightly to remove excess mud and create a smooth surface. For textured walls, use a texture sprayer or hawk and trowel to match the existing finish. Practice on scrap pieces first.
Prime the entire wall before painting to seal it and provide a uniform base for paint. Always follow manufacturer’s instructions for best results.
Finishing Touches: Priming, Painting, and Long-Term Maintenance
Choose primers based on substrate and previous bulge causes, and verify the area is fully cured before painting. Use breathable primers for plaster or sealed primers for patched drywall as needed. Check moisture history to guide the product choice.
Match topcoat to the wall type and expected wear, then consider mold resistance and washability in damp spaces. Plan a long-term maintenance and inspection routine to catch issues early and avoid re bulging.
Primer and Paint Recommendations
After repairing your bulging plaster wall, it’s crucial to prime and paint the area properly for a durable finish. Here are some recommendations:
Plaster Walls: Use a breathable primer like PVA or acrylic primer to allow moisture to escape. For repaired zones, apply a stain-blocking or shellac-based primer before painting.
Drywall: If you’ve replaced the bulging section with drywall, use a non-breathable sealant primer to prevent moisture from entering and causing future issues. Always match your topcoat to the existing wall finish – latex/acrylic for most cases.
For high-humidity areas or past leaks, consider using a moisture-blocking primer like Zinsser’s B-I-N to prevent mold growth and further damage.
Monitoring and Maintenance Plan
Regular monitoring and maintenance are key to preventing re-bulging. Here’s a simple plan:
Monthly Checks: Inspect the repaired area for any signs of recurrence, such as hairline cracks or separation.
Quarterly Moisture Checks: Test for moisture using a moisture meter to ensure no hidden issues are developing. If high humidity is an issue, consider using dehumidifiers or improving ventilation.
Annual Re-inspection: After heavy rain or snow melt, re-inspect the area for any signs of water intrusion or damage. Address minor issues promptly to prevent them from becoming major problems.
Small Repairs and Touch-ups Over Time
Hairline cracks or minor separations can occur over time. Addressing these promptly prevents larger failures:
For hairline cracks, use a paintable caulk or spackling compound to fill the gap, then sand and prime before painting.
If you notice minor separation, re-secure the loose area with drywall screws or plaster anchors. Fill any gaps with joint compound, let it dry, sand, prime, and paint.
Regular touch-ups will keep your wall looking great and prevent bigger problems down the road.
Cost, Time, and DIY Vs Professional Considerations
Outline typical project timelines by scope, including prep, curing, and finish. Consider how long each stage should take and what potential delays may arise. Use these guides to align expectations with your plan.
Break down costs by materials, labor, tools, and possible rentals. Weigh when a professional makes sense, especially for structural concerns, persistent moisture, or hidden framing issues. Have a contractor ask list ready for clarity on scope and guarantees.
Cost drivers and budgeting tips
Plaster repair costs vary widely depending on the scope of work. Here’s what drives your budget:
Materials: Expect to spend $20-$50 per sq ft on materials like plaster/patch mix, mesh, bonding agents, and tools. National average for equipment rental is around $100/day.
Labor: Pros charge $30-$80 per sq ft, with complexity adding to the cost. Add 15-25% for disposal fees.
Tip: Get at least three estimates from reputable pros and ask about discounts for larger jobs or multiple rooms.
When to hire a plaster specialist or structural pro
DIY is great, but know when it’s time to call in the pros:
Red flags: Large bulges, cracks at corners or ceilings, or signs of water damage may indicate structural issues. If you notice any, stop work and consult a pro immediately.
Check credentials: Ensure they’re licensed, insured, and have experience with your specific issue. Ask for references and check online reviews.
Tip: For serious problems, consider hiring an engineer or structural specialist to assess the damage before starting any repairs.
Timeline examples for each repair type
Here are rough timelines for common plaster wall repairs:
Re-keying (small patch): Assessment (1 hr), prep (2-4 hrs), repair (2-6 hrs), finish (1-3 hrs). Total: 6-14 hrs. Drying time: 24-72 hrs.
Flattening (medium patch): Assessment (1 hr), prep (4-8 hrs), repair (6-12 hrs), finish (3-6 hrs). Total: 14-27 hrs. Drying time: 48-96 hrs.
Full replacement: Assessment (1 hr), demo (2-6 hrs), prep (4-8 hrs), install lath/scratch coat (6-12 hrs), skim-coat (3-6 hrs). Total: 20-33 hrs. Drying time: 72-168 hrs.
Conclusion
Fixing a bulging plaster wall is about safety, durability, and a clean finish you can trust. Start with a clear plan, control the moisture, and choose the approach that will hold up over time.
First, assess the bulge for moisture and structural clues, protect what you can, expose the area, and decide whether re-keying, patching, or full replacement is the right path. Gather the needed tools and materials, test any repair on a small area, and work in controlled stages, finishing with priming and paint for a lasting seal.
Common mistakes to avoid include skipping a moisture check or failing to address the underlying cause, attempting repairs without proper support or backing, and rushing patches or finishes that crack or peel. Follow simple safety rules: wear eye protection and a mask, keep the work area dry and well ventilated, and test a patch in a hidden spot before you commit to the whole wall.
If you uncover structural issues, extensive rot, or uncertain framing, it makes sense to call a professional rather than push through. Stay methodical, stay patient, and you’ll end up with a wall that looks solid and stays that way. You’ve got this—get to it and finish strong.
FAQ
How do I evaluate the condition of a bulging plaster wall?
Look for moisture signs, soft spots, and old crack patterns. Tap the surface lightly to hear hollow or crumbling areas. If the bulge changes with weather or drywall behind shows, plan a careful repair approach.
What’s the right way to clean and prep the wall surface before repairing?
Remove loose plaster and dust with a stiff brush or vacuum. Wipe down greasy or damp areas and let the wall dry completely before you start repairs. Use a sealer or primer if the surface is dusty or porous, following the product label.
How should I choose between flattening, re-keying, or full replacement?
Flattening and re-keying work best for localized bulges with solid back-up. Full replacement is needed if the plaster is severely cracked, water-damaged, or losing adhesion to lath or studs. Check the extent of damage, the underlying structure, and follow manufacturer or local guidance for the safest choice.
What tools and safety steps should I follow for these methods?
Use appropriate hand tools for scraping, troweling, and patching, plus eye protection and a mask when dust is present. Protect adjacent areas with plastic and drop cloths, and work calmly to avoid destabilizing the wall. Always check product labels and local guidelines for any special prep or sequencing requirements.