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Don't Panic! Crack Repair Hacks for Your UK Home's External Walls

Updated December 26, 2023
Ugly cracks got you down? Learn to fix them yourself with this UK homeowner's guide. DIY home repairs External wall cracks UK homes Masonry repair Maintenance tips

Cracks in your external walls can be an unsettling sight, conjuring up visions of structural woes and damp problems. But before you start picturing yourself knee-deep in bricks and mortar, take a deep breath. In many cases, repairing cracks in your UK home's exterior walls is a manageable DIY project.

Assessing the Cracks:

First things first, let's assess the situation. Cracks come in all shapes and sizes, and the approach to repair will vary depending on the type and severity. Here's a quick guide:

Hairline cracks:

These thin, barely visible cracks are often nothing to worry about. They're common due to natural settling and minor temperature fluctuations.

Fine cracks:

Cracks up to 1mm wide are still considered minor and can usually be repaired with simple filling compounds.

Wider cracks:

Cracks exceeding 5mm warrant closer attention. These could indicate underlying structural issues and may require professional help.

Essential Tools and Materials:

Before you dive in, gather the necessary tools and materials:

  • Safety gear: Gloves, goggles, and a dust mask are essential for protecting yourself from debris and harmful particles.
  • Cleaning tools: Wire brush, stiff brush, and damp cloth for removing dirt, debris, and loose mortar.
  • Crack preparation tools: Hammer and chisel (for widening stubborn cracks) and a caulk gun (for applying filler).
  • Filling materials: Choose a suitable exterior filler based on the crack width and wall material. Options include masonry caulk, flexible sealant, or epoxy resin.
  • Finishing tools: Trowel or putty knife for smoothing the filler and sandpaper for final touches.

DIY Crack Repair Steps:

Now, let's get down to business! Here's a general guide to repairing cracks in your external walls:

  1. Clean the crack: Thoroughly remove any dirt, debris, and loose mortar from the crack using the wire brush and damp cloth.
  2. Widen the crack (if necessary): For wider cracks (over 5mm), use the hammer and chisel to create a V-shaped groove. This ensures the filler penetrates deep into the crack and adheres properly.
  3. Apply the filler: Choose the appropriate filler based on the crack width and wall material. Follow the manufacturer's instructions for application, typically using a caulk gun for smooth application.
  4. Smooth the surface: Use a trowel or putty knife to smooth the filler flush with the surrounding wall.
  5. Let it dry: Allow the filler to dry completely according to the product instructions.
  6. Paint (optional): Once dry, you can paint over the repaired area to match the existing wall color.

Bonus Tips:

  • Address the root cause: If the cracks are due to underlying issues like foundation movement or faulty guttering, it's crucial to address those problems before attempting repairs.
  • Seek professional help for complex cracks: Don't hesitate to consult a qualified builder or mason for wider cracks, structural concerns, or if you're unsure about the repair process.
  • Prevent future cracks: Regular maintenance like repointing loose mortar and ensuring proper drainage can help prevent future cracks from forming.


Repairing cracks in your external walls is achievable with the right approach and knowledge. By following these steps and using the appropriate materials, you can restore your home's exterior and maintain its structural integrity.

Repairing Cracks in Your UK Home's External Walls: FAQs

Most hairline and fine cracks (up to 1mm) are safe to repair DIY with proper preparation and tools. However, it's crucial to assess the severity before starting. Wider cracks (over 5mm) could indicate structural issues, and seeking professional help from a builder or mason is recommended. Always prioritize safety, and if unsure, consult a qualified expert.

Here's a basic list:

  • Safety gear: Gloves, goggles, dust mask
  • Cleaning tools: Wire brush, stiff brush, damp cloth
  • Crack preparation tools: Hammer and chisel (optional), caulk gun
  • Filling materials: Masonry caulk, flexible sealant, or epoxy resin (choose based on crack width and wall material)
  • Finishing tools: Trowel or putty knife, sandpaper

The best filler depends on the crack width and wall material. For hairline and fine cracks, masonry caulk or flexible sealant is often sufficient. Wider cracks may require stronger options like epoxy resin. Check product instructions for compatibility with your specific wall type.

Repair time varies depending on the crack size and complexity. Simple hairline cracks can be filled in minutes, while wider cracks requiring preparation and drying may take several hours or even days. Always follow the manufacturer's drying instructions for the filler you use.

Once the filler is completely dry, painting over the area to match your existing wall color is optional but recommended for a seamless finish. Choose exterior paint suitable for masonry surfaces.

Regular maintenance is key! Look for and address loose mortar, ensure proper drainage around your house, and avoid excessive pressure on external walls. These proactive steps can help minimize the risk of future cracks.

  • If the cracks are wider than 5mm.
  • If you suspect underlying structural issues like foundation movement.
  • If you're unsure about the cause or severity of the cracks.
  • If you're uncomfortable tackling the repair yourself.


Richard Renderman, your trusted rendering expert at MidRender, is passionate about the art of rendering. With years of experience,he crafts…

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