A crack in your facade may seem like an easy thing to ignore. A fine line above a window, a handful of spidery marks near a corner. But between the sun, rain and temperature fluctuations exterior walls in Spain are subjected to year round, even small cracks tend to grow.
This guide will cover what causes facade cracks, how you can tell if repairs need to be made or just a few cosmetic cracks sealed, and how to make the most durable repair possible.
Why Do Exterior Walls Crack?
Cracks are a symptom, not a root cause. Understanding what led to the development of a crack is an important step to ensuring an effective repair. Some common causes of cracks in exterior walls, particularly in Spain, include:
Thermal Movement
The climate in Spain can be very hot from May to October, causing walls to expand from the heat, and very cold in other seasons, causing them to contract again. This places a lot of strain on render and paintwork, particularly on facades exposed to the sun all day.
Moisture and Water Ingress
Sun, humidity, and coastal air have a cumulative weathering effect on render coatings and joints. Water entering a crack can cause further expansion, pushing the render away from the wall. In colder parts of Spain, freeze-thaw cycles will have an accelerating effect.
Ageing or Poorly Applied Render
Poor mixing or application or using a formulation unsuitable to the wall type can cause cracks to develop.
Structural Movement and Settlement
Underlying foundation issues or changes in ground level can cause more substantial movement that requires more involved structural reinforcement.
Weak Points Around Openings
Corners of windows and doors are prone to cracks forming in the render or plaster.
Cosmetic or Serious? How to Read a Crack
Before you pick up a trowel, take a careful look.
Hairline Cracks
Fine cracks under a millimetre wide are typically cosmetic, and are often the result of shrinkage during the curing process, though they allow moisture ingress and should be filled or sealed. They tend to be concentrated around areas of high stress like corners.
Map or Spider-Web Cracking
A network of smaller cracks across the wall surface typically indicates some kind of issue with the coating or render, such as incorrect application or age.
Wider or Diagonal Cracks
Cracks that are wider, growing or diagonal may indicate structural movement, as can cracks that follow the edge of mortar joints. The same applies to a crack that is noticeably wider at one end or is visibly out of alignment with one side of the wall, or when one side of the wall feels uneven to the touch.
To confirm whether a crack is structural, mark its ends with a pencil and revisit the mark after a few weeks to see if it has grown. If it has, an exterior wall professional should be contacted to assess the situation if not already done.
Signs You Need an Expert
A professional inspection should be obtained before attempting to repair a crack if:
The crack is wider than a few millimetres or still growing
Doors or windows are sticking or becoming harder to open
Cracks are visible inside the wallspace and align with those outside
Moisture ingress, bulging or hollow feel in the render are apparent
How to Repair Cracked Exterior Walls: Step by Step
For minor cosmetic repairs, the following steps offer a basic guideline. For larger-scale cracks or repairs to a full exterior facing, follow the steps relevant to the product you are using for the repair and follow all instructions provided.
1. Find and Fix the Cause First
Any leak from an adjacent roofline or window that may be contributing to cracks should be resolved first before attempting to repair the cracks themselves.
2. Clean the Area
Use a stiff brush to remove any loose material, algae, dirt or peeling paint from the crack.
3. Open Up the Crack
Cracks less than a millimetre wide may only need to be cleaned, but for larger cracks, use a scraper tool to gently widen the crack to form a shallow V, taking care to not damage the substrate underneath. Remove any dust from the crack after scraping.
4. Choose the Right Filler
Choose an appropriate flexible exterior filler or mortar for the surface you are repairing. For cracks that may flex slightly, a flexible filler will typically offer a more durable repair than a rigid material. Select a product based on the surface type and consult a specialist if unsure.
5. Apply and Smooth
Press the filler into the crack, ensuring that it is fully packed and smooth. For larger cracks, fill in layers, allowing each layer to cure sufficiently before adding the next.
6. Reinforce Where Needed
Once the repair mortar or filler has fully cured, apply an appropriate exterior coating to the repaired area to protect the repair from the elements and ensure it blends in with the existing coating.
7. Finish with a Protective Coating
Once the repair is fully dry, finish with a suitable exterior paint or coating. A good coating seals the surface against water and UV, and helps the repair blend in with the rest of the wall.
Should You Repair or Re-Coat the Whole Facade?
While repairing individual cracks is a good option to restore a single area of damage, when cracks are appearing across the surface it is often an indication the entire facade may need recoating. This is especially true if the wall is suffering from damp, rendering defects, discolouration or peeling of the coating. In these instances it can be more effective to treat the wall as a whole, possibly with an internal base coat. If heat loss is also a concern it is worth considering thermal insulation at the same time, as this can be applied in conjunction with a new coating.
How to Prevent Cracks Coming Back
To avoid future cracks appearing, take care to:
- Regularly inspect your walls once or twice a year and after major weather events such as periods of heavy rain or dry heat
- Keep gutters, drains and downpipes clear to avoid water running down your walls
- Seal any gaps around windows, doors or other openings in your walls
- Repaint, recoat or repair as necessary on a maintenance schedule before surface deterioration sets in
- Use flexible, breathable products appropriate to your wall type in your climate
Need a Hand With Your Facade?
If you’re unsure whether a crack needs to be repaired or are looking for something more substantial than a simple sealant repair, we’re here to help. Discover more about our work and get in touch with the team at Ever-Coat to discuss your project.
Frequently Asked Questions
What causes cracks in exterior walls in Spain?
Common causes of cracks in exterior walls in Spain include thermal movement due to intense sun exposure and wide fluctuations in temperature, moisture ingress, poor application or age of the wall coating or render, and sometimes structural settlement.
Are hairline cracks in my facade serious?
While generally not structurally concerning, hairline cracks do allow moisture ingress and should be sealed to avoid further damage.
How do I know if a crack is structural?
Cracks that are notably wide or diagonal, or that appear to be spreading, or that are accompanied by cracks inside the wall or doors/windows that are becoming harder to open, may indicate a structural issue. It is always best to have a professional inspect a potentially structural crack.
Can I repair a wall crack myself?
Minor structural repairs to surface cracks can be undertaken by most people with the right materials. Repairs that are notably wide or continuing to spread should be left to professionals.
What filler is best for exterior cracks?
An exterior repair mortar or flexible filler that is appropriate to the surface type. For cracks that may flex, a flexible material will typically provide a more durable repair than a rigid material. Choose a product that is appropriate to your surface type or consult a specialist if unsure.