Cracks in walls are a common problem faced by owners of houses, garages and even apartments. They appear due to shrinkage of the building, temperature changes, vibrations or poor-quality building materials. If defects are ignored, they can lead to destruction of plaster, moisture penetration and even a threat to the integrity of the structure. But don’t rush to call the experts: most cracks can be repaired yourself, saving on repairs.
In this article, we will look in detail at how to properly repair a crack in a wall - from analyzing its type to finishing. You will learn which materials are suitable for concrete, brick and plastered surfaces, how to avoid mistakes during repairs and when to sound the alarm. And for owners of garages and workshops, we will provide separate recommendations for working with cracks in unheated rooms.
1. Determine the type of crack: when to repair it yourself and when to call a specialist
Not all cracks are equally dangerous. Before grabbing a spatula, assess the nature of the damage:
- 🔍 Hairline cracks (up to 1 mm) - appear due to shrinkage of the plaster or micro-vibrations. You can fix them yourself using sealant or putties.
- ⚠️ Medium cracks (1–5 mm) - often occur at the joints of plates or due to seasonal deformations. Requires jointing and reinforcement serpyanka.
- 🚨 Wide cracks (more than 5 mm) - a signal of problems with the foundation or supporting structures. Expert judgment is needed here!
- 🔄 Dynamic cracks - if the fault expands over time (checked using
plaster beacons), repairs are pointless without eliminating the cause.
A simple test: place paper tape over the crack and observe for 2-3 weeks. If it breaks, the defect is active, and repairing it is only a temporary solution. Critical for garages and outbuildings through cracksthrough which moisture and cold penetrate. Their repair requires an integrated approach with waterproofing.
⚠️ Attention: If the crack is accompanied distortions of doors/windows, peeling of plaster in layers or crunching in the walls - Contact an engineer immediately! These are signs of the building's emergency condition.
2. Materials and tools: what to choose for different types of walls
There is no universal solution: for concrete, bricks and drywall different compositions are needed. The table below shows the tested materials and their purpose:
| Crack/Surface Type | Recommended Material | Brands/examples | Cost (per unit) |
|---|---|---|---|
| Hairline cracks (up to 1 mm) | Acrylic sealant or finishing putty | Ceresit CT 99, Knauf Fugen | 200–400 ₽/tube |
| Cracks 1–5 mm (concrete, brick) | Cement-sand mixture with plasticizer or repair composition | Bergauf Bau Repair, Perel Repair | 300–600 ₽/25 kg |
| Wide cracks (more than 5 mm) | Epoxy resin + quartz sand or injection compound | SikaTop-107, Emaco S88 | 1,500–3,000 ₽/set |
| Dynamic cracks (with risk of expansion) | Reinforcing tape (serpyanka) + elastic putty | Oscar Reinforcing, Sheetrock | 50–150 ₽/lin. m |
| Cracks in garage/basement (wet conditions) | Waterproofing mixture + penetrating composition | Penetron, Hydrotex-V | 800–2,000 ₽/5 kg |
Tools you will need:
- 🔨 Spatulas (narrow 5–10 cm and wide 20–30 cm)
- 🧹 Stiff brush or sander for cleaning
- 🛠️ Hammer and chisel (for opening deep cracks)
- 🎨 Primer brush
- 📏 Level (to control evenness)
For cracks in the garage, use frost-resistant compounds (from -30°C). Ordinary putty will crumble in winter!
3. Surface preparation: why 80% of success depends on this stage
A common mistake: applying repair compound to an unprepared crack. Without cleaning and priming, the material will not adhere to the base, and the defect will return within a month. Follow the algorithm:
Remove loose plaster and dust with a brush or vacuum cleaner|
Use a chisel to widen the crack to a depth of 5–10 mm (for better adhesion)|
Sand the edges (round off sharp edges)|
Apply a deep penetration primer (eg Ceresit CT 17>)|
For wet areas, use an antiseptic primer
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For For through cracks in a garage or basement, add a waterproofing step:
- Fill the cavity with foam (if the crack is wider than 1 cm).
- Once dry, cut off excess and cover penetrating composition (for example, Penetron).
- For added protection, use
waterproofing membrane(for example, TechnoNIKOL).
⚠️ Attention: Do not use to seal cracks gypsum plaster (type Rotband) in unheated rooms! It absorbs moisture and is destroyed by frost.
4. Sealing technology: step-by-step instructions with photos
Let's consider a universal method for cracks with a width of 1–5 mm (the most common case). To work you will need repair mixture (for example, Bergauf Bau Repair) and serpyanka.
Step 1. Joining the crack
Use a chisel and hammer to widen the crack at a 45° angle. The depth should be at least 5 mm - this will ensure reliable “anchoring” of the mixture. For concrete walls You can use a grinder with a diamond blade.
Step 2: Primer
Apply the primer with a brush, liberally wetting the edges of the crack. For porous surfaces (e.g. aerated concrete) use primer with effect hardening (for example, Knauf Tiefengrund). Let dry for 2-4 hours.
Step 3. Reinforcement
Paste serpyanka (fiberglass mesh) over the crack. It will prevent repeated cracking. For wide cracks (more than 3 mm), use a metal mesh secured with dowels.
Step 4. Filling with mixture
Prepare the repair solution according to the instructions on the package. Apply it with a spatula perpendicular to the crack, pressing deep. Remove excess with a wide spatula, leveling the surface. For vertical cracks convenient to use trowel.
Step 5: Finishing
After drying (24 hours), putty the surface finishing putty (for example, Vetonit LR+). Then sand with sandpaper P120–P150 and cover with paint or wallpaper.
What to do if the crack appears again?
If the crack returns after repair, the reasons may be as follows:
1. Uncorrected shrinkage of the building (relevant for new houses up to 2 years old).
2. No expansion joint at the junctions of materials (for example, brick + concrete).
3. Use of hard materials (for example, cement without plasticizers) for dynamic cracks.
Solution: use elastic sealants (for example, Soudal Fix All) or install deformation tape (for example, Dilatationsband).
5. Features of repairing cracks in the garage and outbuildings
Conditions in unheated rooms impose additional requirements on materials:
- ❄️ Frost resistance: the composition must withstand a minimum
50 freeze/thaw cycles. Look for markings "F50" on the packaging. - 💧 Moisture resistance: For basements and garages with high humidity, use penetrating compounds (for example, Penetron).
- 🔧 Compressive strength: no less
30 MPa(indicated in the characteristics of the mixture). - 🛡️ Resistance to fuels and lubricants: If the wall comes into contact with gasoline or oil, coat it epoxy paint after repair.
For through cracks In the garage, a two-layer system is recommended:
- From the inside: penetrating waterproofing + cement repair composition.
- From the outside: bitumen mastic (for example, TechnoNIKOL No. 24) + reinforcing mesh.
In the garage, cracks wider than 3 mm must be reinforced with metal mesh! Fiberglass (serpyanka) cannot withstand mechanical loads from tools or vehicles.
6. How to prevent cracks from appearing: preventive measures
The best repair is preventing defects. Here's what will help you avoid cracks:
- 🏗️ Expansion joints: in new buildings, leave 1–2 cm gaps between the slabs, filled elastic sealant.
- 🌡️ Humidity control: install in the garage ventilation or desiccant (for example, Silica Gel).
- 🔨 Strengthening the foundation: for old buildings use injection strengthening (compositions based on microcement).
- 🎨 The right finish: for facades use vapor permeable paints (for example, Caparol Amphibolin).
For cinder block garages or foam concrete critical insulation. Temperature changes in winter lead to microcracks. Solution: Sheet the walls expanded polystyrene (5 cm thick) and cover reinforcing plaster.
⚠️ Attention: Do not seal cracks in first year after construction home or garage! The building is shrinking and repairs will be useless. Wait for stabilization (usually 12–18 months).
7. Common mistakes and how to avoid them
Even experienced craftsmen make mistakes. Here TOP-5 errors when repairing cracks:
| Error | Consequences | How to avoid |
|---|---|---|
| Using gypsum plaster for exterior use | Destruction after 1–2 seasons due to moisture | Apply cement or polymer compositions |
| Sealing a crack without jointing | The mixture does not penetrate deep, the crack returns | Expand the crack with a chisel or grinder |
| Ignoring primer | Poor adhesion, material peeling off | Use soil deep penetration |
| Savings on reinforcement | Repeated cracking in the same place | Always use serpyanka or metal mesh |
| Repair at temperatures below +5°C | The mixture does not gain strength | Work in warm weather or use winter supplements |
Another typical problem is incompatibility of materials. For example, you cannot apply gypsum putty on top cement screed without primer: they have different porosities and the layer will fall off. Always check the packaging for compatibility!
FAQ: Answers to frequently asked questions
Is it possible to repair a crack in a wall without putty?
Yes, for hairline cracks (up to 0.5 mm) suitable acrylic sealant (for example, Moment Germent). But for cracks wider than 1 mm, putty is required - the sealant will not provide the required strength. Better to use in the garage polyurethane sealant (for example, Soudal Fix All), as it is vibration resistant.
How long after repair can I paint a wall?
The period depends on the material:
- Gypsum putties: 12–24 hours (totally dry).
- Cement compositions: 48–72 hours (takes longer to gain strength).
- Epoxy resins: 24 hours + sanding.
The humidity in the room should not be higher than 60%. Use in the garage quick drying paints (for example, Tikkurila Tempo).
How to repair a crack in a brick wall if it is through?
Algorithm for through cracks in brick:
- Expand the crack on both sides to a depth of 2–3 cm.
- Clean the cavity from dust and treat antiseptic primer.
- Fill the inside polyurethane foam (for thermal insulation).
- Apply outside and inside cement-sand mortar (1:3) with the addition plasticizer (for example, Ceresit CC 81).
- Reinforce the seam metal staples (hammered into masonry joints) or reinforcing mesh.
For the garage add a layer waterproofing mastic (for example, Bitumast) outside.
What is the difference between repairing cracks in a concrete wall and a brick wall?
Key differences:
| Parameter | concrete wall | Brick wall |
|---|---|---|
| Repair material | Repair compounds based on Portland cement (for example, Emaco) | Cement-sand mortar with lime milk for plasticity |
| Reinforcement | Fiberglass mesh (serpyanka) | Metal mesh or staples |
| Preparation | Mandatory sandblasting to remove weak layer | Cleaning with a stiff brush is sufficient. |
| Drying time | Up to 7 days (due to low porosity) | 2–3 days (brick absorbs moisture faster) |
What cracks in the wall are dangerous for the building structure?
Contact a specialist immediately if you notice:
- 📏 Horizontal cracks in load-bearing walls (a sign of foundation subsidence).
- 🔺 Ladder-shaped cracks along the masonry seams of a brick wall.
- 🚪 Skewed door/window openings (gaps between the box and the wall).
- 💧 Wet cracks with the release of salts (efflorescence) - a signal about the destruction of waterproofing.
The garage is especially dangerous cracks in the gate mounting points - they can lead to the collapse of the structure.