Balcony Cracks: Types and How to Seal Them?

Written By Adam Paul - Waterproofing Expert

Balcony cracks are mainly 4 types such as hairline cracks, nonstructural cracks, structural cracks, and expansion joint cracks. Balcony cracks occur due to these reasons such as improper balcony waterproofing, decreased material strength, uneven load distribution, lack of expansion joints, poor drainage system, structural movements, and improper balcony construction.

A cracked balcony allow water to seep into it. This causes so many negative impacts and water damages the balcony structure over time. In order to prevent these problems, the balcony cracks should be sealed properly. As waterproofing experts, Aqviz, we highly recommend you waterproof your balcony during the construction or once you see this type of behavior at the beginning.

What is Balcony Crack?

A balcony crack is a visible or hidden fracture in the concrete, tiles, or surface layers of a balcony. Balcony cracks weaken the balcony structure. As well as balcony cracks allow water to seep into the balcony, which increases the mold and mildew growth, paint peeling, blistering, corrosion, and material deterioration, and increases the safety hazard over time. Balcony cracks can occur due to improper balcony waterproofing, decreasing material strength, uneven load distribution, no expansion joints, poor drainage systems, structural movements, and improper balcony construction.

What are the 4 Types of Balcony Cracks?

Aqviz’s expert team has investigated that balcony cracks are of four types according to their width and shape. Here are the balcony crack types and their width:

Hairline cracks (Less than 1 mm): Hairline cracks are thin surface cracks caused by shrinkage, minor temperature changes, or aging of materials.
Nonstructural cracks (1 mm to 5 mm): Nonstructural cracks appear due to thermal expansion, moisture absorption, or slight foundation shifts but do not affect the structural integrity.
Structural cracks (More than 5 mm): Structural cracks are deep and wide cracks that extend through the slab, usually caused by heavy loads, foundation movement, or construction defects.
Expansion joint cracks (Varies, usually 2 mm to 10 mm): Expansion joint cracks can be found along expansion joints, these cracks result from temperature fluctuations and material movement, requiring flexible sea

If you don’t consider this, even small cracks can worsen and lead to water infiltration into the balcony structure. Need help with sealing your balcony cracks? Aqviz can guide you with the best waterproofing solutions!

What are the Reasons for Balcony Cracks?

Balcony cracks occur due to several factors, often linked to structural stress, environmental conditions, and poor construction practices. Here are seven main reasons for crack formation in the balcony.

Improper balcony waterproofing: Lack of a proper waterproofing membrane in the balcony allows water to seep into the concrete, weakening it over time and leading to cracks.
Decreased material strength in the balcony: Poor-quality concrete, weak reinforcement, or improper curing reduces the balcony’s durability. These materials cause cracks in the balcony.
Uneven load distribution in the balcony: Placing heavy furniture, planters, or excessive weight on certain areas of the balcony creates stress points that result in cracks.
Lack of expansion joints in the balcony: Without proper expansion joints in the balcony, temperature changes cause the concrete to expand and contract, leading to uncontrolled cracking.
Poor drainage system in the balcony: Poor drainage system can clog drains and keep the surface damp. This causes concrete deterioration and eventual cracking over time.
Structural movement in balcony structure: Building settlements, foundation shifts, or seismic activity cause stress on the balcony.
Improper balcony construction: Weak concrete mix, poor reinforcement, or bad workmanship create vulnerabilities in the balcony.

Regular inspections, proper waterproofing, and quality construction materials can prevent balcony cracks. Aqviz recommends using flexible sealants, epoxy injections, and liquid waterproofing membranes for long-term protection. Want to know the best repair solutions? Read this guide: 6 Types of Waterproof Membranes for Balcony with Essential Features

How to Repair Balcony Cracks in 7 Steps?

At first you should inspect the balcony crack area: Assess the size, depth, and cause of the crack. If it’s a structural crack (wider than 5mm), consult an engineer before proceeding.

Tools and products for balcony crack sealing

Wire brush, vacuum, or pressure washer
Chisel & putty knife
Polyurethane sealant or epoxy injection
Suitable waterproofing membrane
Protective gloves & safety goggles

6 Steps to Seal Balcony Cracks

Clean balcony crack area: Remove dust, debris, and loose particles using a wire brush, vacuum, or pressure washer. A clean surface ensures better adhesion for sealants and fillers.
Widen cracks if needed: For hairline cracks, slightly open them with a chisel to create a V-groove. This allows fillers to penetrate deeply and bond properly.
Apply fillers in the balcony crack: Use a polyurethane sealant for flexible cracks or an epoxy injection for deep structural cracks. For tile cracks, use epoxy grout to prevent water seepage.
Level the sealed crack surface: Smooth out the filler or sealant with a putty knife. Allow it to cure as per the product’s instructions (typically 24-48 hours).
Waterproof the balcony: Once the crack is sealed, apply a liquid waterproofing membrane, cementitious coating, or elastomeric paint to prevent future water penetration.
Inspect the balcony area for further cracks: Regularly inspect the area for new cracks, water pooling, or signs of weakness. Maintain a proper drainage slope in the balcony to avoid standing water.

Aqviz experts have prepared a guide for balcony waterproofing from start to finish. You should read the guide “How to Waterproof Balcony”

We highly recommend you to follow these environmental conditions.

Perform repairs in dry weather for best adhesion.
Avoid working in extreme heat, as fillers may dry too quickly.
Ensure proper ventilation when using chemical-based products.

What are the Negative Impacts of Balcony Cracks?

At Aqviz, we have seen how minor cracks turn into costly repairs over time. Here are six negative impacts of balcony cracks and how they affect your balcony if you do not fix it at the starting stages.

Water seepage in the balcony: Cracks allow water to penetrate the balcony concrete structure. It leads to rusting of reinforcement bars and gradual structural deterioration.
Mold & mildew growth in the balcony: Moisture trapped in cracks promotes fungal growth. It causes to unpleasant odors and potential respiratory issues.
Balcony tile surface damage: Water infiltration weakens tile adhesives and it leads to loose, cracked, or discolored tiles that ruin the balcony’s look.
Weaken the balcony structure: Deep cracks compromise the strength of the slab. It makes the balcony unsafe to hold heavy furniture, planters, or multiple people.
Increase safety hazard: Large balcony cracks create uneven surfaces, which can cause tripping hazards, especially for children and elderly individuals.

What Balcony types are Mostly Cracked?

At Aqviz, we have repaired cracks in various types of balconies and noticed that some balcony designs are more prone to cracking due to their structure, material, and exposure to environmental factors. Here are the balcony types that mostly crack and why?

Concrete slab balconies: Solid concrete balconies expand and contract with temperature changes, leading to surface and structural cracks over time.
Cantilevered balconies: These balconies extend outward without vertical support underneath, making them more vulnerable to bending stress and cracks due to load-bearing pressure.
Tiled balconies: Balconies with ceramic or porcelain tiles often develop cracks due to tile expansion, grout deterioration, and improper waterproofing, allowing water to seep in.