The main things to know
- A photograph alone cannot tell you whether a building is safe.
- Record where the crack is and when you noticed it.
- Growing cracks, sagging or leaning need prompt attention.
- Find the cause before paying for a cosmetic repair.
Start with what has changed
When did you first notice the crack? Has it grown? Are doors suddenly sticking, floors changing level or pieces of concrete coming away? These details help an engineer understand what needs attention.
If a wall is visibly leaning, a floor or roof is sagging, material is falling or movement is sudden, keep people away from the affected area and seek urgent professional help. Do not wait to collect a long record of changes.
Different cracks can have different causes
Plaster can crack as it dries. Cracks can also appear where different materials meet or where parts of the building move differently. Changes in the ground, leaks, structural damage and corrosion are other possibilities.
A diagonal or stepped crack is a reason to look more closely, not a diagnosis by itself. The engineer needs to consider the building around it, rather than matching the crack to a picture online.
| What you notice | Useful detail |
|---|---|
| A crack in a wall | Does it appear on both sides, or only in the surface finish? |
| A crack near a door or window | Has the opening changed shape or become difficult to use? |
| Cracked concrete or rust stains | Is concrete loose, falling away or exposing steel? |
| Changes after rain or dry weather | When did they happen, and were there leaks or drainage problems? |
Only check what you can see safely. Do not chip away material, climb onto damaged parts or enter areas that may be unstable.
Does the width tell you how serious it is?
Width is useful information, but it cannot establish safety on its own. A narrow crack that is changing quickly may need more attention than a wider one that has been stable for a long time.
Cracks in beams, columns, balconies or other supporting parts deserve particular care. If you are unsure what part of the building you are looking at, ask rather than assuming it is only plaster.
Keep a simple record
- Take a wider photo showing where the crack is in the room.
- Take a closer photo with a ruler beside it, if you can do so safely.
- Write down the date and the location.
- Record related changes, such as sticking doors or a nearby leak.
- Follow the engineer’s advice on whether and how often to repeat the checks.
Monitoring helps with an investigation. It is not a reason to postpone an inspection when there are signs of a problem.
The ground and water may be part of the story
On clay soils, changes between wet and dry conditions can affect the ground. Leaking pipes, overflowing gutters and water collecting beside a wall are useful things to mention.
Also tell the engineer about nearby excavation, an added water tank, removed walls or recent extensions. A change elsewhere in the building or plot may be relevant.
Should you fill it and repaint?
Not before you understand what needs fixing. If the cause is ongoing movement, covering the crack may only hide it for a while. If the damage is limited to a stable surface finish, a simpler repair may be enough.
Ask for a clear explanation of the cause, the recommended repair and whether further checks are needed. If you are buying the property, arrange the assessment before committing to work or assuming the seller’s patch has solved the problem.
Further reading
Questions we get asked
- Are cracks always dangerous?
- No, but you cannot decide from appearance alone. Location, movement and other signs of damage need to be considered.
- How wide is too wide?
- There is no single width that proves a building is safe or unsafe. A growing crack or one in a supporting part needs professional attention.
- Why do cracks change with the seasons?
- Moisture and temperature changes can affect the ground and building materials. An inspection is needed to establish the cause in your home.
- Can I fill the crack and repaint?
- First establish whether the cause needs attention. A cosmetic repair will not resolve continuing movement or structural damage.
- What does a stepped crack mean?
- It follows the joints in the wall and can be associated with movement. It needs to be assessed in the context of the building.
- What will an inspection cost?
- Ask for a quotation that includes the visit, written findings and any further investigation proposed.
Written by
Eng. Samson Gitonga
Civil & Structural Engineer
Samson Gitonga is TimberStone’s civil and structural engineer. Based in Nanyuki, he helps clients understand how the ground, the building plans and the materials come together to create a safe, practical structure.
- Registered Civil & Structural Engineer, Engineers Board of Kenya
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