Reading Wall Cracks and Ground Settlement in a House

Almost every resale house has cracks in its walls. What you need to know is which cracks are only cosmetic and which ones mean the ground under the house is moving.

In Banjarmasin and the lowlands of South Kalimantan, that question matters more, because many houses stand on soft ground, swampland and fill. This guide is for anyone buying a resale house who wants to read the signs before making an offer.

Hairline cracks and structural cracks

Bring a torch and your phone. Cracks are easiest to see when light falls across the wall from the side. If the house was freshly painted for the sale, ask which areas were patched before painting.

A hairline crack is as thin as a pencil line. It runs at random or in a web pattern and stays in the plaster or paint. It is usually caused by plaster shrinking as it dries. Cracks like this generally just need filling and repainting.

Structural cracks are different. Signs to look for:

• Wide enough to slip the edge of a card or a coin into.
• Running right through to the brickwork, or showing on both sides of the wall in the same place.
• A clear direction, diagonal, horizontal or vertical, rather than random.
• In a concrete column or beam, especially with rust stains.
• Coming back after being patched. A crack that keeps returning means the movement hasn’t stopped.

Reading the direction of a crack

The direction of a crack hints at what is going on.

• Diagonal from the corners of doors and windows. The corners of openings are a wall’s weak points. Diagonal cracks there often point to uneven settlement. If the same pattern appears at several openings on one side of the house, that side is probably the one moving.
• Long and horizontal, especially near the ground beam (sloof) or under a beam. This can mean the wall has come away from its base or is being pushed from the side. Get an expert’s opinion.
• Vertical, often where a column meets a wall, or where an older house joins an extension. An extension on a different foundation can settle at a different rate. A gap that is wider at the top or the bottom is a sign of movement.

Check the outside walls as well. A crack that runs right through lets rainwater in and speeds up the damage.

Other signs the ground is moving

Cracks rarely come alone. Look for these as well:

• Sloping floors. Put a marble or small ball down at several points and see which way it rolls. Use a spirit level or a level app on your phone. Builders also use a clear hose filled with water to compare the height of two points far apart.
• Sticking doors and windows, or a gap above a door that is wider on one side. If many doors stick in the same direction, suspect the building is moving rather than swollen timber.
• A gap at the floor line, between the floor and the base of the wall or skirting. This often happens when the walls stand on piles while the floor just rests on fill that keeps sinking.
• Floor tiles cracked in a line, lifting, or sounding hollow when tapped.
• A porch, steps or fence pulling away from the house.
• Leaking pipes where they enter the house.
• Loose ceiling trim, or gaps where the walls meet the ceiling.

Why the ground around Banjarmasin settles

Banjarmasin is low-lying and tidal. Much of South Kalimantan’s lowland is swamp (rawa) and peat (gambut).

Soft ground has a low bearing capacity and compresses under load. Peat also shrinks as it dries, so cracks sometimes grow after a long dry spell. Low land is usually filled to keep it above water, and the fill adds weight on top of that soft layer. If the fill was not compacted, or the soft layer was not removed first, settlement can go on for years.

Settlement becomes a problem when it is uneven. One side of the house sits on thicker fill, or an extension uses a different foundation, and the two parts sink at different rates. How to check the history of filled land is covered in buying filled land.

Common foundations on soft ground

Ask what foundation the house sits on. The right foundation depends on the ground and the load of the building, so no single type is always right. Common ones on soft ground:

• Galam piles (cerucuk galam), galam timber poles driven into soft ground under the footings. Galam lasts well as long as it stays under water.
• Concrete piles, driven deeper toward firmer layers.
• Cakar ayam, a foundation system developed in Indonesia for soft ground: a concrete slab supported by concrete pipes cast beneath it.

Questions for the seller:

• Who built the house, and are there construction drawings?
• Was a uji sondir (a cone penetration test of the soil’s bearing capacity) done before building?
• Does the floor rest on the structure, or only on fill?
• Has the foundation or floor ever been repaired, and when?

Foundation methods for wetlands are covered in more detail in building a flood-resistant house in swampy areas.

Monitoring a crack over time

A crack that has stayed still for years is very different from one that grows every month.

• Mark both ends of the crack in pencil and write the date.
• Measure its width with a crack gauge or an ordinary ruler, and take a photo with the ruler in the frame.
• Stick a thin strip of plaster or paper across the crack. If the strip breaks, the crack is still moving.
• Check again after a few weeks or months, especially after the change between the wet and dry seasons.

Simple records like these also help if you later ask an expert for an opinion.

As a buyer, you rarely have months to wait. Ask the owner when the crack appeared, whether it has been patched and whether it has widened. Ask for old photos if there are any, and ask the neighbours whether their houses show the same thing.

When to call a structural engineer, and how to negotiate

Call a structural engineer or civil engineer if you find:

• Structural cracks, or diagonal cracks at several openings.
• Cracks in concrete columns or beams.
• Clearly sloping floors, or many doors that stick.
• Cracks that return after patching, or suspicious fresh patches.
• A house standing on recent fill.

If the seller already has an engineer’s report or soil test results, ask for a copy. An engineer can judge the cause, recommend a uji sondir if needed, and estimate the repair cost. Repairing a foundation once a house is built is generally complicated and expensive, so that figure matters when you negotiate. Use the report to negotiate the price down, ask the seller to repair first, or walk away.

Other signs of build quality are covered in signs of a well-built house.

If you are looking for a house in Banjarmasin, the homes Vorneo is marketing are on our houses for sale in Banjarmasin page.