Iron ochre in your home

Updated March 23, 2023

Do you see orange patches on your front lawn? Does part of your basement floor look like it’s rusting? Is there an accumulation of a slimy, orange-coloured sludge in the rainwater catch basin? Do you detect an odour similar to rotten eggs?

If you answered yes to all or any of these questions, you may have iron ochre on your property. Read on to find out what iron ochre is, how to prevent it, how to protect your home, and how it could impact your home insurance.

Large house with iron ochre deposits visible along foundation

What is iron ochre?

Iron ochre, or ferrous ochre, is a sludge- or gel-like substance that results from the presence of iron, oxygen, and water in the soil. Iron ochre can form from a chemical or a biological process, or a combination of both.

The chemical reaction occurs when iron in the soil migrates along with water towards the drainage system of the home. When this mixture comes into contact with the atmosphere, it forms iron hydroxide, a sludge-like substance.

Biologically, iron ochre forms when iron bacterium or Ferra-bacteria within the water table comes into contact with the atmosphere. The resulting oxidization of the iron creates a gelatinous, orange-coloured substance.

What conditions favour iron ochre?

Certain conditions favour the formation of iron ochre:

  • Neutral soil (pH of approximately 7)
  • A drain with a corrugated wall, which allows iron deposits to accumulate
  • A drain wrapped in a filtering membrane
  • A warped drain
  • Sandy, aerated soil with silt
  • A drain with a tip that has been punched rather than cut, which allows iron deposits to accumulate
  • A high water table
  • A region with a substantial risk of flooding

How can I tell if I have iron ochre on my property?

The tell-tale sign of iron ochre is its orange colour. You may see patches of orange on your front lawn, in your French drain, or on the basement floor and walls. A sulphur-like smell, like rotten eggs, can also indicate the presence of iron ochre.

The presence of iron ochre can also create very high humidity in your home. This will be visible by the appearance of condensation on the windows, or even mould.

What are the consequences of iron ochre?

Iron ochre can lead to water damage to your home, due to several issues it causes:

  • It causes ochre-colored slimy sludge deposits to accumulate in the rainwater catch basin and in ditches.
  • It obstructs backflow valves.
  • Iron ochre deposits cling to the inner and outer walls of the French drain, which prevents proper drainage. As a result, water accumulates around the foundation of the home, as well as under the concrete slab.
  • Iron ochre blocks storm sewer lines and water catchment area.

Health-wise, iron ochre itself is not fatal. However, if it does come into contact with your skin, you will need to wash the affected area with soap and water.

Remember, too, that iron ochre can lead to the formation of mould, which can cause health problems.

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How to prevent iron ochre and protect your home

Since iron ochre forms naturally from the presence of iron and water in the soil, it is impossible to prevent the chemical reactions that lead to its formation.

That said, there are some steps you can take to protect your home from iron ochre:

  • Changing the grade of your property
  • Sealing any gaps between concrete walls and the foundation
  • Installing vertical cleaning conduits
  • Installing waterproof coating
  • Installing a waterproof membrane on the foundation
  • Raising the basement slab and draining everything beneath it
  • Installing and cleaning drainage chimneys in your French drain

The University of Michigan State recommends a number of measures to mitigate iron ochre, such as increasing soil aeration, using the right kind of pipes, and eliminating the oxygen supply.

As mentioned earlier, iron migrates with water towards the home’s drainage system. Aerating the soil prevents iron from becoming soluble and travelling towards the drain.

Pipes with larger circular perforations (0.5 to 1.3 cm) will take longer to get blocked up. Pipes with slotted perforations allow iron ochre to bridge the narrower width much faster and thus clog the pipes.

Since the combination of iron, water, and oxygen forms iron ochre, eliminating or reducing the supply of oxygen will help prevent the substance from forming. The installation of deeper drain pipes (1.2 to 1.5 m) lowers the risk of iron ochre formation since the pipes are farther away from the air.

Home insurance considerations

If a home sustains damage from iron ochre, insurance coverage will depend on the circumstances.

Much of the potential damage iron ochre causes is gradual, taking place over a long period of time—this type of damage is generally not covered by home insurance. For example, damage from gradual groundwater infiltration, which can happen after iron ochre plugs up a French drain system, would not be covered.

However, if an iron ochre buildup causes (for example) a blocked wastewater pipe in the basement to suddenly back up or burst, the resulting water damage may be covered.

The important aspect to retain is the notion of suddenness.

If iron ochre spills into the basement after a sudden pipe burst, the resulting property damage may be covered. On the other hand, damage caused by iron ochre sludge slowly oozing into the basement or into the walls over a long period of time would not be covered, because the homeowner neglected to address it.

Commonly asked questions

Is iron ochre a hidden defect?

A hidden defect is any problem that is serious, hidden, exists at the time of sale, and is unknown to the buyer at the time of the transaction. Depending on the situation, the presence of iron ochre can be considered a hidden defect that is the seller’s responsibility.

For example, if the seller did not disclose that there were iron ochre deposits in the French drain, this would be considered a hidden defect.

However, if iron ochre were to form after the sale of the property, it would not be considered a hidden defect, as it was a problem that did not exist at the time of sale. Equally, if the buyer could see patches of orange-coloured iron ochre on the front lawn when they visited the property, the presence of iron ochre would not be considered a hidden defect.

Can iron ochre be eliminated?

No. Iron is a naturally occurring substance in the soil that mixes with water and air, so eliminating iron ochre altogether is not feasible.

Besides seeing visual evidence of deposits, is there any other way to detect the presence of iron ochre?

An iron ochre analysis performed by a professional can detect the presence of iron ochre.

Typically, a sample of water is taken from inside the drainage system or from shallow groundwater and analyzed for Ph level, bacterial activity, and the amount of iron. An iron indicator test strip is used to measure the concentration of ferrous iron in mg/L. A reading of below 1 is considered negligible, 1-5 is low, 5-10 is moderate, 10-25 is high and anything above 25 is very high.

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