Iron Ochre: The Toxic Enemy

Given the significant damage iron ochre can cause, it definitely poses a substantial threat. This corrosive iron substance demands particular concern, whether for homeowners already contending with its adverse consequences or for prospective buyers apprehensive about its potential impact. In any case, here's all of the relevant information you need about the tell-tale signs of iron ochre.

What is iron ochre?

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Iron ochre deposits are a result of iron, oxygen, and water in soil. Specifically, the presence and growth of ochre in soil depends on a biological or chemical reaction, or a combination of the two. The chemical process responsible for iron ochre formation occurs as a result of iron naturally existing in the soil, and it rises when mixed with water. Iron hydroxide is created when this mixture is exposed to air.

The biological reaction results in an iron-containing bacterium within the water table. This is known as an iron-oxidizing bacteria. Once this bacterium is exposed to air, the formation of a gelatinous substance occurs through iron oxidation. Note that the combination of the biological reaction and the chemical one will greatly increase the quantity of iron ochre.

Certain conditions will be favourable to iron ochre growth, and these include:

• the presence of a filtered drain;

• a warped drain;

• the presence of sandy soil;

• soil with a neutral pH level, or nearly neutral, and therefore around 7;

• a drain with a punctured tip instead of a clean cut, results in a build-up of iron deposits;

• living in an area with elevated groundwater;

• residing in a flood-risk zone.

What are the consequences of iron bacteria?

The presence of iron ochre (a waste byproduct of iron bacteria) in the soil underneath a home or building will result in many undesirable side effects. Firstly, the presence of iron ochre will compromise your drain and sump pump function, as the substance's deposits will cling to the inner and outer walls of the drain, as well as the pump's water inlet. Furthermore, iron ochre deposits can clog drain openings, which prevents proper drainage following water buildup, heavy rainfall, or melting snow. As a result, water will begin to accumulate around the foundation of your home, as well as under the concrete slab.

Water may seep into the house by way of the foundation walls and will appear as a reddish or brown slime deposit with a sulphur-like smell. It's also worth noting that iron ochre can clog your storm sewer line, as well as the water catchment area.

Another common cause of iron ochre is very high humidity levels in your home. This will be quite obvious by the appearance of mould and condensation on and around your windows and window frames, and moreover, traces of efflorescence at the bottom of concrete walls.

Should you buy a house without first testing for iron ochre?

Before purchasing an existing house, be sure to request a soil analysis to detect the presence of iron ochre. This will help prevent any unpleasantness associated with having to undertake expensive repair work to deal with it. A soil core sample can be obtained and will indicate the current pH level, in terms of ground composition as well as any changes to the groundwater during the course of the year. This test generally costs around $1,000.

If the results test positive, you may be able to negotiate the price of your future house accordingly. Furthermore, the assessment will be helpful in measuring the extent of the clogging, which could pinpoint any maintenance needs or replacement where necessary.

If you decide to sell your property, an assessment is also required. This will give you the upper hand should iron ochre be detected, as you'll avoid any legal action taken against you by the new owners. It's important to remember that the issue isn't so much the presence of iron ochre itself, but rather the damage it may cause to a property or home in the long run.

How to Mitigate or Prevent Iron Ochre

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Naturally, after reading about the consequences of iron ochre, one would instinctively ask, "Is there a prevention method?" Unfortunately, the Régie du bâtiment du Québec confirms that it's impossible to avoid iron ochre growth. However, you can take the necessary steps to mitigate the chances of iron ochre growth.

Raise the concrete slab above groundwater level

The purpose of the assessment above-mentioned isn't to give up on the construction project you’ve already undertaken, but instead, to take the necessary measures to prevent the negative effects caused by iron ochre. Considering the specifics inherent in each iron ochre case, your contractor may choose to raise the slab above the water table before undergoing the construction process. This will help prevent water infiltration as well as complications resulting from drainage obstructions. Again, it's worth noting that it only takes a few years for obstructions to become an actual issue to deal with if appropriate preventative measures aren't taken accordingly.

Change your home's French drain system or intended location

To maximize drainage of the surrounding property as well as limit the build-up of deposits inside your drain, your contractor may decide to change the intended location of your home's drainage system and its openings, as well as their size. Instead, they might install a model that's less likely to cause buildups and that's larger in size, thereby replacing the existing drain.

Also, some contractors may opt to put in a drainage access chimney to easily access the drainage system, thereby allowing for proper maintenance. Furthermore, said French drain connections can be installed to remove iron ochre residue, and thus, prevent further clogging of the drain. Also, the type of granular backfill can be changed during the new drain installation.

Bactericidal and chemical treatments

Another iron ochre decontamination solution is to opt for bactericidal and chemical treatments. These treatments will directly eliminate the Ferro-bacterium present in the soil while simultaneously controlling the soil's pH level. Nevertheless, it's important to remember that this is a costly treatment, and will have to be completed once a year. In addition, the products used during the course of this treatment are harmful to the environment, and, as a result, can directly contaminate the water table.

Waterproof the inside of your foundation

Another measure one can take against iron ochre is to waterproof the inside of the structure's foundation. This option is known for being rather successful. Interior waterproofing helps mitigate high humidity levels on the interior walls of semi- or below-grade level foundation walls due to the use of cement as well as a water-repellent coating. However, like the previously mentioned treatment, this is an expensive endeavour.

Structural work

You can also choose to move up the entire structure of your future home, including the foundation, drainage system and concrete slab. This will keep the structure and drainage system as far away as possible from the property's surface area and limit the risk of flooding.

Install a geotextile membrane

Additionally, the positioning of the geotextile membrane may be adjusted depending on the presence of iron ochre. Moreover, watertight membranes can be installed on foundation walls subsequent to applying a bitumen coating. Note that this type of project doesn’t come cheap; it requires a substantial investment, ranging between $10,000 to $15,000.

Change the slope of the land

Altering the slope of your property could be the key to avoiding any damage due to the presence of iron ochre. It's mainly a question of preventing water from reaching the ground surrounding your home's foundation.

Is iron ochre harmful?

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In the case of a new home, your warranty may exclude damage caused by iron ochre-contaminated soil. This makes it imperative to use the expertise of a professional to detect the presence of iron ochre in the soil. Some homeowners, as well as new buyers, have defended their case in court by arguing that it is inaccurate to consider ferrous ochre (aka iron ochre) a contaminant. This is because you can't do anything about iron ochre-contaminated soil.

However, this is simply one interpretation, as the APCHQ (Quebec's Provincial Home Builder's Association) would argue to the contrary (based on Article 29 of the Regulation.) The Régie du bâtiment du Québec has ruled that this is covered by the Guarantee Plan with new constructions. Furthermore, they let it be understood that it’s not an issue of contaminant, but rather a matter of design.

However, many homeowners have won their court cases, and have had the necessary work done to eliminate hazards as well as the consequences of iron ochre covered by the Guarantee Plan, including lifting or installing waterproof casing around their foundation. The ACQC (Association des consommateurs pour la qualité dans la construction) has also intervened to encourage the amendment of this regulation in support of consumers affected by the presence of iron ochre, deploring the APCHQ’s position on the subject.

However, the decisions regarding this subject may vary based on the evidence submitted. Indeed, you must be able to prove that damage has been suffered. In this regard, the Canadian Commercial Arbitration Centre is explicit that the arbitral jurisprudence typically requires foundations to be built within the water table to classify this type of issue as a major defect.

Some are even challenging the fact that houses can be built on iron ochre-contaminated land, as there is no regulation to prevent this situation. This is an ongoing matter since the regulation has yet been changed.