Sulphation causes concrete to swell and crumble
Sulphation causes the concrete slab itself to swell and crumble. It can produce swelling up to 15 cm. The humidity under the slab tends to creep upward, transporting the sulfuric acid produced by oxidation. When sulfuric acid comes into contact with the bottom of the slab, the concrete swells from sulphation and starts flaking and disintegrating from the bottom. The swelling concrete expands. The foundation walls restrain horizontal expansion; so heaving usually occurs upwards from the centre of the slab, creating large bulges.
Damage to foundation walls
In some cases, the lateral forces of the swelling backfill will produce cracks in the foundation walls around the garage. This does not usually occur in basement walls, since the pyritic backfill is found only at or below the footings.
What areas are affected
Pyritic backfill comes from quarries with rock containing pyrite or from excavations of public works. The majority of properties affected are located in the Montérégie. Cases are also reported in some sites on the island of Montreal and on Île Jésus. Most cases occur in buildings from 8 to 20 years old. A few older buildings (30 - 40 years old) have also been affected. For residential buildings constructed before 1970, the layer of crushed stone is either non-existent or quite thin. This explains why there are very few problems for buildings constructed before 1970.
Pyrite and health
Can the swelling of backfill have harmful effects on the health of the occupants of the house? In the opinion of the Montérégie Public Health Department, the quantities of sulfuric acid are too minute to cause health problems.
Tracking progress of the swelling
Damage attributable to swelling caused by pyrite usually appears 10 or more years after construction. Some swelling may occur sooner if oxidation of the backfill has already started during construction. This may happen if the crushed stone has been exposed to a lot of moisture. Pyritic swelling of backfills will stop when all the sulfur has been oxidized. The speed of reaction will depend on several factors; it takes between ten to forty years to fully oxidize.
Tips to slow the rate of swelling
Reduce ground level humidity
Absence of humidity can slow down the swelling of pyritic backfill. In practical terms, the process of oxidation cannot be totally stopped but oxidation over a long period of time could cause less damage than rapid oxidation. Ground level humidity can be reduced by better surface drainage as follows:
- Provide gutters and extend downspouts to divert water at least six feet from the foundations.
- Make sure that grading slopes away from foundations. The slope should be at least one inch per foot. If the required slope is not possible, drainage ditches, swayles and/or catch basins may be needed.
- When possible, check to make sure the foundation perimeter drain is working well (not clogged or damaged).
Sealing cracks
Cracks allow water and air to reach the backfill and this could speed up any potential reactions. Fill in cracks with a concrete repair product or a flexible polymer sealant.
Solution
If the backfill is still in the process of swelling, the only sure solution to resolve the problem is to:
- Break and remove the slab
- Excavate and the backfill and any contaminated subsoil
- Put down new "DB" certified backfill
- Pour a new slab
The repair should be done by professionals specializing in this type of work. It is the most expensive and disruptive option so is usually considered as last resort.
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Vermiculite Insulation
Vermiculite is a mineral used in many commercial and consumer products including insulation. Vermiculite itself has not been shown to pose health problems. However, some vermiculite insulation can contain asbestos fibres.
Of concern is Zonolite, a product made from vermiculite which was used in many Canadian homes. The vermiculite insulation sold in Canada under the name of Zonolite was extracted from the Libby Mine in Montana, USA. This mine had a natural deposit of asbestos which resulted in the vermiculite being contaminated with asbestos.
Vermiculite produced by the Libby Mine has not been on the market in Canada for more than 10 years. Not all vermiculite sold in Canada before 1990 contains asbestos fibres. However, if you believe that your home may contain vermiculite insulation, it is reasonable to assume that it may be contaminated with asbestos.
Asbestos can cause health problems when inhaled into the lungs. Exposure to asbestos fibres has been associated with asbestosis, mesothelioma and lung cancer.
The best way to minimize asbestos exposure from vermiculite is to avoid removing or disturbing the insulation. The following precautions will prevent releasing asbestos fibres into the air:
- Do not use the attic for storage.
- You and your children should not go to the attic.
- If you plan to renovate, hire a professional trained and certified to handle asbestos.
- You should never attempt to remove the insulation yourself.
- Seal all cracks and holes in the ceilings to prevent insulation to sift through.
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EIFS - Exterior Insulation and Finishing Systems
What are EIFS?
Exterior Insulation and Finish Systems (EIFS) are multi-layered exterior wall systems that are used on both commercial buildings and homes. EIFS were introduced in the U.S. almost 30 years ago and were first used on commercial buildings and then later on homes. EIFS typically consist of an insulation board make of polystyrene foam (which is secured to the exterior wall surface with an adhesive and/or mechanical attachments), a water-resistant base coat applied on top of the insulation and reinforced with fiberglass mesh, and a finish coat typically using acrylic co-polymer technology. This type of system is often referred to as artificial stucco.
The Potential Problem with EIFS...
The potential problem with EIFS is that moisture can get trapped behind the highly water resistant material with no way out. This can cause the framing to rot and foster the growth of mold between the exterior and interior walls. Damp and rotting wood is also a prime target for subterranean termites. It should be stated that the potential for these conditions exist with any type of exterior siding product be it brick veneer, wood, or vinyl siding. The potential for this condition with EIFS however can be exacerbated by its superior water resistance. Once moisture gets in, regardless of its origin, it usually has no escape.
The main locations where water tends to infiltrate into the framing structure of a building using an EIFS is around doors and windows, where the roof connects to the EIFS (roof flashing), and below extended exterior deck connections. Also, any moisture from within the home trying to find a path out will likely be thwarted by the EIFS.
The EIFS industry has been plagued by class action, and individual lawsuits (particularly in humid climates). The public's confidence in the products have been shaken to say the least. The lawsuits contend that the problem is with the nature of the product and the manufacturers contend that sloppy installation and poor maintenance are the culprits.
Regardless of who is "right", its clear that homes with EIFS require special scrutiny during inspection.
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A Couple of Quotes
There is nothing like staying at home for real comfort.
Jane Austen
British novelist and writer, 1775-1817
Age is an issue of mind over matter. If you don't mind, it doesn't matter.
Mark Twain
American humorist, writer and lecturer. 1835-1910 |
