Peat bogs and soft soils: what Vancouver buyers and sellers should know

Long before Vancouver had streets, parts of it were swamp. Several neighbourhoods across Metro Vancouver sit on old peat bogs that were drained and filled more than a century ago. The homes look like any others, but the ground underneath behaves differently, and that can mean sloping floors, cracked foundations and expensive repairs. Here is what peat is, how to spot it and how to protect yourself, whether you are buying or selling.

What is peat, and why does it matter?

Peat is a soft, wet, organic soil made of partly decayed plants that built up in bogs over thousands of years. It holds water like a sponge. When it is loaded with the weight of a house, or when the groundwater level drops, the water is squeezed out and the peat compresses and shrinks. It can keep doing this for decades.

Groundwater is the part people often miss. When a nearby construction project pumps water out of the ground to dig a parkade, the peat under the neighbouring lots can dry out and sink too. The City of Vancouver's own groundwater bulletin warns that pumping groundwater in areas with peat or other soft organic soils can make the ground subside and damage city infrastructure and nearby properties.

When the ground moves, the house moves with it, and usually not evenly. That can lead to:

• Settlement, or uneven (differential) settlement, where one side of the house sinks more than the other
• Cracked foundations, slabs, drywall and brick
• Sloping floors, and doors or windows that stick
• Sinking driveways, patios, walkways and fences
• Gaps or stress at utility connections: sewer, water and gas lines
• Expensive fixes such as underpinning, piles or re-levelling the house

Warning signs: look around the neighbourhood

Peat is under the ground, so you will not see it in the house itself. The neighbourhood often gives it away. On your next showing, take five minutes to walk the block.

• Bumpy, wavy or dipping sidewalks and roads, often with lots of patchwork repairs. This is one of the easiest signs to spot.
• Neighbouring houses that lean or sit unevenly, or have visible foundation repairs
• Stairs, porches or decks pulling away from the house
• Gaps under fences, gates or garage doors, or exposed foundation where the ground has dropped
• Soggy yards or standing water after rain

Inside, look for floors that slope (a marble or a level app on your phone helps), diagonal cracks above door and window corners, and doors that have been trimmed to close.

Where to watch for it

Vancouver

• Mount Pleasant and the old "Tea Swamp": roughly 15th to 20th Avenue, between Main and Fraser. The bog was named for the Labrador tea that grew there and was drained in the early 1900s. Settling homes and bumpy, patched roads are common here.
• Trout Lake and John Hendry Park (Grandview–Woodland and Cedar Cottage). The lake was once surrounded by a deep peat bog.
• Douglas Park (South Cambie and Riley Park)
• Dunbar and Southlands near Camosun Bog, at the edge of Pacific Spirit Park
• Low-lying areas along the Fraser River in South Vancouver

For a specific address, check the City of Vancouver's Groundwater Areas of Concern map. The Mount Pleasant peat bog is one of the mapped areas.

The rest of Metro Vancouver

• Delta and Ladner, especially near Burns Bog, one of the largest raised peat bogs on the West Coast
• Richmond, where much of the island has peat and soft river silt. The city requires a geotechnical report, confirmed compaction and an engineered foundation to build on lots with peat.
• Burnaby: the Burnaby Lake area and the Big Bend area of South Burnaby
• Pitt Meadows
• Langley: the Langley Bog and Derby Reach area
• Parts of Surrey, mainly the low-lying lands

Higher-risk homes are older houses, homes built without piles or preloading, and homes with additions, where the old and new parts can settle at different rates. If you are not sure about an area, ask.

If you are buying

1. Ask early. If the home is in or near one of the areas above, ask your realtor and the seller whether there has been any settlement, foundation repair, engineering report or insurance claim. Get the answers in writing.
2. Read the Property Disclosure Statement closely, especially the questions about structure, foundation and drainage. "Do not know" is a reason to ask more questions, not a clean bill of health.
3. Review the title search for covenants. In soft-soil areas, municipalities often register a Section 219 covenant: a geotechnical or "save harmless" covenant that can require the house to be built to an engineer's report and release the city from liability if the ground settles. Have a lawyer or notary explain any covenant before you remove subjects.
4. Check with the municipality for building permits, geotechnical reports and other records on file for the property.
5. Use the right inspections. A home inspector will spot signs of movement. If there are any, add a structural or geotechnical engineer. A sewer camera inspection is worth it too, because settlement can crack or separate the sewer line where it meets the house.
6. Check your insurance. Most home insurance policies exclude damage caused by settling, so talk to your insurance broker about what is and is not covered.

If you are selling

1. Disclose what you know. In BC, sellers must disclose known material latent defects: problems a buyer could not find with a reasonable inspection that make the home dangerous, unfit to live in, or expensive to fix. Known settlement, foundation repairs, engineering reports and past claims all belong in that conversation. Your realtor also has a duty to disclose known material latent defects, whatever you decide.
2. Fill in the Property Disclosure Statement yourself, accurately and in full. Do not answer "do not know" when you do know.
3. Gather your paperwork early. Engineering reports, repair invoices, warranties and permits show buyers that a problem was found and properly fixed, which is far better than letting them discover it during their inspection.

Protecting yourself

Peat is not a reason to rule out a neighbourhood. Many homes in these areas were built on piles or preloaded soil and have performed well for decades, and an older home that has already been properly underpinned may be in better shape than its neighbours. What matters is knowing what you are buying or selling: the history of the house, what the paperwork says and what an engineer thinks of the foundation.

If you are looking at a home in one of these areas, or selling one, talk to Alan before you write an offer or list. He can help you ask the right questions and line up the right inspections.

This article is general information, not legal, engineering or insurance advice. For a specific property, speak to a lawyer or notary, a geotechnical or structural engineer and your insurance broker.

• Buying
• Selling
• Due diligence
• Neighbourhoods

Sources

• City of Vancouver: Groundwater Management Bulletin and Groundwater Areas of Concern map
• City of Richmond: building on peat soils (geotechnical report, compaction and engineered foundation required)
• BCFSA: material latent defects, guidance for real estate professionals
• BCFSA: material latent defects, consumer guide
• Mount Pleasant BIA walking tour: Brewery Creek and Tea Swamp (Vancouver Public Library)
• Scout Magazine: Vancouver Lexicon, Tea Swamp
• Burns Bog, Delta: history of drainage and peat extraction