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(Information in this document was gathered from MTO standards, aggregate companies and the Ontario Building Code)

In Ontario, construction aggregates need to be gravel that have been washed and graded to meet the standards of the Ontario Building Code. Depending on the resources in your area, gravel will either be:

• natural gravel, which has been ground and deposited by glaciers, or
• quarried stone, furnace slag and recycled concrete which has been mechanically crushed.

In either case, gravel has to be screened or washed to make specific graded aggregate products.

The Ontario Building Code Specifies:

9.3.1.4. Aggregates

(1) Aggregates shall,

(a) Consist of sand gravel, crushed rock, crushed air-cooled blast furnace slag, expanded shale or expanded clay conforming to CSA A23.1, “Concrete Materials and Methods of Concrete Construction”, and

(b) Be clean, well graded and free of injurious amounts of organic and other deleterious material.

Common Types of Aggregate in Ontario

Here are the most common types of Ontario aggregates and what they are typically used for

Granular “A” gravel:

Ministry of Transport of Ontario (MTO) sets the technical standards for A and B gravel, which can be found by searching: “Material Specification for Aggregates – Granular A, B, M And Select Subgrade Material”

A mix of sand and gravel with stone being no larger than 1” and a low silt content to allow for drainage.

“A” gravel is used as the top layer of laneways, gravel floors and directly under concrete slabs. “A” gravel can be used as engineered fill when placed and compacted to engineer specifications.

Granular “B” gravel (also known as Pit Run)

As stated above, MTO sets the technical standards for A and B gravel which can be found by searching: “Material Specification for Aggregates – Granular A, B, M And Select Subgrade Material”

B gravel is a mixture of sand and gravel with stone being no larger than 6”

“B” gravel can be used as engineered fill when placed and compacted to engineer specifications.

This granular is further classified by two types:

• Type I contains natural gravel
• Type II contains only crushed stone

“B” gravel is typically used to backfill foundation walls, to build up road bases and under “A” gravel below concrete floors.

Clear Stone (also known as drainage stone)

Available in a variety of sizes, clear stone typically means that the granular has a uniform particle size. This is achieved by screening out undersized and oversized particles and sometimes washing.

Clear stone is used as a drainage medium and as a topdressing over “A” granular driveways.

Sand

Sand can be either natural or manufactured. Manufactured sand is a quarry product.

Natural sand is mined from clear sand pits or is found with gravel deposits and separated by screen. Sand can be used as fill, engineered fill and for drainage beds.

Gabion

Gabion is 4”-8” quarried stone, it can be used for erosion control and slope stabilization.

Rip Rap

Rip rap is 8”-20″ quarried stone, and, like gabion, it can be used for erosion control and slope stabilization.

Amour Stone

Armour stone consists of pieces of quarry stone multiple feet in dimension. This aggregate can besed for retaining walls, waterways, shoreline protection, and landscaping.

Railway Ballast

Railway ballast is a reused material that is mined from decommissioned railbeds. This material will vary from one rail line to another. Typically, it is a course quarried aggregate around 2” in size. Reclaimed railway ballast typically cannot be used as engineered fill, as it is usually inconsistent in quality, and could contain organic material.

Soils of Concern

In addition to aggregates you’ll want to use, there are some that you should stay away from when building a barn in Ontario. We’ve outlined these below.

Pyrite Fill

Some parts of Ontario have concentrations of pyrite in sedimentary rock. If gravel containing pyrite is used for fill, it can react with moisture causing extreme swelling and heaving.

Organic Soil

Ontario has several thousand acres of prime farmland that has been reclaimed from wetlands. This soil is extremely high in organic matter to a depth of several feet and usually has a shallow water table. It can be difficult to excavate to subsoil that is free of organic matter, so foundations must account for the expansion of organic matter with water, the degradation of organic material over time, and the reduced bearing strength of the soil.

Leda Clay

Leda clay is a sensitive soil found in Eastern Ontario which is very unstable. When subject to moisture and extreme pressure, this material behaves as a fluid and has been the cause of many landslides and sink holes. Leda clay also can expand and contract with moisture changes causing significant foundation heaving.