QUICK GUIDE TO PIER FOUNDATIONS

Working in the Beach, I’ve been exposed to various ways of building. One common question I get asked is why homeowners should build their addition on piers rather than a foundation.

What are piers? They are vertical load bearing supports driven into the soil at least 4 feet down that carry the load of the structure above. Based on the soil conditions and size of addition, Structural Engineers provide calculations for the appropriate type, size and number of piers required.

Piers are commonly used within the Beach for residential construction, which makes it beneficial to be briefly educated on the pros and cons for this type of construction.


Pros:

  • Most economical structure to support an addition

    • avoids the need to excavate

  • Tree Protection

    • a main reason why many build on piers in the Beaches is due to the Tree Protection zones required by the City.  The tree’s roots are two or three times the diameter of the canopy above, so with proposed additions near a city protected tree, it is best to build on piers.   This also means excavation is not required; as excavating will cut the roots which can injure the tree and will eventually kill it.

Cons:

  • Slightly raised above grade

    • the addition will not be at ground level (about 6” above grade), so you’ll need to block the gap to keep rodents out; an example is to install lattice.

  • Heat loss

    • when building on piers, per building code, the underside of the floor structure must be insulated and in-floor heat is recommended. The use of in-floor heating makes the floor temperature consistent in the house - from the existing portion to the addition on the piers.  However, only during severe cold temperatures will you feel the difference. (Only 2 months a year in Toronto, while the majority of the year you will not need it).

    • although additional insulation and heat is added to the floor, one will notice the difference in temperature between floor surface with and without a foundation below.

If interested to learn more, don’t hesitate to contact your contractor or designer.

Stephanie Haddad