Construction does not need to stop when the temperature drops. The Alberta Building Code (ABC) sets out specific requirements for winter construction to protect property owners and contractors from costly mistakes as a result of failed building materials due to exposure to the cold.
Some property owners have chosen not to backfill or partially backfill an excavation after removing the damaged foundation. Resulting moisture and ground freezing can cause issues with the integrity of the foundation.
The ABC sets out the following requirements regarding your excavation:
Excavations, specifically the soil under the foundation, must not be compromised by excessive moisture as it can degrade the soil. If an excavation is left open, accumulated water should be removed immediately and moisture levels must be constantly monitored, conducting onsite testing, if necessary (ABC, Articles 18.104.22.168 and 22.214.171.124).
The soil under a foundation must be protected from freezing for the entire construction period as this will likely result in frost heave that will cause damage. Contractors planning to build during the winter season will need to provide a continuous source of heat at the foundation to prevent this (ABC, Article 126.96.36.199).
If concrete becomes too cool, its ability to cure to its ultimate strength is compromised, resulting in a substandard foundation.
The ABC requires:
- Concrete must be kept at a temperature of not less than 10 degrees Celsius while being mixed and placed.
- Concrete must be maintained at a temperature of not less than 10 degrees Celsius for 72 hours after placing.
- Concrete shall not be placed in mud, standing water, or on, against or above any frozen material (i.e. a wet or frozen excavation).
- No frozen material or ice shall be used in concrete.
- Form work may need to remain in place for up to 72 hours.
Residents are encouraged to speak to their contractor and/or concrete supplier as they are responsible for ensuring equipment is in place to be sure these requirements are met.
If a foundation (existing or new) is in place prior to cold temperatures and construction continues through the winter, the building (or at least the foundation) must still be heated continuously to prevent freeing of the sub grade.
Testing and Remediation
If the excavation becomes saturated and/or freezes, remediation will be required before a permit will be granted to pour a new foundation.
Prior to re-building, soil shown to have reduced bearing capacity will have to be removed under the supervision of a geo-technical engineer, in order to meet the minimum requirements. The geo-technical engineer may also propose an alternative solution for review and approval by a Safety Codes Officer.
For questions, call the Safety Codes Branch 780-743-7813 or email firstname.lastname@example.org.