Skip Navigation

Residential Decks for Single Detached Dwellings

General Regulations:
  • Deck means a floor-like structure without a roof having a foundation to hold it erect, and attached to or abutting one or more walls of a building, with or without direct access to the ground, the floor of which is greater than 0.6m above finished grade and which is designed and used as a sundeck, but shall not include a landing or stair.
  • Building permits are required for decks if the deck surface is 0.6m (23 5/8") or more above finished grade level or where full depth foundations are required, such as when decks are attached to a building having full depth foundations.
  • Decks attached to a building with a full foundation are typically required to be supported on a foundation (such as posts) extending not less that 1.5m (5'0") below grade
  • Decks independent of the dwelling may be built with on-grade structural supports
  • Guardrails must be provided where the Deck surface is 0.6m (23 5/8") above the adjacent surface or grade
  • Required guardrail balustrades must be vertical, non-climbable, have no openings exceeding 0.1m (4") and meet strict "new in1998" mandatory requirements of the Ontario Building Code for structural requirements
  • Minimum Guardrail Heights (based on deck height) are as follows:
Deck Height           
Below 0.6m (23 5/8") No guardrail required
Up to 1.8m (5'11") 0.9m (36") guardrail
Above 1.8m (5'11") 1.07m (42") guardrail            r> Where a deck is to be added to a single detached dwelling constructed prior to March 16, 1987 which has less than the required mimimum side yards according to the Zoning By-law, the deck shall be located not closer to the side lot lines than the dwelling or 0.6m (23 5/8") from the side lot line, whichever is greater.

Do I need a building permit?

  • Yes, if the deck surface is 0.6 metres (23.6 inches) or more above the finished grade level
  • Yes, if full-depth foundations are required

Building Permit Application Form Adobe PDF, 3 pages, 69KB

What do I need to provide to the city in addition to the completed Building Permit application?

  • Schedule 1: Designer information, completed, with designer’s signature Download Schedule 1  Adobe PDF, 1 page, 33 KB
  • Written authorization from the owner of the building
  • Proof of ownership (either a property deed or tax notice)
  • Two sets of deck floor plans
  • Two sets of deck cross-section plans
  • Current site plan or survey, indicating existing buildings and the proposed structure
  • Required fee: set at $10 per $1,000 of construction value, minimum fee is $50
  • Other approvals as needed (e.g. Thunder Bay Hydro) – see below for more information

What other information do I need?

  • If there is a septic tank or field near the building site, contact the Thunder Bay District Health Unit, Sewage Systems and Land Development Program, at (807) 625-7991 for information on clearances.
  • If you are carrying out electrical work as part of the project, you must contact the Electrical Safety Authority at or call 1-877-372-7233 for information and inspections. Ontario One Call logo

Excavations - call before you dig!

At least five days before you start digging, contact Ontario One Call to arrange for the location of underground utilities.

Dig safe - it's the law.

More information on Ontario One Call.


Once you receive a building permit, it is your responsibility to arrange for building inspections.

Call (807) 625-2570 (North Ward) or 807-625-3124 (South Ward) at least 48 hours in advance to book an appointment. You can call at any time to leave a message.

In most cases, there will be only one final inspection when the deck is complete with foundation, flooring, stairs, guardrails, and balustrades.

City of Thunder Bay

Building Services Division


Victoriaville Civic Centre

111 Syndicate Avenue S P.O. Box 800             Thunder Bay ON P7C 5K4

Tel: (807) 625-2574
Fax: (807) 623-9344
Hours: Counter Service Only Available on Monday, Wednesday and Friday - 8:30 am to 4:30 pm