Deck Building Codes 

The Basics Of Building Code Requirements For Decks  

Deck Railing

If deck surface is less than 30” (24” in Canada) above ground – no railings required

If deck surface is 30” (24” in Canada) to 5’10” above ground – minimum 36”railing is required

If deck surface is 5’10” or more above ground – minimum 42” railing is required

For loads, guardrails must withstand:

• a concentrated horizontal load of about 200 lbs at any point along the rail
• a concentrated horizontal load of about 200 lbs over a 1sft area at any part of the rail
• a simultaneous vertical load of about 100 lbs and a horizontal load of about 50 lbs along a rail

Glass panels - Glass must be tempered safety glass so that if it breaks, it breaks into tiny non-shard like pieces.

Deck Stairways

Width - At least 35” between wall faces or guardrails or a protruding hand rail

Unit Rise and Unit Run - Unit rise and run refer to the overall vertical and horizontal change between each stair tread – not the actual tread size.

• Maximum unit rise of 7-3/4”
• Minimum unit run of 8 ¼”
• Minimum tread width of 9 ¼” (2x10)
• No more than 3/8” difference between any rises (but you should always make them equal)

Stringers - The building code specifies that wood stringers meet minimum sizes for obvious reasons. Here is a list of the key points.

1.5” thick (2x material) minimum if no supports along its length
1” thick minimum if supported along its length
3.5” minimum effective depth size (the narrowest part after cutting all the rise and run notches) 9 ¼” width (2x10) minimum
Stringers must not have direct contact with ground unless treated with wood preservative
Stringers must be secured at top and bottom
36” maximum space between stringers with open rises
48” maximum space between stringers with closed rises
Check your local building code for the maximum spacing of stringers with open rises because it is quite common to see exterior stairs with open rises that are 48” wide.

Deck Stair Treads - The building code has different standards for residential and commercial stair treads. Basically residential stairs can be steeper and have narrower treads. But if anything, consider building deck stairs with wider treads and lower rises. It just feels better.

List of the key points:

• At least 1” thick if used with notched stringers
• At least 1.5” (2x material) thick for open risers and stringers spaced 30” or more apart
• At least 1” nosing if the unit run (not the actual tread) is less than 10”
• At least 9 ¼” (2x10) wide

Stair Rails - Deck stair rails also have special requirements under the building code.

• 4” maximum space between balusters
• A 6” ball must not pass between the triangular space created underneath the bottom rail, the riser and the tread
• At least 32” (not more than 36”) measured vertically above a line drawn through the outside edges of stair nosing – So be sure to extend (cantilever) the top rail over the nose of the last tread
• At least 36” above landings

Handrails

• Must be between 1.5” to 2” in either width or thickness
• Handrail must be at least 1.5” away from wall and its outside edge not more than 4” from wall
• At least one handrail required if stairs are less than 43” wide
• At least two handrails required is stairs are 43” or greater
• No handrail required for deck stairs with 3 risers or less
• If more than 3 risers, only one handrail is required (subject to the width requirements above)

Foundation - Just as with a house, deck building code requirements will have something to say about the kind of foundation needed for your deck. This is mostly a concern if you build a deck on soft soil.

Foundation

Just as with a house, deck building code requirements will have something to say about the kind of foundation needed for your deck. This is mostly a concern if you build a deck on soft soil. Check with your local building department about the dept of a frost line or size of concrete pads.

This is a general guide only. Go to your local city building department to confirm the exac building code requirements in your local area.