Deck Building Code Issues

Your editor of Ideas-For-Deck-Designs.com Deck building code requirements are not something that should be ignored just because you are building a deck and not a house.

Even basic deck building construction techniques involving joist spans, post size and loads, beam sizes and spans between deck posts, decking board dimensions, height of railings and load capacity are all discussed in the building code.

Building code requirements for decks Most of the building code requirements that apply to building decks are universal standards based on the physical properties of deck building materials commonly in use around the world today.

However, there are often local variations because of different climates and material preferences.

The final authority that you should rely on is the local building code that pertains to your area. The best place to get a copy is to visit your local city building department - even speak to an inspector if you prefer.

Important Deck Building Code Issues

The main areas of decks that the building code speaks directly about are railings, glass railing panels, stairs, treads, stair rails, handrails, foundations, covenants and easements, setbacks and variances.

I will discuss each topic and try to cover as many of the keys points as possible.

Deck Railing - Building Code Requirements

For height, keep it simple and think of it this way...

Deck surface is less than 24” above ground – no railings required
Deck surface is 24” to 5’10” above ground – minimum 36”railing is required
Deck surface is 5’10” or more above ground – minimum 42” railing is required

See a simplified image of deck railing building code requirements for height...

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

See a simplified image of deck railing building code loads for vertical and horizontal forces...

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

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 8”
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.

Here is a 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

A 2x4 or 2x4 flat, or on edge does not constitute a proper handrail according to the deck building code. So if you truly want to follow the code, check out this list.

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.

A soil engineer has a special meter that they stick into soil to give them an accurate idea of the quality of the soil.

This is really important for building a house. Just talk to your local city building inspector if you are particularly concerned.

Covenants

You probably never thought deck building would involve covenants but sometimes it does. Drop in to your local city building department and chat with the officials about any covenants that may specify size, style, and location or material restrictions for you deck.

Easements

This usually isn’t a deck building issue but if there is an existing easement that allows your neighbors or public officials access to a portion of your property, make sure you don’t build in a way that impedes this access. If you own your property you should have an entire history of its title from when you purchased the property.

Setbacks

Again, the city will tell you right up front what the setbacks from property lines or sidewalks are. There are usually limits to how close your deck can be to another building. Be sure to find out - You don't want any surprises after its built.

Variances

Basically any regulation can be challenged and depending on your circumstances, may be set aside. But you’re building a deck not a high-rise so this should not be an issue.

But before you start building your deck you owe it to yourself to learn how the code requirements will apply to deck building.

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