DECK STAIRS

[VLADIMIR LEVIN]

Anything in the residential code specifically talk about bottom of deck stairs requiring attachment to a foundation that extends below frost depth?

 

[steveray]

Why yes there is (sort of):

R507.3 Footings. Decks shall be supported on concrete footings
or other approved structural systems designed to
accommodate all loads in accordance with Section R301.
Deck footings shall be sized to carry the imposed loads from
the deck structure to the ground as shown in Figure R507.3.
Exceptions:
1. Footings shall not be required for free-standing
decks consisting of joists directly supported on
grade over their entire length.
2. Footings shall not be required for free-standing
decks that meet all of the following criteria:
2.1. The joists bear directly on precast
concrete pier blocks at grade without
support by beams or posts.
2.2. The area of the deck does not exceed 200
square feet (18.6 m2).
2.3. The walking surface is not more than 20
inches (508 mm) above grade at any point
within 36 inches (914 mm) measured horizontally
from the edge.
R507.3.1 Minimum size. The minimum size of concrete
footings shall be in accordance with Table R507.3.1,
based on the tributary area and allowable soil-bearing
pressure in accordance with Table R401.4.1.
R507.3.2 Minimum depth. Deck footings shall be placed
not less than 12 inches (305 mm) below the undisturbed
ground surface.

 

[VLADIMIR LEVIN]

Thanks. I was looking for deck stairs specifically.
In 20 years I've never put a foundation below frost depth for a deck stair. Finally a building inspector is calling me out on it...

 

[Mr. Inspector]

Everyone in my third party inspection company does not require it. Only require a pad.

 

[steveray]

We have amended it to only be 12"

4. The footing for the grade level termination of stairs or ramps attached to decks or landings, whether
the deck or landing is supported by a dwelling or not, shall only be required to be placed at least 12
inches (305 mm) below the undisturbed ground surface in accordance with Section R403.1.4.

 

[VLADIMIR LEVIN]

We have amended it to only be 12"

4. The footing for the grade level termination of stairs or ramps attached to decks or landings, whether
the deck or landing is supported by a dwelling or not, shall only be required to be placed at least 12
inches (305 mm) below the undisturbed ground surface in accordance with Section R403.1.4.

Steveray, what state are you in?
Maybe NY has a code commentary about it...

 

[steveray]

CT

 

[Inspector Gift]

Thanks. I was looking for deck stairs specifically.
In 20 years I've never put a foundation below frost depth for a deck stair. Finally a building inspector is calling me out on it...

Vladimir, if the upper portion of the stairs are supported on footing(s) below the frost depth (as in connected to the house), then we require the bottom of the stairs to also be supported by footings below frost depth. This helps maintain the structural stability at the connections.

 

[BN4537]

We require it here as well, but an explicit code section more specific than the one steveray provided is not to be found.

Edit: Frost depth here is 34", but we allow a 12" deep trench footing instead specifically for deck stairs.

 

[Mr. Inspector]

For the ones that require frost depth for the bottom of the deck stairs, do you go by the deck footings table?
Not sure if you can go by the deck pier table for stairways since there is no definition of a deck.

 

[BN4537]

We just say 12" piers under each stringer to frost depth (34" here), or just thicken the slab to 12" under the stairs. Minimum footing width is 12" for houses, minimum deck pier width is 12". Everyone just thickens the slab to 12" deep under the stairs and calls it good.

 

[Glenn]

Please do not require frost protected foundations to support the bottom of exterior deck stairs. It's solution looking for a problem. That's not what the service of code administration should offer to American communities. I happy to see most comments here are not requiring this. Thank you.