Stringer Support Slab - Rhode Island Code

[Cindysam1123]

Does anyone know the requirements for a stringer support slab in RI? Code says min. 12" below grade, but I've seen 40" below grade if the stairs are on a deck that's attached to the house. Does anyone know if it has to be the full frost depth?

 

[jar546]

This is a great question. When I was in an area with a frost depth, steps typically came down to a slab, whether a sidewalk or landing, when they were wood steps. Concrete steps, however, always went to frost depth because of the weight, whereas the wood was flexible enough to endure the twisting and heaving during the seasonal cycles.

 

[Yankee Chronicler]

Does anyone know the requirements for a stringer support slab in RI? Code says min. 12" below grade, but I've seen 40" below grade if the stairs are on a deck that's attached to the house. Does anyone know if it has to be the full frost depth?

Where does the RI code say 12 inches? I looked, and I couldn't find anything at all.

 

[steveray]

We use 12" for the bottom of the stairs in CT.....

 

[BN4537]

https://www.thebuildingcodeforum.com/forum/threads/deck-stairs.33749/

I think it is not necessary to require a frost-depth footing at the bottom of exterior stairs if they are landing on a standard 3.5" concrete slab. However, if you wanted to require them, you would say that since the stairs are a structure, the following section would apply.

R403.1.4.1 Frost protection.

Except where otherwise protected from frost, foundation walls, piers and other permanent supports of buildings and structures shall be protected from frost by one or more of the following methods:

1. Extended below the frost line specified in Table R301.2.
2. Constructed in accordance with Section R403.3.
3. Constructed in accordance with ASCE 32.
4. Erected on solid rock.

Footings shall not bear on frozen soil unless the frozen condition is permanent.

Exceptions:

1.Protection of free-standing accessory structures with an area of 600 square feet (56 m2) or less, of light-frame construction, with an eave height of 10 feet (3048 mm) or less shall not be required.

2.Protection of free-standing accessory structures with an area of 400 square feet (37 m2) or less, of other than light-frame construction, with an eave height of 10 feet (3048 mm) or less shall not be required.

 

[ICE]

Stairs are generally an engineered component here in earthquake territory.

 

[mp25]

AWC DCA6, states that stringers must sit on a foundation. I interpret that to mean, if frost protection is not required, then 12" foundation, and if frost protection is required (typically when the deck is attached to the building), frost protected foundation to support the stringers is required. DCA6 can be slightly different than IRC in certain things, but it is definitely clearer on the stair footing question.

See AWC DCA6 2018 Figure 34 and text of "Stair Footing Requirements [R403] within the same document