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I never understood how a deck needs footings 3'+ in some zones, yet the stairs are placed on a 3" concrete slab that might heave and thus crack where the stringers connect to the deck frame.
 

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Eater of sins.
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Well perhaps the stairs are designed just for this eventuality.

Depending on your climate zone, and especially the type of soil at the project location, there may be a low risk for ice lenses to form under the soil and create heaving.

Heaving will occur more in soils that are susceptible to forming ice lenses. Usually soils that are composed of coarse sands and gravels will not heave as that soils does not allow ground water to wick up it.
Same with many dense clay soils.

The prescriptive frost depth is, I think, there in lieu of obtaining a soils analysis on every property.

Andy.
 

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Talking Head
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We do footers for the stairs, anything else is hackery. Then we pour a small pad in front of the stairs
Come on. Take it easy with throwing around the "hack" label.

With a properly designed stair/deck attachment you can safely land stairs on a pad and allow for substantial heave without damaging the connection. If the stringer is cut with a slight miter where it meets the rim and attached with a LSCZ connector it can easily absorb a few inches of vertical movement at the far end of the stair. Obviously, the longer the stair, the less movement of the stringer attachment.

On a side note, what do you guys do for waterfall steps when it's only one or two steps?
 

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We did 100's of decks with stairs landing on the 4" slab, and we still doing it that way. There is never a single issue.

With that said, have you ever seen a sidewalk heave, never... It will sink or roots will lift it up, but it will never heave due to frost, unless of course the base was never tampered and someone did a half fast job, then and only then it might.
 

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On a side note, what do you guys do for waterfall steps when it's only one or two steps?
We just did a 16' box step and I hung it the same way we hang stringers, 16ga bulk roll strapping. 12-16 inches for a box step, 18-22 inches for stringers.

Oh and we land ours on a landing with no frost protection, never had an issue.
 

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We did 100's of decks with stairs landing on the 4" slab, and we still doing it that way. There is never a single issue.

With that said, have you ever seen a sidewalk heave, never... It will sink or roots will lift it up, but it will never heave due to frost, unless of course the base was never tampered and someone did a half fast job, then and only then it might.
High water tables and loamy soil. If the base was done right, then there isn't any problem.
 

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Around here building code states that any stringer over 3 steps requires a footing.
They require things they don't understand themselves.
You can also have problems associated with doing concrete footing in the ground also since they don't require the footing to be 12" wide and some places they don't require to go 36" deep depending on the region. When you place concrete footing below frost line it might not help to prevent stairs from heaving, especially some will dig a hole and put the post in the concrete and attach stringers to it.
The top of concrete footing above ground or (or the post itself) provides source for heat transfer from the concrete to the surrounding dirt or air, keep in mind that concrete is a very good conductor of heat and the change from moisture to ice requires that heat transfer.
When you have the ingredients, you get ad-freeze and that is what causing the heave... That is when the moisture in the soil tends to move from areas of higher temperature to areas of lower temperature and when it happens, you end up with is a cylinder of ice which will form around the whole footing column and post (if present). That ice can lift the entire footing and it don't matter if the bottom is bellow frost line.

Luckily in most places frost will not even reach even a 1/4 of the footing depth from above. I remember doing one deck in the middle of the winter and it was fk brutal cold which lasted for weeks, the frost penetration was 12". I was talking to some guy from Mane a while back at the deck show, talking about dealing with this stuff, he said he has building on slabs and his deck stair rest on the slab and with the winters they have he said, everything as it was built yesterday.

IMO you have less chances have stairs heave being on the slab then on the footing. Look at structures like sheds on slabs or on 4x right on the ground, etc including my shed on the slab its been standing there for 12 years now and it nothing got out of whack... my other shed in the old house been there for 11 years with double doors also on the slab, nothing ever heaved and doors never needed adjustment, etc. As long as you have proper drainage, your stairs will not go anywhere being on the slab and you don't have to do s^*t to them to allow movement.

Good luck
 
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