I'm trying to finish up my attached deck. The deck surface is 3 feet
above the ground where I intend to place the steps. My question is, given
that the end of the deck furthest from the wall is supported by three
columns that sit on 4-1/2' concrete piers, do I also need to dig (and pour)
4-1/2' deep holes for each of the three stringers to land on? Or can I get
away with a 6" thick slab? If a slab, what would be the minimum width and
length? Do I have to bolt the bottom og the stringer to the cement or is it
enough to anchor the tops of the stringers to the deck rim joist? Thanks
for any suggestions!
I don't think you need to put a footing for each stringer. Generally ,
it would be ideal on a slab, but I've seen people use those brick and
patio pavers in the dirt as a footing.
As far as anchoring, I used a joist hanger for each stringer at the
top. On the bottom, you should put some kind of anchoring. If you are
using a slab, just anchor each stringer to the slab. Or if you are
putting posts at the bottom for the railing, anchor the stringer to the
posts, and the posts to the ground. But in general, the top anchoring
is most important.
Thanks for your reply Mikepier, I wonder if you could answer a
couple more questions...
How far should the slab extend the stringers? (What are the dimensions
of the slab knowing that the width of the steps is 6 feet? And would
4 stringers suffice?)
If the deck is on frost piers, won't the slab move with the ground?
(I'm just trying to understand why the steps wouldn't be pulled from
the deck's rim joist if they are anchored at both the slab and the deck.)
Thanks again for your help!
4 stringers should be enough for a 6 foot wide stairs. If you are using
2X6 as treads, then that means they will span appox. 20" between each
stringer. The max you can span with 2X6 is I believe 24". And make sure
you use 2X12's for stringers, not 2X 10's like some people I've seen.
I'm not sure what frost piers are. Are those the piers that look like
elephant feet for a floating deck? Also what is at the ground level of
the deck, grass?
A frost pier is just another name for a cement column that extends past
the frost line. They keep the deck from heaving with the season changes.
Mine have a 19" diameter (overkill) and are 5' in length (4-1/2' deep with
6" extending out of the ground). The deck is attached to the house and
supported on the other end by 6x6 posts anchored to three of these piers.
And yes, the ground level is grass.
As a supplement to Mikepier: Check the beam to which the steps are
attached for strength.
Steps dropping three feet should be anchored at the bottom.
I'd consider shims or spacers to let water drain from the bottom end
International Residential Code requires a "Guard" 36 inches high if
deck or stair is more than 30 inches above grade.
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