How Thick Cement Slab for Bottom Stair

Posted by Manjo on August 14, 2006, 7:57 am

I've leveled the previously bottom stair cement slab (20" x 48" x 20"
deep).

I now need to pour a new 7 3/4" high "bottom" stair in front of the
leveled slab, above.

I intend to use rebar in the new bottom stair (2 - 4' rods and 2- 1'
rods in a rectangle supported by two wire cradles to position the rebar
in about 5" about the bottom of the slab).

I like to ask the group how much deeper/thicker should the slab be to
sit firmly in the ground? Asphalt will be laid right up to the front
of the new bottom stair, which should hold it in place, some.

TIA for any tips, suggestions, comments.

_________
| 7 =BE" rise
old stair |________
leveled | new stair |
| |_7 /34" rise_____________ground
level
| ? deep |

Manjo

Posted by dpb on August 14, 2006, 11:52 am

Manjo wrote:

> I've leveled the previously bottom stair cement slab (20" x 48" x 20"
> deep).
> I now need to pour a new 7 3/4" high "bottom" stair in front of the
> leveled slab, above.
> I intend to use rebar in the new bottom stair (2 - 4' rods and 2- 1'
> rods in a rectangle supported by two wire cradles to position the rebar
> in about 5" about the bottom of the slab).
> I like to ask the group how much deeper/thicker should the slab be to
> sit firmly in the ground? Asphalt will be laid right up to the front
> of the new bottom stair, which should hold it in place, some.
> TIA for any tips, suggestions, comments.
> _________
> | 7 =BE" rise
> old stair |________
> leveled | new stair |
> | |_7 /34" rise___________ground level
> | ? deep |

Well, imo the more effective way would be to drill into the existing
pouring in three or four locations and insert some rebar into the holes
to effectively tie the new step to the existing one. Then, the more
effective way to hold the new step is to enlarge the base area, not
make it simply deeper. I'd probably lay at least a couple feet of 4"
sidewalk in front rather than deepen it further. I would then use wire
mesh in it and only one or two bars in the step itself at most just
tied to the tie-pieces. That should last a long time.

Of course, you'll want to make sure the ground under the new pour has
been well packed and has good sub-base before pouring. If it's been
dug up in the previous repair, a goodly amount of tamping will be
essential. Such a small area would hardly justify renting a tamper,
however.

HTH...

Posted by Manjo on August 14, 2006, 2:25 pm

HTH,

I think you're sayinhg buy/rent a hand tamper? I think they're the
pnes with a handle and a flat piece about 1 foot square to bang the
dirt and stuff down??

I never thought about a 4" walkway in front fo the last stair. I was
thinking the asphalt would hold the last stair in place.

Thanks,

Manjo

dpb wrote:

> Manjo wrote:

> > I've leveled the previously bottom stair cement slab (20" x 48" x 20"
> > deep).
> > I now need to pour a new 7 3/4" high "bottom" stair in front of the
> > leveled slab, above.
> > I intend to use rebar in the new bottom stair (2 - 4' rods and 2- 1'
> > rods in a rectangle supported by two wire cradles to position the rebar
> > in about 5" about the bottom of the slab).
> > I like to ask the group how much deeper/thicker should the slab be to
> > sit firmly in the ground? Asphalt will be laid right up to the front
> > of the new bottom stair, which should hold it in place, some.
> > TIA for any tips, suggestions, comments.
> > _________
> > | 7 =BE" rise
> > old stair |________
> > leveled | new stair |
> > | |_7 /34" rise___________ground level
> > | ? deep |

> Well, imo the more effective way would be to drill into the existing
> pouring in three or four locations and insert some rebar into the holes
> to effectively tie the new step to the existing one. Then, the more
> effective way to hold the new step is to enlarge the base area, not
> make it simply deeper. I'd probably lay at least a couple feet of 4"
> sidewalk in front rather than deepen it further. I would then use wire
> mesh in it and only one or two bars in the step itself at most just
> tied to the tie-pieces. That should last a long time.
> Of course, you'll want to make sure the ground under the new pour has
> been well packed and has good sub-base before pouring. If it's been
> dug up in the previous repair, a goodly amount of tamping will be
> essential. Such a small area would hardly justify renting a tamper,
> however.
>=20
> HTH...

Posted by dpb on August 14, 2006, 3:55 pm

Manjo wrote:

> HTH,
> I think you're sayinhg buy/rent a hand tamper? ...

Actually, what I said was "Such a small area would hardly justify
renting a tamper" which sounds to me like the exact opposite. In
renting, I figured it would be clear I was speaking of a powered one,
however, implying you should make one or borrow one, and yes, I'd
expect it to be hand-powered...

> I never thought about a 4" walkway in front fo the last stair. I was
> thinking the asphalt would hold the last stair in place.

...

You're the one w/ the sinking steps from before, right? The
recommendation is as I said, to make the base area larger to
prevent/minimize future/further settling. It ain't goin' nowhere
laterally unless it's on a steep hillside or somesuch, particularly
once it's tied into the existing steps.

I'm just suggesting that doing it this way will leave you w/ a more
nearly single pour that just laying a square block down in front of the
existing one. Your choice, of course.

Posted by Italian on August 15, 2006, 1:16 am

First you want to address "how am I going to connect this new add on to
your existing stairs"
and how you would is drill 4 holes equally spaced along the last steps
face in the center.
---o---o---o---o--- in to these insert rebar that will come no closer
than 3" from the front of the new stair front.

Second is what kind of base (footing) is this addition going to
need.....what you are doing is increasing the total footprint of the
stairs by adding this step and it needs to have footing under it just
as it would if it was poured with the original steps. Which means it
needs to be doug into the ground and formed above ground. I dont know
if you mentiond what your cause of movement for the stairs but this
needs to be taken into consideration with this last step as well.
I would make the last step at least as thick below the ground as it is
above the ground and add about 3" on the 3 sides (2 sides and 1 front)
for the footing. in other words the part in the ground will be 6"
larger (from left to right) and 3" larger (from front to back) than the
step itself. This is where the steel should go in the footing and again
keep it 2-3" back from the dirt (sides & bottom) place it on a pieces
of brick or broken cement (not wood).

there is no need for additional steel in the step other than the dowels
---o---o---o---o---

This will hold its own there is no need to place anything up against it
to "hold it".
Please note where the old meets the new you will have a "cold Joint"
make sure you moisten the existing concrete prior to pouring the new
stuff to help the 2 bond. If you want the new one to not look new add a
little bit of black color to the mix this will take away the brighness
of the new concrete. Also to match the texture of the old steps you can
"face" the new one ......remove the forms after the concrete has set
and starts to pull away from the forms...depending on weather could be
as little as a couple of hours....CAUTION..doing this prematurely will
cause the stair to "slump".....actually you know what just wait till
the next day and do it... When removing froms from concrete ALWAYS hit
the forms DOWN with a hammer to loosen them and then pull them away
this avoids chunks comming off wiith the forms....after this make up a
mixture of sand and cement (and a little black color) and rub this on
the newly exsposed concrete in a even mannor (kinda like Icing a cake)
only very thin maybe 1/4 inch at the max more like 1/8 inch. when
applying this coat try to make the inside of the step (where the new
and old meet) slightly concave use a piece of pvc or a old broom handel
to do this or even a small rubber ball if you have it drag it along the
seam from side to side in one motion to make a smooth line. As a matter
of fack if you would like to give the stairs a "face lift" you can do
this to the whole thing. If you do this I would suggest painting the
stairs with a bonding adheasive first. (H.D. Lowes) concrete section
"consrete bonding adheasive" youre stairs will look brand new.....good
luck....Hmmmm....let me see did I leave anything out..........

Manjo wrote:

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