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-   -   Concrete walkup stairs from the basement (http://www.diychatroom.com/f19/concrete-walkup-stairs-basement-26440/)

handy man88 09-07-2008 07:21 PM

Concrete walkup stairs from the basement
 
I know dirt is laid down before the molds are set up to pour concrete stairs coming up from a walkup basement. This dirt is probably very hard to pack, if at all, since it's sloped and is probably temporary just to hold the concrete until it dries.

After the stairs are poured, is it common for a cavity to form, unbeknown to the homeowner?

Termite 09-07-2008 10:06 PM

Yes, in many instances concrete slabs and stairs are poured on poorly compacted earth. Yes, in time is is not uncommon for that earth to settle. Wetness will greatly increase the soil's settlement. When that settlement occurs, three things can potentially happen.

1) The soil settles, resulting in a floating structure with a gap underneath it. I've seen structural slabs floating over 24" above the settled earth because the subgrade was not properly prepared.

2) The soil settles and takes the structure with it.

3) The soil surrounding the stairs prevents real erosion from taking place, so settlement is the only possible issue...Not displacement.

Ideally, the soil is properly compacted and a gravel base is placed over it. The gravel helps facilitate some drainage in many instances. Geo-mesh fabric can also help prevent displacement of soil, but nothing replaces good compaction.

handy man88 09-08-2008 07:45 AM

Quote:

Originally Posted by thekctermite (Post 156058)
Yes, in many instances concrete slabs and stairs are poured on poorly compacted earth. Yes, in time is is not uncommon for that earth to settle. Wetness will greatly increase the soil's settlement. When that settlement occurs, three things can potentially happen.

1) The soil settles, resulting in a floating structure with a gap underneath it. I've seen structural slabs floating over 24" above the settled earth because the subgrade was not properly prepared.

2) The soil settles and takes the structure with it.

3) The soil surrounding the stairs prevents real erosion from taking place, so settlement is the only possible issue...Not displacement.

Ideally, the soil is properly compacted and a gravel base is placed over it. The gravel helps facilitate some drainage in many instances. Geo-mesh fabric can also help prevent displacement of soil, but nothing replaces good compaction.

How critical is it to get this repaired?

My initial thoughts were to somehow have gravel poured into the hole/cavity and then dump in some dirt up to level.

I spoke to a landscaping neighbor and he said that he usually pours in bags of concrete mix, top with dirt, and then put in seed around the perimeter.

Who is better to resolve this issue? A landscape professional, a foundation professional, or a basement waterproofing professional?

Termite 09-08-2008 05:05 PM

Sometimes you can fix it with gravel. Most of the time you'll want to use flowable fill (very wet special concrete). Mudjackers can "inject" flowable fill to raise the stairs back up and fill the void. If the stairs haven't moved, contact a concrete company in your area to get a small load of flowable fill, assuming you can get it in the gap.


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