Basement floor "rolling"

In an old house the concrete basement floor has peaks and valleys. Is this a foundation problem(structural) or a cosmetic issue?

 

[Ron]

If there are no significant cracks associated with the surface irregularity, it is probably just poor initial concrete placement. Otherwise, it is likely a soil issue such as swelling (or shrinking) clayey soils beneath the slab. For active clays or clayey materials, changes in the moisture content control volumetric changes in the material. For example, in wet conditions, the clay tends to swell, but under dry conditions, it will shrink.

 

[erich]

The concrete basement floor in nearly all residential construction is a thin (4&quot slab that floats between the actual foundation walls. Therefore cracks in the floor are purely cosmetic, however they may be indicitive of the stresses also placed on the walls, if cracks begin to appear in the basement walls, that is wen I'd begin to worry.
-- Erich

 

[jheidt2543]

Depending on how old the house is, the "rolling" you describe may be from the original "finishing" operation. Many a basement floor was poured and only bullfloated off, no power troweling. If you have ever watched a slab being finished, the bullfloating operation, which is done to compact the concrete, leaves a rolling or regular humps in the surface of the slab. The troweling operation gives the slab its flat surface. However, many years ago, the only troweling done in the housing market was by hand, so the floors were not as flat as is typical today. I've also seen some of these old basement floors as thin at 2".

 

[AlohaBob]

I did some repairs on a house that showed a rolling basement floor. The house had obvious signs of settlement. A critical visual look at the neighboring houses showed every house in that neighborhood suffered from similar effects. After investigating, the house was built on a landfill. Settlements were atrocious. Sections of the unreinforced concrete basement floor were actually floating like a trampoline, the space between the slab and support soil was in places a full 12inch void. Main underground sanitary sewer pipes were broken, but the void spaces in the landfill decomposition were so huge, no one knew the pipes were broken. I feared a sink hole would develop and swallow the house and everyone. It was a terrible mess. No professional would have anything to do with making repairs. We got things fixed, but there will always be the issue of the house being built on a landfill which can't be undone.