Sinking walls, rising floor...


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Old 01-05-07, 07:53 PM
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Smile Sinking walls, rising floor...

I'm thinking about finishing my basement this spring and before I can do that, I will need to address an issue with the concrete floor - here's the details:

4 level split built in 1988 -
I have several cracks in my concrete floor which look to be the result of my foundation walls sinking. The effect of the walls sinking have dropped the floor around the perameter of the foundation. This sinking, of course, has resulted in the floor cracking leaving it raised in the centre. The walls have no cracks and I do not have any moisture coming up through the floor cracks (up to 1/8" wide). The walls also look to be straight (no bowing). IN a nut shell, it looks like the center of the floor has not moved but the peramter has sunk due to the walls sinking. This sinking has caused some serious cracking of the floor only.

My question is, how much trouble am in if I want to level this floor. Would the answer be to lift the perameter back into the original position some how or to pour more concrete on the floor in an effort to level the existing floor as it is? As stated, I do not have any problems with leakage or moisure today - but I would like to level the floor for a planned reno. any advice would be much appreciated.
 
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Old 01-05-07, 08:17 PM
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Sinking walls, rising floor

You are just making some assumptions about relative movement.

You need tp have a professional look at the structure to determine what is happening.

Without looking at the structure, It is difficult to determine if the foundation is settling or the floor has heaved upward.

Since there is no damage or cracking in the foundation, but there is cracking in the floor, it appears there may be no settlement of the foundation. Only a professional on-site can determine what is happening, why it is occuring and how to correct it.

Normally the floor is sitting on the foundation and not attached. There would be no way for the footings and walls to "pull" the edge of the floor slab downward. Also, the fact that the floor is cracked and not level indicates that the floor has differential pressure under it.

Contact a structural engineer for an investigation before you make other assumptions or take any remedial action. He will look at the house to determine if there is settlement. He knows what to look for as indicators.

It sounds like you have a sound house with a cracked basement floor.

Dick
 
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Old 01-05-07, 08:54 PM
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Thanks for the advice Dick - I'll call someone in to have a look at it.

The reason I assumed it was the walls dropping is the fact that the center of the floor is level between the floor cracks that run along each wall - in other words, the majority of the floor is level. However, when you put the level on the other side of the crack, closer to the wall, the floor is not level - it actually sloped down toward the wall. So I have this large section of very level concrete covering the majority of the floor center and i have a perameter of approx 3 feet from the walls around the foundation that slopes in toward the exterior walls.
 
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Old 01-06-07, 05:37 AM
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Sinking walls, rising

Good move to have a professional look at it you are concerned and planning to finish the area. You have to know where you are when you start a trip.

You probably used a 4' level, which is good for wood work, but not accurate for larger areas or engineering dimensions/tolerence.

Dick
 
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Old 01-08-07, 12:54 AM
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Sounds like the floor is heaving

I agree with Concretemasonry with the fact that had the footings and walls been sinking that much, some cracks should be visible in the foundation walls and also in the drywall of the structure above. The basement floor should not be tied into the footing and walls so when the footings settle the floor is not pulled down around the perimeter.

Sounds like the floor is heaving up in the center and who knows what kind of base is under that floor. You may have a floor that has been poured on mud and is only two inches thick… hard to say without looking at it. “IF” your floor is heaving due to a poor base the best way to repair it is to tear it out and replace the base properly, than pour a new basement floor, with wire mesh as reinforcement… or you may have the same problem again in several years.
 
 

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