Slab tilt

[jives]

Need some insight here prior to putting down a new floor. House build 15 years ago, stem/frost wall with concrete slab. Slab is the finish floor (stained) and is tilting. Slab has radiant floor hydronic heating. Slab is not notched into the stem wall, but is butted up against the stem wall with an angle cut. The angle cut allows for insulation to separate the stem wall from the slab. The center of the house has a thickened slab (grade beam) that is monolithic with the slab. This grade beam supports the load bearing center wall. The slab has sunk/tilted compared to the stem wall, but not at the center grade beam. BTW, the slab sinking is also on the stem wall on the other side of the house. No discernable sinking is the past 5-10 years. The grade beam is exactly level with the stem wall. . . no sinking, raising, tilting. There is NO discernable cracking in the slab anywhere.

We plan on putting down a new floor, most likely quality vinyl that will go directly to the sill plate. But the drop is a problem. I could grind off the stain and use a floor leveling compound, then vinyl over the top. But is there a better way, such as some sort of sleepers and a partial wooden subfloor? I do not think that raising the slab is a good idea as there are too many unknowns, such as the radiant floor.

 

[BillK]

I think it would be at least worth a call to one of the slab jacking companies to see what they think. What could it hurt ? That would be my preferred solution.

 

[tmp]

Is an inch over 15’ even perceptible when you walk the floor?

I’m a bit confused about how the slab would sink a full inch to the walls on either side of the grade beam without cracking. Are you saying the grade beam is the high spot and the slab sinks out on either side? Like it’s crowned in the middle?

 

[PCustoms]

Why can't you lay the jew floor on 0.5% slope?

If you want it level, self leveling compound is the way to go IMHO, especially with such a small slope

 

[ipgenie]

I agree, self leveling compound is perfect for this.

If you decide to jack up the floor, an infrared camera will show you where the tubes are. I was surprised at how clear they show through the tile in my house when the heat is on.

 

[jives]

The slope is imperceptible, and a ball won't even roll. The problem is that new vinyl flooring will need to step up from the tilted floor to the stem wall. If I were laying down a 1.5" thick wood floor, I would just rabbet the ends or edges of the boards where they hit the step.

 

[Fav Onefour]

Hydronic heating works better with conductive material.
Self leveler would help retain more efficiency in the heating system.

The other side to this is what is happening under the slab to let it sink that much? Where are you hydronic lines entering the slab? One inch of drop would start to be an issue if they're entering on that side. I'm assuming everything is still working/no leaks.

Good news on the 5-10 years with no more sinking. That is in your favor. On the other hand, it's not a guarantee. I just did a basement project that required opening about 10sq ft of 1970s slab. Level indicated 5/8" drop in six feet. Slab was intact but I could hear hollow with tapping. When I broke out the section, I found a void 8" deep under the slab. The area of subsoil settling was about 30sq ft. Interestingly enough, the low area of the slab was closely matched to the subsoil settling. It honestly looked like the initial pour settled right after finishing and then cured before the subsoil finished settling. Maybe the slab would have been fine for another 50 years?

It's not easy doing tap tests on top of foam but it might be helpful to get an idea of how much open space is under your slab.

 

[PCustoms]

The slope is imperceptible, and a ball won't even roll. The problem is that new vinyl flooring will need to step up from the tilted floor to the stem wall. If I were laying down a 1.5" thick wood floor, I would just rabbet the ends or edges of the boards where they hit the step.

If there's no slope it sounds like the stem is just higher then the floor.

Got a pic of the area you're concerned with?

 

[jives]

If there's no slope it sounds like the step is just higher then the floor.

Got a pic of the area you're concerned with?

I'll see if I can get some tonight when I am home.

 

[jives]

Okay, finally got around with some pics. Just bought a laser level (Lowes gift card from the kids). In this case the slab has tilted 9/16ths from the center of the house, which has a grade beam.The first pic shows the laser sitting on the grade beam, shooting a beam diagonally across the floor to a door threshold. The closeup shows the amount of tilt. The slab height at the grade beam in the center of the house is at the bottom of the blue tape.

 

[PCustoms]

Okay, finally got around with some pics. Just bought a laser level (Lowes gift card from the kids). In this case the slab has tilted 9/16ths from the center of the house, which has a grade beam.The first pic shows the laser sitting on the grade beam, shooting a beam diagonally across the floor to a door threshold. The closeup shows the amount of tilt. The slab height at the grade beam in the center of the house is at the bottom of the blue tape.

So your slap slopes (likely since day 1) about the width of the blue tape, but the slope is not perceptible and nothing rolls away?

What is your concern again?

Lay the flooring to that step then trim on the wall. Looks to me like that lip is the top of your stem wall/footing. Plenty of people have had to work around similar in their garages

 

[jives]

So your slap slopes (likely since day 1) about the width of the blue tape, but the slope is not perceptible and nothing rolls away.

Lay the flooring to that step then trim on the wall. Looks to me like that lip is the top of your stem wall/footing. Plenty of people have had to work around similar in their garages

Wife said that balls will roll (she's had daycare kids), but still not much. The problem is that the exposed frost wall is too wide to be covered by trim. The frost wall lip is too much to be spanned by any flooring. I want the new flooring to cover the slab and frost wall and get tucked under the baseboard.

 

[PCustoms]

Wife said that balls will roll (she's had daycare kids), but still not much. The problem is that the exposed frost wall is too wide to be covered by trim. The frost wall lip is too much to be spanned by any flooring. I want the new flooring to cover the slab and frost wall and get tucked under the baseboard.

How long have you lived in this house?

Any water issues?

Looking at (what I can see) of your trim details it almost looks like there was another floor at one point, as well as water stains

 

[jives]

How long have you lived in this house?

Any water issues?

Looking at (what I can see) of your trim details it almost looks like there was another floor at one point, as well as water stains

We built the house 15 years ago. The builder had an idea to make sure there was some insulation between slab and frost wall. Should have used a cut-out (rabbet) in the frost wall to accept the slab. No other floor, we stained the concrete to keep it as the finish floor. It acts as a thermal mass for the passive solar.

 

[PCustoms]

So the trim has always sat this high?



Is this water damage?

 

[manwithtools]

So the trim has always sat this high?



Is this water damage?

Yes the trim has always been where it is, because the trim is sitting on top of the frost wall and the slab has moved downward as the OP said. You can see the expose edge of the frost wall (bare concrete)

 

[PCustoms]

Yes the trim has always been where it is, because the trim is sitting on top of the frost wall and the slab has moved downward as the OP said. You can see the expose edge of the frost wall (bare concrete)

Thanks, I was asking the OP.

I don't see a sunken slab, I'm trying to ascertain if this has been "sunken" since day 1, and also determine why his trim looks to have water stains

 

[manwithtools]

I don't see a sunken slab

Not sure which of these is closest to you

 

[PCustoms]

Not sure which of these is closest to you

I'm due next month, thanks for the reminder. 20/17 and 20/20 last year so I think I'm fine. Looks like the slab was finished lower then the stem wall since day 1, otherwise that's some remarkably even settling.

I'm not here to argue with anyone, and it seems this all we're doing here so I'm out.

Hopefully the OP doesn't end up mixing self leveler by the trashcan in an attempt to fix this.