'floating Foundation' What Is It?

[Caterina Platt]

Hi all!!

I'm doing an REO report on a smallish ranch style and cannot get an answer out of the former listing agent, nor can I get a copy of the former owner's structural engineer's report. The report was done for the former owner, and the engineering firm can't release info without her consent. She, of course, is MIA. The expired listing references a 'floating foundation'.

The home is a concrete slab foundation on stable, but somewhat sandy soil. There is a small crack evident from the exterior of the home, nothing I would have taken serious note of, had I not seen the 1/2" crack traversing across several rooms with the carpet/lino pulled up. No other symptoms of settlement or structural distress were evident.

The photo is posted below.

 

[Greg Hyland]

I would note what you saw on exterior and interior, include the pictures, and recommend structural engineer evaluate.
This is not our area of expertise or knowledge.

Good luck.....

 

[Tina]

Oh boy!

I'd call for engineering inspection.

Slabs are constructed by first building footings for support, although some slabs (known as "floating slabs") are built without footings.

TB

 

[Scott Kibler]

From Essentials of Home Inspection, Home Reference Book, 2003 Edition from Dearborn Publishing

3.2 Floating Foundations: Where the soil strength is poor, and there is uucertainty about how successful a conventional foundation and footing system will be, one alternative is to use a floating foundation. This could be a raft or a mat foundation. The characteristics of both include a reinforced concrete foundation which forms a continuous pad under the entire building.

A raft foundation has side walls (forming a basement or crawl space) of con crete, with steel reinforcing integral to the pad, forming a raft or boat. The goal in this type of construction is to end up with the soil below the building carry ing the same weight as it did before the building was there. This is done by excavating the amount of soil that weighs roughly the same as the finished building.

A mat foundation is a thick floor slab which extends under the full area of the building. It is slightly thicker at the edges (and sometimes at intermediate points), and it floats on top of the soil distributing the building weight evenly over a large area. This is a stronger version of the slab-on-grade configuration described in Section 4.3.

Once a building is up, not much can be seen of floating foundation details. Like other footing and foundation systems, time is the best measurement device, and evidence of building shifting or settlement are the only clues for the home inspector. These special foundations usually have special design work done by engineers. It is desirable to know who designed and built the structure in case of questions or problems in the future.

 

[Caterina Platt]

Thanks guys!! Mucho fast too!!

I had honestly thought it was the stem wall with an independent slab poured on top, but was not certain and was not about to run with my guess at the definition. The Realtor has the comments worded "...home has floating foundation. Call for engineer's evaluation of crack." It almost sounded like the term was being used as the diagnosis of the problem.

As for the effects and repairs required, unfortunately I have to have some estimation as the client requires the 'As Is' and 'As Repaired', list of repairs, etc. We are trying to obtain the quotes from the current listing agent.

The scary part is, without the floor coverings being partially removed and the verbiage in the expired listing, this would have been easy to miss. It was certainly a reminder of why it's so important to have my 'no warranty implied or expressed on the structure, etc...' statement in each and every report.

Check out this photo. This is the only other visible indication and is more likely what we'd see everyday. It's not everyday that you find the neon sign and flashing arrows pointing at the damage like this one.

 

[Terrel L. Shields]

We see a lot of them in shop buildings with pole construction and concrete floors...no stem wall foundation.

 

[Farm Gal]

Cat:

Whew! I see what you mean about that exterior easy to miss it crack!!! :blink:

Thank heavens for neon signs, eh?

I'd stick an additional CYA comment in about mechanical systems (water supply and waste and GAS LINES... and your assumption that they are all intact... subject to some expert verification!

Quite possibel that the floating slab contains all of the above... and that 1/2 inch diagonal may run through more than one of them lines!

 

[Otis Key]

Cat - Call George - Not him - the structural engineer. I'll call you later. Need more details because it could be a case that I'm already on that you don't want to be on.

 

[Pat Butler]

Some floating slabs have a trench foundation where they basically dig a trench around the foundation and fill it with concrete at the same time as they fill the slab. Also called a monolithic slab. The only way to tell if this is the case is to start to dig a hole next to the foundation.