slab foundation, house built in 1977, Question

Specific Inspection Topics Structural Inspections
1

The sellers were installing ceramic tiles thoughout the
entire house…the bedrooms were bare concrete on the day
of the Inspection…Two of the three bedrooms had settlement cracks.
The cracks were less that 1/4 of an inch and did not go completely across
room…I need help with good verbiage for this type of situation. Here’ an
example:

David

2

This is in all my reports:

“…In accordance with our standards of practice, we identify foundation types and look for any evidence of structural deficiencies. However, cracks or deteriorated surfaces in foundations are quite common. In fact, it would be rare to find a raised foundation wall that was not cracked or deteriorated in some way, or a slab foundation that did not include some cracks concealed beneath the carpeting and padding. Fortunately, most of these cracks are related to the curing process or to common settling, including some wide ones called cold-joint separations that typically contour the footings, but others can be more structurally significant and reveal the presence of expansive soils that can predicate more or less continual movement. We will certainly alert you to any suspicious cracks if they are clearly visible. However, we are not specialists, and in the absence of any major defects we may not recommend that you consult with a foundation contractor, a structural engineer, or a geologist, but this should not deter you from seeking the opinion of any such expert.”

3

Joe,
That is a great comment. Thanks for sharing. That just went into the header of my structural section template.
Greenie for you! :o)
Mark

4

Thanks…

5

David,

As a builder I do my own tile installations… have been putting tile down since at least 1992 and as such I know that CTIOA (ceramic tile institute of America) does not recommend that tile be installed on concrete slabs; not all concrete is suitable for tile installation for several reasons:

  1. Slabs above grade ARE designed to flex or move it if you will…they have to account for both live and dead loads as well as any seismic activity…for this very purpose you can expect to have cracks… often though without displacement.
  2. Slabs generally have a slick for finish…when installing tile on concrete you should have a broom finish
  3. There should be a substrate or finish that can help account for any flex… I personally have been using Schluter Ditra for over 10 years…if not longer. This is the only product that I use on a slab…otherwise I do not install on a slab of ANY kind.
    Schluter Ditra can be install on decks and exterior porches as well.
    Ditra allows the tile to move independently of the concrete itself which is why it is far superior to any product I have ever come across…and its relatively cheap (my cost is about $1.00 per square foot).
  4. Depending on the size of the room an expansion joint may be required for the tile since it is unlikely an inspector will not be privy as to weather the concrete was reinforced.

There are some other issues that can crop up however the above is more then enough not to install tile over concrete.

As to verbiage;
Because concrete is an unstable material, many tile association do not recommend that tile be installed over same; an approved membrane should first be installed over the concrete slab prior to installing ceramic tile.

I can not stress enough the use of Schluter Ditra… it is an excellent product.
I will advise though that when using it…DO NOT use modified thinsets (more expensive) to install tile onto the Ditra… it is fine to use modified thinset to install the product (Ditra) on top of concrete and wood subfloor but not on the product itself.

regards

Jeff

6

Thanks…