Foundation: should i be concerned?

[Michael R. Boyett]

Here's a pretty good link, written by a couple of PE's, regarding PT design and construction: http://www.houston-slab-foundations.info/Buyer's%20Guide%20to%20Slab-on-Ground%20Foundations.pdf . If you go to the main page there are numerous other articles on foundations. Warning! this is for the serious only : www.houston-slab-foundations.info .

[ccoombs]

Chris –

I think the engineering inspection is a great idea. Texas is a major area with foundation/soil problems.

I would also ask about the “white” stuff on the side of the foundation. It looks like it might be coming from the location of the tendons and may be a sign of other issues.

Jeff –

As always: a wealth of information. Of all the thousands of PT foundations I have been involved in, there was one that was poured as a two-pour foundation. It was actually a mat PT slab with deepened perimeter footings. The poured the perimeter footings first and the placed the mat slab on top. A very strange project overall. Actually, the perimeter footings weren’t even poured with structural concrete.

Barry –

Your list of items to look for is pretty complete. I also verify that there is 1.5” between the form board and the dead anchor. In my area you also need to have a continuous perimeter rebar or “hair pin” rebar at each anchor. For some bathroom issues they will place a box to create a void in the slab. It is important that these do not reduce the concrete around the tendons. This is very important at the slab edges and corners.

It is also very important that they vibrate around the anchors to avoid voids near the anchors. I like to walk the recently poured foundations to verify they don’t have too many voids. If they do, I would make a point to come back after the pour but prior to them “fixing” the issue.

As for the tendon going above and below the pipes, I see this as an issue. It appears to be a beam tendon, so these should be placed towards the bottom of the beam (draped). The plans will show the exact placement of the tendons. Also, the tendons can be placed and run around objects in the foundation. Most plans will show the allowable movement. It typically is a 6:1 slope.

Thanks for the link. I am giving the link to my project engineers to review and read.



On a side note: I will be going to a job site today to view the fix of 7 cut tendons in an existing home. The contractor was cutting out the front edge of the garage slab to tie in a new driveway.

[Jeffrey R. Pope]

Originally Posted by ccoombs

Of all the thousands of PT foundations I have been involved in, there was one that was poured as a two-pour foundation. It was actually a mat PT slab with deepened perimeter footings. The poured the perimeter footings first and the placed the mat slab on top. A very strange project overall. Actually, the perimeter footings weren’t even poured with structural concrete.

"Mat slabs (also referred to as "raft" slabs) are a completely different animal. Typically they include interior caissons (piers). Often they are poured over a deep base of sand. Depending on the slab thickness, there may even be a "two-way" placement of the reinforcing steel in upper and lower layers (heavy placement over piers/supports in the top layers and heavy in the mid-spans of the lower layer).

Originally Posted by ccombs

On a side note: I will be going to a job site today to view the fix of 7 cut tendons in an existing home. The contractor was cutting out the front edge of the garage slab to tie in a new driveway.

Depending on the extent of the damage to the tendons, these may not require replacement cables. I'm sure you have an idea of what needs to be done