Thread: Horizontal crack in Foundation

Hi,

I am a new buyer. San Mateo/CA area. This area was reclaimed from dredged sand from san francisco bay. So salty soil is what I am told.

We are looking at a property and the inspection report says:

Type of Foundation: Concrete Perimeter with Slab fill
Comment: This structure has been subject to horizontal cracking. The cracks extend through majority of visible subarea foundation stem walls.
Additional info from agent: This could be due to rebar within concrete rusting (see salty soil comment).

Inspector has suggested a repair that does the following:

- Support structure around areas will be removed and repaired.
- Remove upper portion of foundation where horizontal cracks are present
- Drill and install epoxy coated rebar of approx 35 lineal feet of horizontal foundation where needed, vertically install steel reinforcing bars.
- apply epoxy in 110 lineal feet of foundation
- clean foundation before apply epoxy
- clean foundation and apply one coat of coating cement on all foundation
- Foundation will be reinforced with acnhor bolts, 6 on center and 12 inch from end.
- Horizontally install steel reinforcing bars, that will be installed to vertically installed steel reinforcing bars
- install concrete forms using concrete with Xypex (a water resistant additive).
- After concrete dries remove forms and supports
- Contractor will remove debris

Cost $50K

Q: Will the solution fix the problem? Anything else to be done?

We are interested in making an offer.

thanks

Nick

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Does the proposed fix have an engineers stamp on it? Is liquifaction in an earthquake a concern? Does your contractor have experience using Xypex? Best, T.G.

I have never seen a horizontal crack in a stem wall, but this seems like a reasonable fix.

I hope that inspector is also a structural engineer to design and offer such a detailed repair. Just saying.

However, what is described for the cracking fits the description of what we call "spalling" down here (caused by the use of unwashed beach sand back in the old days, and sometimes happens to more modern houses, condo buildings and balconies, and other structures (such as bridges) due to the salt spray environment affecting the steel within the concrete, rusting the steel, which expands the surface of the steel and pushes the concrete out. Typically, down here, we see two horizontal (sometimes vertical, but usually horizontal) cracks which lead back to the steel rebar.

The fix described is similar to the fix used for spalling repairs - remove the concrete, reuse or replace the steel (per the engineer, their choice depending on how bad the steel is rusted), then re-concreted (typically by spraying the concrete onto the repair area, pneumatically placed shotcrete).

Here is a typical description of spalling and its various repair methods:
- http://faculty.washington.edu/nemati/shilshole.pdf

As your estimate shows, these repairs are not cheap.

Unless the inspector is a structural engineer, I recommend that you get the opinion from an engineer. What the inspector said sounds more Ike a contractor's proposal. The repair sounds like it makes sense, but I would want another opinion, and not one from a forum like this.

I have seen what you are describing in older houses east of Bayshore. They sometimes have bright red lines as a result of rust, and the concrete cracks as the rebar expands and slowly blows the foundation apart. People have given you good advice here. I would add that the 50K price tag seems very low - that's only a fraction of what a proper repair will cost. With the construction boom going on here in the bay area and the shortage of qualified workers, you will be lucky to find anyone willing and qualified to tackle the job.

Douglas Hansen

Douglas is correct, that the 50K could escalate to $100K pretty quick if there are complications.
No mention of jacking the house up before even starting? That can be even more costly if access is difficult. Have you ever tried to jack up a car in the sand? Does the house have masonry chimneys, fireplaces, attached garages? Throw in more money.
Also, the repair will need to be earthquake proof to whatever the new standards are. Sand fill sounds like trouble.

Don't get me wrong. My house is built on a slab on sand and it is great. I can dig a 10 foot trench in about an hour, no rocks, no roots. But when sand dries out, it has nothing to bind it together.

Originally Posted by John Kogel

No mention of jacking the house up before even starting?

No need to jack the house up, simply make the repairs in 5-10 foot long increments, done all the time. That allows for proper lap of the steel as the repairs are being made ... open up a section, make the steel repair, gunite/shotcrete that section back up ... open up the next section ... repeat as necessary.

Hi nick.
I have several things to say but first wish to ask you a question.
Did you preform the inspection or did a agent hand you a previous home inspection report?

If it was your inspector, I see liability written all over this home inspection report.

Home inspectors report on condition.
Such elaborate recommendation would require a rider in their PIA.
Read the inspector PIA to see what limits his/her liability.
Like Calypso, the inspector is bond in their bones if a client uses his/her recommendations & cost projections.
You do not get much foundation repair work for $50,000 thousand dollars.

Misguided cost projections allowed B.C. to introduce licensing and regulations in their home inspection industry.
The B.C. Supreme Court ordered a home inspector. Toth, to pay nearly $200,000 in compensation to a North Vancouver couple for a faulty home inspection he performed.
The court ordered Toth to pay the $192,000 difference between his estimate and the final repair bill.

Nick, if you are will to put out $50,000, any difference might be made up by that inspector if you are willing to take that chance.
Have a lawyer read his PIA to insure his liability bonds him to his bones.

Questions:
1: Is slab post tension or rebar reinforced?
2: Was a floor level survey performed?
3: Was the plumbing surveyed to insure the piping has not be corrupted?

Recommend a structural engineer evaluate the slab.

Originally Posted by Nick Rai

Hi,

I am a new buyer. San Mateo/CA area. This area was reclaimed from dredged sand from san francisco bay. So salty soil is what I am told.

We are looking at a property and the inspection report says:

Type of Foundation: Concrete Perimeter with Slab fill
Comment: This structure has been subject to horizontal cracking. The cracks extend through majority of visible subarea foundation stem walls.
Additional info from agent: This could be due to rebar within concrete rusting (see salty soil comment).

Inspector has suggested a repair that does the following:

- Support structure around areas will be removed and repaired.
- Remove upper portion of foundation where horizontal cracks are present
- Drill and install epoxy coated rebar of approx 35 lineal feet of horizontal foundation where needed, vertically install steel reinforcing bars.
- apply epoxy in 110 lineal feet of foundation
- clean foundation before apply epoxy
- clean foundation and apply one coat of coating cement on all foundation
- Foundation will be reinforced with acnhor bolts, 6 on center and 12 inch from end.
- Horizontally install steel reinforcing bars, that will be installed to vertically installed steel reinforcing bars
- install concrete forms using concrete with Xypex (a water resistant additive).
- After concrete dries remove forms and supports
- Contractor will remove debris

Cost $50K

Q: Will the solution fix the problem? Anything else to be done?

We are interested in making an offer.

thanks

Nick

I believe San Mateo is in a high risk seismic zone. You might want to talk to someone about the risk of liquifaction.

Thanks for your help.

The Inspection report was from Sellers agent, who hired a local foundation repair agency to provide a quote.

We will bring in a structural engineer to get second opinion.