EXISTING BLOCK FOUNDATION REVIEW 1

[rgsdez]

I HAVE BEEN REQUESTED TO INSPECT AND "CERTIFY" AN EXISTING 8 INCH BLOCK FOUNDATION/FOOTING (ASSUMED TO BE HOLLOW CORE, NONGROUTED, AND WITHOUT ANY REBAR OR REINFORCING) OF A RAISED RANCH HOUSE (35 YEARS OLD)THAT HAS HAD FIRE DAMAGE. THE HOUSE IS LOCATED IN THE NORTHEAST. THE OWNER ANTICIPATES TEARING DOWN THE EXISTING FRAMING TO THE BLOCK AND REPLACING IT WITH A MODULAR OF SIMILAR DESIGN. AN INITIAL REVIEW INDICATES THAT THE HOUSE LOADINGS WILL BE SIMILAR. THE QUESTION IS IN REVIEW OF THE FOUNDATION. THERE IS NO PHYSICAL DAMAGE TO THE BLOCK FOUNDATION FROM THE FIRE AND THE IT IS GENERALLY IN GOOD CONDITION,ONLY A FEW RANDOM HAIRLINE CRACK ARE VISUALLY EVIDENT. THERE IS VISUALLLY NO EVIDENCE OF DAMAGE TO THE FOUNDATION FROM HEAVING, WATER DAMAGE OR AFFECTS OF AN UNBALANCED BACKFILLL LOADING. WOULD THE INTENSITY OF THE FIRE (ON THE TOP FLOOR) HAVE CAUSED DAMAGE TO THE BLOCK STRENGTH THAT I MAY NOT BE AWARE OF. ALSO, THE CONCRETE FOOTING (ASSUMED TO CONTAIN NO REINF.)WAS UNCOVERED AND IT VISUALLY APPEARS TO BE IN BETTER THAN GOOD CONDITION, HAVING UNDERDRAIN ADJACENT TO IT. THE EXTERIOR FOOTING WIDTH VISIBLE IS 5 INCHES AND I ASSUME (??) THE SAME OFFSET WIDTH ON THE INTERIOR, WITH A MEASURED DEPTH OF 7 +/- INCHES. I AM CONCERNED WITH THE INTEGRETY OF THE CONCRETE FOOTING. THE EXTERIOR SURFACE (APPROX 1/8 INCH IN DEPTH) APPEARS SOFT AND EASILY SCRAPED OFF. IS THERE A METHOD OF EVALUATING THE SOUNDNESS OF THE CONCRETE FOOTING WITHOUT DESTROYING IT? THANKS FOR ANY HELP ON THIS ISSUE.

 

[Focht3]

Hmmm,

It's hard to get excited, although I understand your concern. If the loads are similar (same?), you can't find evidence of damage to the foundations, and the owner understands the risks - I'd move forward. But I'd give both options in my report (re-use vs. new) and explain the risks and rewards of both. That way, you make it the owner's call - which is where the decision should rest. After all, it's his money -

BUT I wouldn't CERTIFY a damn thing. I don't do it for new construction - why should I do it for an old foundation that has been through a fire? I wouldn't accept the risk. Period.

Are you working for the insurance company?



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[rgsdez]

I am an P.E. contacted by the property owner. I'm new to this type work, doing it part time, and tend to proceed rather slowly with these type of requests. I guess you might say I'm trying to get my "ducks in a row" before I discuss futher with the property owner and determine the next steps to take.

 

[Focht3]

How much effort would it take to prepare a foundation plan for new footings? Are you on time & materials, or lump sum? If you have a lump sum agreement, I'd eat the (presumed) small additional cost and prepare a set of foundation plans for new footings. Make your 'above foundation' plans suitable for both the existing and 'new' footings. That way, the owner is literally prepared to go either way at no additional cost to him. Once you outline the pros and cons (of new vs. re-use) in a letter to him, you have done about all you can to protect yourself.

By the way, who is asking for the 'certification' of the existing footings?



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[rgsdez]

It's a lump sum but putting the foundation plan together is a good idea. The property owner says he needs it to provide to the Building Inspector. I think it's time to discuss this with the B.I. Thanks

 

[jheidt2543]

Just a couple of additional thoughts:

1. This sounds like it is a 8" block frost wall, not a basement wall, is that correct? Then you have the wall supported on both sides with backfill material.

2. Check with the Building Inspector to see what code the foundation and house have to meet. My guess is that the foundation will have to meet the current code requirements because of the extensive repairs. The new requirements for anchor bolt anchorage in foundations are pretty tough and my guess is you will have to meet them to anchor the new house down. It might only mean grouting the block cores at each bolt, it could mean a continous bond beam at the top of the wall, it could mean solid grouting of all cores, you should check with the inspector.

3. The fire might not have damaged the wall, but there is some chance that the cracks you see are the result of sudden cooling from the water hitting the hot block. If you check the block and the mortar joints and they seem solid, not chalky or loose, then you are probably OK.

4. If this is a basement wall, then you have to do some calculating to see if you can meet the Unreinforced Masonry Wall provisions of the code.

Just a few more things to add to your list! Good luck.

 

[rgsdez]

The 8 block wall is half the height of the basement, the rest is framed up. I checked the unbalanced backfill, its approx. 32 inches, sufficient for an unreinforced concrete masonry unit design. The first words from the Building Inspector were, " does the foundation meet current code?"
The uncovered footing looks to be approximately 7"x16", the current code says minimum 8"x16". In the area of the foundation that was uncovered the depth from ex. ground to top of footing is only 32" and the current code says 48", that could be a problem. I will explain to the BI that the existing foundation has performed acceptably for the past 35 years, but I don't know if that will be enough for him to agree to accept the current nonstandard frost depth. I assume he will have the final say in accepting use of the existing foundation. As for the anchors, I expect to indicate that the 4" cap will need to be removed and the hollow cores grouted, then anchor bolts can be placed and the 4" cap replaced.
The hairline crack appear solid but they also don't appear new ( from the fire).
Thanks for the input, it's helping me work through the issues.

 

[dutchie]

another consideration is the type of soil you are bearing on. a well graded granular is not frost susceptible, and therefor should not be an issue to the building inspector. if clays or silts, then i would not be comfortable with the cover. It is also my opinion that if you are comfortable with the footing the way it is and were to put your seal on it, the building inspector will generally allow it (at least in our parts). However, it gets back to a point made earlier, why take on that risk.

It would be my thought that the cost of doing the foundations over within the overall framework would not be excessive, and would ultimately ensure that the homeowner recieved a home built to code, with no chance of problems. (provided it's a good contractor)

good luck

 

[RDK]

Be very careful using the word certify.

If you certify something then you are assuming a risk under contract. This type of risk is expressly not covered by any professional errors and omissions policy issued in Canada and I would assume that the US situation is similar.

Instead of using the word “certify” you should state that ‘based on my examination of the site in my professional opinion the foundation is satisfactory” or similar words. This moves the issue form one of you assuming a risk under contract and therefore uninsurable to one where you have offered a professional opinion as to the condition of the foundation and this is an insurable risk.

Similar logic applies to “certifying” construction. You should state that based on my (periodic) inspections and knowledge of the site, the finished building to the best of my knowledge and belief, conforms to the design intent of the drawings.

Of course, I’m not a lawyer or insurance expert so I recommend that you get some individual advise from these people before taking my opinion as gospel.

For further reading see

http://www.encon.ca/english/lcb

(Click on Architect and Engineer Liability insurance programs then Professional Liability and see bulletin #11 on this issue)

Econ is the largest provider of professional liability in Canada and has a wealth of good information on their web site regarding professional liability and practice issues. (May not apply in the US but since the legal systems are so similar the information may be a good place to start.)


Rick Kitson MBA P.Eng

Construction Project Management
From conception to completion

http://www.kitsonengineering.com

 

[rgsdez]

Thanks for the tips on wording. I am very concerned with the amount of risk I am willing to assume, yet still providing appropriate service to the property owner.