Residential Contractor Foundation Install 4

[UofAGrad]

Hey guys, a little background on the situation that was brought to my attention today. Last fall I was approached by a homeowner who bought a property with a home on stilts (12 L4X4X1/4 on 12"X12"X12" footings). The supporting footings if you want to call it that were way undersized, access under the home was limited, I brought a contractor to the site to discuss construct-able solutions. Long story short I did an evaluation of the structure and provided repair sketches for new spread footings and cripple walls to support the home.

The contractor recently did the install of the spread footings and failed to call the county out to do a pre-pour inspection, the county stopped work and told him he needed to get me to sign off on the install. I met with him today and reviewed the photos he has. He captured alot of pertinent information but not all, so I told him I cannot sign off on it. I'd like to help him and the homeowner out, but I'm not sure what all of our options are? Can I:

Demo a footing to verify install was done correctly?

Verify dimensions and locations of footings then state that what was visible is correct and the contractor is liable if rebar was not placed correctly? Would this be acceptable?

(preferred) Evaluate the footings as if the rebar wasn't installed at all and propose install of adjacent footings where needed?

Are there other options I should be considering? TIA!

 

[SlideRuleEra]

I... provided repair sketches for new spread footings and cripple walls to support the home.

If you "verify dimensions (including thickness, I presume) and locations of footings" and "evaluate the footings as if the rebar wasn't installed at all" (and it passes), what else is there to do?
Why would it be necessary to "install of adjacent footings where needed" if field investigation determines the Contractor followed your plan?

Edited: BTW, the existing wood 4x4's, 12 feet long supporting an elevated house are grossly undersized. They may "work" based on structural calcs, but are not good practice and do not meet building codes, if memory serves. Believe eight inch (square) is the minimum code requirement. This, plus the small footings, could be a clue that plenty of other "shortcuts" taken when the house was built.

http://www.SlideRuleEra.net

 

[BridgeSmith]

SRE, I read that as the house is supported on a dozen 4X4X1/4 steel angles; no length given. The OP said "access under the home was limited", so I assumed they were fairly short.

 

[SlideRuleEra]

Thanks, HotRod, I see you are right. Will strike out that comment on my previous post.

http://www.SlideRuleEra.net

 

[dhengr]

UofAGrad:
This story sounds like one of those cabin/shack projects, on ten acres back in the remote sticks someplace. A DIY’er. in three or four weekends, with the buddies, kegs of beer, some light steel angles picked up at a scrape yard, and a few multi-ply fl. beams picked out of the IRC tables, without much understanding of how things structural really work. While these structures are loose enough so a little differential settlement won’t hurt much, you have to guess at an allowable soil pressure. And, a few of those angle columns/piers will see (might see) higher loads than most of the others because of the funny continuity of the fl. beams, which may or may not exist, given how they built the multi-ply beams. The gravity loads are usually fairly light, except for concentrated loads from above, so ftg. size is usually not a big problem. The real problem is usually that nobody gave any thought to lateral loads on the bldg., and that pier/column/found. system can be pushed over with a feather. You have to get all the lateral loads down into the soil; through the bldg. walls, the fl. diaphragm, those no moment connection light angle legs and into ftgs. which can withstand and distribute those lat. loads.

 

[NorthCivil]

Sounds like the kind of work I used to do:

Shoddy existing work to start with. Totally incompetent contractor. scenario leads to big personal involvement/ buddy-type obligations. poor work leads to engineer being asked to take one for the team and sign off on it, cause "she's right, mate!". No opportunity to inspect. this leads to some big uncertainty and significant liability.

let me guess, there is no money in this either?

Though residential wood frame alterations are interesting projects, I'm glad I'm not involved in them anymore.

 

[UofAGrad]

I'm glad to hear this situation isn't as unique as I had thought lol. Dengr you hit the nail on the head, this place is about 45 minutes out of town, 3 miles down a private dirt road on it's own 20 acre lot. NorthCivil this is the same scenario as you described too, only the contractor is working with me and accepting their screw up. I will be compensated for my time through him.

SlideRuleEra, if everything passes without the rebar you are correct, there are no issues. The engineering was done by me and rebar was called out to be within the footings, the contractor says he installed the rebar per my drawings and I have no reason not to believe him. I just can't sign off having not witnessed it. I was wondering if there were other options I may not be considering. Possibly some writing within one of the codes that allows "construction to continue under the assumption the footings were installed per the drawings, if new information becomes available in the future that proves the contractor did not install per the prints he would be liable for any damages and repairs." Sounds like some sort of precedence may have been set for this scenario. If this doesn't exist we are going to continue on Monday with the re-evaluation without rebar and new adjacent footings if necessary.

 

[TehMightyEngineer]

Can you get sufficient access to use a rebar scanner to investigate the footings? Do you have someplace you can rent or a person you can sub rebar scanning out to? If it's close enough to the scannable surface this should be sufficient to determine location, spacing, and definitely presence of any rebar.

If no access, or it's not feasible, I'd just power chisel out some of the [tt][sup]footer[/sup][/tt] FOOTING to verify you find rebar and call it a day. Write a letter stating you didn't verify 100% but you random spot checked and see no indications it wasn't built to your drawings (assuming you find rebar).

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)

 

[CANPRO]

I've signed off on footings based on pictures with a note on the city form stating the inspection was via pictures - obviously this route is a function of the importance of the footing and your level of trust in the contractor.

 

[Ingenuity]

...of the footer...

If Ron sees you 'footer' nomenclature...well, you have been warned...and there is an EDIT button too

 

[Ron]

@Ingenuity...

@TME....you know better!! [flush]

 

[TehMightyEngineer]

Errr. That wasn't me, that was clearly some other TME from a mirror universe out to ruin my reputation!

Anyway, back to designing footers out of cement.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)

 

[Rabbit12]

So who required the foundation be retrofitted? Did the county come in and say it was undersized and needed updating or did the homeowner do it on his/her own? Seems that if the owner was doing this on their own that the requirement for a letter is somewhat silly. It's certainly better than it was.

 

[WinelandV]

Anyway, back to designing footers out of cement.

I just about spit my donut out of my mouth!

 

[UofAGrad]

The county had no record that there was even a home on the property, when the home owner purchased the property and requested to do some development to the land, when the county inspector showed up they had no records that a home existed there. I feel the homeowner should have pursued some compensation from the previous land owner he purchased it from but that is another story. Anyway, the county requested that an engineer evaluate the structure as a whole. There were other deficiencies I found (over-stressed joists, insufficient handrails, missing handrails, spiral staircase not installed properly....) but those have been repaired and given the OK by the county.

TME have you had success with rebar scanners in the past? We had a company come out and showcase their rebar scanner once in the past and it was a joke. Admittedly, that was 6 or 7 years ago.

 

[CANPRO]

Are the original vertical supports still there? Were there any issues, settlement wise before your evaluation? Did you check the footing as plain concrete as you mentioned, how did that check work out?

By the sounds of it, you took a structure that failed on paper, but was functioning in reality, and you made it considerably stronger. Based on the photographs, you know there is rebar in the footing and you can verify the dimensions of the footing. I'd be inclined to sign-off on the structure - especially if your footing works on paper without rebar. Its a judgement call, and you're the one with all the facts to make the decision, but it doesn't sound crazy to sign-off on this situation.

 

[Ingenuity]

TME have you had success with rebar scanners in the past? We had a company come out and showcase their rebar scanner once in the past and it was a joke. Admittedly, that was 6 or 7 years ago.

I am not TME, but I have owned and operated a GPR concrete scanning units for more than a decade. Most of the major brands (GSSI, Sensors & Software, Hilti, Proceq etc) are very good at locating the rebar, and their approximate depth in typical concrete elements, like slab, walls, and beams, to say a depth of less than 18". Near impossible to accurately determine rebar diameter non-destructively.

When we have to be definitive on rebar diameter, we supplement NDT scanning with a bit of invasive probing (aka concrete chipping and patching).

By their nature of size and proximity, footings would be classified as tough to scan with reliable results. For a 12"x12"x12" footing it is such a small element you would not get a lot of scan data in the 1' long pass, and that assumes easy access, which is often not the case for foundations.

 

[TehMightyEngineer]

UofAGrad: I've got a fair bit of experience using a Hilti PS 1000 scanner.

In short, it's not a miracle tool and not worth $30,000 unless you're actually using it for what it's intended for (locating rebar to avoid drilling or coring it when setting anchors).

For uses of locating or confirming the presence of rebar it's pretty good, but it's usable depth is limited to about 6-8 inches for this purpose and one cage of rebar will block another cage of rebar. If you're on top of a slab or footing trying to see the bottom layer of reinforcement, you'll see only the top layer and some vague ghosts of the bottom bars, but you will at least see the lower bars somewhat if you only need to confirm their presence.

Essentially I've found it to be great for when you know what should roughly be there and just need to confirm. For example, if you're not sure how many strands are in a prestressed slab, or what spacing the columns ties were placed at, etc.

Plus, it's invaluable when you cannot destructively examine something. Makes some really pretty pictures as well.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)

 

[Ron]

We have a GSSI GPR unit, a Proceq, and a cheap Hilti....GPR is the more accurate of them. We built a "calibration" wall behind our office to check them all.

If a strip FOOTING (sorry TME...couldn't resist ), it will be difficult to detect rebar because of clearance issues. If a pad footing, you can usually be more successful.

 

[UofAGrad]

Interesting information regarding the rebar scanners. I'll keep this in mind for future/larger projects in heavy industrial environments.

As for a status update, I checked the footings and a couple fail for flexure without the rebar. Talking to the contractor he has the forms made and extra materials so we are going to install a few new footings in select locations and I will sign off on the project.

Something I did find that was interesting, in ACI 318-11, 20.2.2 it provides some guidance for these situations. Probably pertaining more to 10+ year old structures than 10 hours old lol. it recommends spot checks of 5% of the reinforcement in the critical sections to verify rebar was placed per the drawings. I discussed this with the contractor and he felt it would take as much work to access these locations as it would to install new ones. I wasn't going to argue.

Thanks for everyone's input!