Masonry Foundation Wall

[ChipB]

I have a high foundation wall (27'). I have a basement floor framed in so that it's unbraced for approx 17'. I don't remember my reinforcing because I did this a while back. I called out for truss-type joint reinforcing at every other coursing, and spec'ed for ACI 530.1 and ASCE 6 for materials and workmanship.

Ok, here is my delimma:

Ladder reinforcing was used by the contractor instead of truss-type.

I can EASILY slide a credit card (this is great to do because it destroys the magnetic strip thereby making it unusable! Use your wife's) between the webs of the blocks between coursings.

I designed for 10' of maximum backfill and show "10' max. backfill" on the plans. He has 14'.

Obviously the contractor has not built the wall per my plans and specifications. I'm writing a letter to outline this and basically not standing behind the wall (I'm a structural engineer! I stand beside my structures! (Not under them! )) due to these shortcomings.
Do I tell him the wall needs to come down?
Do I CC the building department on this letter?

 

[jheidt2543]

Here are some thoughts to consider:

1. I would first provide temporary bracing for the wall until you figure out what its condition is for sure. I would NOT take it down, yet.

2. I would next find out what the vertical rebar is for size and spacing and whether it was actually installed per the plan. Vertical rebar is more important than the horizontal "Durrowall" reinforcing for a basement wall.

3. How much is the wall deflected? A crack the thickness of a credit card is not that big, I've seen worse that where repairable.

4. I would reinforce the wall instead of taking it down. There are a number of ways it could be done, here are two:

A) Add vertical rebar either from the top or through access holes cut in the block and grout the cores.

B) Provide vertical steel columns anchored into the concrete floor at the bottom and the floor joist at the top. W3 or W4 vertical at 4' centers are approximately what you would need and then a wall can be firred out to cover them up.

5. Once you decide on a fix, sit down with the contractor and hammer out a deal. He may not have followed the plan, but how much onsite inspection was provided? Usually, there is enough blame to go around when things go wrong. A 10' unbraced length for a fully backfilled basement wall is greater than is recommended by the Masonry Institute.

Good luck!

 

[ChipB]

jheidt,

The credit card is slipping between the webs of two blocks at their bed joints. It's grouted at 16" centers so I could inspect this where he has cut the wall for fdn vents.

Basement floor to main floor height is 9', then you have the crawlspace below. 18 inch trusses used. My 10' backfill is from top of ftg to t.o. wall.

He's being an ass about the suspended garage slab because I showed a bond beam underneath the steel beam, which he figured was the bond beam at the top of the wall and built the wall as such, thereby not allowing for the steel to be placed where it needed. I did not show an elevation for this bond beam because we've done it hundreds of times, and all contractors (ok, not all) know that this is in addition to the bond beam around the top.

 

[boo1]

The maximum force on the wall depends on the total wall height, soil backfill height, wall support conditions, soil type, and the existence of any soil surcharges. You did not indicate wall thickness, laterally supported at the top,soil conditions, gouting or reinforcement.

Depending on soil equivalent fluid pressure a 12" cmu will work with #60 reinformcement at:
30 psf/ft No. 9 at 40 O.C.

see guide at

http://www.ncma.org/etek/homefrm_map.cfm?spdm=cemexusa.com

 

[CSEllc]

I agree w/ JHeidt2543/

Get all your facts together, size and spacing of reinforcing steel. If you can determine that amount of lap (if any) on the reinforcing.

Once you have all your parameters, look into how you can best save the wall....if possible. To reinforce the wall, you can install additional vertical reinforcing or interior columns and girts. You might want to look into "anchoring" the wall, depending on you soil conditions, with helical piles (AKA screw piles). I have used them in a similar application and they worked fine.

Regarding the horizontal joint reinforcing, ladur or truss type can be interchanged. Typically, with reinforced masonry, I specify the ladur type since it is easier for the contractor to grout the wall. (You don't have to worry about the diagonal webs interfering with the grouting operations.) The drawback of ladur type reinforcing is the "cross-ties" are normally spaced at 15" oc which is not coursing. You need to special order the 16" oc cross ties. (I would like to talk to the rocket scientist who started spacing the ties at 15" oc in an industry that uses an 8" module......but I digress)Inevitably, the mason does not special order the 16" spacing, the ladur type is usually not stocked by the masonry yard so you wind-up with truss type jt reinforcing anyway.

About the lateral soil pressure, since the wall is braced at the top it is not a retaining wall therefore, you don't use the active soil pressure which is generally about 30 psf/ft. You need to use the at-rest pressutre which is, depending on your soil conduitions, about 55-60 psf/ft.

 

[ChipB]

Now that I'm in the office, I can check my detail further:

Sorry, 10' feet is from top of footing to top of wall. Main floor is 3'-6" above grade. My max backfill is 8'-0" (the 10 foot is from above). 35 psf e.f.f. design is correct per ASCE 7

I was alwayd under the impression to use truss reinforcing at all exterior shear walls and ladder on partition walls. Reason being it distributes the shear more evenly through the wall. Is this not correct?

I have tried to work with this guy. I used the "customer is always right" attitude on the suspended slab/bond beam detail, when we've never had a problem before. I came up with a viable option to correct it. I agree there are ways to fix it (the wall), however, he is holding our fee due to the suspended slab, and, I feel the building department should know that this wall is not built per our plans and specs. Do you guys not agree with this? Should he decide to say "To hell with him I've got signed plans" and not correct it....I am still liable if I don't inform anyone in the building department. Should I tell him to have the wall x-rayed to verify splices and spacing of rebar? Typically I (try to) catch these things quicker, but this guy just called me and the wall is built.

 

[jheidt2543]

Regarding notifing the building department, I would wait to see how your negotiations go with the contractor. I agree, if the wall doesn't get repaired you must notify the building Owner and the Building Inspector. However, you don't have to notify them as long as the negotiations to fix it are going along. Why muck up the prospect of a solution with another hat in the ring? You can also use the notification as a bargining chip.

I agree with CSEllc's comments. There are a number of ways to reinforce the wall, but in situations like these, cost is a big factor too. Personally, I think small vertical steel columns would be the least expensive, cutting in rebar and grouting cores would be next, then screw anchors as the most costly. It probably would be a good idea to start costing out solutions, because in the end someone's going to pay for the fix and regardless of how you feel about the guy, you don't want him to choke on the fix, because next time it could be your turn!

PS Don't forget the temporary support for the wall!