building brick walls on "propped" structure ? Now it cracks after de-propping
building brick walls on "propped" structure ? Now it cracks after de-propping
(OP)
Hi, I have some problem because the contractor was building brick walls on propped structure.
Now what happens after they "de-propped" the slabs, the bricks started to crack here and there.
How can I prove to the contractor that this was wrong? Obviously he is now arguing that why was he not supposed to build the brick walls on propped structure.
Where can I get some written proof that this is not allowed? Do the building regulates and codes mention it?
Now what happens after they "de-propped" the slabs, the bricks started to crack here and there.
How can I prove to the contractor that this was wrong? Obviously he is now arguing that why was he not supposed to build the brick walls on propped structure.
Where can I get some written proof that this is not allowed? Do the building regulates and codes mention it?






RE: building brick walls on "propped" structure ? Now it cracks after de-propping
BA
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
www.PeirceEngineering.com
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
Probably one of the first things you need to do (if you don't already know) is figure what the deflection of the "slabs" would be long-term and what they would be at the point he removed the supports/forms. If the former is in excess of the latter.....you don't have a leg to stand on. You may not have one anyway if the long-term deflection exceeds something like L/600. (IIRC that's the requirement for supporting masonry under some circumstances.)
If he's not following your directions (or the drawing notes) and the deflection meets the criteria I was talking about in the previous paragraph.....it's time to talk to the owner/PM about getting him off the project.
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
Specifications and design drawings should specifically require that slabs and beams be unpropped before masonry and brittle finishes are added.
Any engineer who does not specify this cannot base their design on the deemed to comply deflection / span/depth ratio rules in design codes because they assume unpropped conditions and "incremental" deflections are controlling the design, not total deflection.
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
Can it be remedied in a simple and cost effective manner?
Dik
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
https://www.facebook.com/AmericanConcrete/
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
It is the designers responsibility to both specify it and check that it is done correctly in my opinion.
The contractor is supposed to do what he is told.
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
Maybe the brick wall should have been designed as a deep beam, with a substantial bond beam, tension reinfr’g. region at the bot. of the wall height, to distribute the tension forces and provide some self spanning ability, and better distribute the wall DL. You might have been better off waiting to build the wall until the slab didn’t need to be propped for early strength, deflection and curing reasons. Thus, some deflection would already exist when starting the wall and some added deflection due to wall weight might be accommodated by a softer wall which was still compliant. Maybe the slab should have been formed and built with some camber in this wall area so that it would still have a bit of camber after the wall was built. Some of this problem falls back on the EOR for not designing the wall and the slab in anticipation of this sort of potential problem.
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
Dik
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
Sorry, Precamber does not help! It is the amount of movement that affects brickwork, not the final deflected position. Precamber has no effect on the amount of movement, only on the visible deflection, unless you make it an arch, and I doubt that you want that much Precamber!
Otherwise, yes some Engineering input into it as you have described might have been useful.
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
I just regrade that I did not have a note on my drawings which clearly stipulates that this is not allowed to built walls on a propped structure
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
I assume "regrade" should read "regret". The question is, if the props had been removed before building the walls, would there have been a cracking problem?
BA
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
Juston Fluckey, SE, PE, AWS CWI
Engineering Consultant
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
Brian C Potter, PE
Simple Supports - Back at it again with the engineering blog.
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
" Of course the engineer could not know ahead of time how much it would deflect after removing the props"
Why wouldn't the designer know. It is part of the design calculations, if the designer wants to put in the effort to do them properly.
"I wish I could anticipate every dumb thing a contractor might do and place a note on my plans to warn him not to do it, but I don't have a crystal ball."
That is normally what Notes are for. So that the designer can tell the builder the limits on how he wants it built to suit the design. It is possible to design the floor to allow the brittle wall to be built on a shored floor if you want to do the calculations and pay the extra cost for the improved deflection control.
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
yes, a note should be on the plans and that will at least protect the engineer. But don't count on a contractor reading it
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
"" Of course the engineer could not know ahead of time how much it would deflect after removing the props"
Why wouldn't the designer know. It is part of the design calculations, if the designer wants to put in the effort to do them properly."
and, of course, you would expect the contractor to know this?
Dik
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
apparently neither was done on lolobau's project.
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
"quaint old practice"
Probably not in other countries either, more in past times, before the age of project managers, where designers had more control and were actually paid to do their job properly, until the construction was completed. I should have added a smiley (or sad) face!
dik,
I have never made the assumption that a builder actually understands engineering or design. Some understood if explained properly, others simply have no idea what you are talking about. And getting them to read notes on a drawing!! And that is where the problem with lack on involvement of the building designers in the construction process and supervision/inspections rears its ugly head.
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
Dik
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
BA
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
And don't forget that 'pesky' creep and shrinkage deflection that will occur over the lifetime of the slab.
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
Dik
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
BA
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
You missed the bit about the slab still being propped when the wall was built. So the wall experiences the full deflection including the slab Sw and the wall weight as well as loads added afterwards and the resulting cracking effects. And the long term effects as mentioned by Ingenuity.
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
Yes, I missed that. So, what is the total deflection?
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
and this is what is happenign after removing of the propps
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
So unless you told him to build the brickwork with the props still in place, the responsibility and schedule for any temporary construction works remains with the contractor. End of.
I'm a little surprised something that size moved enough to cause significant issues, but you have the evidence in front of you.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
Dik
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
I like your statement " "why was he not supposed to build the brick walls on propped structure" is that the prop was a temporary construction feature" this covers me a bit
I attached a photo of the site
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
I'd be interested to know whether sufficient reinforcing is in the correct position in the cantilever slab. I can't see cracks in the slab in the photo, but it seems like there's more at issue than just the timing of the shoring removal.
If all the reinforcing is in place and you're satisfied that the structure has the capacity that it needs, then you can patch the cracks, right?
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
I second Wallache’s funny brick wall comment. It looks like your wall is pivoting on the left exterior window wall and conc. beam below, in your elevation view. The back span isn’t much longer than the canti. span, and it would appear that there is not enough rebar in the wall, at the door jambs, at the door head, or at the top of the wall. The wall is likely picking up a good share of the balcony slab loading too. Your wall is trying to act like a deep beam, but has not been properly designed, reinforced or supported. You may also want to check the concentrated reaction under your wall right at the ext. window wall.
(Edit) Also, it would be reasonable to assume that the canti. balcony slab and conc. beams below would be propped during the forming and pouring of your wall, and during its curing. Your wall and the slab below should be (should have been) properly tied together, bent tension rebars, etc. to tolerate this framing configuration. The forming joints don’t seem to make much sense, except as intentional stress raisers, or crack inducers.
RE: building brick walls on "propped" structure ? Now it cracks after de-propping
Dik