Knowing that GFRC may creep over time, what is the best way to reinforce a 12-14" canteliver? I am looking at a 36"x10' outdoor bar top with a curved canteliver the full lngth. What is best practice for this situation?

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Not sure they want 3" thickness. So your still using laddur wire in your GFRC Alla? I was thinking two layers of scrim close to the top and maybe 1" foam core.
I think your right Mark. I think wet cast is the way to go on this one. She will be a heavy one.
Well until I get more consistant results with ZRFC I better stick with what I know. It will be under 500lbs which isn't that bad. I just need to put up a gantry to flip it.

Alla: I'm not sure the hastle of foam core in wet cast is worth the 100lb savings? My wet cast mix doesn't set as fast as yours does, do I have to keep it weighed down longer before I can do the back side. a 100lbs just means another guy on delivery day, plus I can cast it at 1 1/2". I think in the end the extra 1/2" would weigh more than 1" foam in a 2" slabover the 12" canteliver. I don't mind doing foam in GFRC becasue the mix is stiffer.

I will have to give all the options to the client and see which way we go. So many choices, and non that won't do the job.

I did a 3' cantilever which was fixed to a wall using homemade brackets, I used 19mm solid bar which slid into 20mm plastic conduit, this was cast into the concrete to allow for the shrinkage differential.


Is there anything wrong with using a rigid steel such as tube or angle iron then covering with something that gives a little like a few layers of pvc tape or rubber, this would effectively be concrete clad steel, no bond between the two. 

I have to re-do a piece which I blew the face off with the weed torch only days after the 'exploding concrete' discussion.

This is the first re-pour i've had to do so I am now officially in the re-pour gang.


It is 8' x 3' with a drop down leg on one side and a 14" cantilever on the other end, the front is also an unsupported 12" cantilever  it is 40mm thick


I originally did this solid GFRC with scrim and I can stand on the cantilever end without much flex even if I move the pivot point to 16" I still only get slight movement when bouncing my weight up and down. could this still have suffered from creep? 


how bad does creep look? just a small crack on the face or full Salvador Dali style sagging? neither is good


After reading this thread I'm scared of casting this the same way and I'm thinking of using some steel tube like Remik suggested. would it give me extra insurance if I placed a couple of strategically placed 20mm steel tube, 15mm off the face and 5mm below the bottom (covered in pvc of course) 


John - have you decided which option you're going with yet?



an option that the Granite guys use is to bolt/screw a piece of plate steel on the underside for the slab to rest on.  It is hidden by the drop edge and gives enough support for a foot or two, depending on the steel.  It can be an expensive way to go, but if that is what they want, they can pay for it, or you can do wetcast.  I do agree with Jeremy, a 12" overhang with a good mix should not sag.  If it does, it will take it a while and will be very minimal.
is there anything you don't know Brandon!!?  :)

Gore Design Co. said:



What does the small precentage of Metakaolin do in the mix? Going to give it a try.



Is there a rule of thumb regarding unsupported spans?  I guess there are a lot of variables....

I ask because I have a long vanity with an integral ramp sink to do.  there will be support in the back ledge but there is roughly 7 feet unsupported in the front (see diagram).  There's a 5" drop down edge in the front.  This is a public restroom so I'm assuming at some point someone (probably Akebono sized) is going to jump up and sit on the front edge.  Any reinforcement suggestions?  Thank you.


Since this is an outdoor situation, don't you need to have at least 2 inches of concrete covering the steel to prevent spalling over time?

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