Stirrups moving

[dan76n]

Hi all,
Im currently building my second deck and have found that the first few stirrups I have concreted in are sinking.
I have attached all the stirrups to the bearers and leveled out the bearers and am filling the holes with concrete with the stirrups hanging in the hole.
how can i stop this same problem happening to the next 40 stirrups and how can I fix the 4 that I have already done?

They have been setting for 3 days now,
I can move them up and down about 20mm.

[mako]

Are the stirrups moving in the concrete? I presume the concrete isnt moving? If the stirrups are 'loose' in concrete you may of got air pockets around the stirrups. How to fix it?...hmmm , jack hammer the stirrrups out again. then re concrete making sure you push the concrete tight around stirrups with no air pockets.

[dan76n]

The stirrups are 450 deep so I dont like my chances of jackhammering it out.
What if I hit it down as far as it will go then rase the bearer back to level.
also, I compacted the concrete as much as I could, whats the best way to compact it?

[DJ’s Timber]

Sounds like the stirrups have a round pipe that sits in the concrete, if this is the case, it really needs some cross bars welded to it so that the concrete can grip it. Bits of 12mm reo bar is good for this

Any steel work that is going in concrete really should have crossbars welded to them. I have seen 100mm square posts pull straight out of the concrete as the concrete couldn't grip the smooth walls of the post

[mako]

True Djstimber. although most stirrups that go in concrete have the small flat plate at bottom which should stop movement/pull out. The ones yopu have already done you will get away with your idea of pushing them right down and compensating witht he bearer hight. For the rest maybe use djstimber's idea. as far as compacting the concrete i just use the end of a shovel handle and poke it all down.

[watson]

G'day Dan,
did you use real concrete, or QUikset???

[Tools]

Sounds like you stood on the bearers as you were filling the holes and caused them to sag and create a pocket in the concrete.You will have to jackhammer them out.
Tools

[dan76n]

I used real concrete ,not quick set.
I didnt stand on the bearers, but It wouldnt mater if I did until I moved the bracing

[Dirty Doogie]

Those stirrups that have a round pipe shank and a U shaped bracket on top are absolute rubbish unless the concrete is reinforced around the shank and has 150 mm of reinforced concrete underneath the base plate.

The Pryda design manual makes this very clear. People use them thinking they are quick way out but by the time you engineer the concrete they sit in to design standards you would have been better off using shs or concrete block piers.

It sounds like the bottom of your footing has broken out. The weight of the bearer being concentrated on a 50mm x 50mm patch of green concrete has cracked the concrete under it.

For the other stirrups
1) put some short (100mm) pieces of Y 12 bar across under the little foot plate,
2) make the concrete under deeper
3) use more cement in your mix
4) Wait 7 days before applying any load to the footing

You'll have to dig the broken footings out and start again.

[dan76n]

would I be better off grinding the post off at concrete level and using some kind of mounting bracket for the bearers. Its a low level deck, about 60mm from ground to bottom of bearer.

[thebuildingsurv]

sounds like to me u never got enough concrete to the underside of the styrrup and formed an air void. Was the mix to dry ? I think you could either push them down and pack them out or bolt a styrrup to the pad. I wouldnt put ur plinth boards on though cause its possible you might have to pull the pads out and start again.

[dan76n]

It seems your right "thebuildingsurv" I had a friend have a look, he is pretty sure my concrete mix wasnt wet enough so it formed a small void underneath. He suggested drilling a small hole through the shaft of the problem ones and puttig a bit of steel through then toppong up with concrete as I have compacted it down enough to fit 150mm more concrete in the post trenches.
Heres a quick scetch<SCRIPT type=text/javascript> vbmenu_register("postmenu_597293", true); </SCRIPT>