Piers\Footing poured at same time as slab?

Gunna · Aug 26, 2015 9:17 pm

In our plans we are supposed to have 15 piers and if I read the plans right these have to be 350mm wide and 2.5m deep. I'm also assuming we would have concrete channel\beam along some of the perimeter as well. Depth and width unknown. Originally our site supervisor had advised that piers\footings would be poured on Monday 24th Aug. He went on annual leave on Monday and after no works on site I called his temporary replacement to ask why no work was completed.

He advised that the concreter was on another job and decided he would pour the piers\footings at the same time as the slab. Is this normal as I would have thought they would need curing time prior to slab pour.

Another question would also be how could the box they slab, have the polystyrene in place for our waffle slab and have the rio in place while digging the piers, I would have thought this not to be possible. We are in SE QLD as a point of interest for building codes

Thanks

StructuralBIMGuy · Aug 26, 2015 11:39 pm

Please check your engineering plans and geotech report.

goody59 · Aug 27, 2015 10:48 am

Gunna

In our plans we are supposed to have 15 piers and if I read the plans right these have to be 350mm wide and 2.5m deep. I'm also assuming we would have concrete channel\beam along some of the perimeter as well. Depth and width unknown. Originally our site supervisor had advised that piers\footings would be poured on Monday 24th Aug. He went on annual leave on Monday and after no works on site I called his temporary replacement to ask why no work was completed.

He advised that the concreter was on another job and decided he would pour the piers\footings at the same time as the slab. Is this normal as I would have thought they would need curing time prior to slab pour.

Another question would also be how could the box they slab, have the polystyrene in place for our waffle slab and have the rio in place while digging the piers, I would have thought this not to be possible. We are in SE QLD as a point of interest for building codes

Thanks

That sounds impossible to me. I had a slab done a week ago, waffle pod slab on H2 site. 15 large bored piers were done about a week before the slab and filled with concrete and a week later the waterproof membrane was placed down over the slab site and over the piers and it was sealed up against pipe penetrations. Then the voids were put in place with the steel after that and the form work for the slab including the set downs for porch and Alfresco before the slab was poured. I can't see how the bored piers could be poured at same time as the slab is poured myself but there may be a way. I just can't picture it myself. My bored piers of concrete were done even before the drains were put in place.

insider · Aug 27, 2015 9:33 pm

goody59

Gunna

In our plans we are supposed to have 15 piers and if I read the plans right these have to be 350mm wide and 2.5m deep. I'm also assuming we would have concrete channel\beam along some of the perimeter as well. Depth and width unknown. Originally our site supervisor had advised that piers\footings would be poured on Monday 24th Aug. He went on annual leave on Monday and after no works on site I called his temporary replacement to ask why no work was completed.

He advised that the concreter was on another job and decided he would pour the piers\footings at the same time as the slab. Is this normal as I would have thought they would need curing time prior to slab pour.

Another question would also be how could the box they slab, have the polystyrene in place for our waffle slab and have the rio in place while digging the piers, I would have thought this not to be possible. We are in SE QLD as a point of interest for building codes

Thanks

That sounds impossible to me. I had a slab done a week ago, waffle pod slab on H2 site. 15 large bored piers were done about a week before the slab and filled with concrete and a week later the waterproof membrane was placed down over the slab site and over the piers and it was sealed up against pipe penetrations. Then the voids were put in place with the steel after that and the form work for the slab including the set downs for porch and Alfresco before the slab was poured. I can't see how the bored piers could be poured at same time as the slab is poured myself but there may be a way. I just can't picture it myself. My bored piers of concrete were done even before the drains were put in place.

I agree with this statement, can't be done.The slab formwork and plastic membrane reo etc can't be placed until all the piers are in.
Usually will require a inspection by the engineer of the pier excavation before they are poured anyway.
My best guess is they meant they will bore the piers and pour them on the same day.

Gunna · Aug 27, 2015 10:36 pm

Well I visited site. The boxing is done, waffle pods in place and the rio has been tied.

Checking the perimeter and the holes for the piers are in place, so they have been dug at least and must of been done this morning as they were not there yesterday afternoon.

insider · Aug 28, 2015 11:48 pm

Gunna

Well I visited site. The boxing is done, waffle pods in place and the rio has been tied.

Checking the perimeter and the holes for the piers are in place, so they have been dug at least and must of been done this morning as they were not there yesterday afternoon.

So the piers have been poured? Ask if they were inspected and if they were can you see the documentation .

insider · Aug 28, 2015 11:48 pm

Gunna

Well I visited site. The boxing is done, waffle pods in place and the rio has been tied.

Checking the perimeter and the holes for the piers are in place, so they have been dug at least and must of been done this morning as they were not there yesterday afternoon.

So the piers have been poured? Ask if they were inspected and if they were can you see the documentation .

Gunna · Aug 29, 2015 11:56 am

insider

Gunna

Well I visited site. The boxing is done, waffle pods in place and the rio has been tied.

Checking the perimeter and the holes for the piers are in place, so they have been dug at least and must of been done this morning as they were not there yesterday afternoon.

So the piers have been poured? Ask if they were inspected and if they were can you see the documentation .

Not poured. Just the holes dug. I called our independent inspector and he said it's sometimes done and is normal. I was just nervous as it was due to rain and they were boxing the slab. At the time I checked no pier holes had been dug.

building-expert · Aug 29, 2015 12:50 pm

I don't think its normal and how are you going to keep bottoms of pier holes clean whilst working on top. Its a shortcut and I would not try it.
I have seen two pier holes poured with slab but only because they were missed when the rest was done and building inspector allowed it.

insider · Aug 29, 2015 6:12 pm

But how have they put the plastic membrane down for the slab if the piers haven't been poured yet but the slab has been prepared?
This doesn't make sense, do you have photos ?

Gunna · Aug 31, 2015 2:55 pm

So it would seem the bored the holes, laid the black membrane, reo, pods then more reo. They cut circles around the pier holes. Building inspector said they will get holes inspected, pour and then re-inspect. They will then lay some more membrane and then pour the slab. Said there will be some cure time before that last bit of membrane goes on though.

insider · Aug 31, 2015 9:38 pm

Gunna

So it would seem the bored the holes, laid the black membrane, reo, pods then more reo. They cut circles around the pier holes. Building inspector said they will get holes inspected, pour and then re-inspect. They will then lay some more membrane and then pour the slab. Said there will be some cure time before that last bit of membrane goes on though.

I have never heard of that before.They have to tape the circular plastic membrane over each individual pier hole after it is been poured.
Sometimes you just have to wonder what the hell is going on in this industry.

building-expert · Sep 01, 2015 9:41 am

Option 1 Drill out pier holes, clean out and have them inspected, then back up concrete truck and have them filled with concrete, then proceed to form slab on top, then pour slab(pump concrete in)(I have done it many times)

Option 2 Drill out pier holes, have them inspected and approved then keep them open whilst forming slab on top, (don't forget there will be volume of excavated soil from pier holes how will you prepare level base for slab without some of the dirt falling back in?) then pump concrete into piers, fix membrane and pour slab. Option 2 makes no sense to me( what if it rains overnight and pier holes fill with water and sides collapse?). It's a free country and making wrong choices is perfectly legal.

insider · Sep 01, 2015 3:14 pm

Option 1 is the correct option in my opinion not sure why anybody would do it another way but I suppose people can try and make the construction more efficient but I don't think this is the way

SaveH2O · Sep 02, 2015 6:33 pm

Was the site pour supervised by Schrodinger's cat perchance?

mgilla · Sep 02, 2015 8:27 pm

It's easy to do and very common.
Drill pier holes then cover the entire pad with plastic, mark pier location on plastic with paint so you dont stand on them.
Box up and prep the slab, then when its all done you take a knife and cut the plastic where the piers are. No mess No fuss and no need to think there has been anything untoward done on your slab.

insider · Sep 03, 2015 12:01 am

mgilla

It's easy to do and very common.
Drill pier holes then cover the entire pad with plastic, mark pier location on plastic with paint so you dont stand on them.
Box up and prep the slab, then when its all done you take a knife and cut the plastic where the piers are. No mess No fuss and no need to think there has been anything untoward done on your slab.

Interesting mgilla
Then after you have poured the piers do you put more plastic down and tape it ?

mgilla · Sep 03, 2015 6:39 pm

insider

mgilla

It's easy to do and very common.
Drill pier holes then cover the entire pad with plastic, mark pier location on plastic with paint so you dont stand on them.
Box up and prep the slab, then when its all done you take a knife and cut the plastic where the piers are. No mess No fuss and no need to think there has been anything untoward done on your slab.

Interesting mgilla
Then after you have poured the piers do you put more plastic down and tape it ?

why?

insider · Sep 03, 2015 7:12 pm

The piers are in contact with the soil and moisture could travel up the pier onto the slab.Defeats the purpose of a moisture barrier but I'm guessing because I haven't seen it done before.

building-expert · Sep 03, 2015 7:46 pm

insider

The piers are in contact with the soil and moisture could travel up the pier onto the slab.Defeats the purpose of a moisture barrier but I'm guessing because I haven't seen it done before.

I agree
I am with Structural BIMGuy, check your engineering design and specification and ensure it is followed.