problem with footings

[nelliedee]

Hi all

We are in the process of building a 2 story extension and have come to the stage of putting in the steels. 1 of our steels is going to be Vertical and we forgot about this and after footings were finished (450 wide by 1 metre deep) we laid the garage floor slab. The asseser came and asked where the footins are for floor plate for vertical steel (6" by 6"). We have now dug a hole back thru the floor slab and located the footings but they are sitting in water as our water table is high.
Can we put more footings on top of original footings? to bring up the level and is there a specific amount in width and depth?

 

[Deluks]

This doesn't make sense to me. If you dig through the slab, then you will be into the hardcore and ground beneath. If you dig through at the edge of the slab (where the FOOTINGS are) then you will be into the footings, (concrete or blockwork.)
~
Q1) Is the column going into the footings where it's a metre deep, or somewhere in the middle where you just have the slab on hardcore?

If its the middle then you will need to dig down and pour a deeper section to support the steel, to avoid whats known as 'punching shear'

If it's at the edge where you already have metre deep footings
(Q2 concrete or blockwork footings?)....

A metre is plenty deep for a column, but you may have to widen the footing to project into the slab (or slightly outside) to give a sufficient sized base.

Q3) What has been specified on the plans for the column base?

 

[nelliedee]

Hi
sorry i wasnt clearer. We had a nib on original drawings which was built on top of the footings. We have removed the nib and have been told to set the new column 100mm into block wall. By doing this we should have enough footing to support the column.
Q1.. The column is going in at the edge of new wall on top of footings
Q2 . concrete footings
Q3.. base for coloumn is 200 x 200 x12 plt 6fw 2 - m16 resin anchors.
Our problem is that the colomn will sit in water and I wondered if we could pour more footings on top of footings or would this weaken it?
Thanks

 

[nelliedee]

Me again
Footins are 450 wide and we used concrete and trench blocks

 

[Deluks]

Our problem is that the colomn will sit in water and I wondered if we could pour more footings on top of footings or would this weaken it?
Thanks

I'm still a bit confused.

You mean you are supposed to have a raised section of the footings to sit the steel on, and you have removed nor omitted this, and now you want to pour more 'crete to built it back up again?

You most definitely do not want to install a steel column in water. I would've thought it goes at or above the main slab level, above the dpc.

Concrete doesn't stick very well to itself, you can add more on top but will need resibars drilled and resin fixed into the existing before pouring any more.

I am thinking that you will need to shutter off a section where the steel goes and pour an raised pad which sits on and is tied into the footing. Resin fix is specced but you can build the bolts into and projecting from the surface of conc pad.

 

[nelliedee]

Hi
Our footings were built as per plans, 450 by 1 metre deep but the problem is that the water table here is high and most of the time the footing will be sitting in water. The steel column is supposed to be placed on top of the footings but if we do this then the base of the column will also be sitting in water. Thats why i thought maybe we could shutter off an area and build another lump of footing on top of the waterlogged footing and that way the column will remain dry. I need to know what size the new footing should be or there abouts.

 

[noseall]

it begs the question: why did you remove the nib?