Footing depth variation 😮‍💨

[flanagaj]

I should have been more forceful here as I think the excavator driver I hired has monumentally xxxx up.  We didn't pour our footings on Friday as the JCB broke down which caused a 1/2 days delay.  We are scheduled to pour tomorrow am at 1000hrs, but whilst putting the pins in for the top of the concrete, I have spotted that the dug footings are 200mm deeper at the front of the attached garage than the back.   The garage has a stepped footing relative to the house.

 

If I am correct, this is a big issue and although the garage is single storey, I am sure the 200mm depth variation will just cause significant settlement variation and I have no choice but to shutter up the garage and pour it another day.

 

The footings where the attached house is going are +/- 20mm

 

I was contemplating getting up early and try and correct the depth variation myself.   If I didn't have a working hours planning condition, I'd have done it this afternoon.

 

Any pearls of wisdom?

Edited 2 hours ago by flanagaj

[Oz07]

I dont think its a problem. You step bottom of footings all the time when trees are nearby. Any pics?

[flanagaj]

13 minutes ago, Oz07 said:

I dont think its a problem. You step bottom of footings all the time when trees are nearby. Any pics?

I can't show a photo and maybe I wasn't clear, but the variation means that the concrete depth at the front of the garage will be 200mm thicker compared with the back of the garage as the finished top level needs to be the same height.  I'm just concerned that the front of the garage will be bearing more weight down onto the ground than the back of the property and as a result, it will settle more.

[Oz07]

No it will be fine. One place I built had stepped footings from 2.4 to 1.5 due to trees. Top of conc all level. 

[flanagaj]

38 minutes ago, Oz07 said:

No it will be fine. One place I built had stepped footings from 2.4 to 1.5 due to trees. Top of conc all level. 

But this isn't a step.  The footing is sloping down 200mm over a 6m run

Edited 45 minutes ago by flanagaj

[Oz07]

8 minutes ago, flanagaj said:

But this isn't a step.  The footing is sloping down 200mm over a 6m run

Not ideal but I'd stop worrying on this. Its not going anywhere. 30mm a metre I bet a lot worse has been done. 

[flanagaj]

11 minutes ago, Oz07 said:

Not ideal but I'd stop worrying on this. Its not going anywhere. 30mm a metre I bet a lot worse has been done. 

As previously mentioned, I'm a catastrophiser and worry the house will collapse.

[Gus Potter]

1 hour ago, flanagaj said:

I can't show a photo and maybe I wasn't clear,

Ok I'm going to give you the benefit of the doubt here. No photo as it's dark o clock! I might be able to reassure here, but not promising anything. 

 

If you want hand sketch what you have on A4 paper, photograph and post.

 

Show a plan view and annotate the depth to the bottom of the trenches you have dug relative to the highest finished ground level 0.000 m . If the ground is sloping mark the highest ground level as 0.000m and then assign values to any ground that is lower. 

 

Also show you main house founds. Show all foundation widths, mark the plan dimensions to the outside of the masonry walls and the outside edge of the foundation. Confirm anything you are placing on the founds is single storey.

 

1 hour ago, flanagaj said:

'm just concerned that the front of the garage will be bearing more weight down onto the ground than the back of the property and as a result, it will settle more.

Provided that the highest part of the found is on competent ground then an extra 200mm is unlikely to result in excessive differential settlement. All parts of the house will settle differentially due to variation in loads, depths and soil variations, SE's design for this. The most common problem is folk leaving a soft layer where everyone has tramped about, essentaily laying the concrete on a slurry. 

 

If you are stepping the foundations then make sure the mesh extends over the step.