[TheGreenMachine]

I've just put some footings in for a retaining wall but I've somehow ended up lower one side than the other.

I used a spirit level, pegs and a straight piece of wood to find a level fill height but I've obviously done something wrong. I just don't have the energy to mix up more concrete tonight so can I just mix up enough to level up and grade in the low side or will it not bond properly?

Cheers.

[Zipp]

before you add the extra concrete tomorrow cover the existing cement with some watery cement this will act as a primer tgm so they will bond mate

[Budgie]

and rough up the surface well for extra bite

you could also cover with dsmp sackcloth/hessian to slow the cure a bit.

[Funky]

What you''ll have is what's called a cold joint. It depends on what it's retaining how bad this is.

[Anonymiss]

[isn't a builder]

I'd be thinking about how the low side relates to the high side, and where the new layer will meet the old.

I'd be concerned about whether the thinnest part of the new layer (where it feathers out) might end up being a weak point, especially if it was at or near an existing edge, and would be wondering whether it might be worth raising the high side by 50 mm or so at the same time (effectively casting a contiguous top slab) just to be safe.

[Budgie]

[isn't a builder]

shit, and i always had you down as a brainy bricky missy ;p

[Anonymiss]

shit, and i always had you down as a brainy bricky missy ;p

 
I'm more of an esoteric engineer

[Slippery]

Best would be keep bed joints tight one side and raise them the other, depends on how much out of level it is.

 

Work out the gauge of the brick then lay the two ends and string line between them

[TheGreenMachine]

Hey guys,

Thanks for all the replies. I've got some more information regarding what I'm doing.

These are the footings and they're aprox 1ft deep x 1ft wide. I've marked on the picture (which was taken before the concrete went in) the fill level pegs and this has brought the level of the pour to just below the level of the slabs.

You can also see the height of the mud the wall is going to hold back. It's mainly clay and the new soil level is around 3ft so the wall will be around 4ft making around 1 - 1.5ft of wall above the soil line.
I'm building the wall with dense concrete blocks.

 footings.jpg   245.86KB   0 downloads

This is a plan view of what I'm trying to achieve.

 PlanView.jpg   25.94KB   0 downloads

If I were to pour an additional layer of concrete, I could pour it up to 2 inches thick on the lowest side going down to around 1 - 1.5 inches thick on the high side to level the whole footings off to the same level as the slabs.

I should have poured it to that height originally anyway but it physically killed me barrowing a ton of ballast and sand from front to back, into the mixer, out of the mixer and pouring it all on my own in 3 hours trying to get it down quick
I just couldn't lift another shovel full by the end. All my lower back felt like it was gonna snap. Drenched my back in deep heat last night.

 

Obviously as has been pointed out, I've now got the worry of whether that new concrete layer would bond or would just be a weak point. I can see a year down the line the wall has fallen over where the new layer has lifted off the old?
Someone mentioned a cold joint? I think I read about scrubbing in a thin slurry mix before pouring to fill all the pores to make a "cold joint"? Get a brush and rub the slurry in well and pour new concrete before the slurry dries.


If pouring another layer isn't an option, how about laying a mortar bed 2 inch thick when I lay the first course? Let it firm up before laying the blocks or would that be too much of a depth for a mortar bed?


Thanks again!





 

Edited by TheGreenMachine, 21 May 2016 - 09:07 AM.

[Slippery]

If it;s only a half inch out you could build up the bed joint on the first course, or run two courses to level it.

 

If there is three feet of soil to hold back, it may be worth using hollow bock and filling the cavity with concrete and re-bar.

 

If the land is sloping towards the wall, a land drain may be a good idea. It is quite short though so has good support from the corners