Varying depth shuttering

[bsr]

Hi All

I want to pour a 6m x 1.2m slab on a sloping driveway. The top edge needs to be flush with the existing level. The slope is 150mm over 1.2m so about 1:8. There is also some cross-slope; about 100mm over the 6m.

I was thinking of excavating to 100mm below the final level. This means part of the base would be flush with ground level, and part would be varying up to 200mm deep as per the attached picture.

How would you shutter this? I was thinking that I might have to use 4x1 for the top and then infill at the bottom by scribing against the top piece and cutting with a jigsaw. To restrain the shuttering I could hammer road pins or rebar pins into the drive every 1m and fix to the shuttering with strapping?

Would you suggest a movement joint half way along the 6m length or would I need more than one?

Would you use mesh? A142?

Thanks

 

[bsr]

Any thoughts please?

 

[Notch7]

Would you need timber at the top - I would think the cut tarmac edge would act as the shutter.

I’ve not fixed to tarmac - would pins drive in, I guess so.

mesh is a good idea - esp as concrete won’t bond well to tarmac.

In theory a 100mm thick concrete needs a joint every 3 metres, but I’m not sure you should - I wonder what others think

 

[bsr]

Pins go into tarmac easily in my experience. If adhesion is a problem then I could prime with a cement slurry?

 

[bsr]

Any thoughts on the best way to knock up shuttering of varying depth?

 

[oldbutnotdead]

Which way (on the pic) is 1200? If it's left to right then run the sides as high as you like and set the bottom end carefully-that plus the tarmac will be your levels to sit a 4x2 on and wodge the mix into position.