Suggestions? (Measuring depths)

[paulweller84]

Hi,

I am due to start digging foundation trenches very soon, and it will have to be done in sections due to being in quite soft clay. What I'm trying to figure out is: what is the easiest way to ensure the tops of all the concrete foundations are perfectly level with each other, so they all eventually join up to form one continuous level slab?

I've attached an image to illustrate. I need to ensure all the sections have the same concrete level (green line) - an equal depth down from the DPC level (red). Someone suggested a laser level but didn't elaborate on what to buy or how it should be used. They seem to range from under £100 to over £1000. Are there alternative methods?

 

[noseall]

it will have to be done in sections due to being in quite soft clay

Why?

Someone suggested a laser level but didn't elaborate

A laser level with a sensor-on-a-stick is ideal. Put the laser on a solid surface so that the beam is shining across the site and is in the 'sensor' setting. You then set your first datum peg in the ground at the desired height and set your sensor to this peg. All the other pegs can be set from this datum point using the bleeping sensor.​

 

[paulweller84]

Why?

Should've mentioned - it's soft clay and we're building very close to neighbouring foundations for an extension and retaining wall.

 

[^woody^]

Has that foundation been designed? It's a very poor foundation that will not form a continuous strip for load bearing - which is exactly what you need on soft ground.

As for leveling, a level string line above ground and use a gauging rod not a tape.

 

[paulweller84]

Has that foundation been designed? It's a very poor foundation that will not form a continuous strip for load bearing - which is exactly what you need on soft ground.

This method was given by a structural engineer. 600mm wide footings and quite deep (final depth of concrete TBC), interconnected with reinforcing bars. Structure is a single storey extension with flat roof, so not excessively heavy.

 

[^woody^]

That's ok then. Btw, it's not the weight of the extension that matters, but the stability of the ground.

 

[noseall]

a level string line above ground

How do you set your line level?

 

[^woody^]

I level a profile or stake and run the line from this to the DPC.

The levelling is done with one of the several methods of levelling, if that is the next question.

 

[noseall]

The levelling is done with one of the several methods of levelling

Eh?

Do you understand the crux of the thread? Let the OP know when you have arrived at your line levelling explanation.

 

[^woody^]

I level like an Egyptian.

 

[bobasd]

due to the wonders of google:

for the pyramid foundations the Egyptians used water channels to find their base level - the blocks were, of course, squared by pei, and all subsequent levelling was done with the ingenius A-frame.

friday, apparently, was world pei day.

 

[^woody^]

friday, apparently, was world pei day.

Saturday. I had a steak and ale with chips to celebrate

 

[bobasd]

they deliver to lofts now!

 

[Nige F]

squared by pei, ........ the ingenius A-frame.

pei day.

When's world dyslexia day ?

 

[IT Minion]

When's world dyslexia day ?

October 4th. Dyslexics untie!