Tips for excavating for solid floor

[thias]

We're replacing our existing suspended timber floor with a new solid floor. We plan to dig down to 485mm for the builder to build it up again in a couple of weeks.

The final floor build up will be;

150mm MOT 1
25mm Sand Blinding
DPM
150mm Concrete
100mm Insulation
60mm Screed

The existing void ranges from 80mm (where the joists sitting on the ground and were rotten!) to 550mm. The overall area is 60sqm.

I plan on hiring a micro digger and dumper that I can fit through the internal doors to make the work a little easier, but how do you guys recommend we tackle it?

I was thinking of pegging out in strips so we can measure depths and levels as we go, but is there a better way?

 

[Mr Chibs]

I have similar make up.

I pegged wooden spikes in to get the hardcore level, once whacked. 30sqm.

After the dpm, I used some spare bricks and blocks packed out to give the level for concrete. Also around the wall edge. These were removed as I went along ramping down.

Once the concrete was in I used a hose and kept it wet to help curing.

managed to get it pretty flat.

the guys who did the liquid screed said it was very flat, they see some ‘rubbish’

I borrowed everything in and out.

Good luck.

Oh and put wet UFH in the screed. I’m a new convert and wouldn’t go back to rads now.

 

[Deluks]

You don't need that much MOT or concrete, 100mm is ample for each. Just take your time getting each layer compacted and level (ish)
Although you will obviously need to fill out the lowest bits.
Increasing the insulation depth would be a better way to make up the height.

It seems a lot of work compared to just replacing the rotten joists and excavating a little bit.

 

[thias]

The required quantities have been defined and agreed between our architect and local building control so I don’t really want to faff with them.

Given this is work we didn’t plan on having to do, we’re trying to save costs by doing most of it ourselves, so the question was really around the best way to dig out level, so we can avoid having to fill more than 150mm MOT 1 in places.

Other than a laser, I guess a load of pegs, level and marked, are the next best thing?

 

[Paulg31]

I wouldn't bother with 150 mm slab. 100 mm will be fine for a domestic slab.