How much does sand compact when plate compacted?

[Digmixfill]

I've started to barrow in the hardcore for my floors, and very pleasing it is too to finally see something other than dirt 130mm is whacking down nicely to 100mm.

I don't seem to be able to turn up any info on sand compaction. How much sand do i need to put down to have a 50mm layer after compacting?

[PeterW]

It only needs to blind the gaps in the stone so you don’t need a lot. You can also use a layer of 25mm EPS below the DPM which does the same job 

[Russell griffiths]

Just be careful not to be too over enthusiastic with the whacking, it is possible to move thin walls by compacting tight up to them, outer load bearing should be fine. 

If you have any thin internal walls fill both sides evenly and whack both sides evenly 

[Digmixfill]

On 21/02/2019 at 08:08, Russell griffiths said:

Just be careful not to be too over enthusiastic with the whacking, it is possible to move thin walls by compacting tight up to them, outer load bearing should be fine. 

If you have any thin internal walls fill both sides evenly and whack both sides evenly 

 

Fortunately i've not got anything to worry about movement wise. All the internal perimeter base blocks are solid concrete and they're filled between them and the 9 inch external walls. Three internal walls are 9 inch load bearing too.

 

I don't think i've been too enthusiastic.  Six passes with the plate have so far compacted the mot1 sufficiently.

 

On 21/02/2019 at 06:53, PeterW said:

It only needs to blind the gaps in the stone so you don’t need a lot. You can also use a layer of 25mm EPS below the DPM which does the same job 

 

My plans have 50mm, but I'm more than happy to barrow less :)

25mm EPS is i nice idea, but the prices i have for 8ft boards make it much more expensive than sand. a LOT less barrowing though!

 

[Russell griffiths]

The eps boards you use under your dpm aren’t wasted, you just subtract the amount from your final insulation layer 

so if you are having 150mm for arguments sake, you still use 150 mm but 25mm under the dpm to protect it then another 25mm on top of dpm then another 100mm. 

So total 150mm you have just trapped the dpm in between the bottom two layers. 

Minimal sand, just a very light dusting to take out any undulations, then lay your first board. 

 

[Onoff]

I sharp sanded over the 40mm hard-core. I also slung in any half bags of off cement etc just to fill gaps:

 

 

 

 

& 25mm EPS'd:

 

 

[Digmixfill]

@Onoff Is that a concrete edge to the top and right of that room? If it is, did you EPS that also?

 

5 hours ago, Russell griffiths said:

The eps boards you use under your dpm aren’t wasted, you just subtract the amount from your final insulation layer 

so if you are having 150mm for arguments sake, you still use 150 mm but 25mm under the dpm to protect it then another 25mm on top of dpm then another 100mm. 

So total 150mm you have just trapped the dpm in between the bottom two layers. 

Minimal sand, just a very light dusting to take out any undulations, then lay your first board. 

 

 

I don't think i can subtract any EPS blinding from my total. There's another slab before my floor insulation.

I have a picture here showing construction. floor construction

 

The hardcore and lower slab are now 100mm and the insulation is 200mm.

 

[Digmixfill]

I'm sure it varies by sand type, but in my case it's compressing by about 1/5th in height.

[Onoff]

On 23/02/2019 at 16:14, Digmixfill said:

@Onoff Is that a concrete edge to the top and right of that room? If it is, did you EPS that also?

 

 

I don't think i can subtract any EPS blinding from my total. There's another slab before my floor insulation.

I have a picture here showing construction. floor construction

 

The hardcore and lower slab are now 100mm and the insulation is 200mm.

 

 

Only just read this sorry! The concrete edge is where I shuttered and squared off the wall footings to make it easier to eps it.

 

 

Eps over the concrete edge, stuck with Soudal low expanding foam. The inner leaf dpc is at the joint just under the pipe which was originally the room's ffl. That incidentally was 60mm higher in places than the rest of the house, to correct this was one of the reasons I embarked on the "big dig".

 

 

I painted the blocks up to the dpc with liquid waterproofer then chucked dry sand at the second coat:

 

 

Then glued perimeter eps on with Soudal low expanding foam:

 

 

Imho I think your 50 sand blind is way too thick.  I just got my hard-core v.level and the sand was just a token thing. The eps does all the work protecting the dpm.  

Edited March 6, 2019 by Onoff

[Digmixfill]

On 06/03/2019 at 06:26, Onoff said:

Only just read this sorry!

 

I'm just as bad. For some reason i don't get alerts for posts, so i don't check the site as often as i should...

 

On 06/03/2019 at 06:26, Onoff said:

The concrete edge is where I shuttered and squared off the wall footings to make it easier to eps it. 

 

I've got something similar along one wall where the underpinning is a bit high.

 

On 06/03/2019 at 06:26, Onoff said:

Imho I think your 50 sand blind is way too thick.

 

I'm of the same mind, but when i enquired with building control about increasing insulation by dropping the thickness of hardcore & lower slab they didn't offer changing the blinding layer, or even comment on it.

 

I've done nearly 40sqm so far. That's roughly half way. If it is to change it's now or never.