Filling in a cellar

[thias]

Our cellar is approx 1m below the internal ground floor level, so there's a void between the cellar ceiling and the first floor level.

We plan on filling it in to extend the ground floor space in prep for a new extension across it early next year.

What's the best way of doing it? We were thinking rubble/soil, all whacked down at ~ 150mm intervals until around 430mm below the final floor level, then carry on like the rest of the floor build up (150mm MOT 1, 25mm sand blinding, 100mm slab, 100mm insulation, 55mm screed)

Is that ok?

 

[Deluks]

What volume are we talking?

 

[thias]

It's pretty small, around 7sqm.

 

[jeds]

Anything over 600mm is at risk of sinking - however well you compact it. Sub-floors over 600mm normally require engineered fill. How critical to your new extension would a bit of sinking be?

 

[thias]

Well, the plan is to continue the new solid floor pour over this section so any sort of sinking wouldn't be great as it could end up cracking the new slab too.

The cellar's also in the corner of the existing property so sinking would more than likely impact the foundations holding up that corner.

The builder's coming over on Tuesday so I'll bother him about it too

 

[freddiemercurystwin]

Mr BCO would draw the line at 600mm of fill down this neck of the woods and even if you fill it you don't wanna be filling it with soil and rubble!

 

[thias]

Got it. What would the options be? A structural in-fill or suspended floor across that section?

 

[JohnD]

people like cellars. Don't fill it in.

if your other floor in the extension is concrete, maybe beam and block?

 

[thias]

We wouldn't fill it in if we didn't have to. The hallway into the extension will be over the cellar's current location, we spent a load of time with the architect trying to figure something else out but it's the only place that it would really work.

 

[Deluks]

I'm with JohnD. There's no reason why you can't beam and block in place of a 'solid floor' for such a small area.
It would likely be cheaper too.