concrete oversite under block and beam floor?

[Moonshine]

Is a concrete oversite needed under block and beam floor? i see some designs specify a concrete oversite, and other that the vegetation needs to be striped and weed killer down.

 

my build proposes the latter, what is typical?

[Oz07]

spoil from the nearest spoil heap. I think it depends how wet your ground is likely to be. @nod concreted and put drains in his but never seen it done around my area

[Buzz]

Mine was just leveled off to the concrete trench ,nothing else was done .

Edited July 23, 2021 by Buzz

[Russell griffiths]

Crushed concrete, compacted with the digger. 

[Temp]

Think we used crushed limestone hardcore but then my builder used that stuff  everywhere. Think he had shares in the company ?

[nod]

I’ve just been having this conversation today The sites I work on don’t even bother with hardcore Quick weed kill 

Done 

 

As I stated in my previous post Quite a while back I thought it was way over the top to put 6 cube of concrete under the BB and a drain But once it was on my foundation design I had little choice 

Probably the most miserable day of the job 6 cube in pouring rain 

 

Now After done the freak storms we’ve had I’m not so sure Our tank is only 10 metres away from the house We could easily end up with the contents under the house 

 

our next one is on clay also I will at least stone up under the BB 

Or May concrete and drain like the last one 

It was a days work and about 500 quid so not a lot in the grand scheme of things 

[Dave Jones]

as long as you have a 150mm gap thats it. nothing else needs doing. 

[Buzz]

57 minutes ago, Dave Jones said:

as long as you have a 150mm gap thats it. nothing else needs doing. 

Double check with local BC, round these parts they insist on 225 only going lower by negotiation and good reason. 

[Oldsteel]

On 23/07/2021 at 14:34, Buzz said:

Mine was just leveled off to the concrete trench ,nothing else was done .

Same here. BC quite happy. All clay and sloping site, can’t see anything growing under there. By the way, BC strict on ventilation under the beams. 

[SimonD]

IIRC Building regs calls for either concrete or inert layer. I've ended up with both - concrete where I had excess pumped for foundations and inert where I just couldn't find the energy to do a lean mix myself. BC happy with both.

[ruggers]

@nod or anyone, I'm having my site cleared and the foot print of the house plus 360 perimeter path around it down to clay level ready for setting out and founds dug.

 

I haven't spoken to B.C yet but had some saying to stone the whole foot print in 150mm compacted crush stone then set out and dig through, and using the stone removed back on the drive area. Or to leave it as clay, build up to DPC, and dont put anything under the beam and block floor just leaving the air 150mm gap. I think I'd be looking at 80t of stone so £1000..

 

Whats the drain you refer to underneath?

[nod]

No 

That would be a waste of money 

You will have to put some stone down for the lorries Just to get upto the foundations Get them dug 

Then get some stone around the perimeter and anywhere you will need to get a delivery crane BMs etc 

This is all that I did prior to concreting 

[ruggers]

This is exactly what i was going to do, i have the stone to the front for vehicles to drive in and park up to be loaded, i just wasnt sure if B.C ask for something under the beam and block, like stone or dry mix. It seems a waste to me if vegetations removed and its away from light, but i was unsure if there was another reason for it.

 

Despite not wanting to due to cost, The only reason i was going to stone the footprint, was with it being a wet site and needing an 8t machine on to dig the mass fill founds, it could all get chewed up if it continues to rain on and off.

 

I need the founds dug in the next few weeks to meet the pre 2022 regs cut off, currently its all graded nice and flat but its wet after just being completed and no land drains in yet.

[nod]

On our first build we put concrete under the BB As there was a possibility of flooding 

There’s no requirement to put anything under there Most large site give the area a spray with weed killer then put the BB in