Is 804 always required for concrete slab?

Xcellor · 08-07-2019 11:58AM #1

I'm putting in a slab 2.7 x 6.1. Ive done the form and excavated. I've removed a significant amount of soil and am hitting a lot of rock.

Where I've come across soil Ive dug this out and filled with stones. I asked for a tonne of 804 but the builders merchant delivered a tonne of sand + stone aggregate. If this is whacked down am I good to lay? It seems like Im pulling rocks out to put them back in again...

For the moisture barrier Im going to put this on top of the sand / aggregate and feed under the form or inside it? doesn't make a difference probably?

m5ex9oqjawdg2i · 08-07-2019 12:06PM

The lad I worked with as a youngster used 804 gravel/hardcore. Whacked it until it was good and firm, then put sand on top of that and whacked it until it was good and firm. The sand helps keep the slabs level. 804 is just crushed rock that's a certain size. Not sure if it has to be a certain rock though.

If the hardcore you ordered is just sand and stones I would question it. Does it look like thisor this?

Never laid a moisture barrier as we only laid slabs outside, not good for drainage. If it's an inside job, then you more than likely need one. I am not a professional though, so hopefully you find more advice on here from somebody that knows more than I do

Lumen · 08-07-2019 12:20PM

What's going on the slab?

Calahonda52 · 08-07-2019 12:54PM

Lumen wrote: »

What's going on the slab?

Great question

iff the slab is structural in any way and needs to be building regs compliant, 804 is not longer acceptable
from memory its sr 21 of 2014 with a 2016 annex along with IS 888: 2016 from NASA

Xcellor · 08-07-2019 02:01PM

Calahonda52 wrote: »

Great question

iff the slab is structural in any way and needs to be building regs compliant, 804 is not longer acceptable
from memory its sr 21 of 2014 with a 2016 annex along with IS 888: 2016 from NASA

Its just a lightweight shed for fridge freezer, place to put washing in when it starts raining. An outside utility room really... It's flat pack to be assembled type shed that will be bolted down to the concrete.

Xcellor · 08-07-2019 02:05PM

Irene Sharp Geisha wrote: »

The lad I worked with as a youngster used 804 gravel/hardcore. Whacked it until it was good and firm, then put sand on top of that and whacked it until it was good and firm. The sand helps keep the slabs level. 804 is just crushed rock that's a certain size. Not sure if it has to be a certain rock though.

If the hardcore you ordered is just sand and stones I would question it. Does it look like thisor this?

Never laid a moisture barrier as we only laid slabs outside, not good for drainage. If it's an inside job, then you more than likely need one. I am not a professional though, so hopefully you find more advice on here from somebody that knows more than I do

Nah it's just sand with pebels and grit. Like the following.
http://www.ndyoungtransport.co.uk/images/slide15.jpg (the last pic in the series)

Since it's gonna have fridge and other electrics want it to be dry enough hence the moisture barrier to stop wicking from below.

Is 804 always required for concrete slab?

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