Laying ready mix concrete slab

The big problem here is that without the actual hands on experience of pumping, spreading, leveling and all that that entails is not for the faint heart, if only one large or small component fails or is not in place then you are left in total limbo, with a full truck of wet concrete with no where to go?

I have been on sites when someone forgot to go and get the petrol to run the vibrators, we had four or five concrete trucks lined up in the street, a tower crane waiting, the concrete crew on stand down, need I say more?

Even worse I recall on a November night, as I recall was later than 1800 hrs. on a Multi-Million £ Government site in Milton Keynes with a critical Concrete pour over running on time, the Concrete plant had shut down we had exhausted its entire stock of Cement, with five or more Concrete trucks stacked, all perilously close to being out of their tachograph times when the Concrete pumps engine water pump failed, the pump overheated and the engine cut out. No spare pump, no where to go. pour water over the pump engine, cool it down get it started and put in an emergency stop end to finish the pour of a suspended floor in a safe position.

NOT A GOOD DAY!!

Ken.

I keep getting confused in this thread, with mentions of concrete and screed, but the OP does say insulation and screed afterwards, so its obv oversite.

On extensions, I find oversite can vary quite a bit, often 12mm, sometimes 20-25mm. Not ideal but get overable.

One problem Ive found is inexperienced pump operators that stop too late. A pain with founds, Ive had occasions of having to put 1/2 metre in the skip.

Maybe you could screw 50 x 50 level all round 150 up , then get some strips of 12mm ply screw on so bottom edge is say 10mm above finish. Raking the concrete around, it will be possible to get level all around perimeter. Doing that, gives you a datum around perimeter that would otherwise be hidden by dpm

The middle wont be far out. If you are concerned make a tamp board 150 × 50 with a bit timber screwed on top and over hanging end -forms notch to sit over wall batten -but you can only use diaginally since its fixed length. Or check level with laser and mark on wood.

The difficulty moving around in the concrete and not disturbing what youve levelled.

It will all get pumped in an hour or so.

You need a couple of bags of cement, they need to use it to wash pipes out. And somewhere to put waste as pipes are flushed.

Dont be near end of pipe when the cleaning ball gets pumped through

When screwing 50 x 50 om, make sure there is some fullness in dpm, so it doesnt get stretched down when concrete goes on.

Your right notch this is oversite with insulation to go on top and then a self level screed later on. It’s an awkward space to screw on battons around perimeter due to odd features (see pic) although not impossible.
Don’t worry, the washing machine and dryer will be moved out before I start.
Around the corner from the pic I’ve got the stairs terminating which are currently floating in mid air, another awkward feature to work round. Had this been a simple rectangle or just a slab inside the new extension it would have been much more straight forward

youdid well to stop mate - your photo shows a few things that would have caused you problems.
heres how we do interior slabs -
harcore/firm soil
blindin sand on hardcore
membrane
insulation - taped sheets
edge insulation
some put a membrane on top of insulation as well - i dont
concrete slab.

lot of other stuff to take into account but thats the bones for how we do it.

screed is a thin layer on top of the concrete.
the slab is not the screed.

Thanks bobasd,

Finding a contractor to do the work has been a challenge but today I think I’ve sorted it.
Originally it was going to cost me 1400 for 10.5 m3 plus pump. I’ve now found a company who are going to barrow it in for 1700. All they request is that I set up perimeter battons as a reference. Another guy was similar price but wanted me to arrange a gang of people to muck in which is difficult.
I’ll post an update once it’s done

Well I never used the barrow guys in the end. Had a call back from another company who pump it in and they said they offer a laying service too. No messing around with battons. Cost me extra but they’ve done a decent job in my opinion

And not a footprint in sight??

Haha yes. What was even better is I wasn’t at home when it was done. Nice to come home and see progress - if I had the money I’d have trades do the lot - mind you, where’s the fun in that

DIYer Damo said:

if I had the money I’d have trades do the lot - mind you, where’s the fun in that

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In the pocket.