7m3 of concrete coming the Friday for my floor…here’s my plan, how’s it sound?

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Hi all,

First time I’ve done a floor slab, so read lots of other posts, but would like some validation of my plans for the day please. Here’s the site as it is now, BC signed off this today :)

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There are two spaces to be filled:

1. Kitchen [at rear] – 4.1 x 5.1m with 6mm rebar. Concrete will be 100mm deep, with a 65mm screed on top (at a later date). 2.1m3 concrete needed.

2. Garage [at front]– 6.2 x 5.1m with 7mm rebar. Concrete will be 150mm deep. This will be the finished floor level. 4.74m3 concrete needed.

The cement company have recommended C30. Although initially they tried to rent me a pump for £350, when I said I’d prefer to shop around for a company that would barrow it in, they’ve agreed going to barrow the concrete in (with a labourer supplied, although I guess I will assist too). They will mix on site.

The driveway is pretty wide (and old/knackered) so they can park the truck right up to the entrance to the new garage, so I imagine they will pour some of the concrete straight in without the barrowing.

I have 2 or possibly 3 people to help me on the day, although not skilled people – just extra pairs of hands.

I’m going to hire 3m and 5m Hand Concrete Tampers with handles and a Concrete Easy Float with brush attachment.

Kitchen will be filled first, with two people tamping down (using 3m tamp over the 4m width). I will rake out to roughly level concrete / assisting with the barrow.

Garage fill second, following the same process but using the 3m tamp to start, then 5m one (over the 6m width) once the concrete truck is gone).

Then use the bull float on each to get it smoother.

I will then use the brush attachment on the kitchen surface to give a key for the screed. Unsure if I should use on the garage floor or just leave it with the bull float finish.

I have bought a concrete rake and I have a Flooring Trowel and a hand Mag Float too as there’s a couple of pipes to tidy up around.

I also have 2 tarps of 5.4 x 7m which I will cover it over with afterwards to help the curing process.

Would welcome any advice, but especially about the following points:

1. When to start using the bull float? – seems to be once the surface water has gone from what I’ve read.

2. My local hire shop has these Petrol 1 Man Screedemon which is £100 for the day – is that worth hiring rather than the hand tamps?

3. Any tips about getting the height right – I cant fix battens, etc due to the DPM – can I just invert some of the spacers (50mm kitchen and 75mm garage) on top of the rebar, or am I missing a trick on some other way to do it?

4. Should I use the brush on the garage floor, or just leave it smoothed with the bull float?

5. Any info about the wetness/slump of the mix to ask for in order allow me a decent amount of time to work it?

Any other tips you guys have too?

Thanks!
Andy
 
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If the house floor is going to be screeded, why are you floating/messing about with it?
You normally tamp the slab off your walls and can fix battens to existing house at the other end. Doesn’t have to finish at that height, make a notched tamp so it levels below at whatever height
Garage floor is where you want the bull float, personally I’ve had more luck with getting on it with a hand trowel after it’s set enough to hold my weight on a square of celotex. Make sure you tamp the garage floor really level in that case.
 
If the house floor is going to be screeded, why are you floating/messing about with it?
You normally tamp the slab off your walls and can fix battens to existing house at the other end. Doesn’t have to finish at that height, make a notched tamp so it levels below at whatever height
Garage floor is where you want the bull float, personally I’ve had more luck with getting on it with a hand trowel after it’s set enough to hold my weight on a square of celotex. Make sure you tamp the garage floor really level in that case.

Morning,

Thanks for your input.

Every thread I've been able to read/watch shows that at as a minimum there was a bull float over the surface to tidy the holes and bring up the cream, even floors to be screed.

I was thinking about the battens and how to fix, but everything I could figure out would mean/risk damaging the DPM - either through adding batten, or through the tamping motion itself hitting the DPM.

Cheers
Andy
 
You definitely wouldn’t bull float (or hand trowel) a slab that’s going to be screeded over, no one does that. You just get the concrete roughly level. That info is wrong.

Not sure why you’d damage your dpm just by running the end of the tamp over it? It’s a really common way of doing it, loads of posts on here about it.
 
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You definitely wouldn’t bull float (or hand trowel) a slab that’s going to be screeded over, no one does that. You just get the concrete roughly level. That info is wrong.

Not sure why you’d damage your dpm just by running the end of the tamp over it? It’s a really common way of doing it, loads of posts on here about it.

Thanks for your help...

Pretty much every video i've seen of tamping has the brickwork at the same depth as the finished concrete pour, so nice and easy to tamp down as the guiding brickwork is flush. As my garage floor will be 100mm below the brick course, the lapped up edge of the DPM is exposed and I'm just concerned about piercing it with the tamp as it's moved around.

I guess that bit of the DPM will eventually be cut away, so not something to be overly concerned about I guess. This is why I like bouncing ideas out on the forum. Thanks again :)
 
Are you thinking of putting nails in the bottom of the tamp?

1200g polythene is very tough.

Maybe they don't make it like they used to, but I've already had to replace one 4 x 4m sheet where I put a bit of 3 x 2 down on it (reasonably gently in my opinion) and managed to puncture it.

I've got some scant, so think I'll just lay that on top of the DPM on the brick course to add some protection. Following @23vc comments, I've put some buttons down the existing wall and made a 5m tamp with some handles out of spare 3 x 2, which should make life easier tomorrow.

Pictures to follow. Might even do a time lapse of the pour tomorrow, which could give the professionals a laugh if nothing else :)
 
Well that was a long day! Started outside at 6.30am, concrete arrived at 8.15am and I finished up with everything at 9.55pm!!!

The wind today has been a ruddy nightmare. I have literally spent half the day picking leaves and bits of grass out of the concrete as each one was dragging/scratching the concrete as I floated it :mad:

Anyways, 7m3 of concrete actually ended up being 9m3 of concrete so must have been a bit deeper than anticipated in places.

As it rained a lot last night there were puddles in the floor before the pour/barrowing started. The the mix seems pretty wet and there was a lot of surface water. All the concrete was in before 10am, but really I could only start floating about 2pm, and even there there were still puddles, but I wanted to get some practice in with the bull float. Did a bit of floating in the kitchen too to help get my eye in, but as that's getting screed I didn't bother too much.

I won't be winning any prizes at the garage floor of the year awards, but I'm happy enough with it :)

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Good effort. Hard work with concrete at the best of times. You can still get a perfect floor in the garage with SLC
 
Good effort. Hard work with concrete at the best of times. You can still get a perfect floor in the garage with SLC
Thanks again for your help - tamping down was easy with the battons and the tamping contraption I made :)

I'm thinking I'll probably epoxy paint the garage floor, or may rubber tiles for it anyway.
 

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