Troweling slab
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Not sure, I was kinda thinking I could try and grind them down / scrape them the next morning with the trowel...
Also the idea of the bull float was to get rid of the tamp lines as much as possible
Also the idea of the bull float was to get rid of the tamp lines as much as possible
You mention you have batons screwed to the wall level with the pour and have notched wood to tamp down. Am I naive in thinking you can just drag your wood over the top along the levelled batons to avoid tamp lines?
You bull float straight after its been laid. Then a Fresno blade after about 4 hours if your not power floating it.
To get the concrete the necessary level for ffl is not rocket science just set your guides at the correct height , ffl minus floor finish.
Make sure you don't add any additional water to the mix to make it flow easier, don't float it with water on the surface, you can bull float it as that leaves the surface open.
You should fairly easily get a good enough finish to tile over with some time and enough help to place it so you are not too tired to finish it off.
To get the concrete the necessary level for ffl is not rocket science just set your guides at the correct height , ffl minus floor finish.
Make sure you don't add any additional water to the mix to make it flow easier, don't float it with water on the surface, you can bull float it as that leaves the surface open.
You should fairly easily get a good enough finish to tile over with some time and enough help to place it so you are not too tired to finish it off.
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Noseall is right to make you aware that concrete is a cruel mistress and not to be taken lightly. You only get one chance and your under physical and mental pressure until the moment you have it tamped and floated.
That said its perfectly possible for a first timer to get a good result and the key ingredient is to have help so it takes the pressure off. I would be tempted to leave your floating until later than normal. Usually after tamping and levelling the concrete is bull floated to bring up some cream to the surface and to tighten up the surface but this is the moment where and inexperienced person will push waves into the still fluid concrete with the unweildy bullfloat on a pole.
If you hold off floating until the concrete is a little firmer then you will not risk doing this but will end up with a coarser surface when you come to trowel it.
The crust will still be soft at this stage so after the bleed water has gone you can trowel it by hand to get off tamp marks and flatten the surface once its hard enough to take your weight (on a piece of kingspan or similar so you dont leave dents).
The larger the tile you are using the flatter it needs to be as a small bump here and there will throw off large format tiles.
At the end of the day its only concrete, you can grind off a high spot if its really bad but if your careful and take your time you should get a decent result. The timing and technique of floating is where most people get it wrong by pushing waves into the slab
That said its perfectly possible for a first timer to get a good result and the key ingredient is to have help so it takes the pressure off. I would be tempted to leave your floating until later than normal. Usually after tamping and levelling the concrete is bull floated to bring up some cream to the surface and to tighten up the surface but this is the moment where and inexperienced person will push waves into the still fluid concrete with the unweildy bullfloat on a pole.
If you hold off floating until the concrete is a little firmer then you will not risk doing this but will end up with a coarser surface when you come to trowel it.
The crust will still be soft at this stage so after the bleed water has gone you can trowel it by hand to get off tamp marks and flatten the surface once its hard enough to take your weight (on a piece of kingspan or similar so you dont leave dents).
The larger the tile you are using the flatter it needs to be as a small bump here and there will throw off large format tiles.
At the end of the day its only concrete, you can grind off a high spot if its really bad but if your careful and take your time you should get a decent result. The timing and technique of floating is where most people get it wrong by pushing waves into the slab
Thanks all I really appreciate the replies.
I am definitely going to get help at least 2 other people. I have a plan b which is if it really goes pear shaped I will only try and get a flattish finish on the one half (kitchen diner to be knocked through) and on the rest I'll just leave it rough tamped and put a screed on it and a step up into it. The wife will hate me but that's an absolute last resort which I'll try to avoid!
One thing I will promise to do is report back here when this is done to either confirm its an absolute ball ache or explain how I got on for anyone else considering doing it !
I am definitely going to get help at least 2 other people. I have a plan b which is if it really goes pear shaped I will only try and get a flattish finish on the one half (kitchen diner to be knocked through) and on the rest I'll just leave it rough tamped and put a screed on it and a step up into it. The wife will hate me but that's an absolute last resort which I'll try to avoid!
One thing I will promise to do is report back here when this is done to either confirm its an absolute ball ache or explain how I got on for anyone else considering doing it !
Please do - I'll be doing this in a couple of months.
Why? Why don't you plan for a screed FFS!
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Speaking as an amateur, who has done this more than once on a smaller scale - if you're planning on tiling the floor, any ridge lines won't interfere with the tiling. The key thing is to aim for flat, rather than smooth. My first attempt showed me that nothing can mess up a nice flat concrete slab surface as quickly as enthusiastic trowelling, if you lack experience. I did exactly what you're suggesting, from a scaffold board, and wrecked it. On subsequent efforts I made no attempt at trowelling. Flat is your goal. Unless you want to see the surface, dead smooth isn't necessary. Be satisfied with flat.
Also, allow for the thickness of tiling when matching an adjacent floor. For example, 20mm is about right for slate and adhesive.
Cheers
Richard
Also, allow for the thickness of tiling when matching an adjacent floor. For example, 20mm is about right for slate and adhesive.
Cheers
Richard
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Thanks Richard v much appreciated
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Just another comment - it's quite a lot of effort tamping down wet concrete with a batten. Ideally you need to be able to execute a side to side sawing motion, moving the concrete towards you as you flatten it. You're also tamping it downwards to get rid of air and knock the aggregate down from the surface.That was the idea but not sure as I've never done it before, I'll let ya know
Cheers
Richard
this is your best advice so far,
what you really want is one or two of you in there with an aluminium screed levelling and several other barrowing it in, as your concrete will be going off from the first barrow. tomfe is about right 4 hours is about what you'll have from start to finish dependant on temperature and wind, in really warm weather it could be as little as 2 hours. You could increase the slump of the concrete to give you a bit more working time but then you run the risk of it not going off quick enough and you end up floating it in the middle of the night.
After screeding it as tomfe says bull float it off with a mag float on a chained pole, don't steel float it other wise you will seal off the surface and bring water to the top which will weaken the top layer. when the sheen has gone off of it and kneeling on a bit of 18mm ply only leaves an impression about an 1/8 of an inch deep you can steel float it, again with a chained pole. the chained pole allows you to tip the floats from one edge to the other so you can float backwards and forwards.
At 50 sqm you will almost certainly get contraction cracking as the concrete cures, in warmer weather this could happen over night so you need to cut wet joints straight away but in cooler weather you can get away with doing this the next day. cut to about half the depth of the concrete at an area ratio of no more than 2:1 fibres in the mix will help as will smaller aggregate in the mix.
Thanks chappers appreciate the info
Can't use metal to tamp it will be bits of 4x2 as I need different lengths for different areas and it's notched to sit on the battens I've put up
Will look to see if I can get a mag float but the 2 guys I've got helping me are bringing their float but I suspect it's a steel one. They've done garage bases in the past which they reckon they got spot on "like a mirror" with the bull float but we'll see. At least there will be 3 of us.
Can't use metal to tamp it will be bits of 4x2 as I need different lengths for different areas and it's notched to sit on the battens I've put up
Will look to see if I can get a mag float but the 2 guys I've got helping me are bringing their float but I suspect it's a steel one. They've done garage bases in the past which they reckon they got spot on "like a mirror" with the bull float but we'll see. At least there will be 3 of us.
Will be screeding over the UFH, but keen to get a flat as possible slab to lay insulation on.
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