Amtico over mix of concrete and floor board with slight height difference

3 Jun 2016
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United Kingdom

I've had an extension on the house and the rear lounge now had about 5ft extra on it which has a new concrete floor, there used to be a bay patio window there and that was removed, it was the typical U bay shape. So the original floor board are also in the bay type shape meeting the new concrete floor (see pic).

The issue I have is the builder used a laser to measure the height of the floor however I think they measured at the far end or the middle and the floor actually sloped down a little so the concrete floor ended up around 7-9mm higher than the floor board. They removed the bay and then sloped down slightly were that was to meet the floor boards (see other pic)

I plan to have Amtico or similar in the extension part up until the original internal wall line (around 7 floor boards in) in the lounge where I will then have carpet in the rest of the room. The reason being that I will be using the bifold a fair bit so I don't want to be walking in on carpet or rug or such like. Also it gives a bit of a feeling of separation at the end of the reading area and sun area when finished.

So my issue is how to I make sure the Amtico floor is flat across the whole area including where the slight drop is to the floor boards. Also will I have any issues with the concrete being totally solid but the floor boards obviously having some slight movement.

IMG_20201028_172501 (1).jpg
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I had a similar thing when I had a front extension done. My levels were spot on between solid extension floor and existing suspended floor in my downstairs toilet. Even then, my Amtico fitter said the join will show through so he boarded it before laying the Amtico. I’d check with whoever is laying your Amtico.
You want 6mm sp101 or FG1 plywood on the wood section. Then some fibre smoothing compound to sort out the levels. Then a 4-5mm fibre smoothing compound over the whole room.
Great thanks for that Dazlight, that is something like I thought would be needed. I'll have a look fibre smoothing compound, that's a new one on me.
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Here is a list of a few

Mapei renovation
Ardex FA10 or FA20
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Uzin NC196

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