Poorly laid concrete floor

22 Aug 2007
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United Kingdom
Hi all, am having difficulties with the concrete floor laid in my new extension. There have been numerous issues with it, firstly the concrete poured into the extension hardened before it could be levelled off properly.

Our builder promised that it wasn't an issue and attempted to fix it after the house was fully built with self levelling compound, but it just made the floor even more bumpy, uneven and unlevel. He's accepted it is unacceptable and hired a local groundworks professional to dig up his bad screed and level off and fix the floors.

He's finished the floor now, and although it is better, it still isn't within NHBC tolerance (4mm over 1m) in many areas with hollows and lumps and bumps. Also he's used a sand and cement mix, it has been about 5-6 days since it was laid and when you rub your foot over the floor, it rubs off sand. For example, our fridge was a dragged across the floor by the workers leaving marks along the floor, I rubbed over the marks with my foot and they sanded away.

All we want is a floor that is fit for purpose for us to lay solid oak/engineered oak/laminate on and not come into any problems in the future.

We've been moved out of the house for 2 months while he's been trying to fix this and we're desperate to move back in. We've given so many chances to our builder to get this right, and now I'm concerned that we have another bad floor laid. Who should I turn to to check over the work, as I really have no idea what is acceptable beyond tolerance guidelines, and have no idea if it's a failed floor? Any advice very much appreciated, thanks guys!
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Idiot builders and floors! It's not the first time on this forum and won't be the last.

Did he lay the floor slab with the intention of adding a (50mm - 75mm) floor screed then realised that he had little or no thickness tolerance to lay a floor screed?

Or did he lay the floor slab full height and attempted to float the concrete off to a finished standard but did it poorly?
Thanks for the reply mate. Yeah he laid the floor slab nearly full height and then attempted to float the concrete to the finished level with a fairly thin screed, and it was completely botched, lumpy and bumpy and was probably around 35mm out total from highest to lowest point across 5 rooms. This was across Dining Room (existing) and new Sitting room (which are open plan), then through door threshold from sitting room to playroom which then leads to Utility room and Study.
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Jeepers, sounds like an expensive and rather naive bodge.

Cement based products are not good when spread thinly and +/-35mm is awfully thin. He'd be better off thinking of a way to finish it with ply or similar, using packers etc.

Either that or re-doing the whole slab.

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