Concrete Subfloor help

UnknownGnome · 9 Oct 2015

Hi everyone,

I need some advice on Subfloor preparation. I have recently moved into a new build house. We chose not to have flooring put down as we didn't like their options and would do it ourselves so currently we have exposed concrete downstairs which we intend to put a floating wood floor on. The floor seems to be quite level but what is worrying me is how coarse the floor is. I can see gravel in the mix and am worried the coarseness will damage the damp proof membrane. Is it normal for new build properties to be finished in such a way or should there be another smoother layer ontop of this? Has anyone had any experience laying a floating engineered wood floor over the top of a Subfloor like this?

Any input on this will be appreciated as I'm not sure whether to proceed just yet. Thanks in advance.

ree · 9 Oct 2015

What you describe is a badly finished surface - no way should a slab of any kind be left like that. If it is a sub-floor for screeding it should still be finished (but not polished).

If you are supposed to have a S&C screed then FFL's come into play - the door thresholds determine FFL's - so your slab surface should be well below any threshold level.

UnknownGnome · 9 Oct 2015

Hi ree, thanks for your reply. Sorry, not too familiar with some of your terminology. What is an s&c screed and ffl in layman's terms please?

ree · 9 Oct 2015

google

UnknownGnome · 9 Oct 2015

The floor level is currently pretty much in line with the door frames, maybe a centimetre under with some of them. They even put the skirting boards on flush with the subfloor which I didn't want them to do because it means I have to undercut or refit them to install the flooring. Will the floor need to be screeded before I can do anything else with it? Anybody who lives in the UK and has experience with new builds, is this a common practice to leave the subfloor like this now?

dazlight · 9 Oct 2015

Who is the Bulider.
I just did a redrow house. It was a joke.
The subfloor was sand and cement and a terrible mix then that had a water mix smoothing compound on it. Which hadn't been primed.
We had to grind top loose section off all over then use a smoothing compound called Ardex NA
Then as floor was damp we put on Ardex DPM 1c. Then another coat of NA.
It sorted it out but wasn't cheap.
I see loads of bad subfloors these days as everything is rushed and sub contractors do it on a price.

UnknownGnome · 9 Oct 2015

The house was built by Taylor Wimpey. They've already tiled the bathrooms and kitchen and installed kitchen units. Height difference between the floored rooms and the unfinished rooms is the width of the tile so they didn't add another layer to the finished rooms. Do you know if there are any regulations regarding this that must be adhered to? I've had a look online myself but can't find anything definitive.

ree · 9 Oct 2015

BCO's enforce the Regs not the quality of the work.

Are you saying that the concrete surface is level with the FFL of the tiled rooms? What about the front door and kitchen door thresholds - will your wood floor surface be level or lower than the outside door thresholds?

UnknownGnome · 9 Oct 2015

Where the hallway and kitchen meet, the concrete is lower than the tile by only the height of the tile. The wood floor and underlay will be lower than the outside door threshold but will be raised above the tile floor to the kitchen so I'll need to use a reducer transition strip.

UnknownGnome · 10 Oct 2015

Would it be feasible to use a self levelling compound like ardex na or ardex a55 to smooth out the floor? I am using 6mm thick underlay tiles and a DPM sheet so would it be necessary to use self levelling compound? My primary concern is the rough floor puncturing the dpm.

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Concrete Subfloor help

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