Floor sloping by 40mm - should I try to level?

3 Jan 2021
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United Kingdom

I am just in the process of rewiring my flat and after measuring all of the new locations for the plug sockets at 480mm above floor level I checked them with a laser and noticed that they aren't level.

As it turns out one side of the concrete floor is 40mm lower than the other (the room is approx 4m wide).

Now, i'm unsure wether to try and level out the floor and cut out all the holes for the plug sockets relative to each other/a flat floor, or keep the floor as it is and cut out the holes for the plug sockets relative to the current sloping floor.

Looking online some screed can be used up to a depth of 40mm, but how do I apply this? Do I just need to fill the entire room with screed in one go or do I need to do it in layers?

FYI, I was also hoping to install engineered wood floorboards on top of the concrete floor. Will the slope be an issue if I decide not to level with screed? the floor is flat, just sloping.
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You don't say 40mm relative to what length?
I am a believer in "if it ain't broke... "
does everything look level?
Are there any doors or such that would be made worse afterwards?

If I were to cut the plug sockets out at 480mm above the floor level, then on one side the plug sockets are 40mm lower then the other side of the room

There's only two doors in my small flat (bathroom and bedroom) but assuming both doors would need to be planed to make them open.

I personally don't have an issue with the floor sloping as it doesn't feel noticeable, but if it's going to be an issue installing the engineered wood floor on top then i'll need to level

So far I haven't seen anything online discussing using screed for such a large slope over such a big area.

For example would I need to do the screed in layers, or just pour enough in one go that would cover the entire 50sqm of the flat?
You still didn't say how long this 40mm drop is over?

40mm should be fine for screen if self levelling compounds can go up to that i'm sure... though 40mm is a lot of compound.

If its flat(but not level) across it there wouldn't be a problem with flooring materials. Put a large spirit level/straight edge on it and look for any gaps/humps.
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40mm will make a nasty trip hazard if the deep end of the floor has doors at it.
If the floor is smooth and flat i'd be tempted to set sockets at x above floor level at that point, especially if any thresholds would be affected by levelling the floor

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