How sloped is too sloped?

[confused30000]

My parents have recently had an extension built, flooring laid etc. It looks great, but when I was in there in felt like there was a slight slope towards one of the walls - nothing major but noticeable I thought. I laid a 60cm spirit level and it is out, with the bubble lying as in the photo below. I don't think my parents are that bothered really so it's not a disaster, but it got me wondering, how tolerant would you be of a floor where, at its worst, the bubble of a spirit level was slightly touching one of the lines?

How

 

[oldbutnotdead]

Not very. On a new build (ie ground up, not a repurposed shed base) there's no reason to be more than 10mm out across 4 or 5 metres. What is the actual drop, how long is your level, is it true (if you reverse it does the bubble go to the same place).
Oh, just noticed it's a short level . That's going to be min 10mm/metre out, not good at all. NHBC requires 4mm/metre max (according to Google)

 

[freddiemercurystwin]

Whilst your extension is not NHBC https://nhbc-standards.co.uk/2018/9-finishes/9-1-a-consistent-approach-to-finishes/9-1-5-floors/ this gives a pretty good guide, based on the British Standards. But a good builder would only be a few mm out here and there at most, anthing else is just poor quality.

 

[confused30000]

Thanks both. Yes, it's a 60cm level, don't have access to a 2m one unfortunately.

I think the slope isn't consistent - the picture is as bad as it gets, move the level along a little towards the wall and it goes a bit more central. It doesn't really seem to bother anyone else, but it got me wondering!

 

[Deleted member 174758]

Thanks both. Yes, it's a 60cm level, don't have access to a 2m one unfortunately.

Then do what we used to do before 6ft/2m levels were generally available - tape a shorter level to a straight piece of planed, 3 x 2in softwood. There haven't always been 6ft/2m levels. In fact they are a relatively recent phenomenon. The long straight edge also allows you to check for hollows and crowns with only an oblique light source (such as your mobile phone light). Very often "levelness" is less of an issue than "hollowness", which is something you can feel as you walk across a floor

 

[big-all]

yes a short level will on average be up to 3 times the average deviation but can be much more as a dip can give you a say flat a up hill left and a uphill rh side dependent on position where as a long level will be far more average as it can pass over several high and low spots

and dont forget to flip end over end to average any deviations from level or timber baton deviations and as jxk says tape together to stop a small deviation on both the timber and level "fighting each other" and muddying the average results off flipping

 

[confused30000]

Thanks everyone who responded to this. For those interested, I had completely forgotten that I had a self-levelling laser level at the back of the shed so out of interest dug it out.

I set it up at the highest point and pointed it to the other wall, where I feel like I can feel the slope. Let it self level and then measured the height of the laser mark right in front of the level, and then where it projected onto the opposite wall.

Over a span of about 3.36m, it appears to be about 22mm lower on one side - way over the recommended 3mm per metre from the NHBC (which I assume means the drop should be no more than about 10mm?).

Anyway, it isn't my extension and parents don't seem to mind so I haven't said anything. Just a bit gutted on their behalf that it seems way over!

Please let me know if there's any flaws in my methodology here. Anyway, photo below of the laser against the run of the slope, which I think demonstrates it better.

 

[freddiemercurystwin]

At least the radiators level.

 

[oldbutnotdead]

If it's a cheapish laser it's worth doing a reverse check to make sure it is accurate (on my cheapo the horizontal line is level but it drifts up by about 2mm a metre from source to target.
EDIT For this particular job it's doing its job. Level errors (in theory) can happen either plus or minus so the overall level ought to average out- never seems to work that way though.

 

[confused30000]

Thanks - yes, did it the other way too and the result was the same. It says there might be a deviation of +/- 5mm but even taking that into account, best case scenario I guess it's still going to be a drop of around 17mm?

 

[oldbutnotdead]

Yup. If that's the only fault with the build then it's not the end of the world, just annoying (some people, me included, would be massively irritated by it)

 

[confused30000]

Yup. If that's the only fault with the build then it's not the end of the world, just annoying (some people, me included, would be massively irritated by it)

Yes, I think it's the kind of thing that will annoy me the first few times I go round then I'm sure I'd forget about it. Other than that, everything else seems good so could certainly be worse!