Everything is level, so why…

stuart45

It's obvious that the wall is out of plumb.

Section62

WIAWSNB said:

The spirit level - it has a central vial for taking horizontal levels, and an end one for verticals? Just one end one, or one at each end? And it has a flat  bottom for placing against objects, and a 'top' surface, but this top is also 'flat'?
Test a spirit level like this - slap it upright against the LH wall. Note where, exactly, the bubble sits. Is it really slap bang in the middle? Ok, keeping the tool standing upright, rotate it 180o so that that the top surface is now against that wall. Observe the same bubble - where does it now sit?
Repeat on the back wall - align it with a vertical groove. Rotate.

Most spirit levels only have one long edge which is accurate - the 'back' (your 'top') would generally only give a roughly accurate reading... so as a method of checking for accuracy it doesn't work well.

With two spirit levels the easiest check is to put them 'face to face' (i.e. the measuring edges together) in a vertical position (i.e. upright) with them resting on the ground.  Move the pair around to check to see both indicate 'vertical' at the same time.  Then flip one of the levels end-to-end, so the end nearest the ground is now the one up in the air.  Repeat the process of checking to see both indicate 'vertical' together.

This 'flip' ensures they are both accurate, rather than them being inaccurate by the same amount.

With only one spirit level the same end-to end flip also works, but you need to find a surface which indicates vertical/level to start with.

WIAWSNB

Section62 said:

Most spirit levels only have one long edge which is accurate - the 'back' (your 'top') would generally only give a roughly accurate reading... so as a method of checking for accuracy it doesn't work well. 'Most'. Mine has two machined surfaces, and that's why I asked. In any event, t'top ain't going to be nearly 20mm 'out' over a ~1m length regardless of how rough. So, as a guide for somone I suspect isn't fully au fait with the spirits, I thought my suggestion was pretty awesome.

With two spirit levels the easiest check is to put them 'face to face' (i.e. the measuring edges together) in a vertical position (i.e. upright) with them resting on the ground.  Move the pair around to check to see both indicate 'vertical' at the same time.  Then flip one of the levels end-to-end, so the end nearest the ground is now the one up in the air.  Repeat the process of checking to see both indicate 'vertical' together. There you go, mummy - buy another spirit to check the first one by. 

This 'flip' ensures they are both accurate, rather than them being inaccurate by the same amount.

With only one spirit level the same end-to end flip also works, but you need to find a surface which indicates vertical/level to start with. And be ready to prostrate yourself on t'floor as you eye up the solitary vertical vial wot you have just flipped.

Blah blah blahs in bold :-)

teaselMay

That is out by more than it appeared on my phone screen. If you look at the floor to the right (picture right) of the toilet the gap that end is a lot bigger than the gap the other end. I'm a bit spatially challenged but that looks the opposite to what I'd expect with the vertical misalignment in the corner.

Most things you end up accepting it's out of plumb and making it look as right as you can - and avoiding vertical lines

Section62

WIAWSNB said:

Section62 said:

Most spirit levels only have one long edge which is accurate - the 'back' (your 'top') would generally only give a roughly accurate reading... so as a method of checking for accuracy it doesn't work well. 'Most'. Mine has two machined surfaces, and that's why I asked. In any event, t'top ain't going to be nearly 20mm 'out' over a ~1m length regardless of how rough. So, as a guide for somone I suspect isn't fully au fait with the spirits, I thought my suggestion was pretty awesome.

Ah, you said 'flat' rather than 'machined', so that makes a difference.  So for clarity - spirit levels with two machined long edges should be accurate on both faces, but most spirit levels with one 'machined' and one 'flat' edge won't necessarily be accurate on the 'flat' edge.

20mm in 1m is a gross error - so unlikely to be a spirit level error, unless the vial is one of the adjustable-to-any-angle type which has been left on an odd setting.

With two spirit levels the easiest check is to put them 'face to face' (i.e. the measuring edges together) in a vertical position (i.e. upright) with them resting on the ground.  Move the pair around to check to see both indicate 'vertical' at the same time.  Then flip one of the levels end-to-end, so the end nearest the ground is now the one up in the air.  Repeat the process of checking to see both indicate 'vertical' together. There you go, mummy - buy another spirit to check the first one by.

I suggest just using one of the other ones mummystudent said she'd used already. (Quote: "I’ve used two traditional spirit levels and a laser one")

That was the point of my suggestion - if you've got more than one spirit level already then the best check is comparing two together as described.  All three could be checked against each other in a matter of seconds.

With only one spirit level the same end-to end flip also works, but you need to find a surface which indicates vertical/level to start with. And be ready to prostrate yourself on t'floor as you eye up the solitary vertical vial wot you have just flipped.

Why would you use the floor?  "A surface" which is vertical/level to start with could be a table, windowsill, or worktop, or a wall or doorframe.  Failing that, a hard floor (i.e. no carpet) might be an alternative, but honestly not the most obvious to pick.

WIAWSNB

I like you, S62. You are clever and funny

stuart45

I check my levels with 2 screws on the work bench for level, and 2 in a post for plumb. Easy to adjust to get them spot on. When the 4ft level is checked, I put the 3ft one on top as Section62 said, and then the 2ft one etc. They are Stabila, so they are accurate. 
The problem with cheap levels is that the bubble is often quite small, so it will appear between the lines without being really level or plumb.
The bubble on a Stabila is very close to the lines, so it shows hard to the line if the wall is slightly out.

FreeBear

stuart45 said: The problem with cheap levels is that the bubble is often quite small, so it will appear between the lines without being really level or plumb.

If you want to improve on accuracy, it is possible to get bubbles with multiple lines (see image below). Have a similar type of bubble in a level I made many years ago. Sensitive enough to detect a sheet of paper under one end.

stuart45

Stabila produce digital levels now which are easy to read. I still use the traditional ones for brickwork. NHBC guidance for brickwork is 8mm +/- plumb in a 2500mm storey height, and 5000mm level. 
Certain other trades demand greater accuracy, so these levels are more use for them.