I’ve asked this on another thread, but in case it gets missed there, I’ve started a new one specifically for this question.

I’m building an 8090×6740 wall around an existing building, so I can’t check the diagonals.
It’s a sloping site as well, which makes it harder.
I reckon I’m within 20mm over 8m, or 1:400.

Would that be acceptable for a new build ?

Not in the building trade but my house, built 5 years ago, has worse than that.

No idea on tolerance, but the screed guys I used in the barn managed 5mm over 25m. Bloody impressive.

So that’s both extremes then. 😕

Thinking about this a bit more, I fitted some kitchen worktops at MuddyPuddle’s house.
Where they met at the corner, I had to taper one by 5mm over 600mm. that’s a 1:120 out of square error.

• Accuracy in measurement: Use instruments and methods described in BS 5606, Appendix
A:
– Linear dimensions: [± 3 mm up to and including 10 m
± 6 mm for over 10 m and up to and including 30 m].
– Angular dimensions: [± 201/21/2 (± 5 mm in 50 m)].
– Verticality: [± 5 mm in 10 m].
– Levels: [± 5 mm in 15 m distance].

HTH

Thanks Creamegg, I’ve just downloaded the full BS5606 and I’m skimming through it now.
+/-3mm over 10m sounds out of my reach with a string line, tape measure, spirit level and bits of wood stuck in the ground. 🙁

Table 1 gives;

Walls up to 7 m apart
At floor ± 15
At soffit ± 20

I think I’ll go with that one. 😀

Hire yourself a decent dewalt laser site level for a day or two. Their range is huge, like 500m!

Alternatively, a stanley interior laser level wil cover that span but will be be very hard to see outside unless the light is low. I’ve got the CL2, just about the most useful thing i’ve ever bought.

I think I’m OK for level, it’s the square where I’ve got a little bit of error.
I’m using the back wall as my datum.
I couldn’t use Pythagoras on the insides of the corners as there’s an existing building in the way.
I had to mark out the 3:4:5 outside the new walls, then extend the line back the opposite way, if that makes sense.

out of interest where did you download a full BS from? have you got access to IHS or similar website as did you google it (there arent that many of them you can download by googling from past experience)

To check your levels you just need a length of hose pipe and a couple of funnels. Fill the lot with water and the surface at both ends will be level.

I just googled BS5606 and found this.
http://www.4shared.com/document/GRgeDo4G/BS_5606.html

I’ve got a proper water level with sight glasses, like this;

When I built the shed, I marked out all four sides, then checked the diagonals to make sure it was square.
With an existing building in the way, I can’t do that now.
It doesn’t help that the existing building is so far out of square its self.

Why are you bothered ? If it’s out of square it won’t affect its performance, and you are governed by the existing building anyway – you can’t square that up if it’s out of square.

I’d rather live in a straight house than a crooked one.
Would you be bothered if someone dented your car, scratched the paint on your bike, or splashed ink on your favourite shirt ? It wouldn’t affect the performance.

I’m allowed to go up to 300mm outside the existing walls with my “self supporting cladding”.
The brick plinth is 225mm thick, the timber wall on top of that will be 150mm. That gives me a bit of leeway to straighten it all up.

The stanley level does vertical as well as horizontal and a cross that can be plum or locked at an angle

Stanley CL2
It does a horizontal and a vertical line, but I can’t see how it could be used to mark out a rectangle on the ground. Am I missing something ?
It’s all a bit academic now, as I’ve done the job, but what I could have done with is a laser level to mark out one wall, with a second laser at a calibrated 90 degrees to mark out a second wall.

Ah, now I understand. there is a laser for doing that, can’t remember who makes it though. I think its advertised regularly on the back page of professional builder. Its more for tiling large floors though

why not use pythagoras/trig on the outside (i,e. four triangles with their 90degs back to back with your building 90degs) to get square.

Should be doable with a string and tape measure.

Stoner, read here, 😉

That’s what I did.
I measured 4m along the back wall, then 3m away, as that’s all the room I had.
I then extended that line by nearly 7m for the side wall. That must be where the error crept in as I was then about 1m above ground level at the front, so I had to plumb down from there.

blindbat strikes again…