Dimensions of the base plate do not match

I would check DIN 18202 tolerances in building construction to see if it is still within limits.

Example: For a length of 6 to 15 m, a clear dimension in the floor plan may deviate from the target by +/- 24 mm. Phew, that’s going to be tricky ...

Just measured again. Exactly from corner to corner it is 24mm too little. When I measure exactly in the middle of the base plate, it is 10mm too little. And the other side from corner to corner it is 5mm.

Example: For a length of 6 to 15 m, a clear dimension in the floor plan may deviate by +/- 24 mm from the target.

No, not for a "length," but for a "measuring point distance." The specified tolerance therefore applies to the distance, e.g. if you set the first measuring point at 7.32 m and the second at 22.32 m, for these 15 m in between just as for the 15 m from 3.24 to 18.24 m. The total length can also be 27.11 m.

That means you do not have to start measuring at a corner and accordingly do not have to find a new deviation from the standard table for each total length. Rather, for any section of a maximum of 15 m, the 24 mm must not be exceeded.

Only when the total length is so short that the second measuring point could no longer be found at a distance of 15 m (logically the case with 14.99 m or less total length), do you have to look for the corresponding tolerance for 1 to 5 m.

So firstly, no magic, and secondly (before the original poster asks the same again): yeah yeah, all good!

No, not for a "length," but for a "measurement point distance." The specified tolerance therefore applies to the distance, for example, if you place the first measurement point at 7.32 m and the second at 22.32 m, for this 15 m in between just as for the 15 m from 3.24 to 18.24 m. The total distance can also be 27.11 m long.

That means you do not have to start measuring at a corner, and accordingly, you don't have to look up a new deviation from the standard table for every total length. Rather, for any section of up to 15 m, the 24 mm must not be exceeded.

Yes, you have to start at a (measured) corner. The deviation between arbitrary points that have no nominal coordinate is always zero – you can measure 1000 times, nothing will come of it. At best, a calibrated measuring tape.

Only when the total length is so short that the second measurement point cannot be found at a 15 m distance anymore (logically the case at 14.99 m or less total length) do you have to look for the corresponding tolerance for 1 to 5 m.

14.99 > 5m. Therefore, a tolerance class for 1-5 m applies in any case.

So first of all no magic, and secondly (before the OP asks the same again): yep, everything is fine!

Indeed.

Best regards
Dirk Grafe

No, not with a "length", but with a "measurement point spacing".

Do I have to understand the difference?

before the OP asks the same again): yeaaaah, all fine!

He measures between two points about 10 m apart. He finds a deviation from the expected value of 24 mm. Are you sure that's okay? Can you explain that? If he measures again and finds a 25 mm deviation, is everything still okay?

BTW, I also measured my base plate at the time, but only determined "10 meters". Not to give the wrong impression here; I didn't write the DIN.

More important than a 25mm tolerance is probably that the base plate is not only a parallelogram but also a rectangle. THAT is what I would check.