ᐅ The dimensions of the foundation slab are incorrect.

I would check the tolerances for building construction in DIN 18202 to see if it is still within the acceptable range.

Example: For a length of 6 to 15 m (20 to 49 feet), a clear dimension in the floor plan may deviate from the specified value by +/- 24 mm (1 inch). Phew, that’s quite tricky...

I measured again just now. From corner to corner exactly, it is 24mm (about 1 inch) too short. When measuring precisely in the middle from the base plate, it is 10mm (about 0.4 inches) too short. On the other side, from corner to corner, it is 5mm (about 0.2 inches) too short.

Bieber0815 schrieb:

Example: For a length between 6 and 15 m, a clear dimension in the floor plan may deviate by +/- 24 mm from the nominal value.

No, it’s not about a "length," but rather a "measurement point distance." The specified tolerance applies to the distance, for example if you set the first measuring point at 7.32 m and the second at 22.32 m, the 15 m in between is subject to this tolerance just as much as the 15 m from 3.24 to 18.24 m. The total distance can also be 27.11 m.

This means you don’t have to start measuring at a corner, and you don’t need to find a new tolerance from the standard table for every total length. Instead, for any section up to a maximum of 15 m, the 24 mm tolerance must not be exceeded.

Only if the total length is so short that the second measuring point can no longer be found 15 m away (which logically applies to total lengths of 14.99 m or less), do you need to look up the appropriate tolerance for 1 to 5 m.

So first, it’s nothing complicated, and second (before the original poster asks the same question again): yep, everything’s fine!

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11ant schrieb:
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 (24.0 feet) and the second at 22.32 m (73.2 feet), for this 15 m (49.2 feet) in between just as for the 15 m (49.2 feet) from 3.24 to 18.24 m (10.6 to 59.8 feet). The total length can be 27.11 m (89.0 feet), for instance.

That means you don’t have to start measuring from a corner, nor do you have to look up a new deviation from the tolerance table for each total length. Instead, for any section up to 15 m (49.2 feet), the 24 mm (0.94 inch) tolerance must not be exceeded.

Actually, you must start from a (surveyed) corner. The deviation between arbitrary points without specified target coordinates is always zero — no matter how many times you measure, it won’t show any variation. At best, a calibrated measuring tape might yield minor differences.

Only when the total length is so short that the second measurement point at 15 m (49.2 feet) distance can no longer be found (which logically applies if the total length is 14.99 m (49.2 feet) or less), you need to find the corresponding tolerance for 1 to 5 m (3.3 to 16.4 feet).

14.99 m (49.2 feet) > 5 m (16.4 feet). Therefore, the tolerance class for distances over 1 to 5 m (3.3 to 16.4 feet) always applies.

So, first of all, it’s nothing complicated, and second (before the original poster asks the same again): yes, all good!

Indeed.

Best regards
Dirk Grafe

11ant schrieb:
No, not for a "length," but for a "measuring point distance."

Do I need to understand the difference?

11ant schrieb:
before the OP asks the same again): yesss, all good!

He measures between two points about 10 m (33 feet) apart. He finds a deviation from the expected value of 24 mm (0.94 inches). Are you sure that’s acceptable? Can you explain? If he measures again and finds a 25 mm (1 inch) deviation, is that still okay?

By the way, I also measured my foundation slab at the time, but only determined "10 meters" (33 feet). Not to give the wrong impression here; I didn’t write the standards.

More important than a 25mm (1 inch) tolerance is to ensure that the concrete slab is not only a parallelogram but also a perfect rectangle. I would definitely check that.