Diete + Siepmann Ingenieurgesellschaft mbH is an owner-managed engineering firm based in Kaarst with an additional office in Berlin and provides services according to Lph.6-8 HOAI in object planning and technical building equipment. The company serves medium to large projects in administration, production, hotel, retail, gastronomy, housing, museums and logistics and works closely with project developers, architects and contractors. Core tasks include consulting, client representation and construction supervision; in fiscal 2024 the firm employed on average 80 permanent staff and 22 working students. In 2024 the subsidiary Diete + Siepmann Baumanagement GmbH was founded to enable the handling of larger-volume projects in the future.
Beratung, Betreuung und Vertretung von Bauherren in den mit der Planung und Ausführung von Vorhaben, zusammenhängenden Angelegenheiten sowie Überwachung von Bauausführungen.
Converted using the official Destatis and Eurostat correspondence tables; ISIC Rev. 4 is the United Nations' international industry classification.
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Source: German Commercial Register (Handelsregister) Neuss Local Court, HRB 8522 (as of 31 October 2026)
| Name | Type | City |
|---|---|---|
| Manfred Nießen | Geschäftsführer(in) | Düren |
| Dag Ortkraß | Geschäftsführer(in) | Berlin |
| Bastian Overbeck | Geschäftsführer(in) | Kaarst |
| Christoph Petsanis | Geschäftsführer(in) | Kevelaer |
Source: German Commercial Register (Handelsregister) Neuss Local Court, HRB 8522 (as of 31 October 2026)
| Date | Event Type | Event |
|---|---|---|
| 29.10.2010 | Business Address Registered | Rathausstr. 3, 41564 Kaarst |
| 06.05.2002 | Company Name Registered | Diete + Siepmann Ingenieurgesellschaft mbH |
| 06.05.2002 | Registered Seat | Kaarst |
| Date | Type | Change | Total Capital |
|---|---|---|---|
| 13.02.2003 | Capital Decrease | -146.400 € | 153.600 € |
| 06.05.2002 | Share Capital Set | — | 300.000 DM |
Source: German Commercial Register (Handelsregister) Neuss Local Court, HRB 8522 (as of 31 October 2026)
| Year | Revenue | Profit | Balance | Employees |
|---|---|---|---|---|
| 2025 | Rohergebnis€18.1M2 | €3,455,384 | €59,952,020 | — |
| 2024 | Rohergebnis€15.5M2 | €2,412,063 | €43,690,051 | — |
| 2023 | Rohergebnis€18.2M2 | €4,117,904 | €31,771,921 | — |
| 2022 | Rohergebnis€13.7M2 | €3,002,892 | €29,151,165 | — |
| 2021 | Rohergebnis€13.3M2 | €3,419,988 | €18,953,874 | — |
| 2020 | Rohergebnis€11.5M2 | €2,878,816 | €16,917,208 | — |
| 2019 | Rohergebnis€6.8M2 | €1,377,753 | €16,490,927 | — |
| 2018 | ≤ €12M1 | €1,900,536 | €10,083,750 | — |
| 2017 | ≤ €12M1 | €1,493,659 | €9,439,101 | — |
| 2016 | ≤ €12M1 | €1,780,507 | €8,788,665 | — |
1 Small companies are not required to publish a profit-and-loss statement (§ 326 (1) HGB). The figure shown is the statutory ceiling under § 267 HGB where the balance-sheet total makes it binding — a company may exceed at most one of the three size criteria.
2 Rohergebnis nach § 276 HGB: Umsatzerlöse abzüglich Materialaufwand bzw. Herstellungskosten. Kleine und mittelgroße Kapitalgesellschaften dürfen diese Posten zusammenfassen; die Umsatzerlöse selbst sind dann nicht veröffentlicht und liegen über dem Rohergebnis.
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Source: German Commercial Register (Handelsregister) Neuss Local Court, HRB 8522 (as of 31 October 2026)
| Cost type | Amount | Share |
|---|---|---|
| Personnel Costs | €10,065,189 | 97.8% |
| Depreciation | €220,259 | 2.1% |
| Interest & Similar | €1,210 | 0.0% |
