Height reference point zoning plan, what is correct?

Hello everyone,

we recently commissioned the surveying of our property in NRW and received feedback from the surveyor that the actual elevations of the channels in our new development area do not correspond with the elevations specified in the development plan.

The planning engineer of the development area informed us that his planning is based on the channel inventory of the affected municipality, which has a difference to NHN of about 10 cm. These 10 cm should be considered as a correction during the on-site measurement.

However, the surveyor refers his elevations to NHN, so these do not correspond with the official development plan. According to the surveyor, the approach of the planning engineer is neither usual nor permissible.

Is there anyone with expertise here who can give us a tip on what is normally customary?

Thank you in advance

Where is your problem now? The height specifications in the development plan are usually not called ridge heights 43.70 m DHHN 2016 but 8.50 above street level.

This means that only the local heights are relevant for your new building, and it does happen that a planner cannot distinguish between NHN and DHHN 2016.

Is there anyone here who is an expert and can give us a tip on what is normally customary?

It is customary that the height reference is indicated on every plan. It is not customary that a municipality has not adjusted its sewer cadastre, at least not to NHN (DHHN92), since DHHN2016 was only introduced in June last year. However, it is customary that the heights in development plans that are older than 13 years refer to NN.

Height specifications in the development plan are usually not called ridge heights 43.70 m DHHN 2016 but 8.50 above street level.

That depends on the municipality. In newer plans known to me, absolute height specifications are now even predominant.

According to the surveyor, the approach of the planning engineer is neither usual nor permissible.

Perhaps you should specify the concrete problem that has arisen from the existence of the three usual height systems.

It is common that the height reference is indicated on every plan. It is unusual that a municipality has not adjusted its sewer cadastre, at least to NHN (DHHN92), since DHHN2016 was only introduced in June last year. However, it is usual that the heights in development plans older than 13 years refer to NN.

It depends on the municipality. In more recent plans known to me, absolute height determinations even predominate.

Perhaps you should specify the concrete problem that has arisen from the existence of the three common height systems.

Good morning everyone,

so specifically our problem lies in the height of the sewer connections. The development plan specifies the manhole cover height as 250.66, the surveyor indicates having measured 250.76 on site. Accordingly, since we are building a basement and initially assumed in the planning phase to just manage without a lifting station, with the 10 cm difference we may possibly be missing exactly 10 cm afterwards.

The development plan is from 2016/2016 and the new development area with about 120 plots was only developed a few months ago.

Thanks again to you all!

if it’s about 10 cm with the lifting system, I would rather calculate with a lifting system.

That depends on the municipality. In more recent plans known to me, absolute height determinations now even predominate.

That really opens the door to faulty building applications... it only makes planning more difficult for the layperson/ builder.

The development plan specifies a manhole cover height of 250.66

I still don’t understand the problem. Then just build 10 cm higher. What height reference is specified on the development plan? Is that an existing condition or a planned height? What exactly was the surveyor supposed to measure or how far along is your construction project? Was it about the topographical survey for the site plan or was it meant to be staked out already? Normally, it should go like this: The surveyor comes to the property, does the topographical site survey including manhole cover and invert elevations, prepares a preliminary site plan for the planner, who adjusts the project’s position and height on the property based on the actual heights and considering the requirements of the development plan. He must pay attention to any differences in height reference systems between the preliminary site plan and the development plan. Ideally, he asks the municipality if there is already a development plan for the building area. Any discrepancies are best clarified immediately with the building authority. At this point it should already be clear whether a lifting station is necessary or not. The surveyor completes the site plan with the project details including ground floor slab, eaves, and ridge heights, and the planner submits the construction documents to the building authority. After approval or expiration of the objection period, the surveyor stakes out the approved or applied-for building.

This basically opens the door wide for faulty building applications… it only complicates planning for the layperson/homeowner.

Why is that? On the contrary! It saves the cumbersome and sometimes misleading description of height reference points.