House planning from scratch - financial calculation, basement...

Dear forum members,

I have now spent half (the whole) evening reading in and following along here and am totally impressed by how much competence, knowledge, and experience is gathered here. In this respect, I would also like to ask for advice (and in five years contribute my experiences...).

We are currently at zero with our house planning - almost:

1. Financial planning

We have a budget of around 500,000 euros.
However, the plot of land (ideal location for us) will cost about 190,000 euros including incidental purchase costs.

We have further planned 15,000 euros for furniture, kitchen, moving, small buffer, etc.
Outdoor facilities/garden/garage are budgeted at 25,000 euros - parts of which do not need to be implemented immediately; only the cistern (from the development plan: "a cistern with a forced-drained specific volume of at least 25 l/m² of sealed surface area (projected area - roof area overlay) with subsequent infiltration via swales") will probably have to be done immediately - although I do not understand at all what is required here/what it costs. Here, too, there could be a buffer.

We currently have additional incidental building costs set at 15,000 euros. Without floor slab, earthworks, basement, etc. (see under 3.1).

This leaves approx. 255,000 euros remaining.

2. Our plot
Our plot is approx. 1.3m below the current street level. It slopes slightly (approx. 50cm over 20m). Sealing of the basement against non-pressing groundwater is required.

3. Ideas/Concepts/Wishes
Our ideal idea would be a house of approx. 130-140 sqm:
Besides living room/kitchen/WC, a combined small study/guest room. Two children's rooms, one bedroom, one bathroom. In addition, storage space for household appliances + a place to dry laundry in the utility room.
Additionally, we would need a place for garden tools/bicycles and actually at least a small basement/storage room.

4. Questions
Apart from what you generally think of the plans, the following specific questions:

to 1.: a) Is the financial plan basically realistic as a first rough guideline? If not, - we can hardly increase the budget - the plot is not yet purchased, should we rather look for a less favorable (and cheaper) location?
to 3: b) Against the background of the geography of the plot, the consideration whether we would basement part of the house or even convert it into living space - to what extent would it be noticeable that only a little excavation is possible/otherwise, possibly a fill would have to be made? Then the living area, which would otherwise be realized, would be smaller. Does this result in reasonable savings?
to 3: c) How do we best proceed in searching for a house provider? d) Do you simply contact various solid house providers with this rough concept? Do I now just go to prefab house manufacturers in a prefab house center with these rough framework data and ask them for offers?
e) How is it generally with prefab house manufacturers? Generally, in the last four hours, I repeatedly read about individual manufacturers "low-cost segment," "high quality," etc. Can the manufacturers at least roughly be classified into groups in this respect - does the rule apply: the more expensive, the more quality? Can it be said that "X" is of higher quality than "Y," but also more expensive? (and by what is quality measured: wall thickness/insulation and used components?)

I thank you already for your help - if it works out, I will definitely keep a construction blog already now! Have a nice rest of Saturday/Sunday.

2) I wouldn’t buy the property now. You’d be surprised what kind of nonsense municipalities come up with for road construction. This "relative elevation" to the property does not necessarily improve; the opposite often happens.

3) The ideas about the house size are appropriate and almost unusually realistic.

4b) I recently put forward the rule of thumb that from a height difference of 2m under the house footprint, the measures for a foundation without a basement are no longer cheaper than building a basement, even if you don’t have any specific use planned; and at 1m difference, half the price.

These living space requirements can be implemented as one-and-a-half or even two-story buildings without using the basement for living. Wastewater from basement rooms can require complex lifting systems to transport it into the sewer if it is at a higher elevation.

4c/d) The largest selection is available if you are not fixed on prefabricated or solid construction; but even otherwise, the choice is still quite overwhelming. However, current market conditions have reduced this due to numerous providers, so you might have to wait.

The problem with the offers is comparing apples and oranges. The so-called "construction service description" — what kind of bricks, how many sockets, which tiles (as well as "ready for painter" or fully move-in ready and who pays for construction electricity, etc.) — is different everywhere and a jungle for laypeople. Simply put, the "cheapest" provider calculates most heavily on your ignorance or lack of knowledge; none of them give anything away.

All providers have ready-made offers for every size and price class in their drawer. First, to always have an answer, and second, so the customer has a basis for discussion, including the visual idea of the house type.

4e) One can roughly say, the specialist doctor or lawyer builds with Weberhaus, the authorized signatory with Schwörerhaus, the employee with company car A4 takes Bien-Zenker, the skilled worker Fingerhut Haus etc., but you don’t have to hang every sentence of mine over your bed ;-)

Wall thickness / insulation are no yardstick. You must comply with legal requirements. Whoever wants to go further can receive funding. Therefore, there are offers for the legal standard (Energy Saving Ordinance 2016) and for KfW55 and KfW40. Providers all try to achieve the respective standard in the most profitable way for themselves.

Electrical and sanitary standards are significant price factors, alongside windows and doors with everything that goes with them (burglar resistance, shading, etc.). And of course aesthetics: clinker bricks and cladding are more expensive than plaster facades.

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A good house provider — whether prefab or solid — listens, advises, and also knocks foolish ideas out of your head. You can also recognize them by customers who suit you. Look at the reference building families: if they are people who don’t fit you, then the provider won’t either.

Prefab builders are mostly positioned regionally to nationwide, solid builders mostly only in cooperative networks nationwide and rarely operate beyond a radius of 100 km, often less. And all cook with water and don’t reinvent the wheel. If you come from southern Rhineland-Palatinate, then only ask in Rhineland-Palatinate, Saarland, Hesse, northern Baden-Württemberg. Comparison offers from Ulm or Schwerin won’t give you any aha moments there.

Look at reference houses. Many providers — prefab but also solid builders — invite you to tours at housewarming parties of customer houses. You will also meet other interested parties and can chat to them.

Or you do it the other way around and consider the building areas around you as an "exhibition." Either the houses are still under construction, in which case you will see who is doing it; or people have already moved in, and on Saturdays you have a good chance of getting friendly information at the garden fence.

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"a cistern with a forced-drained specific volume of at least 25l/m² of sealed surface (projected surface – roof area top view) with subsequent infiltration via swales") will probably be necessary immediately - although I don’t have the slightest idea what is required here/what it costs.

That means in plain German: for example, with 200 sqm of built-over/covered/paved area (i.e., house, terrace, driveway) you would have to be able to hold 5,000 liters of rainwater in a container that cannot overflow. You are supposed to be able to buffer heavy rain so that the sewer initially only has to take water from the street.

Yes, it may overflow. It is about a basin after all. How large is the property, or did I overlook that? Basins need space. Is there a soil report available, especially regarding infiltration capacity in this context? If it is not that good, the basin will be even bigger ...

Short answer regarding financing: the land price is usually not for a cheap location, meaning not the far east where you can still build relatively cheaply.

With €255,000 and no earthworks calculated yet.... Even without a basement and only 140 sqm... In a not cheap region.... I see little chance there.

The ratio of land costs to the house would be too high. I would spend about €100,000 on the land in relation to the construction sum.

Hello, wow so many good answers on a Sunday morning. @11ant: Thanks for your tips on how to proceed. We have now decided to drive to Mannheim to the show house center this morning to see different house types and shapes as simply as possible. About the rainwater: (also Alex85): the plot is about 450 sqm. There is no independent soil survey yet because we have only reserved it and not bought it yet. And before we know how realistic the project is there, we did not want to commission a soil survey. So I don't know much more than these specifications from the draft development plan. What cost range are we actually dealing with for this wastewater solution? I haven't even found rough estimates on the internet. and Bau-Schmidt: it is already difficult here in the region to find plots at all (near Mannheim, Heidelberg, Karlsruhe). I know people here who have been looking for 4-5 years. But I was also stunned by the price of the plot at first. Therefore, I consider 100,000 euros including incidental purchase costs fully developed unrealistic. If I keep an eye on the plot (or similarly priced plots), by how much would I possibly need to increase the budget? Or rather: this was now an inquiry through a municipality to a developer. There are currently no municipally owned plots in our region. The online portals also have hardly any meaningful building land. Does it then make sense to work with real estate agents (which increases the price again?) or to contact construction companies directly (similarly higher incidental purchase costs because of coupling?). Do they then have plots that I can't access otherwise? What other options would there be?