Total costs of construction with architect

Hello everyone,

We are currently considering various fundamental questions before building a house, and one option is to build on an existing plot with an architect, either using the existing building or tearing it down and building new.

The question is: are there rough cost estimates for something like this (possibly per sqm of living space)?

I understand that the costs for an architect are billed according to HOAI and a single-family house falls in HOAI zone 3 or 4. We would probably like to invest a bit in design and therefore end up more likely in zone 4 (or is something like this typically already zone 5? My understanding here is that zone 5 is rather for public or larger buildings). So far so good, but what about the construction costs:

We would like to build a detached house with 160-200 sqm of living space. So far, I had assumed 2,000-3,000€ per sqm for the house costs. At 200 sqm, that would be around 500,000€ at an average (2,500€). Deduct 19% VAT -> 405,000€ (construction takes place at the earliest next year).

In the HOAI tables I find values for 300,000 or 500,000. Is an average then taken here or is it rounded up/down?

Let’s assume we have to plan for 500,000 chargeable costs. Then an architect’s fee according to HOAI for the complete commission in zone 4 would be about 80,000€ + VAT = 95,000€? Then the total volume would be about 600,000€?

Is there anything else that would be added? For example, I have read that there are renovation surcharges, where the existing building is also somehow factored in, minimum 20%. If we want to convert/rebuild a house that is estimated online to be worth 250,000€, but would only have 300,000 costs for the rest, would the chargeable costs then be 550,000€, plus the renovation surcharge (80,000*1.2*1.19=~115,000)? That means from the architect’s side a renovation would be significantly more expensive?

Apart from the plot/building incidental costs, are there any further costs through using an architect that one doesn’t see now?

And is there any safeguard to prevent the costs from getting out of control? I know the architect only estimates, but what happens if they miscalculate not by 5%, but by 20%? That quickly adds up to 100,000€ - you can of course plan with such a buffer and dimension the house smaller, but I would find that rather unfortunate.

And in the other direction: does the rule of 2,000-3,000€ per sqm apply with an architect, or do you save that price element by using a general contractor and the sqm prices are usually somewhat lower?

Thank you very much for your input!

In principle, the application of HOAI is not mandatory, and you don't bring a house into a higher fee category just with "more design," but also, for example, with more difficult terrain or the like. For a project using an existing building, I would strongly advise against building without an architect. And of course, renovation is trickier than a standard new build. Basically, an architect is rather cost-neutral: you would have to pay the general contractor’s planner for the approval anyway, even if it's not billed separately there. The independent architect usually plans more creatively and cleverly, also manages construction more client-oriented; and when it comes to awarding contracts, he clearly pays off because a layperson easily falls into a dozen cheap traps. If the property already exists, then tell me more about it, also about its existing building. What is the overall intended design of the object?

There are two options for us:

1) Purchase of an existing property (in the city) of unknown form and on an unknown plot. However, the plots where we are searching are generally flat. Here we would want/must renovate.

2) 1950 sqm plot (5 km outside the city) with a relatively small existing building for the plot:
- The plot itself is 19*50 m, with on the short sides once the (quiet) street (SW) and once a riding facility (or a field) (NO). On the long sides to the NW a neighbor and to the SO a farm (no livestock -> riding school)
- 110 sqm living space
- partially basement
- 1 full floor + gable roof
- dimensions approx. 9x8 meters
- garage directly on the property boundary to the neighbor
- year of construction 1963
- photovoltaic system from 2010 on the roof
- roof renewed in 2006
- oil heating
- was also an architect’s house back then

In both cases, we are looking for a house for 4 people + frequent guests + 3 days/week home office. Roughly estimated, we come to about 180 sqm.

With 1) I find it extremely difficult to find a reasonable approach. For example, currently existing properties in a size range that can be brought to our goal through renovation cost 500-700T€, including ancillary purchase costs. Our total budget then allows 200-400T€ for the renovation. But if, for example, fees for the architect would already amount to 100,000€, we could exclude some properties from the outset. Does it possibly make sense here to look for the architect beforehand, discuss wishes and then take him/her to a (second) viewing?

With 2) it would of course be nice if the existing structure could continue to be used, for example the basement, the photovoltaic system and possibly the garage. I could well imagine an extension in the same style, but that would of course be left to the professional.

Regarding 2), much sounds to me like outdoor areas – thus raising the question of what one would be allowed or required to do there as a non-farmer (or rather as a riding stable continued operator) – that might possibly be more decisive than what an architect could perceive during a joint inspection.

Oh sorry, not 1950 but 950 sqm plot.

It is a completely normal residential area, the development plan was cancelled in 2012 and now development follows the neighborhood.

The question of whether the architect should come along is more relevant for option 1. For 2), we already own the plot and can take it easy.